Professor Bill Dennison

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Professor Bill Dennison

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Bill Dennison Integration and Application Network Professor Bill Dennison Vice President for Science Applications dennison@umces.edu cell(443) 496-0196 workfax(410) 228-3843 work(410) 221-2004 University of Maryland Center for Environmental Science

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PO Box 775
/ 2020 Horns Point Rd

Cambridge MD 21613 USA

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PROFESSIONAL EXPERIENCE

Dr. Bill Dennison is a Professor of Marine Science and Vice President for Science Applications at the University of Maryland Center for Environmental Science (UMCES). Dr. Dennison’s primary mission within UMCES is to coordinate the Integration and Application Network (IAN), a group of scientists committed to solving, not just studying, environmental problems. IAN is a collection of Science Integrators and Science Communicators that work closely with various agencies, foundations and non-government organizations to develop integrated science products using principles of science communication.Bill rejoined UMCES in 2002 following a ten year stint at the University of Queensland in Brisbane, Australia. He originally started at UMCES (then the Center for Environmental and Estuarine Science) in 1987 as a Research Assistant Professor based at Horn Point Laboratory.  In Australia, Bill worked with an active Marine Botany group at the University of Queensland. Bill obtained his academic training from Western Michigan University (B.A), the University of Alaska (M.S), The University of Chicago (Ph.D), and State University of New York at Stony Brook at Stony Brook (Postdoc).  Bill began studying seagrasses for his MS in Alaska in 1978, did his PhD research in Woods Hole, and then joined Stony Brook to study Long Island seagrasses and the “brown tide” algal blooms. Bill is currently co-leading an international group of seagrass scientists through the National Center for Ecological Analysis and Synthesis on global trajectories of seagrasses, building a global seagrass database, writing a series of scientific papers and producing a suite of science communication products to raise the profile of seagrasses and seagrass conservation.

Some current activities:

• Chair, Science and Technical Advisory Committee, Maryland Coastal Bays Program (2008-)
• Judging Panel, BBVA Foundation (Madrid, Spain) Ecology and Conservation Biology Award; 500,000 Euros (2008)
• Chair, Tidal Monitoring and Analysis Workgroup, Chesapeake Bay Program (2004-present)
• Member, Maryland BayStat
• Director, International Riverfoundation, Brisbane, Australia (2004-present)
• Judging Panel, International Riverprize (Brisbane, Australia) $A300,000 (2003-present)
• Member, Land-Ocean Interactions in the Coastal Zone Scientific Steering Committee (2003-present)
• Overseer, Sea Education Association, Woods Hole, MA (2007-present)
• Member, Science Advisory Panel, Reef Water Quality Partnership, Townsville, Australia (2006-present)

GRADUATE STUDENT SUPERVISION

PhDs

Ben Longstaff PhD 2003 - Investigations into the light requirements of seagrasses in northeast Australia.
Katherine Chaston PhD 2002 -Sediment Nutrient Bioavailability in a Sub-tropical Catchment Dominated by Agriculture: The Transition from Land to Sea.
Simon Costanzo PhD 2002 - Design and Implementation of Baseline Monitoring Tools and Strategies for Assessing Australian Coastal Waters.
David Haynes PhD 2001 - Pesticide and Heavymetal Concentrations in Great Barrier Reef Sediment, Seagrass and Dugongs (Dugong dugon).
Michele Burford PhD 2000 - Fate and Transformation of Dietary Nitrogen in Penaeid Prawn Aquaculture ponds.
Mark O’Donohue PhD 2000 - Environmental Controls of Primary Productivity, Biological Indicators and Ecosystem Health: A case study in Moreton Bay, Australia.
Adrian Jones PhD 1999 - Environmental Management of Aquaculture Effluent: Development of Biological Indicators and Biological Filters.
Christine Perry PhD 1997 - Microbial Processes in Seagrass Sediments.
James Udy PhD 1997 - Seagrass and Sediment Nutrients: Growth and Physiological Responses of Seagrasses to Elevated Nutrients in Australia.
Eva Abal PhD 1996 - Light, Nutrient and Water Quality Interactions with the Seagrass Zostera capricorni Aschers.

Masters

Mark Crossley MPhil 2002 - The Effects of Water Flow, pH and Nutrition on the Growth of the Native Aquatic Plant, Aponogeton elongatus.

Honours/Post graduate diploma

Tracey Saxby BSc (Hons) 2001 - Photosynthetic responses of the coral Montipora digitata to cold temperature stress.
Ian Hewson BSc (Hons) 2000 - Dynamics of Marine Viruses Along Autrophication Gradients in Australian Subtropical Estuaries.
Andrew Watkinson BSc (Hons) 2000 - Ecophysiology of the Marine Cyanobacterium Lyngbya Majuscula (Oscillatoriacea).
Catherine Collier BSc (Hons) 1999 - Internal Nitrogen Cycling in Three Seagrasses: patterns and process.
Joelle Prange BSc (Hons) 1999 - The Cycling of Trace Metals in Seagrass Environments.
Elizabeth King 1999 - Assessment of Water Quality using Phytoplankton in Two Estuaries (Queensland, Australia).
Graham Webb BEnvSc 1999 - Assessing zooplankton grazing in Moreton Bay by measuring short-term changes in chlorophyll a concentrations.
Chris Roelfsema PgDipMarSci 1999 - Spatial Distribution of Benthic Microalgae on Coral Reefs Determined by Remote Sensing.
Phillip Kay BSc (Hons) 1998 - Phytoplankton Bioassays: Technique Development for Assessing Bioavailability of Sediment Phosphorus in Aquatic Ecosystems.
Sabine Roberts PgDipMarSci 1997 - The Effects of Dugong Grazing on Seagrass Communities in Moreton Bay.
Jane Rogers BSc (Hons) 1997 - Responses of Mangrove Forests to Natural and Experimental Nutrient Gradients in Moreton Bay, Australia
Bernard Dudley BSc (Hons) 1996 - Nitrogen Fixation and the Seagrass Halodule uninervus (Forsk) Aschers.
Scott Lowe BEnvSc 1996 - Estuarine Macrophytes as Nutrient Bioindicators for Tracing Sewage Effluent in the Maroochy River, Queensland.
Simon Costanzo BSc (Hons) 1996 - Marine Macroalgae (Rhodophyta) as a Biological Indicator of Pulsed Nutrients in Oligotrophic Waters.
Rhona McPhee BEnvSc 1995 - Assessing Red Algae Associated with Mangroves as Bioindicators of Nutrient Availability.
Ben Longstaff BSc (Hons) 1995 - The Effects of Light Deprivation on the Survival and Recovery of the Seagrass Halophila ovalis.
Adrian Jones BSc (Hons) 1994 - Influence of Nitrogen Source and Availability on Amino Acids, Pigments and Tissue Nitrogen of Gracilaria edulis (Rhodophyta).
Shane Dawson BSc (Hons) 1994 - Effects of Ultraviolet and Photosynthetically Active Radiation on Five Seagrass Species.
Angela Grice BSc (Hons) 1993 - Light Intensity Effects on the Carbon and Nitrogen Stable Isotope Ratios and Tissue Contents of Five Seagrass Species.
Tracey O'Connell BSc (Hons) 1993 - Nutrients in a North Stradbroke Island Mangrove Forest.
Patricia Bowen BSc (Hons) 1993 - Morphological and Genetic Variation in the Seagrass, Zostera capricorni.
Janine Horrocks BSc (Hons) 1992 - Tissue Nutrient Content of Gracilaria spp. (Rhodophyta) and Water Quality of Logan River and Southern Moreton Bay.

RESEARCH

Seagrass Ecophysiology

I have been studying seagrass ecophysiology since my Master’s thesis. My investigations have encompassed a wide range of experimental field and laboratory studies. These studies have recently benefited from the high seagrass diversity in Australia, providing a unique comparative approach to each of the ecophysiological investigations. With my PhD and Honours students, I have developed a comprehensive conceptual model that relates seagrass morphology to physiology so that light, nutrient, water motion and grazing effects on seagrasses can be placed into a successional and evolutionary context (Walker et al., 1999). We have also related seagrass responses to sediment biogeochemical processes, interpreted dugong grazing as corals-evolution with selected seagrass species, provided an interpretation of seagrass δ¹³C and δ¹⁵N values, pioneered photosynthetic assessment of seagrasses using PAM fluorometry, determined effects of ultraviolet light, high and low light regimes, and total light deprivation through in situ and laboratory experiments, developed new techniques for measuring sediment nutrient pools and fluxes relevant to seagrasses, assessed the effects of metals, and using laboratory and in situ ¹⁵N tracer additions to assess uptake, assimilation and translocation.

Ecological Health Assessment

A series of projects beginning with a water quality study in 1992 has led to a program of assessing ecological health of various coastal marine ecosystems. The development of a suite of nutrient bioindicators using marine plants has provided essential tools for assessing ecological health. Phytoplankton productivity responses to nutrient additions are used to delineate nitrogen vs. phosphorus limitation, macroalgal metabolic profiling is used to discern form of nitrogen taken up and amount of ambient dissolved nutrients in a wide variety of locations, seagrass depth range transects are used as a water quality monitoring tool, vegetation isotopic signatures (δ¹³C and δ¹⁵N) are used to distinguish source of carbon and nitrogen in marine habitats, particularly sewage nitrogen. The creation of conceptual models to encapsulate current understanding of key ecological processes, anthropogenic impact zones, and critical habitats have been used to communicate scientific results and to focus scientific efforts. These assessment tools have been developed and tested in a series of coastal embayment studies culminating in an Ecological Health Monitoring Program in SE Queensland and a national audit of Australian estuaries, a national eutrophication assessment in the US (National Estuarine Eutrophication Assessment, 2007), Chesapeake Bay report card.

Publications

This page provides a reference list in Word and PDF formats, an RSS feed for new publications, a link to browse/search through all Bill's publications in the literature database. You can also view the abstract and keywords and access a pemanent link to the article in our literature database by expanding the citation, or view the full details of each publication in the database, or view the article on the publisher's website, which may include access to fulltext and PDF versions.

Peer-reviewed Publications
2012
Sekovski I, Newton A, Dennison WC (2012) Megacities in the coastal zone: Using a driver-pressure-state-impact-response framework to address complex environmental problems. Estuar. Coast. Shelf Sci. 96(1):48–59 Abstract: The purpose of this study was to elaborate on the role of coastal megacities in environmental degradation and their contribution to global climate change. Although only less than 4 percent of the total world’s population resides in coastal megacities, their impact on environment is significant due to their rapid development, high population densities and high consumption rate of their residents. This study was carried out by implementing a Drivers-Pressures-States-Impacts-Responses (DPSIR) framework. This analytical framework was chosen because of its potential to link the existing data, gathered from various previous studies, in causal relationship. In this text, coastal megacities have been defined as cities exceeding 10 million inhabitants, situated in “near-coastal zone”. Their high rates of the consumption of food, water, space and energy were observed and linked to the high performance rates of related economic activities (industry, transportation, power generation, agriculture and water extraction). In many of the studied coastal megacities, deteriorated quality of air and water was perceived, which can, in combination with global warming, lead to health problems and economic and social disturbance among residents. The extent of problems varied between developing and developed countries, showing higher rates of population growth and certain harmful emissions in megacities of developing countries, as well as more problems regarding food and water shortages, sanitation, and health care support. Although certain projections predict slowdown of growth in most coastal megacities, their future impact on environment is still unclear due to the uncertainties regarding future climate change and trajectories of consumption patterns. Keywords: coastal megacities; DPSIR; climatic changes; coastal zone management; urbanization; environmental effects Permanent link  | Save citation:  RTF  PDF  LaTeX
2011
Short FT, Polidoro B, Livingstone SR, Carpenter KE, Bandeira S, Bujang JS, Calumpong HP, Carruthers TJB, Coles RG, Dennison WC, Erftemeijer PLA, Fortes MD, Freeman AS, Jagtap TG, Kamal AHM, Kendrick GA, Kenworthy WJ, La Nafie YA, Nasution IM, Orth RJ, Prathep A, Sanciangco JC, van Tussenbroek B, Vergara SG, Waycott M, Zieman JC (2011) Extinction risk assessment of the world’s seagrass species. Biol. Conserv. 144(7):1961–1971 Abstract: Seagrasses, a functional group of marine flowering plants rooted in the world's coastal oceans, support marine food webs and provide essential habitat for many coastal species, playing a critical role in the equilibrium of coastal ecosystems and human livelihoods. For the first time, the probability of extinction is determined for the world's seagrass species under the Categories and Criteria of the International Union for the Conservation of Nature (IUCN) Red List of Threatened Species. Several studies have indicated that seagrass habitat is declining worldwide. Our focus is to determine the risk of extinction for individual seagrass species, a 4-year process involving seagrass experts internationally, compilation of data on species' status, populations, and distribution, and review of the biology and ecology of each of the world's seagrass species. Ten seagrass species are at elevated risk of extinction (14% of all seagrass species), with three species qualifying as Endangered. Seagrass species loss and degradation of seagrass biodiversity will have serious repercussions for marine biodiversity and the human populations that depend upon the resources and ecosystem services that seagrasses provide. Keywords: Seagrass; Red List; Extinction; Threatened; Endangered; Biodiversity Permanent link  | Save citation:  RTF  PDF  LaTeX
2010
Fertig BM, Carruthers TJB, Dennison WC, Fertig EJ, Altabet MA (2010) Eastern oyster (Crassostrea virginica) δ15N as a bioindicator of nitrogen sources: Observations and modeling. Mar. Poll. Bull. 60(8):1288–1298 Abstract: Stable nitrogen isotopes (δ15N) in bioindicators are increasingly employed to identify nitrogen sources in many ecosystems and biological characteristics of the eastern oyster (Crassostrea virginica) make it an appropriate species for this purpose. To assess nitrogen isotopic fractionation associated with assimilation and baseline variations in oyster mantle, gill, and muscle tissue δ15N, manipulative fieldwork in Chesapeake Bay and corresponding modeling exercises were conducted. This study (1) determined that five individuals represented an optimal sample size; (2) verified that δ15N in oysters from two locations converged after shared deployment to a new location reflecting a change in nitrogen sources; (3) identified required exposure time and temporal integration (four months for muscle, two to three months for gill and mantle); and (4) demonstrated seasonal δ15N increases in seston (summer) and oysters (winter). As bioindicators, oysters can be deployed for spatial interpolation of nitrogen sources, even in areas lacking extant populations. Keywords: Biological indicators; Crassostrea virginica; Stable nitrogen isotopes; Nitrogen sources; Temporal integration; Chesapeake Bay Permanent link  | Save citation:  RTF  PDF  LaTeX
Orth RJ, Williams MR, Marion SR, Wilcox DJ, Carruthers TJB, Moore KA, Kemp WM, Dennison WC, Rybicki N, Bergstrom P, Batiuk RA (2010) Long-Term Trends in Submersed Aquatic Vegetation (SAV) in Chesapeake Bay, USA, Related to Water Quality. Estuaries Coasts 33(5):1144–1163 Abstract: Chesapeake Bay supports a diverse assemblage of marine and freshwater species of submersed aquatic vegetation (SAV) whose broad distributions are generally constrained by salinity. An annual aerial SAV monitoring program and a bi-monthly to monthly water quality monitoring program have been conducted throughout Chesapeake Bay since 1984. We performed an analysis of SAV abundance and up to 22 environmental variables potentially influencing SAV growth and abundance (1984–2006). Historically, SAV abundance has changed dramatically in Chesapeake Bay, and since 1984, when SAV abundance was at historic low levels, SAV has exhibited complex changes including long-term (decadal) increases and decreases, as well as some large, single-year changes. Chesapeake Bay SAV was grouped into three broad-scale community-types based on salinity regime, each with their own distinct group of species, and detailed analyses were conducted on these three community-types as well as on seven distinct case-study areas spanning the three salinity regimes. Different trends in SAV abundance were evident in the different salinity regimes. SAV abundance has (a) continually increased in the low-salinity region; (b) increased initially in the medium-salinity region, followed by fluctuating abundances; and (c) increased initially in the high-salinity region, followed by a subsequent decline. In all areas, consistent negative correlations between measures of SAV abundance and nitrogen loads or concentrations suggest that meadows are responsive to changes in inputs of nitrogen. For smaller case-study areas, different trends in SAV abundance were also noted including correlations to water clarity in high-salinity case-study areas, but nitrogen was highly correlated in all areas. Current maximum SAV coverage for almost all areas remain below restoration targets, indicating that SAV abundance and associated ecosystem services are currently limited by continued poor water quality, and specifically high nutrient concentrations, within Chesapeake Bay. The nutrient reductions noted in some tributaries, which were highly correlated to increases in SAV abundance, suggest management activities have already contributed to SAV increases in some areas, but the strong negative correlation throughout the Chesapeake Bay between nitrogen and SAV abundance also suggests that further nutrient reductions will be necessary for SAV to attain or exceed restoration targets throughout the bay. Keywords: Submersed aquatic vegetation;Salinity community-types;Chesapeake Bay;Abundance;Nutrients;Nitrogen;Water quality Permanent link  | Save citation:  RTF  PDF  LaTeX
Williams MR, Filoso S, Longstaff BJ, Dennison WC (2010) Long-Term Trends of Water Quality and Biotic Metrics in Chesapeake Bay: 1986 to 2008. Estuaries Coasts 33(6):1279–1299 Abstract: We analyzed trends in a 23-year period of water quality and biotic data for Chesapeake Bay. Indicators were used to detect trends of improving and worsening environmental health in 15 regions and 70 segments of the bay and to assess the estuarine ecosystem’s responses to reduced nutrient loading from point (i.e., sewage treatment facilities) and nonpoint (e.g., agricultural and urban land use) sources. Despite extensive restoration efforts, ecological health-related water quality (chlorophyll-a, dissolved oxygen, Secchi depth) and biotic (phytoplankton and benthic indices) metrics evaluated herein have generally shown little improvement (submerged aquatic vegetation was an exception), and water clarity and chlorophyll-a have considerably worsened since 1986. Nutrient and sediment inputs from higher-than-average annual flows after 1992 combined with those from highly developed Coastal Plain areas and compromised ecosystem resiliency are important factors responsible for worsening chlorophyll-a and Secchi depth trends in mesohaline and polyhaline zones from 1986 to 2008. Keywords: Biotic;Chesapeake Bay;Eutrophication;Health indices;Water quality Permanent link  | Save citation:  RTF  PDF  LaTeX
2009
Dennison WC (2009) Seagrasses: biology, ecology and conservation. Bot. Mar. 52(4):367 Abstract: Seagrasses: biology, ecology and conservation, edited by Tony Larkum, Bob Orth and Carlos Duarte, and authored by 79 active seagrass researchers is the most comprehensive book about these unique flowering plants ever written. It is long, 691 pp, with an excess of 100 pages devoted to references, and it includes 26 chapters on evolution, anatomy, biology, physiology, biogeochemistry, remote sensing, grazing and predation, ecology, and management. It is reasonably priced (~$US 130) considering its size and its relatively narrow audience. Keywords: seagrass; book review Permanent link  | Save citation:  RTF  PDF  LaTeX
Fertig BM, Carruthers TJB, Dennison WC, Jones AB, Pantus F, Longstaff B (2009) Oyster and Macroalgae Bioindicators Detect Elevated delta N-15 in Maryland's Coastal Bays. Estuaries Coasts 32(4):773–786 Abstract: Nitrogen loading from anthropogenic sources, including fertilizer, manure, and sewage effluents, has been linked with declining water quality in coastal lagoons worldwide. Freshwater inputs to mid-Atlantic coastal lagoons of the USA are from terrestrially influenced sources: groundwater and overland flow via streams and agricultural ditches, with occasional precipitation events. Stable nitrogen isotopes ratios (delta N-15) in bioindicator species combined with conventional water quality monitoring were used to assess nitrogen sources and provide insights into their origins. Water quality data revealed that nutrients derived from terrestrial sources increased after precipitation events. Tissues from two bioindicator species, a macroalgae (Gracilaria sp.) and the eastern oyster (Crassostrea virginica) were analyzed for delta N-15 to determine spatial and temporal patterns of nitrogen sources. A broad-scale survey assessment of deployed macroalgae (June 2004) detected regions of elevated delta N-15. Macroalgal delta N-15 (7.33 +/- 1.15aEuro degrees in May 2006 and 6.76 +/- 1.15aEuro degrees in July 2006) responded quickly to sustained June 2006 nutrient pulse, but did not detect spatial patterns at the fine scale. Oyster delta N-15 (8.51 +/- 0.89aEuro degrees) responded slowly over longer time periods and exhibited a slight gradient at the finer spatial scale. Overall, elevated delta N-15 values in macroalgae and oysters were used to infer that human and animal wastes were important nitrogen sources in some areas of Maryland's coastal bays. Different nitrogen integration periods across multiple organisms may be used to indicate nitrogen sources at various spatial and temporal scales, which will help focus nutrient management. Keywords: Stable nitrogen isotopes;Coastal lagoons;Human and animal wastes;Biological indicators;Water quality;Spatial analysis Permanent link  | Save citation:  RTF  PDF  LaTeX
Lookingbill TR, Kaushal SS, Elmore AJ, Gardner R, Eshleman KN, Hilderbrand RH, Morgan RP, Boynton WR, Palmer MA, Dennison WC (2009) Altered ecological flows blur boundaries in urbanizing watersheds. Ecol. Soc. 14(2):10 Abstract: The relevance of the boundary concept to ecological processes has been recently questioned. Humans in the post-industrial era have created novel lateral transport fluxes that have not been sufficiently considered in watershed studies. We describe patterns of land-use change within the Potomac River basin and demonstrate how these changes have blurred traditional ecosystem boundaries by increasing the movement of people, materials, and energy into and within the basin. We argue that this expansion of ecological commerce requires new science, monitoring, and management strategies focused on large rivers and suggest that traditional geopolitical and economic boundaries for environmental decision making be appropriately revised. Effective mitigation of the consequences of blurred boundaries will benefit from a broad-scale, interdisciplinary framework that can track and explicitly account for ecological fluxes of water, energy, materials, and organisms across human-dominated landscapes. Keywords: catchment ecology; Chesapeake Bay; interdisciplinary science; large river; Potomac River; restoration; urban metabolism Permanent link  | Save citation:  RTF  PDF  LaTeX
Waycott M, Duarte CM, Carruthers TJB, Orth RJ, Dennison WC, Olyarnike S, Calladine A, Fourqurean JW, Heck KLJ, Hughese AR, Kendricki GA, Kenworthy WJ, Short FT, Williams SL (2009) Accelerating loss of seagrasses across the globe threatens coastal ecosystems. PNAS 106(30):12377–12381 Abstract: Coastal ecosystems and the services they provide are adversely affected by a wide variety of human activities. In particular, seagrass meadows are negatively affected by impacts accruing from the billion or more people who live within 50 km of them. Seagrass meadows provide important ecosystem services, including an estimated $1.9 trillion per year in the form of nutrient cycling; an order of magnitude enhancement of coral reef fish productivity; a habitat for thousands of fish, bird, and invertebrate species; and a major food source for endangered dugong, manatee, and green turtle. Although individual impacts from coastal development, degraded water quality, and climate change have been documented, there has been no quantitative global assessment of seagrass loss until now. Our comprehensive global assessment of 215 studies found that seagrasses have been disappearing at a rate of 110 km2 yr-1 since 1980 and that 29% of the known areal extent has disappeared since seagrass areas were initially recorded in 1879. Furthermore, rates of decline have accelerated from a median of 0.9% yr-1 before 1940 to 7% yr-1 since 1990. Seagrass loss rates are comparable to those reported for mangroves, coral reefs, and tropical rainforests and place seagrass meadows among the most threatened ecosystems on earth. Keywords: ecosystem decline;global trajectories;habitat loss;marine habitat Permanent link  | Save citation:  RTF  PDF  LaTeX
Williams MR, Longstaff BJ, Buchanan C, Llanso R, Dennison WC (2009) Development and evaluation of a spatially-explicit index of Chesapeake Bay health. Mar. Poll. Bull. 59(1-3):14–25 Abstract: In an effort to better portray changing health conditions in Chesapeake Bay and support restoration efforts, a Bay Health Index (BHI) was developed to assess the ecological effects of nutrient and sediment loading on 15 regions of the estuary. Three water quality and three biological measures were combined to formulate the BHI. Water quality measures of chlorophyll-a, dissolved oxygen, and Secchi depth were averaged to create the Water Quality Index (WQI), and biological measures of the phytoplankton and benthic indices of biotic integrity (P-IBI and B-IBI, respectively) and the area of submerged aquatic vegetation (SAV) were averaged to create the Biotic Index (BI). The WQI and BI were subsequently averaged to give a BHI value representing ecological conditions over the growing season (i.e., March-October). Lower chlorophyll-a concentrations, higher dissolved oxygen concentrations, deeper Secchi depths, higher phytoplankton and benthic indices relative to ecological health-based thresholds, and more extensive SAV area relative to restoration goal areas, characterized the least-impaired regions. The WQI, P-BI and BHI were significantly correlated with (1) regional river flow (r = -0.64, -0.57 and -0.49, respectively; p < 0.01), (2) nitrogen (N), phosphorus (P) and sediment loads (all positively correlated with flow), and (3) the sum of developed and agricultural land use (highest annual r(2) = 0.86, 0.71 and 0.68, respectively) in most reporting regions, indicating that the BHI is strongly regulated by nutrient and sediment loads from these land uses. The BHI uses ecological health-based thresholds that give an accurate representation of the health conditions in Chesapeake Bay and was the basis for an annual, publicly released environmental report card that debuted in 2007. Keywords: Chesapeake Bay; Chlorophyll-a; Dissolved oxygen; Environmental health index; Secchi depth; Submerged aquatic vegetation; Water quality Permanent link  | Save citation:  RTF  PDF  LaTeX
2008
Benson ER, O'Neil JM, Dennison WC (2008) Using the aquatic macrophyte Vallisneria americana (wild celery) as a nutrient bioindicator. Hydrobiologia 596:187–196 Abstract: Human sewage and septic waste are significant sources of nutrient loading to many aquatic ecosystems. Ecologically relevant nitrogen sources can be traced by analyzing nitrogen stable isotope ratios (?15N signatures) in aquatic plants. Elevated ?15N signatures can suggest increased uptake of nitrogen derived from human and/or animal waste. In the current study, Vallisneria americana, a freshwater angiosperm, was collected from several locations in Upper Saranac Lake, NY, USA. Samples were also collected from Lake George, NY and the Sassafras River, MD, USA. Plant material was analyzed for ?15N and % N; some samples were also analyzed for ?13C, % C, and % P. Results suggest that there is variation in septic inputs to Upper Saranac Lake, with some areas of the lake receiving more input than others. Results also show that increased watershed population density is correlated with elevated ?15N signatures of Vallisneria americana. Taken together, these results suggest that nitrogen stable isotope analysis of aquatic plant tissue is an effective method for assessing and monitoring septic inputs to freshwater ecosystems. Keywords: nitrogen stable isotope; Upper Saranac Lake NY; Lake George NY; Sassafras River MD; Adirondack Park; Chesapeake Bay Permanent link  | Save citation:  RTF  PDF  LaTeX
Bricker SB, Longstaff BJ, Dennison WC, Jones AB, Boicourt KE, Wicks EC, Woerner J (2008) Effects of nutrient enrichment in the nation's estuaries: A decade of change. Harmful Algae 8(1):21–32 Abstract: An updated assessment of nutrient related impacts in US estuaries was completed in 2007. This assessment evaluates three components for each estuary: the influencing factors (e.g. land use, nutrient loads), the overall eutrophic condition (e.g. chlorophyll a, presence of nuisance/toxic algae and macroalgae, extent of dissolved oxygen problems, loss of submerged aquatic vegetation), and future outlook. Eutrophication is a widespread problem with 65% of assessed systems showing moderate to high level problems. The most impacted region was the mid-Atlantic. The majority of estuaries assessed, with the exception of North Atlantic systems (Cape Cod north to Maine), are highly influenced by human related activities that contribute to land-based nutrient loads. Conditions were predicted to worsen in 65% and to improve in 19% of the assessed estuaries in the future. Analysis of the extent of change from the early 1990s to the early 2000s, for those systems for which sufficient data were available, shows that conditions mostly remained the same (32 of 58 systems) though changes were observed in several smaller systems; 13 systems improved and 13 systems worsened. Chlorophyll a and HAB impacts have increased in the mid-Atlantic region, the only region with data adequate for comparison. These symptoms are more prevalent in systems with longer residence times, such as coastal lagoons. The successful restoration of seagrass in Tampa Bay is encouraging though future management to sustain the recovery will be difficult given expected population increases. This national assessment illustrates the need for coordinated and integrated action that balances management action, efficient monitoring to assess the effectiveness of the management, focused research, and a communication campaign aimed at engaging the broader community. Keywords: Algae; Dissolved oxygen; Eutrophication; Nitrogen; HABs; Nutrients; Submerged aquatic vegetation Permanent link  | Save citation:  RTF  PDF  LaTeX
Dennison WC (2008) Environmental problem solving in coastal ecosystems: A paradigm shift to sustainability. Estuarine, Coastal and Shelf Science 77(2):185–196 Abstract: The human ecological footprint now extends to the entire globe, and human impacts are the dominant feature of many ecosystems, resulting in our current era being coined the 'anthropocene'. This is particularly apparent in coastal ecosystems as human populations are increasing rapidly in coastal cities and the ecosystem services in these areas are rapidly being compromised. Science has historically progressed as a series of paradigm shifts and this paper reviews this history of paradigm shifts and makes the case that the next major paradigm shift will be directed at sustainability, resulting in a shift in scientific focus on solving rather than just studying our current environmental problems. Traditionally, science has been extremely effective at data acquisition and then successively less effective at translating this into information, knowledge and finally environmental problem solving. The currently required paradigm shift is to focus on environmental problem solving, filling gaps in knowledge, information and data only as required to solve a particular problem. A key element in turning this process around is better science communication between scientists, key stakeholders and the community. This will require more `science communicators' who can use credibility, tenacity, creativity and virtue to effect solutions. Keywords: paradigm shifts; history of science; science communication; degradation; management solutions Permanent link  | Save citation:  RTF  PDF  LaTeX
Duarte CM, Dennison WC, Orth RJ, Carruthers TJB (2008) The charisma of coastal ecosystems: addressing the imbalance. Estuaries and Coasts 31(2):233–238 Keywords: Seagrass; Coastal habitats; Charisma; Media; Decline; Conservation Permanent link  | Save citation:  RTF  PDF  LaTeX
Heisler J, Glibert PM, Burkholder JM, Anderson DM, Cochlan W, Dennison WC, Dortch Q, Gobler CJ, Heil CA, Humphries E, Lewitus A, Magnien R, Marshall HG, Sellner K, Stockwell DA, Stoecker DK, Suddleson M (2008) Eutrophication and harmful algal blooms: A scientific consensus. Harmful Algae 8(1):3–13 Abstract: In January 2003, the US Environmental Protection Agency sponsored a “roundtable discussion” to develop a consensus on the relationship between eutrophication and harmful algal blooms (HABs), specifically targeting those relationships for which management actions may be appropriate. Academic, federal, and state agency representatives were in attendance. The following seven statements were unanimously adopted by attendees based on review and analysis of current as well as pertinent previous data: (1) Degraded water quality from increased nutrient pollution promotes the development and persistence of many HABs and is one of the reasons for their expansion in the U.S. and other nations; (2) The composition-not just the total quantity-of the nutrient pool impacts HABs; (3) High-biomass blooms must have exogenous nutrients to be sustained; (4) Both chronic and episodic nutrient delivery promote HAB development; (5) Recently developed tools and techniques are already improving the detection of some HABs, and emerging technologies are rapidly advancing toward operational status for the prediction of HABs and their toxins; (6) Experimental studies are critical to further the understanding about the role of nutrients in HABs expression, and will strengthen prediction and mitigation of HABs; and (7) Management of nutrient inputs to the watershed can lead to significant reduction in HABs. Supporting evidence and pertinent examples for each consensus statement are provided herein. (C) 2008 Elsevier B.V. All rights reserved. Keywords: Eutrophication; Harmful algal blooms; HABs; Management of nutrients; Nutrient loading; Nutrient composition; Nutrient pollution; US EPA; Water quality Permanent link  | Save citation:  RTF  PDF  LaTeX
2007
Carruthers TJB, Dennison WC, Kendrick GA, Waycott M, Walker DI, Cambridge ML (2007) Seagrasses of south-west Australia: A conceptual synthesis of the world's most diverse and extensive seagrass meadows. JEMBE 350:21–45 Abstract: South-west Australia contains extensive seagrass meadows along 2,500 km of coastline from the shallow subtidal to 50+ m water depths, and in many of the 51 bar-built estuaries along the coast. There are geomorphological differences between the south and west coasts that result in different patterns of swell exposure influencing the processes that structure seagrass habitats. In this paper, 'sheltered', 'exposed' and 'estuarine' seagrass habitat types are defined for south-west Australia to synthesize processes influencing seagrass communities. Sheltered habitats in south-west Australia are characterized by high light, low to moderate water motion and sporadic disturbance from storms, making them ideal habitats for a diversity of seagrass assemblages. Exposed seagrass habitats are characterized by the presence of strong and consistent ocean swells (3-8 m), predominantly from the south or south-west and seagrasses exhibit a suite of adaptive traits to survive the effects of exposure to ocean swell and associated sand movement. These include morphological features such as heavy fiber reinforcement to strengthen the aboveground stems or leaves, deep vertical rhizomes and life history traits such as rapid growth and high seed set. Within estuarine habitats highly dynamic seagrass communities are the result of fluctuating annual cycles in temperature, light and salinity. Compared to global seagrass meadows, coastal south-west Australian seagrass habitats experience high light, low nutrients and high water movement. Despite these differences, similarities with other regions do exist and here we place the habitats of south-west Australia into a global context using comparative data. The wide array of morphology and life history traits displayed among seagrass species of south-west Australia are presented in a conceptual model including habitat type, physical stressors and seagrass responses. The combination of adaptations to the habitats and processes that define them make south-west Australia a region where there is an unusually high number of co-occurring seagrass species, the highest in the world for a temperate environment (19 species), and approaching the species diversity of many tropical environments. Linking aspects of seagrass habitat, physical aspects of the environment and seagrass life history provides a context for applying knowledge gained from seagrasses in south-west Australia to other coastal ecosystems throughout the world. Permanent link  | Save citation:  RTF  PDF  LaTeX
Carter SL, Mora-Bourgeois G, Lookingbill TR, Carruthers TJB, Dennison WC (2007) The challenge of communicating monitoring results to effect change. The George Wright Forum 24(2):48–58 Abstract: SINCE ITS INCEPTION, the National Park Service (NPS) has been charged with preserving the natural and cultural heritage of the United States for future generations. It is only recently, however, that the NPS has fully embraced the need to understand and describe the ecology of parks. The infusion of an ecological perspective into the natural resource management of the national parks is what separates today's park management from much of that which preceded it (Sellars 1997). The guiding principles set forth by the agency's National Leadership Council as part of the Natural Resource Challenge (NPS 1999; hereafter “the Challenge”) shepherded these perspectives into present NPS culture and practice. Ultimately, the insights, common goals, and collaborations we describe in this essay have all been made possible by the vision and funding of the Challenge, the most recent high-water mark for embracing science within the NPS. In this paper, we discuss a special collaboration enabled by the Challenge, in which an inventory and monitoring (I&M) network (National Capital Region Network; NCRN), a research learning center (Urban Ecology Research Learning Alliance; UERLA), and a cooperative ecosystem studies unit (Chesapeake Watershed CESU) partner (University of Maryland Center for Environmental Science; UMCES) coalesced around a common goal: to collect, analyze, and interpret data in national parks, and to promote learning and understanding. We describe a set of tools and principles for integrating and communicating science that we believe have broad utility in the practice of natural resource stewardship. Furthermore, we stress the iterative and collaborative nature of communicating results and how the process of communication leads to shared investment and stimulates new areas of scientific inquiry. Permanent link  | Save citation:  RTF  PDF  LaTeX
Dennison WC, Lookingbill TR, Carruthers TJB, Hawkey JM, Carter SM (2007) An eye-opening approach to developing and communicating integrated environmental assessments. Front. Ecol. Environ. 5(6):307–314 Permanent link  | Save citation:  RTF  PDF  LaTeX
Grinham AR, Carruthers TJB, Fisher PL, Udy JW, Dennison WC (2007) Accurately measuring the abundance of benthic microalgae in spatially variable habitats. Limnol. Oceanogr. Methods 5:119–125 Abstract: Although many studies measure the abundance of benthic microalgae (BMA), at the meters squared scale, comparing these studies is difficult due to the variety of sampling, extraction, and analysis techniques. This difficulty is exacerbated by the fact that BMA abundance has high spatial and temporal variability, at all spatial scales. A suitable standard sampling regimen would reduce variation in estimates due to different sample collection and processing greatly facilitating comparisons between studies. This study examined the effect of varying the volume of extraction solvent, sampling core diameter, and sample replication on BMA biomass estimates. Key findings, applicable to all spatial scales, to accurately determine biomass were the use of a minimum sediment to extraction solvent ratio of 1:2 and use of a sampling core diameter of 19 mm. Across a wide range of sediment types, at the meters squared scale and using spectrophotometric techniques, a minimum replication number of 8 was found to be appropriate. We report the significant effect coring depth and units of expression have on BMA biomass estimates across a range of sediment types, highlighting the potential pitfalls when comparing studies. Permanent link  | Save citation:  RTF  PDF  LaTeX
Kennish MJ, Bricker SB, Dennison WC, Glibert PM, Livingston RJ, Moore KA, Noble RT, Paerl HW, Ramstack JM, Seitzinger S, Tomasko DA, Valiela I (2007) Barnegat Bay-Little Egg Harbor Estuary: Case study of a highly eutrophic coastal bay system. Ecol. Appl. 17(5):S3–S16 Keywords: assessment; Barnegat Bay-Little Egg Harbor Estuary; eutrophication; indicators; nutrient loading; remediation Permanent link  | Save citation:  RTF  PDF  LaTeX
Short F, Carruthers TJB, Dennison WC, Waycott M (2007) Global seagrass distribution and diversity: A bioregional model. JEMBE 350:3–20 Abstract: Seagrasses, marine flowering plants, are widely distributed along temperate and tropical coastlines of the world. Seagrasses have key ecological roles in coastal ecosystems and can form extensive meadows supporting high biodiversity. The global species diversity of seagrasses is low (b60 species), but species can have ranges that extend for thousands of kilometers of coastline. Seagrass bioregions are defined here, based on species assemblages, species distributional ranges, and tropical and temperate influences. Six global bioregions are presented: four temperate and two tropical. The temperate bioregions include the Temperate North Atlantic, the Temperate North Pacific, the Mediterranean, and the Temperate Southern Oceans. The Temperate North Atlantic has low seagrass diversity, the major species being Zostera marina, ypically occurring in estuaries and lagoons. The Temperate North Pacific has high seagrass diversity with Zostera spp. in estuaries and lagoons as well as Phyllospadix spp. in the surf zone. The Mediterranean region has clear water with vast meadows of moderate diversity of both temperate and tropical seagrasses, dominated by deep-growing Posidonia oceanica. The Temperate Southern Oceans bioregion includes the temperate southern coastlines of Australia, Africa and South America. Extensive meadows of low-to-high diversity temperate seagrasses are found in this bioregion, dominated by various species of Posidonia and Zostera. The tropical bioregions are the Tropical Atlantic and the Tropical Indo-Pacific, both supporting mega-herbivore grazers, including sea turtles and sirenia. The Tropical Atlantic bioregion has clear water with a high diversity of seagrasses on reefs and shallow banks, dominated by Thalassia testudinum. The vast Tropical Indo-Pacific has the highest seagrass diversity in the world, with as many as 14 species growing together on reef flats although seagrasses also occur in very deep waters. The global distribution of seagrass genera is remarkably consistent north and south of the equator; the northern and southern hemispheres share ten seagrass genera and only have one unique genus each. Some genera are much more speciose than others, with the genus Halophila having the most seagrass species. There are roughly the same number of temperate and tropical seagrass genera as well as species. The most widely distributed seagrass is Ruppia maritima, which occurs in tropical and temperate zones in a wide variety of habitats. Seagrass bioregions at the scale of ocean basins are identified based on species distributions which are supported by genetic patterns f diversity. Seagrass bioregions provide a useful framework for interpreting ecological, physiological and genetic results collected in specific locations or from particular species. Keywords: Bioregional models; Diversity; Global distribution; Seagrass; Species; Temperate; Tropical Permanent link  | Save citation:  RTF  PDF  LaTeX
Wazniak CE, Hall MR, Carruthers TJB, Sturgis B, Dennison WC, Orth RJ (2007) Linking water quality to living resources in a mid-Atlantic lagoon system, USA. Ecol. Apps. 17(5):S64–S78 Abstract: The mid-Atlantic coastal bays are shallow coastal lagoons, separated from the Atlantic Ocean by barrier sand islands with oceanic exchanges restricted to narrow inlets. The relatively poor flushing of these lagoon systems makes them susceptible to eutrophication resulting from anthropogenic nutrient loadings. An intensive water quality and seagrass monitoring program was initiated to track ecological changes in the Maryland and Virginia coastal bays. The purpose of this study was to analyze existing monitoring data to determine status and trends in eutrophication and to determine any associations between water quality and living resources. Analysis of monitoring program data revealed several trends: (1) decadal decreases in nutrient and chlorophyll concentrations, followed by recently increasing trends; (2) decadal increases in seagrass coverage, followed by a recent period of no change; (3) blooms of macroalgae and brown tide microalgae; and (4) exceedance of water quality thresholds: chlorophyll a (15 lg/L), total nitrogen (0.65 mg/L or 46 lmol/L), total phosphorus (0.037 mg/L or 1.2 lmol/L), and dissolved oxygen (5 mg/L) in many areas within the Maryland coastal bays. The water quality thresholds were based on habitat requirements for living resources (seagrass and fish) and used to calculate a water quality index, which was used to compare the bay segments. Strong gradients in water quality were correlated to changes in seagrass coverage between segments. These factors indicate that these coastal bays are in a state of transition, with a suite of metrics indicating degrading conditions. Continued monitoring and intensified management will be required to avert exacerbation of the observed eutrophication trends. Coastal lagoons worldwide are experiencing similar degrading trends due to increasing human pressures, and assessing status and trends relative to biologically relevant thresholds can assist in determining monitoring and management priorities and goals. Keywords: chlorophyll; coastal bay; coastal lagoon; eutrophication; Maryland, USA; mid-Atlantic Permanent link  | Save citation:  RTF  PDF  LaTeX
2006
Glibert PM, Heil CA, O'Neil JM, Dennison WC, O'Donohue MJH (2006) Nitrogen, phosphorus, silica, and carbon in Moreton Bay, Queensland, Australia: Differential limitation of phytoplankton biomass and production. Estuaries Coasts 29(2):209–221 Abstract: Subtropical estuaries have received comparatively little attention in the study of nutrient loading and subsequent nutrient processing relative to temperate estuaries. Australian estuaries are particularly susceptible to increased nutrient loading and eutrophication, as 75% of the population resides within 200 km of the coastline. We assessed the factors potentially limiting both biomass and production in one Australian estuary, Moreton Bay, through stoichiometric comparisons of nitrogen (N), phosphorus (P), silicon (Si), and carbon (C) concentrations, particulate compositions, and rates of uptake. Samples were collected over 3 seasons in 1997-1998 at stations located throughout the bay system, including one riverine endmember site. Concentrations of all dissolved nutrients, as well as particulate nutrients and chlorophyll, declined 10-fold to 100-fold from the impacted western embayments to the eastern, more oceanic-influenced regions of the bay during all seasons. For all seasons and all regions, both the dissolved nutrients and particulate biomass yielded N : P ratios < 6 and N : Si ratios < 1. Both relationships suggest strong limitation of biomass by N throughout the bay. Limitation of rates of nutrient uptake and productivity were more complex. Low C : N and C : P uptake ratios at the riverine site suggested light limitation at all seasons, low N : P ratios suggested some degree of N limitation and high N : Si uptake ratios in austral winter suggested Si limitation of uptake during that season only. No evidence of P limitation of biomass or productivity was evident. Univ Queensland, Sch Life Sci, Brisbane, Qld 4072, Australia. Permanent link  | Save citation:  RTF  PDF  LaTeX
Orth RJ, Carruthers TJB, Dennison WC, Duarte CM, Fourqurean JW, Heck KLJ, Hughes AR, Kendrick GA, Kenworthy WJ, Olyarnik S, Short FT, Waycott M, Williams SL (2006) A Global Crisis for Seagrass Ecosystems. Bioscience 56(12):987–996 Abstract: Seagrasses, marine flowering plants, have a long evolutionary history but are now challenged with rapid environmental changes as a result of coastal human population pressures. Seagrasses provide key ecological services, including organic carbon production and export, nutrient cycling, sediment stabilization, enhanced biodiversity, and trophic transfers to adjacent habitats in tropical and temperate regions. They also serve as &#65533;coastal canaries,&#65533; global biological sentinels of increasing anthropogenic influences in coastal ecosystems, with large-scale losses reported worldwide.Multiple stressors, including sediment and nutrient runoff, physical disturbance, invasive species, disease, commercial fishing practices, aquaculture, overgrazing, algal blooms, and global warming, cause seagrass declines at scales of square meters to hundreds of square kilometers. Reported seagrass losses have led to increased awareness of the need for seagrass protection, monitoring, management, and restoration. However, seagrass science, which has rapidly grown, is disconnected from public awareness of seagrasses, which has lagged behind awareness of other coastal ecosystems. There is a critical need for a targeted global conservation effort that includes a reduction of watershed nutrient and sediment inputs to seagrass habitats and a targeted educational program informing regulators and the public of the value of seagrass meadows. Keywords: seagrass, decline, sentinels, ecological services, monitoring Permanent link  | Save citation:  RTF  PDF  LaTeX
Roelfsema CM, Phinn SR, Dennison WC, Dekker AG, Brando VE (2006) Monitoring toxic cyanobacteria Lyngbya majuscula (Gomont) in Moreton Bay, Australia by integrating satellite image data and field mapping. Harmful Algae 5(1):45–56 Abstract: Large-scale blooms of Lyngbya majuscula (Gomont) have occurred throughout Moreton Bay (south-east Queensland) and have been documented since 1997. L. majuscula is a toxic cyanobacteria which fixes nitrogen and is found attached to: seagrass, algae and coral. The toxic and smothering nature of L. majuscula has affected human and environmental health in sensitive coastal ecosystems. To reduce these impacts, monitoring is an essential component of studying the origins and development of L. majuscula blooms. An accurate and cost effective means to map the extent of a bloom and its biophysical properties is needed. This study presents an operational approach for mapping the extent of L. majuscula blooms in the clear and shallow water regions of Moreton Bay, eastern Australia, from a combination of field and remotely sensed data sets. The ability to discriminate L. majuscula from other substrate types over a range of depths was first examined using detailed field reflectance spectra, measured optical properties of Moreton Bay waters and a radiative transfer model (Hydrolight 4.1). A two-stage process was then used to map L. majuscula. The spatial extent of L. majuscula and other major substrate types was first recorded from a boat-based survey by marine park authorities using point-based GPS measurements. This sampling was timed to coincide with an overpass of the Landsat 7 ETM+ sensor. When the results of the boat-based mapping detected more than 25% L. majuscula cover in the study area, a cloud free Landsat 7 ETM+ image was acquired for that date. In the second stage of mapping, selected field survey data provided the basis for a supervised classification of the ETM+ image data to map L. majuscula. Effort and accuracy assessment of both field and image mapping methods indicated a trade-off between areal coverage and mapping accuracy. The Landsat 7 ETM+ based mapping procedure provided 100% areal coverage with 58% accuracy. In contrast, the boat-based field survey method covered only 0.5% of the study area, but with almost 100% mapping accuracy. The approach outlined in this work has been adopted as a standard operating procedure in Moreton Bay. This study illustrates how remote sensing can be combined with field monitoring, to provide marine park authorities with useful information to understand and manage blooms. (C) 2005 Elsevier B.V. All rights reserved. Univ Maryland, Ctr Environm Sci, Cambridge, MD 21613 USA. CSIRO, Div Land & Water, Canberra, ACT 2601, Australia. Keywords: Australia; cyanobacterial blooms; Landsat satellite image; Lyngbya majuscula; marine; monitoring Permanent link  | Save citation:  RTF  PDF  LaTeX
2005
Albert S, O'Neil JM, Udy JW, Ahern KS, O'Sullivan CM, Dennison WC (2005) Blooms of the cyanobacterium Lyngbya majuscula in coastal Queensland, Australia: disparate sites, common factors. Marine Pollution Bulletin 51(1-4):428–437 Abstract: During the last decade there has been a significant rise in observations of blooms of the toxic cyanobacterium, Lyngbya majuscula along the east coast of Queensland, Australia. Whether the increase in cyanobacterial abundance is a biological indicator of widespread water quality degradation or also a function of other environmental change is unknown. A bioassay approach was used to assesses the potential for runoff from various land uses to stimulate productivity of L. majuscula. In Moreton Bay, L. majuscula productivity was significantly (p < 0.05) stimulated by soil extracts, which were high in phosphorus, iron and organic carbon. Productivity of L. majuscula from the Great Barrier Reef was also significantly (p < 0.05) elevated by iron and phosphorus rich extracts, in this case seabird guano adjacent to the bloom site. Hence, it is possible that other L. majuscula blooms are a result of similar stimulating factors (iron, phosphorus and organic carbon), delivered through different mechanisms. (c) 2004 Elsevier Ltd. All rights reserved. Keywords: Lyngbya majuscula; bioassay; nutrients; land use; organic carbon; iron; organic-matter; oxidation-kinetics; nitrogen-fixation; upwelling; regime; n-2 fixation; moreton bay; iron; phosphorus; growth;; phytoplankton Permanent link  | Save citation:  RTF  PDF  LaTeX
Carruthers TJB, van Tussenbroek BI, Dennison WC (2005) Influence of submarine springs and wastewater on nutrient dynamics of Caribbean seagrass meadows. Estuarine Coastal and Shelf Science 64(2-3):191–199 Abstract: The east coast of the Yucatan Peninsula, Mexico, consists of highly permeable limestone, such that surface flow and rivers are absent in this region. Extensive underground cave systems connect sink holes (cenotes) to submarine springs (ojos de aqua), which vent into the seagrass meadows of the adjacent oligotrophic coastal lagoons. This study investigated the potential for these submarine springs to influence nutrient processes within seagrass meadows, by assessing nutrient status of Thalassia testudinum meadows in two contrasting coastal lagoons along the north eastern Yucatan peninsula. Tissue nutrient concentrations as well as delta(15) N values of T. testudinum were surveyed in the Puerto Morelos Reef Lagoon and the Nichupte Lagoon System, Cancun Hotel Zone, during an extended dry period and again following heavy rainfall. After a period of heavy rainfall, T. testudinum near submarine springs in Puerto Morelos Reef Lagoon had exceptionally high leaf tissue phosphorus concentrations of 0.38 +/- 0.06%. These submarine springs may have been a direct source of phosphorus and/or a source of iron to this very iron limited carbonate system. Thalassia testudinum nutrient concentrations suggest that nitrogen loading to the Nichupte Lagoon System is regionally high and has increased over the past decade (mean leaf N: 2.04% N in 1991 to 2.71% N in 2002). Nitrogen content in leaf tissue of T. testudinum was significantly higher within the poorly flushed Nichupte Lagoon System (2.93 +/- 0.12% N) than in the well-flushed Puerto Morelos Reef Lagoon (1.80 +/- 0.07% N). Stable isotope ratios of nitrogen suggest that this high and increasing nitrogen loading within the Nichupte Lagoon System is a result of wastewater nitrogen (delta(15) N 9.06 +/- 0.07 in northern Nichupte Lagoon System vs. 1.69 +/- 0.07 in Puerto Morelos Reef Lagoon). (c) 2005 Elsevier Ltd. All rights reserved. Keywords: nutrient sources; sewage; submarine springs; groundwater;; eutrophication; Thalassia testudinum; delta N-15; nitrogen; phosphorus;; iron; seagrass; conceptual diagrams; eelgrass zostera-marina; n-p ratios; thalassia-testudinum; florida bay;; groundwater discharge; terrigenous sediments; carbonate sediments;; light-intensity; south sulawesi; nitrogen Permanent link  | Save citation:  RTF  PDF  LaTeX
Haynes D, Carter S, Gaus C, Muller J, Dennison WC (2005) Organochlorine and heavy metal concentrations in blubber and liver tissue collected from Queensland (Australia) dugong (Dugong dugon). Mar. Pollut. Bull. 51(1-4):361–369 Keywords: bioaccumulation; dioxins; dugongs; Great Barrier Reef; heavy metals; marine mammals; organochlorines; seagrass Permanent link  | Save citation:  RTF  PDF  LaTeX
Pantus FJ, Dennison WC (2005) Quantifying and evaluating ecosystem health: A case study from Moreton Bay, Australia. Environ. Manage. 36(5):757–771 Keywords: ecosystem health index; ecosystem assessment; natural resource management; Moreton Bay; Australia Permanent link  | Save citation:  RTF  PDF  LaTeX
Watkinson AJ, O'Neil JM, Dennison WC (2005) Ecophysiology of the marine cyanobacterium, Lyngbya majuscula (Oscillatoriaceae) in Moreton Bay, Australia. Harmful Algae 4(4):697–715 Abstract: Large blooms of the marine cyanobacterium Lyngbya majuscula in Moreton Bay, Australia (27 degrees 05\\\'S, 153 degrees 08\\\'E) have been re-occurring for several years. A bloom was studied in Deception Bay (Northern Moreton Bay) in detail over the period January-March 2000. In situ data loggers and field sampling characterised various environmental parameters before and during the L. majuscula bloom. Various ecophysiological experiments were conducted on L. majuscula collected in the field and transported to the laboratory, including short-term (2h) C-14 incorporation rates and long-term (7 days) pulse amplitude modulated (PAM) fluorometry assessments of photosynthetic capacity. The effects of L. majuscula on various seagrasses in the bloom region were also assessed with repeated biomass sampling. The bloom commenced in January 2000 following usual December rainfall events, water temperatures in excess of 24 degrees C and high light conditions. This bloom expanded rapidly from 0 to a maximum extent of 8 km(2) over 55 days with an average biomass of 210 g(dw)(-1) m(-2) in late February, followed by a rapid decline in early April. Seagrass biomass, especially Syringodium isoetifolium, was found to decline in areas of dense L. majuscula accumulation. Dissolved and total nutrient concentrations did not differ significantly (P > 0.05) preceding or during the bloom. However, water samples from creeks discharging into the study region indicated elevated concentrations of total iron (2.7-80.6 ?M) and dissolved organic carbon (2.5-24.7 mg L-1), associated with low pH values (3.8-6.7). C-14 incorporation rates by L. majuscula were significantly (P < 0.05) elevated by additions of iron (5 ?M Fe), an organic chelator, ethylenediaminetetra-acetic acid (5 ?M EDTA) and phosphorus (5 ?M PO4-3). Photosynthetic capacity measured with PAM fluorometry was also stimulated by various nutrient additions, but not significantly (P > 0.05). These results suggest that the L. majuscula bloom may have been stimulated by bioavailable iron, perhaps complexed by dissolved organic carbon. The rapid bloom expansion observed may then have been sustained by additional inputs of nutrients (N and P) and iron through sediment efflux, stimulated by redox changes due to decomposing L. majuscula mats. (c) 2004 Elsevier B.V. All rights reserved. dennison@ca.umces.edu Keywords: Lyngbya majuscula; Moreton Bay; cyanobacteria; C-14 incorporation; PAM fluorometry; nutrient COASTAL; GROWTH Permanent link  | Save citation:  RTF  PDF  LaTeX
2004
Costanzo SD, O'Donohue MJ, Dennison WC (2004) Assessing the influence and distribution of shrimp pond effluent in a tidal mangrove creek in north-east Australia. Marine Pollution Bulletin 48(5-6):514–525 Abstract: Effluent from a land based shrimp farm was detected in a receiving creek as changes in physical, chemical and biological parameters. The extent and severity of these changes depended on farm operations. This assessment was conducted at three different stages of shrimp-pond maturity, including (1) when the ponds were empty, (2) full and (3) being harvested. Methods for assessing farm effluent in receiving waters included physical/chemical analyses of the water column, phytoplankton bioassays and nitrogen isotope signatures of marine flora. Comparisons were made with an adjacent creek that served as the farms intake creek and did not directly receive effluent. Physical/chemical parameters identified distinct changes in the receiving creek with respect to farm operations. Elevated water column NH4+ (18.5+/-8.0 muM) and chlorophyll a concentrations (5.5+/-1.9 mug/l) were measured when the farm was in operation, in contrast to when the farm was inactive (1.3+/-0.3 muM and 1.2+/-0.6 mug/l, respectively). At all times, physically chemical parameters at the mouth of the effluent creek, were equivalent to control values, indicating effluent was contained within the effluent-receiving creek. However, elevated delta(15)N signatures of mangroves (up to similar to8parts per thousand) and macroalgae (up to similar to5parts per thousand) indicated a broader influence of shrimp farm effluent, extending to the lower regions of the farms intake creek. Bioassays at upstream sites close to the location of farm effluent discharge indicated that phytoplankton at these sites did not respond to further nutrient additions, however downstream sites showed large growth responses. This suggested that further nutrient loading from the shrimp farm, resulting in greater nutrient dispersal, will increase the extent of phytoplankton blooms downstream from the site of effluent discharge. When shrimp ponds were empty water quality in the effluent and intake creeks was comparable. This indicated that observed elevated nutrient and phytoplankton concentrations were directly attributable to farm operations. (C) 2003 Elsevier Ltd. All rights reserved. Keywords: shrimp; nutrients; nitrogen isotopes; water quality; bioassays;; Australia; environmental-impact; mekong delta; aquaculture; pollution; nutrients;; discharge; budgets; vietnam; growth; mexico Permanent link  | Save citation:  RTF  PDF  LaTeX
Heil CA, Chaston K, Jones AB, Bird P, Longstaff BJ, Costanzo SD, Dennison WC (2004) Benthic microalgae in coral reef sediments of the southern Great Barrier Reef, Australia. Coral Reefs 23(3):336–343 Abstract: The abundance and productivity of benthic microalgae in coral reef sediments are poorly known compared with other, more conspicuous (e.g. coral zooxanthellae, macroalgae) primary producers of coral reef habitats. A survey of the distribution, biomass, and productivity of benthic microalgae on a platform reef flat and in a cross-shelf transect in the southern Great Barrier Reef indicated that benthic microalgae are ubiquitous, abundant (up to 995.0 mg chlorophyll (chl) a m(-2)), and productive (up to 110 mg O-2 m(-2) h(-1)) components of the reef ecosystem. Concentrations of benthic microalgae, expressed as chlorophyll a per surface area, were approximately 100-fold greater than the integrated water column concentrations of microalgae throughout the region. Benthic microalgal biomass was greater on the shallow water platform reef than in the deeper waters of the cross-shelf transect. In both areas the benthic microalgal communities had a similar composition, dominated by pennate diatoms, dinoflagellates, and cyanobacteria. Benthic microalgal populations were potentially nutrient-limited, based on responses to nitrogen and phosphorus enrichments in short-term (7-day) microcosm experiments. Benthic microalgal productivity, measured by O-2 evolution, indicated productive communities responsive to light and nutrient availability. The benthic microalgal concentrations observed (92-995 mg chl a m(-2)) were high relative to other reports, particularly compared with temperate regions. This abundance of productive plants in both reef and shelf sediments in the southern Great Barrier Reef suggests that benthic microalgae are key components of coral reef ecosystems. Keywords: benthic microalgae; microphytobenthos; tropical; carbonate; chlorophyll; water marine habitats; ecological role; secret garden; nutrient flux;; microphytobenthos; lagoon; productivity; nitrogen; estuary; atoll Permanent link  | Save citation:  RTF  PDF  LaTeX
Joyce KE, Phinn SR, Roelfsema CM, Neil DT, Dennison WC (2004) Combining Landsat ETM plus and Reef Check classifications for mapping coral reefs: A critical assessment from the southern Great Barrier Reef, Australia. Coral Reefs 23(1):21–25 Permanent link  | Save citation:  RTF  PDF  LaTeX
Schmidt S, Dennison WC, Moss GJ, Stewart GR (2004) Nitrogen ecophysiology of Heron Island, a subtropical coral cay of the Great Barrier Reef, Australia. Functional Plant Biology 31(5):517–528 Abstract: Coral cays form part of the Australian Great Barrier Reef. Coral cays with high densities of seabirds are areas of extreme nitrogen (N) enrichment with deposition rates of up to 1000 kg N ha(-1) y(-1). The ways in which N sources are utilised by coral cay plants, N is distributed within the cay, and whether or not seabird-derived N moves from cay to surrounding marine environments were investigated. We used N metabolite analysis, N-15 labelling and N-15 natural abundance (delta(15)N) techniques. Deposited guano-derived uric acid is hydrolysed to ammonium (NH4+) and gaseous ammonia (NH3). Ammonium undergoes nitrification, and nitrate (NO3-) and NH4+ were the main forms of soluble N in the soil. Plants from seabird rookeries have a high capacity to take up and assimilate NH4+, are able to metabolise uric acid, but have low rates of NO3- uptake and assimilation. We concluded that NH4+ is the principal source of N for plants growing at seabird rookeries, and that the presence of NH4+ in soil and gaseous NH3 in the atmosphere inhibits assimilation of NO3-, although NO3- is taken up and stored. Seabird guano, Pisonia forest soil and vegetation were similarly enriched in N-15 suggesting that the isotopic enrichment of guano (delta(15)N 9.9parts per thousand) carries through the forest ecosystem. Soil and plants from woodland and beach environments had lower delta(15)N (average 6.5parts per thousand) indicating a lower contribution of bird-derived N to the N nutrition of plants at these sites. The aquifer under the cay receives seabird-derived N leached from the cay and has high concentrations of N-15-enriched NO3- (delta(15)N 7.9parts per thousand). Macroalgae from reefs with and without seabirds had similar delta(15)N values of 2.0-3.9parts per thousand suggesting that reef macroalgae do not utilise N-15-enriched seabird-derived N as a main source of N. At a site beyond the Heron Reef Crest, macroalgae had elevated delta(15)N of 5.2parts per thousand, possibly indicating that there are locations where macroalgae access isotopically enriched aquifer-derived N. Nitrogen relations of Heron Island vegetation are compared with other reef islands and a conceptual model is presented. Keywords: ammonia; ammonium; nitrate; nitrate reductase; N-15; delta N-15; uric; acid; xylem sap; nitrate reductase-activity; n-15 natural-abundance; atmospheric; ammonia; seabird rookeries; plant-communities; penguin rookery;; pisonia-grandis; isotope ratio; vegetation; deposition Permanent link  | Save citation:  RTF  PDF  LaTeX
2003
Burford MA, Costanzo SD, Dennison WC, Jackson CJ, Jones AB, McKinnon AD, Preston NP, Trott LA (2003) A synthesis of dominant ecological processes in intensive shrimp ponds and adjacent coastal environments in NE Australia. Marine Pollution Bulletin 46(11):1456–1469 Abstract: One of the key environmental concerns about shrimp farming is the discharge of waters with high levels of nutrients and suspended solids into adjacent waterways. In this paper we synthesize the results of our multidisciplinary research linking ecological processes in intensive shrimp ponds with their downstream impacts in tidal, mangrove-lined creeks. The incorporation of process measurements and bioindicators, in addition to water quality measurements, improved our understanding of the effect of shrimp farm discharges on the ecological health of the receiving water bodies. Changes in water quality parameters were an oversimplification of the ecological effects of water discharges, and use of key measures including primary production rates, phytoplankton responses to nutrients, community shifts in zooplankton and delta(15)N ratios in marine plants have the potential to provide more integrated and robust measures. Ultimately, reduction in nutrient discharges is most likely to ensure the future sustainability of the industry. (C) 2003 Elsevier Ltd. All rights reserved. Keywords: aquaculture; impacts; sustainability; bioindicators; nutrients;; ecosystem processes; water-quality; mangrove creeks; farm effluent; fresh-water;; phytoplankton biomass; north queensland; prey selection; tidal creek;; nitrogen; sediments Permanent link  | Save citation:  RTF  PDF  LaTeX
Costanzo SD, O'Donohue MJ, Dennison WC (2003) Assessing the seasonal influence of sewage and agricultural nutrient inputs in a subtropical river estuary. Estuaries 26(4A):857–865 Abstract: A combination of physical and chemical measurements and biological indicators identified nutrient impacts throughout an Australian subtropical river estuary. This was a balance of sewage inputs in the lower river and agricultural inputs in the mid-upper river, the combined influence being greater in the wet season due to greater agricultural surface runoff. Field sampling in the region was conducted at 6 sites within the river, over 5 surveys to encapsulate both wet and dry seasonal effects. Parameters assessed were tissue nitrogen (N) contents and delta(15)N signatures of mangroves and macroalgae, phytoplankton nutrient addition bioassays, and standard physical and chemical variables. Strong spatial (within river) and temporal (seasonal) variability was observed in all parameters. Poorest water quality was detected in the middle (agricultural) region of the river in the wet season, attributable to large diffuse inputs in this region. Water quality towards the river mouth remained constant irrespective of season due to strong oceanic flushing. Mangrove and macroalgal tissue delta(15)N and %N proved a successful combination for discerning sewage and agricultural inputs. Elevated delta(15)N and %N represented sewage inputs, whereas low delta(15)N and elevated %N was indicative of agricultural inputs. Phytoplankton bioassays found the system to be primarily responsive to nutrient additions in the warmer wet season, with negligible responses observed in the cooler dry season. These results indicate that the Tweed River is sensitive to the different anthropogenic activities in its catchment and that each activity has a unique influence on receiving water quality. Keywords: phytoplankton growth; north queensland; isotope; biogeochemistry;; denitrification; fractionation; groundwater; temperature; catchment;; australia Permanent link  | Save citation:  RTF  PDF  LaTeX
Saxby TA, Dennison WC, Hoegh-Guldberg O (2003) Photosynthetic responses of the coral Montipora digitata to cold temperature stress. Marine Ecology-Progress Series 248:85–97 Abstract: Coral bleaching events have become more frequent and widespread, largely due to elevated sea surface temperatures. Global climate change could lead to increased variability of sea surface temperatures, through influences on climate systems, e.g. El Nino Southern Oscillation (ENSO). Field observations in 1999, following a strong ENSO, revealed that corals bleached in winter after unusually cold weather. To explore the basis for these observations, the photosynthetic responses of the coral species Montipora digitata Studer were investigated in a series of temperature and light experiments. Small replicate coral colonies were exposed to ecologically relevant lower temperatures for varying durations and under light regimes that ranged from darkness to full sunlight. Photosynthetic efficiency was analyzed using a pulse amplitude modulated (PAM) fluorometer (F-0, F-m, F-v/F-m), and chlorophyll a (chl a) content and symbiotic dinoflagellate density were analyzed with spectrophotometry and microscopy, respectively. Cold temperature stress had a negative impact on M digitata colonies indicated by decreased photosynthetic efficiency (F-v/F-m), loss of symbiotic dinoflagellates and changes in photosynthetic pigment concentrations. Corals in higher light regimes were more susceptible to cold temperature stress, Moderate cold stress resulted in photoacclimatory responses, but severe cold stress resulted in photodamage, bleaching and increased mortality. Responses to cold temperature stress of M digitata appeared similar to that observed in corals exposed to warmer than normal temperatures, suggesting a common mechanism. The results of this study suggest that corals and coral reefs may also be impacted by exposure to cold as well as warm temperature extremes as climate change occurs. Keywords: coral bleaching; photosynthesis; climate change; photoinhibition;; F-v/F-m; cold temperature stress; symbiotic dinoflagellates; great-barrier-reef; chlorophyll fluorescence; photosystem-ii;; stylophora-pistillata; ultraviolet-radiation; bleaching event;; symbiotic algae; photochemical efficiency; elevated-temperatures;; seriatopora-hystrix Permanent link  | Save citation:  RTF  PDF  LaTeX
2002
Burford MA, Preston NP, Glibert PM, Dennison WC (2002) Tracing the fate of N-15-enriched feed in an intensive shrimp system. Aquaculture 206(3-4):199–216 Abstract: The fate of N-15-nitrogen-enriched formulated feed fed to shrimp was traced through the food web in shallow, outdoor tank systems (1000 1) stocked with shrimp. Triplicate tanks containing shrimp water with and without sediment were used to identify the role of the natural biota in the water column and sediment in processing dietary nitrogen (N). A preliminary experiment demonstrated that N-15-nitrogen-enriched feed products could be detected in the food web. Based on this, a 15-day experiment was conducted. The ammonium (NH4+) pool in the water column became rapidly enriched (within one day) with N-15-nitrogen after shrimp were fed N-15-enriched feed. By day 15, 6% of the added N-15-nitrogen was in this fraction in the 'sediment' tanks compared with 0.4% in the 'no sediment' tanks. The particulate fraction in the water column, principally autotrophic nanoflagellates, accounted for 4-5% of the N-15-nitrogen fed to shrimp after one day. This increased to 16% in the 'no sediment' treatment, and decreased to 2% in the 'sediment' treatment by day 15. It appears that dietary N was more accessible to the phytoplankton community in the absence of sediment. The difference is possibly because a proportion of the dietary N was buried in the sediment in the 'sediment' treatment, making it unavailable to the phytoplankton. Alternatively, the dietary N was retained in the NH4+ pool in the water column since phytoplankton growth, and hence, N utilization was lower in the 'sediment' treatment. The lower growth of phytoplankton in the 'sediment' treatment appeared to be related to higher turbidity, and hence, lower light availability for growth. The percentage N-15-nitrogen detected in the sediment was only 6% despite the high capacity for sedimentation of the large biomass of plankton detritus and shrimp waste. This suggests rapid remineralization of organic waste by the microbial community in the sediment resulting in diffusion of inorganic N sources into the water column. It is likely that most of the dietary N will ultimately be removed from the tank system by water discharges. Our study showed that N-15-nitrogen derived from aquaculture feed can be processed by the microbial community in outdoor aquaculture systems and provides a method for determining the effect of dietary N on ecosystems. However, a significant amount of the dietary N was not retained by the natural biota and is likely to be present in the soluble organic fraction. (C) 2002 Elsevier Science B.V. All rights reserved. Keywords: stable isotopes; nitrogen; formulated feeds; bacterial productivity; nitrogen uptake; chesapeake bay; ponds;; phytoplankton; regeneration; sediments; ammonium; ecology; nitrate Permanent link  | Save citation:  RTF  PDF  LaTeX
Carruthers TJB, Dennison WC, Longstaff BJ, Waycott M, Abal EG, McKenzie LJ, Long WJL (2002) Seagrass habitats of northeast Australia: Models of key processes and controls. Bulletin of Marine Science 71(3):1153–1169 Abstract: An extensive and diverse assemblage of seagrass habitats exists along the tropical and subtropical coastline of north east Australia and the associated Great Barrier Reef. In their natural state, these habitats are characterised by very low nutrient concentrations and are primarily nitrogen limited. Summer rainfall and tropical storms/cyclones lead to large flows of sediment-laden fresh water. Macro grazers, dugongs (Dugong dugon) and green sea turtles (Chelonia mydas) are an important feature in structuring tropical Australian seagrass communities. In general, all seagrass habitats in north east Australia are influenced by high disturbance and are both spatially and temporally variable. This paper classifies the diversity into four habitat types and proposes the main limiting factor for each habitat. The major processes that categorise each habitat are described and significant threats or gaps in understanding are identified. Four broad categories of seagrass habitat are defined as \'River estuaries\', \'Coastal\', \'Deep water\' and \'Reef\', and the dominant controlling factors are terrigenous runoff, physical disturbance, low light and low nutrients, respectively. Generic concepts of seagrass ecology and habitat function have often been found inappropriate to the diverse range of seagrass habitats in north east Australian waters. The classification and models developed here explain differences in habitats by identifying ecological functions and potential response to impacts in each habitat. This understanding will help to better focus seagrass management and research in tropical habitats. Keywords: zostera-capricorni aschers; tropical intertidal seagrasses; acoroides; lf royle; reef-marine-park; papua-new-guinea; halophila-decipiens;; hervey-bay; nitrogen-fixation; light deprivation; torres strait Permanent link  | Save citation:  RTF  PDF  LaTeX
Crossley MN, Dennison WC, Williams RR, Wearing AH (2002) The interaction of water flow and nutrients on aquatic plant growth. Hydrobiologia 489(1-3):63–70 Abstract: A long-term experiment was conducted to compare the effects of flowing and still water on growth, and the relationship between water flow and nutrients, in Aponogeton elongatus, a submerged aquatic macrophyte. A. elongatus plants were grown for 23 weeks with three levels of nutrition (0, 0.5 and 1g Osmocote Plus(R) fertiliser pot(-1)) in aquaria containing stirred or unstirred water. Fertilized plants grew much better than non-fertilized. The highest fertilizer level produced 29% wider leaves and 58% higher total dry weight in stirred water. Stirred water increased leaf area by 40% and tuber size by 81%, but only with the highest level of nutrition. These results suggest that this plant depends on its roots for mineral uptake, rather than from the open water, and the major limitation to growth in still water is the supply of dissolved inorganic carbon. It was the combined effects of nutrient availability and stirring that produced the strongest response in plant growth, morphology and composition. This study provides some explanation for the observations of others that these plants grow best in creeks or river systems with permanently flowing water. Keywords: Aponogeton; elongatus; flowing water; nutrition interaction; stream macrophytes; elodea-nuttallii; sediment; photosynthesis;; assimilation; phosphorus; velocity; layers; co2 Permanent link  | Save citation:  RTF  PDF  LaTeX
Jones AB, Preston NP, Dennison WC (2002) The efficiency and condition of oysters and macroalgae used as biological filters of shrimp pond effluent. Aquaculture Research 33(1):1–19 Abstract: Current shrimp pond management practices generally result in elevated concentrations of nutrients, suspended solids, bacteria and phytoplankton compared with the influent water. Concerns about adverse environmental impacts caused by discharging pond effluent directly into adjacent waterways have prompted the search for cost-effective methods of effluent treatment. One potential method of effluent treatment is the use of ponds or raceways stocked with plants or animals that act as natural biofilters by removing waste nutrients. In addition to improving effluent water quality prior to discharge, the use of natural biofilters provides a method for capturing otherwise wasted nutrients. This study examined the potential of the native oyster, Saccostrea commercialis (Iredale and Roughley) and macroalgae, Gracilaria edulis (Gmelin) Silva to improve effluent water quality from a commercial Penaeus japonicus (Bate) shrimp farm, A system of raceways was constructed to permit recirculation of the effluent through the oysters to maximize the filtration of bacteria, phytoplankton and total suspended solids. A series of experiments was conducted to test the ability of oysters and macroalgae to improve effluent water quality in a flow-through system compared with a recirculating system. In the flow-through system, oysters reduced the concentration of bacteria to 35% of the initial concentration, chlorophyll a to 39%, total particulates (2.28-35.2 mum) to 29%, total nitrogen to 66% and total phosphorus to 56%. Under the recirculating flow regime, the ability of the oysters to improve water quality was significantly enhanced. After four circuits, total bacterial numbers were reduced to 12%, chlorophyll a to 4%, and total suspended solids to 16%. Efforts to increase biofiltration by adding additional layers of oyster trays and macroalgae-filled mesh bags resulted in fouling of the lower layers causing the death of oysters and senescence of macroalgae. Supplementary laboratory experiments were designed to examine the effects of high effluent concentrations of suspended particulates on the growth and condition of oysters and macroalgae. The results demonstrated that high concentrations of particulates inhibited growth and reduced the condition of oysters and macroalgae. Allowing the effluent to settle before biofiltration improved growth and reduced signs of stress in the oysters and macroalgae. A settling time of 6 h reduced particulates to a level that prevented fouling of the oysters and macroalgae. Keywords: biofiltration; macroalgae; oysters; particulates; fouling; condition;; efficiency; shrimp effluent; marine fishpond effluents; ulva-lactuca biofilters; water-quality;; fluorescence measurements; photosynthetic oxygen; crassostrea-gigas;; filtration-rate; nitrogen-source; ammonium uptake; pacific oyster Permanent link  | Save citation:  RTF  PDF  LaTeX
Longstaff BJ, Kildea T, Runcie JW, Cheshire A, Dennison WC, Hurd C, Kana T, Raven JA, Larkum AWD (2002) An in situ study of photosynthetic oxygen exchange and electron transport rate in the marine macroalga Ulva lactuca (Chlorophyta). Photosynthesis Research 74(3):281–293 Abstract: Direct comparisons between photosynthetic O-2 evolution rate and electron transport rate (ETR) were made in situ over 24 h using the benthic macroalga Ulva lactuca (Chlorophyta), growing and measured at a depth of 1.8 m, where the midday irradiance rose to 400-600 mumol photons m(-2) s(-1). O-2 exchange was measured with a 5-chamber data-logging apparatus and ETR with a submersible pulse amplitude modulated (PAM) fluorometer (Diving-PAM). Steady-state quantum yield ((Fm'-Ft)/Fm') decreased from 0.7 during the morning to 0.45 at midday, followed by some recovery in the late afternoon. At low to medium irradiances (0-300 mumol photons m(-2) s(-1)), there was a significant correlation between O-2 evolution and ETR, but at higher irradiances, ETR continued to increase steadily, while O-2 evolution tended towards an asymptote. However at high irradiance levels (600-1200 mumol photons m-(2) s(-1)) ETR was significantly lowered. Two methods of measuring ETR, based on either diel ambient light levels and fluorescence yields or rapid light curves, gave similar results at low to moderate irradiance levels. Nutrient enrichment (increases in [NO3-], [NH4+] and [HPO42-] of 5- to 15-fold over ambient concentrations) resulted in an increase, within hours, in photosynthetic rates measured by both ETR and O-2 evolution techniques. At low irradiances, approximately 6.5 to 8.2 electrons passed through PS II during the evolution of one molecule of O-2, i.e., up to twice the theoretical minimum number of four. However, in nutrient-enriched treatments this ratio dropped to 5.1. The results indicate that PAM fluorescence can be used as a good indication of the photosynthetic rate only at low to medium irradiances. Keywords: benthic algae; bioenergetics; electron transport; fluorescence;; nutrient uptake; oxygen evolution; PAM; photosynthesis; primary; production; pulse amplitude modulation; modulated pam fluorometry; seasonal-variation; inorganic-carbon; algal; community; o-2 evolution; quantum yield; in-vivo; fluorescence;; photoinhibition; respiration Permanent link  | Save citation:  RTF  PDF  LaTeX
Roelfsema CM, Phinn SR, Dennison WC (2002) Spatial distribution of benthic microalgae on coral reefs determined by remote sensing. Coral Reefs 21(3):264–274 Abstract: Understanding the ecological role of benthic microalgae, a highly productive component of coral reef ecosystems, requires information on their spatial distribution. The spatial extent of benthic microalgae on Heron Reef (southern Great Barrier Reef, Australia) was mapped using data from the Landsat 5 Thematic Mapper sensor. integrated with field measurements of sediment chlorophyll concentration and reflectance. Field-measured sediment chlorophyll concentrations. 2 ranging from 23-1.153 mg chl a m(2), were classified into low, medium, and high concentration classes (1-170, 171-290, and > 291 mg chl a m(-2)) using a K-means clustering algorithm. The mapping process assumed that areas in the Thematic Mapper image exhibiting similar reflectance levels in red and blue bands would correspond to areas of similar chlorophyll a levels. Regions of homogenous reflectance values corresponding to low, medium, and high chlorophyll levels were identified over the reef sediment zone by applying a standard image classification algorithm to the Thematic Mapper image. The resulting distribution map revealed large-scale ( > 1 km 2) patterns in chlorophyll a levels throughout the sediment zone of Heron Reef. Reef-wide estimates of chlorophyll a distribution indicate that benthic Microalgae may constitute up to 20% of the total benthic chlorophyll a at Heron Reef. and thus contribute significantly to total primary productivity on the reef. Keywords: Australia; benthic microalgae; chlorophyll; classification; coral reef;; distribution; Great Barrier Reef; Heron Island; remote sensing; spatial; variation; water marine habitats; ecological role; secret garden;; microphytobenthos; communities; sediments; reflectance; resolution;; ecosystems; abundance Permanent link  | Save citation:  RTF  PDF  LaTeX
2001
Abal EG, Dennison WC, Greenfield PF (2001) Managing the Brisbane River and Moreton Bay: an integrated research/management program to reduce impacts on an Australian estuary. Water Science and Technology 43(9):57–70 Abstract: The Brisbane River and Moreton Bay Study, an interdisciplinary study of Moreton Bay and its major tributaries, was initiated to address water quality issues which link sewage and diffuse loading with environmental degradation. Runoff and deposition of fine-grained sediments into Moreton Bay, followed by resuspension, have been linked with increased turbidity and significant loss of seagrass habitat. Sewage-derived nutrient enrichment, particularly nitrogen (N), has been linked to algal blooms by sewage plume maps. Blooms of a marine cyanobacterium, Lyngbya majuscula, in Moreton Bay have resulted in significant impacts on human health (e.g., contact dermatitis) and ecological health (e.g., seagrass loss), and the availability of dissolved iron from acid sulfate soil runoff has been hypothesised. The impacts of catchment activities resulting in runoff of sediments, nutrients and dissolved iron on the health of the Moreton Bay waterways are addressed. The Study, established by 6 local councils in association with two state departments in 1994, forms a regional component of a national and state program to achieve ecologically sustainable use of the waterways by protecting and enhancing their health, while maintaining economic and social development. The Study framework illustrates a unique integrated approach to water quality management whereby scientific research, community participation and the strategy development were done in parallel with each other. This collaborative effort resulted in a water quality management strategy which focuses on the integration of socioeconomic and ecological values of the waterways. This work has led to significant cost savings in infrastructure by providing a clear focus on initiatives towards achieving healthy waterways. The Study\'s Stage 2 initiatives form the basis for this paper. Keywords: Brisbane River; Moreton Bay; estuary management; integrated management;; healthy waterways; water quality model; catchment impacts; stakeholder; participation Permanent link  | Save citation:  RTF  PDF  LaTeX
Boesch D, Burreson E, Dennison WC, Houde E, Kemp M, Kennedy V, Newell R, Paynter K, Orth R, Ulanowicz R (2001) Factors in the decline of coastal ecosystems. Science 293(5535):1589–1590 Keywords: upper chesapeake-bay Permanent link  | Save citation:  RTF  PDF  LaTeX
Costanzo SD, O'Donohue MJ, Dennison WC, Loneragan NR, Thomas M (2001) A new approach for detecting and mapping sewage impacts. Marine Pollution Bulletin 42(2):149–156 Abstract: Increased nitrogen loading has been implicated in eutrophication occurrences worldwide. Much of this loading is attributable to the growing human population along the world's coastlines. A significant component of this nitrogen input is from sewage effluent, and delineation of the distribution and biological impact of sewage-derived nitrogen is becoming increasingly important. Here, we show a technique that identifies the source, extent and fate of biologically available sewage nitrogen in coastal marine ecosystem. This method is based on the uptake of sewage nitrogen by marine plants and subsequent analysis of the sewage signature (elevated delta N-15) in plant tissues. Spatial analysis is used to create maps of delta N-15 and establish coefficient of variation estimates of the mapped values. We show elevated delta N-15 levels in marine plants near sewage outfalls in Moreton Bay, Australia, a semi-enclosed bay receiving multiple sewage inputs. These maps of sewage nitrogen distribution are being used to direct nutrient reduction strategies in the region and will assist in monitoring the effectiveness of environmental protection measures. (C) 2001 Elsevier Science Ltd. All rights reserved. Keywords: bioindicator; environmental impact; isotopes; nutrients; pollution; monitoring; sewage; nitrogen isotopes; nutrient inputs; eutrophication; macroalgae Permanent link  | Save citation:  RTF  PDF  LaTeX
Hewson I, O'Neil JM, Dennison WC (2001) Virus-like particles associated with Lyngbya majuscula (Cyanophyta; Oscillatoriacea) bloom decline in Moreton Bay, Australia. Aquatic Microbial Ecology 25(3):207–213 Abstract: Expansive blooms of the toxic cyanobacterium Lyngbya majuscula were observed in 2 shallow water regions of Moreton Bay, Australia. The rapid bloom decline (8 to <1 km(2) in <7 d) prompted an investigation of the role of cyanophage viruses in the ecophysiology of L. majuscula. Virus-like particles produced by decaying L. majuscula were observed using electron microscopy. The virus-like particles were similar in morphology to viruses in the genus Cyanostyloviridae. The effect of viruses on L. majuscula photosynthesis was investigated by: (1) creating a virus concentrate using tangential-flow ultrafiltration of seawater surrounding L. majuscula; (2) inoculating L. majuscula with the concentrate; and (3) measuring photosynthetic response using a pulse-amplitude modulated fluorometer. Virus concentrate addition resulted in decreased initial fluorescence, decreased photochemical efficiency and decreased electron transport rate in rapid light curves after 5 d. Viruses present within L. majuscula filaments may play an important role in the bloom dynamics of this ecologically important cyanobacterium. Keywords: Lyngbya majuscula; cyanophage; virus; lysogeny; marine viruses; phytoplankton; photosynthesis; abundance; seawater Permanent link  | Save citation:  RTF  PDF  LaTeX
Hewson I, O'Neil JM, Fuhrman JA, Dennison WC (2001) Virus-like particle distribution and abundance in sediments and overlying waters along eutrophication gradients in two subtropical estuaries. Limnology and Oceanography 46(7):1734–1746 Abstract: Viruses are recognized as ubiquitous components of marine ecosystems however, there has been limited study of viral abundance and its ecological role in sediments. Viral abundance was determined in both the water column and sediments of a eutrophic (Brisbane River/Moreton Bay; 27 degrees 25\\\'S, 153 degrees5\\\'E) and oligotrophic (Noosa River, 26 degrees 15\\\'S, 153 degrees0\\\'E) estuary in subtropical Queensland, Australia. Viruses, bacteria, and microalgae from both water column and extracted sediment samples were enumerated using SYBR Green I staining and epifluorescence microscopy. Sediment viral abundance ranged from 10(7) to 10(9) particles cm(-1) of sediment. bacterial abundance ranged from 10(7) to 10(8) cells cm(-1) of sediment, and microalgal abundance ranged from 10(4) to 10(5) cells cm(-1) sediment. Pelagic abundances for all microorganisms were 10-1,000-fold lower than sediment abundances. Correlations between viral abundances and suspended solids suggest that viruses sorbed to suspended material in the water column may settle out and contribute to the benthic viral population. Virus production was measured by a time course increase of viral abundance in seawater using a dilution technique. Virus production was highest in eutrophic waters of the Brisbane River, and addition of inorganic nutrients (NO3- + NH + PO43- + SiO3) stimulated viral production rates at all stations by 14-52% above ambient, suggesting that inorganic nutrient availability may play a key role in aquatic viral abundance. Keywords: marine viruses; aquatic environments; viral abundance; size fraction;; bacteria; seawater; phytoplankton; mortality; decay; bacterioplankton Permanent link  | Save citation:  RTF  PDF  LaTeX
Hewson I, O'Neil JM, Heil CA, Bratbak G, Dennison WC (2001) Effects of concentrated viral communities on photosynthesis and community composition of co-occurring benthic microalgae and phytoplankton. Aquatic Microbial Ecology 25(1):1–10 Abstract: Marine viruses have been shown to affect phytoplankton productivity; however, there are no reports on the effect of viruses on benthic microalgae (microphytobenthos). Hence, this study investigated the effects of elevated concentrations of virus-like particles on the photosynthetic physiology and community composition of benthic microalgae and phytoplankton. Virus populations were collected near the sediment surface and concentrated by tangential flow ultrafiltration, and the concentrate was added to benthic and water column samples that were obtained along a eutrophication gradient in the Brisbane River/Moreton Bay estuary, Australia. Photosynthetic and community responses of benthic microalgae, phytoplankton and bacteria were monitored over 7 d in aquaria and in situ. Benthic microalgal communities responded to viral enrichment in both eutrophic and oligotrophic sediments. In eutrophic sediments, Euglenophytes (Euglena sp.) and bacteria decreased in abundance by 20 to 60 and 26 to 66%, respectively, from seawater controls. In oligotrophic sediments, bacteria decreased in abundance by 30 to 42% from seawater controls but the dinoflagellate Gymnodinium sp. increased in abundance by 270 to 3600% from seawater controls, The increased abundance of Gymnodinium sp. may be related to increased availability of dissolved organic matter released from lysed bacteria. Increased (140 to 190% from seawater controls) initial chlorophyll a fluorescence measured with a pulse-amplitude modulated fluorometer was observed in eutrophic benthic microalgal incubations following virus enrichment, consistent with photosystem II damage. Virus enrichment in oligotrophic water significantly stimulated carbon fixation rates, perhaps due to increased nutrient availability by bacterial lysis. The interpretation of data from virus amendment experiments is difficult due to potential interaction with unidentified bioactive compounds within seawater concentrates. However, these results show that viruses are capable of influencing microbial dynamics in sediments. Keywords: benthic microalgae; Moreton Bay; virus-like particles; PAM fluorometry; marine-bacteria; size fraction; dna-damage; viruses; sediments;; seawater; mortality; abundance; growth; microphytobenthos Permanent link  | Save citation:  RTF  PDF  LaTeX
Jones AB, Dennison WC, Preston NP (2001) Integrated treatment of shrimp effluent by sedimentation, oyster filtration and macroalgal absorption: a laboratory scale study. Aquaculture 193(1-2):155–178 Abstract: Effluent water from shrimp ponds typically contains elevated concentrations of dissolved nutrients and suspended particulates compared to influent water. Attempts to improve effluent water quality using filter feeding bivalves and macroalgae to reduce nutrients have previously been hampered by the high concentration of clay particles typically found in untreated pond effluent. These particles inhibit feeding in bivalves and reduce photosynthesis in macroalgae by increasing effluent turbidity. In a small-scale laboratory study, the effectiveness of a three-stage effluent treatment system was investigated. In the first stage, reduction in particle concentration occurred through natural sedimentation. In the second stage, filtration by the Sydney rock oyster, Saccostrea commercialis (Iredale and Roughley), further reduced the concentration of suspended particulates, including inorganic particles, phytoplankton, bacteria, and their associated nutrients. In the final stage, the macroalga, Gracilaria edulis (Gmelin) Silva, absorbed dissolved nutrients. Pond effluent was collected from a commercial shrimp farm, taken to an indoor culture facility and was left to settle for 24 h. Subsamples of water were then transferred into laboratory tanks stocked with oysters and maintained for 24 h, and then transferred to tanks containing macroalgae for another 24 h. Total suspended solid (TSS), chlorophyll a, total nitrogen (N), total phosphorus (P), NH4+, NO3-, and PO43-, and bacterial numbers were compared before and after each treatment at: 0 h (initial); 24 h (after sedimentation); 48 h (after oyster filtration); 72 h (after macroalgal absorption). The combined effect of the sequential treatments resulted in significant reductions in the concentrations of all parameters measured. High rates of nutrient regeneration were observed in the control tanks, which did not contain oysters or macroalgae. Conversely, significant reductions in nutrients and suspended particulates after sedimentation and biological treatment were observed. Overall, improvements in water quality (final percentage of the initial concentration) were as follows: TSS (12%); total N (28%); total P (14%); NH4+ (76%); NO3- (30%); PO43-(35%); bacteria (30%); and chlorophyll a (0.7%). Despite the probability of considerable differences in sedimentation, filtration and nutrient uptake rates when scaled to farm size, these results demonstrate that integrated treatment has the potential to significantly improve water quality of shrimp farm effluent. (C) 2001 Elsevier Science B.V. All rights reserved. Keywords: biofiltration; macroalgae; oysters; polyculture; sedimentation; shrimp; effluent; clam mercenaria-mercenaria; gracilaria-tikvahiae;; crassostrea-virginica; cladophora-vagabunda; nitrogen-source; ammonium; uptake; mytilus-edulis; nitrate uptake; carbon; biodeposition Permanent link  | Save citation:  RTF  PDF  LaTeX
Jones AB, O'Donohue MJ, Udy J, Dennison WC (2001) Assessing ecological impacts of shrimp and sewage effluent: Biological indicators with standard water quality analyses. Estuarine Coastal and Shelf Science 52(1):91–109 Abstract: Despite evidence linking shrimp farming to several cases of environmental degradation, there remains a lack of ecologically meaningful information about the impacts of effluent on receiving waters. The aim of this study was to determine the biological impact of shrimp farm effluent, and to compare and distinguish its impacts from treated sewage effluent. Analyses included standard water quality/sediment parameters, as well as biological indicators including tissue nitrogen (N) content, stable isotope ratio of nitrogen (delta N-15) and amino acid composition of inhabitant seagrasses, mangroves and macroalgae. The study area consisted of two tidal creeks, one receiving effluent from a sewage treatment plant and the other from an intensive shrimp farm. The creeks discharged into the western side of Moreton Bay, a sub-tropical coastal embayment on the east coast of Australia. Characterization of water quality revealed significant differences between the creeks, and with unimpacted eastern Moreton Bay. The sewage creek had higher concentrations of dissolved nutrients (predominantly NO3-/NO2- and PO43-, compared to NH4+ in the shrimp creek). In contrast, the shrimp creek was more turbid and had higher phytoplankton productivity. Beyond 750 m from the creek mouths, water quality parameters were indistinguishable from eastern Moreton Bay values. Biological indicators detected significant impacts up to 4 km beyond the creek mouths (reference site). Elevated plant delta N-15 values ranged from 10.4-19.6 parts per thousand at the site of sewage discharge to 2.9-4.5 parts per thousand at the reference site. The free amino acid concentration and composition of seagrass and macroalgae was used to distinguish between the uptake of sewage and shrimp derived N. Proline (seagrass) and serine (macroalgae) were high in sewage impacted plants and glutamine (seagrass) and alanine (macroalgae) were high in plants impacted by shrimp effluent. The delta N-15 isotopic signatures and free amino acid composition of inhabitant flora indicated that sewage N extended further from the creek mouths than shrimp N. The combination of physical/chemical and biological indicators used in this study was effective in distinguishing the composition and subsequent impacts of aquaculture and sewage effluent on the receiving waters. (C) 2001 Academic Press. Keywords: aquaculture; shrimp effluent; sewage effluent; biological indicators;; stable isotopes; delta N-15; amino acid composition; Moreton Bay; Australia; gracilaria-pacifica rhodophyta; amino-acid levels; zostera-marina l;; physiological-responses; nutrient availability; cyanidium-caldarium;; estuarine gradient; edulis rhodophyta; light-intensity; nitrogen uptake Permanent link  | Save citation:  RTF  PDF  LaTeX
Koop K, Booth D, Broadbent A, Brodie J, Bucher D, Capone D, Coll J, Dennison WC, Erdmann M, Harrison P, Hoegh-Guldberg O, Hutchings P, Jones GB, Larkum AWD, O'Neil JM, Steven A, Tentori E, Ward S, Williamson J, Yellowlees D (2001) ENCORE: The effect of nutrient enrichment on coral reefs. Synthesis of results and conclusions. Marine Pollution Bulletin 42(2):91–120 Abstract: Coral reef degradation resulting from nutrient enrichment of coastal waters is of increasing global concern. Although effects of nutrients on coral reef organisms have been demonstrated in the laboratory, there is little direct evidence of nutrient effects on coral reef biota in situ. The ENCORE experiment investigated responses of coral reef organisms and processes to controlled additions of dissolved inorganic nitrogen (N) and/or phosphorus (P) on an offshore reef(One Tree Island) at the southern end of the Great Barrier Reef, Australia. A multi-disciplinary team assessed a variety of factors focusing on nutrient dynamics and biotic responses. A controlled and replicated experiment was conducted over two years using twelve small patch reefs ponded at low tide by a coral rim. Treatments included three control reefs (no nutrient addition) and three + N reefs (NH4Cl added), three + P reefs (KH2PO4 added), and three + N + P reefs. Nutrients were added as pulses at each low tide (ca twice per day) by remotely operated units. There were two phases of nutrient additions. During the initial, low-loading phase of the experiment nutrient pulses (mean dose = 11.5 muM NH4+; 2.3 muM PO4-3) rapidly declined, reaching near-background levels (mean = 0.9 muM NH4+; 0.5 muM PO4-3) within 2-3 h. A variety of biotic processes, assessed over a year during this initial nutrient loading phase, were not significantly affected, with the exception of coral reproduction, which was affected in all nutrient treatments. In Acropora longicyathus and A. aspera, fewer successfully developed embryos were formed, and in A. longicyathus fertilization rates and lipid levels decreased. In the second, high-loading, phase of ENCORE an increased nutrient dosage (mean dose = 36.2 muM NH4+; 5.1 muM PO4-3 declining to means of 11.3 muM NH4+ and 2.4 muM PO4-3 at the end of low tide) was used for a further year, and a variety of significant biotic responses occurred. Encrusting algae incorporated virtually none of the added nutrients. Organisms containing endosymbiotic zooxanthellae (corals and giant clams) assimilated dissolved nutrients rapidly and were responsive to added nutrients. Coral mortality, not detected during the initial low-loading phase, became evident with increased nutrient dosage, particularly in Pocillopora damicornis. Nitrogen additions stunted coral growth, and phosphorus additions had a variable effect. Coral calcification rate and linear extension increased in the presence of added phosphorus but skeletal density was reduced, making corals more susceptible to breakage. Settlement of all coral larvae was reduced in nitrogen treatments, yet settlement of larvae from brooded species was enhanced in phosphorus treatments. Recruitment of stomatopods, benthic crustaceans living in coral rubble, was reduced in nitrogen and nitrogen plus phosphorus treatments. Grazing rates and reproductive effort of various fish species were not affected by the nutrient treatments. Microbial nitrogen transformations in sediments,were responsive to nutrient loading with nitrogen fixation significantly increased in phosphorus treatments and denitrification increased in all treatments to which nitrogen had been added. Rates of bioerosion and grazing showed no significant effects of added nutrients, ENCORE has shown that reef organisms and processes investigated ill situ were impacted by elevated nutrients. Impacts mere dependent on dose level, whether nitrogen and/or phosphorus mere elevated and were often species-specific. The impacts were generally sub-lethal and subtle and the treated reefs at the end of the experiment mere visually similar to control reefs. Rapid nutrient uptake indicates that nutrient concentrations alone are not adequate to assess nutrient condition of reefs. Sensitive and quantifiable biological indicators need to be developed for coral reef ecosystems. The potential bioindicators identified in ENCORE should be tested in future research on coral reef/nutrient interactions. Synergistic and cumulative effects of elevated nutrients and other environmental parameters, comparative studies of intact vs. disturbed reefs, offshore vs, inshore reefs, or the ability of a nutrient-stressed reef to respond to natural disturbances require elucidation. An expanded understanding of coral reef responses to anthropogenic impacts is necessary, particularly regarding the subtle, sub-lethal effects detected in the ENCORE studies. (C) 2001 Published by Elsevier Science Ltd. Keywords: great-barrier-reef; clam-zooxanthellae symbiosis; acroporid corals;; building corals; pocillopora-damicornis; stylophora-pistillata;; montastrea-annularis; elevated nitrogen; ammonium uptake; growth-rates Permanent link  | Save citation:  RTF  PDF  LaTeX
2000
Arnold RR, Cornwell JC, Dennison WC, Stevenson JC (2000) Sediment-based reconstruction of submersed aquatic vegetation distribution in the Severn River, a sub-estuary of Chesapeake Bay. Journal of Coastal Research 16(1):188–195 Abstract: A paleo-ecological reconstruction of long-term changes in the distribution of submersed aquatic Vegetation (SAV) in a Chesapeake sub-estuary was made using dated sediment cores on transects going from shallow (< 0.5 m) to deep (> 2 m) waters. Maynedier and Saltworks Creeks, branches of the Severn River, have had substantial losses of SAV, similar to many parts of the upper Chesapeake Bay. Dating via Pb-210 established that sediment accretion rates were 0.5-0.7 cm yr(-1) in these two systems, double the rate of sea level rise in this region. Seeds of only two SAV species were found in the sediments despite evidence others were present at one time or another in other tributaries of the Severn Estuary. Of the two species found, Zannichellia palustris seeds were much more abundant than Ruppia maritima seeds, reflecting the high dispersibility of the former species. The vertical pattern of seed distribution in these cores indicates that over the past 100 years, SAV (particularly Z. palustris) has been increasingly confined to shallower water depths. Although there is less riverine pulsing in the two study creeks, than at the head of the Bay (where previous seed records are available), both data sets are consistent with the hypothesis that decreasing light availability due to eutrophication and sediment erosion has been a problem for SAV in Chesapeake Bay, particularly over the last several decades. Furthermore this study suggests that historically low species diversity may be attributable to more chronic and longer term stress in the shallows of the Severn River than present in SAV beds at the head of the Bay. Keywords: eutrophication; Pb-210; geochronology; SAV; seeds; sedimentation rate;; seagrass; shore; water-quality; accumulation; communities; decline; growth; sea;; photosynthesis; populations; pb-210; plants Permanent link  | Save citation:  RTF  PDF  LaTeX
Costanzo SD, O'Donohue MJ, Dennison WC (2000) Gracilaria edulis (Rhodophyta) as a biological indicator of pulsed nutrients in oligotrophic waters. Journal of Phycology 36(4):680–685 Abstract: The response of the marine macroalga Gracilaria edulis (Gmelin) Silva to nutrient pulses of varying magnitude was investigated to test its applicability as a marine bioindicator at two oligotrophic locations. After exposure to nutrient pulses, algal amino acid, tissue nitrogen, and chlorophyll a content were assessed relative to algae incubated under control conditions (no nutrient enrichment), The smallest nutrient pulse involved a nutrient enrichment experiment conducted within a coral atoll, whereas two larger pulses resulted from sewage discharge to a tropical coastal bay. After exposure to the smallest nutrient pulse (10 x ambient), only changes in macroalgal amino acid concentration and composition were detected (mainly as increases in citrulline), At 100 x ambient concentrations, increases in tissue % nitrogen of the macroalgae were detected, in addition to responses in amino acids, Macroalgae exposed to the highest nutrient pulse (1000 x ambient) responded with increased chlorophyll a, tissue nitrogen, and amino acids within the three day incubation period, In contrast to these algal responses, analytical water sampling techniques failed to detect elevated nutrients when nutrient pulses were not occurring, The responses of this algal bioindicator to variable nutrient pulses may provide a useful tool for investigating the source and geographical extent of nutrients entering oligotrophic coastal waters. Keywords: Australia; bioindicators; macroalgae; nitrogen; nutrients; sewage;; water quality; 2 red algae; nitrogen-source; nitrate uptake; florida keys;; availability; growth; bioindicators; gigartinales; macroalgae; ammonium Permanent link  | Save citation:  RTF  PDF  LaTeX
Hansen JW, Udy JW, Perry CJ, Dennison WC, Lomstein BA (2000) Effect of the seagrass Zostera capricorni on sediment microbial processes. Marine Ecology-Progress Series 199:83–96 Abstract: The effect of the seagrass Zostera capricorni on sediment microbial processes was studied in a tank experiment, where vegetated and unvegetated control sediments were incubated in 10 and 50% of incident light. Leaf and root-rhizome biomass, shoot density, and leaf productivity were significantly higher when plants were incubated in 50 % than in 10 % of incident Light. Nitrogen fixation, sulphate reduction, and urea turnover in the Z. capricorni vegetated sediment were higher in the 50% than in the 10% light treatment and higher in the vegetated than in the unvegetated sediment. The stimulation of microbial processes in the Z, capricorni vegetated sediment took place in the rhizosphere, where nitrogen fixation and sulphate reduction in particular were stimulated. The sediment studies were supplemented by measurements of nitrogen fixation, sulphate reduction, and urea turnover by microorganisms associated with the roots and rhizomes of Z. capricorni. The rates of nitrogen fixation and sulphate reduction associated with root-rhizomes were up to 40- and 7-fold higher, respectively, than the highest respective sediment rates, whereas the root-rhizome associated urea turnover was lower than sediment rates. Nitrogen fixation and sulphate reduction associated with root-rhizomes could account for up to 39 and 4%, respectively, of the depth-integrated sediment rates. Nitrogen fixed by microorganisms associated with root-rhizomes could supply up to 65 % of the nitrogen needed for plant growth. Further, it was estimated that 8 to 18% of the carbon fixed by Z. capricorni was released to the sediment by the roots and rhizomes. Urea turnover was suggested to be an important intermediate in the gross production of ammonium, and a low net production of ammonium indicated rapid internal nitrogen cycling within the sediment. Keywords: Zostera capricorni; sediment; roots; rhizomes; microbial processes;; light; bacterial sulfate reduction; halodule-wrightii aschers; dissolved; organic-carbon; nitrogen-fixation; moreton bay; marina l; depth; distribution; thalassia-testudinum; aquatic macrophytes; coastal lagoon Permanent link  | Save citation:  RTF  PDF  LaTeX
Haynes D, Ralph P, Prange J, Dennison WC (2000) The impact of the herbicide diuron on photosynthesis in three species of tropical seagrass. Mar. Pollut. Bull. 41(7-12):288–293 Keywords: diuron; fluorometry; pollution effects; seagrass; toxicity; water quality Permanent link  | Save citation:  RTF  PDF  LaTeX
O'Donohue MJ, Glibert PM, Dennison WC (2000) Utilization of nitrogen and carbon by phytoplankton in Moreton Bay, Australia. Marine and Freshwater Research 51(7):703–712 Abstract: Water samples were collected within river mouths, at river plume sites and at well flushed ocean-influenced sites within Moreton Bay, a shallow subtropical embayment in south-eastern Queensland. Rates of inorganic nitrogen (NH4+ and NO3-) and carbon uptake were determined across temporal and spatial scales by use of N-15 and C-14 incorporation. Phytoplankton productivity, measured as CO2 uptake, was highest at the river mouths. Rates of NH4+ uptake exceeded rates of NO3- uptake at all sites at all times. Relative preference indices demonstrated a consistent preference by phytoplankton for NH4+ uptake, and NH4+ uptake rates were higher at ocean-influenced sites than at river-mouth sites. Inorganic nutrient and chlorophyll a concentrations were highest at river mouths; however, the greatest NH4+ uptake occurred at the ocean-influenced sites, reflecting a greater dependence on 'recycled' N than on 'new' N. Biomass-independent NH4+ uptake increased with increasing water temperature; however, NO3- uptake increased with decreasing water temperature, reflecting the lower temperature optimum for nitrate reductase. The range of NH4+ and NO3- uptake rates was greater than ranges reported for other coastal waters, reflecting the strong temporal and spatial gradients within Moreton Bay. This trend of strong gradients in C and N dynamics from oligotrophic to river-influenced waters with seasonal flows is likely to exist in many tropical and subtropical coastal waters of Australia. Keywords: chesapeake bay; organic nitrogen; seasonal-variations; ammonium;; variability; nitrate; waters; plume; eutrophication; requirements Permanent link  | Save citation:  RTF  PDF  LaTeX
Prange JA, Dennison WC (2000) Physiological responses of five seagrass species to trace metals. Marine Pollution Bulletin 41(7-12):327–336 Abstract: Trace metal run-off associated with urban and industrial development poses potential threats to seagrasses in adjacent coastal ecosystems, Seagrass from the largest urban (Moreton Bay) and industrial (Port Curtis) coastal regions in Queensland, Australia were assessed for metal concentrations of iron (Fe), aluminium (Al), zinc (Zn), chromium (Cr) and copper (Cu), Trace metal concentrations in seagrass (Zostera capricorni) leaf and root-rhizome tissue had the following overall trend: [Fe] > [Al] > [Zn] > [Cr] > [Cu]. Rainfall events and anthropogenic disturbances appeared to influence metal concentrations in seagrasses with the exception of Al, which does not appear to bioaccumulate, In laboratory experiments, five seagrass species (Halophila ovalis, H. spinulosa, Halodule uninervis, Z. capricorni, Cymodocea serrulata) were incubated with iron (1 mg Fe l(-1)) and copper (1 mg Cu l(-1)) and responses assessed by changes in PSII photochemical efficiency (Fv/Fm), free amino acid content and leaf/root-rhizome metal accumulation. Iron addition experiments only affected Halophila spp, while copper additions affected other seagrass species as well, Trace metal contamination of seagrasses could have ramifications for associated trophic assemblages through metal transfer and seagrass loss, The use of photosystem II photochemical efficiency as well as amino acid concentrations and composition proved to be useful sublethal indicators of trace metal toxicity in seagrasses. (C) 2000 Published by Elsevier Science Ltd. Keywords: Queensland; seagrass; trace metals; PSII photochemical efficiency; zostera-marina l; heavy-metals; zinc; limfjord; cadmium; denmark;; copper; toxicity; plants; bay Permanent link  | Save citation:  RTF  PDF  LaTeX
1999
Dennison WC, O'Neil JM, Duffy EJ, Oliver PE, Shaw GR (1999) Blooms of the cyanobacterium Lyngbya majuscula in coastal waters of Queensland, Australia. Bulletin de l'Institut Oceanographique Monaco no special 19:501–506 Permanent link  | Save citation:  RTF  PDF  LaTeX
Longstaff BJ, Dennison WC (1999) Seagrass survival during pulsed turbidity events: the effects of light deprivation on the seagrasses Halodule pinifolia and Halophila ovalis. Aquatic Botany 65(1-4):105–121 Abstract: Pulsed turbidity events caused by factors such as flooding rivers have the potential to seriously impact seagrass communities by depriving the plants of all available light. The effects of light deprivation was investigated on the survival, morphology and physiology of the tropical seagrasses Halodule pinifolia and Halophila ovalis growing in the South-East Gulf of Carpentaria, Australia, a region where pulsed flood events are common. Additionally, physiological:and morphological responses to light availability along natural gradients were examined. Responses to both experimental and natural light gradients were investigated for their potential use as indicators of impending seagrass loss during pulsed turbidity events. H. pinifolia was deprived of light for 80 days using in situ shade screens and the following parameters measured at three depths and under the shade screens: biomass, shoot density, canopy height, amino acid content, chlorophyll content, delta(13)C signature, %C and sugar concentration, The quantity of light was extremely variable, with mean daily irradiances between 9-12 mol photons m(-2) day(-1), and a range of 0.05-42 mol photons m(-2) day(-1) . H. pinifolia leaf amino acid content increased with increased water depth (from 8 to 18 mu mol g fresh wt.), chlorophyll a to b ratio decreased (from 2.4 to 2.1) and delta(13)C values became more negative (from -9 to -12). H. ovalis displayed little tolerance to light deprivation, with plant death occurring after 38 days in the dark. H. pinifolia showed a high degree of tolerance to light deprivation with no biomass loss before day 38 and complete die-off predicted after 100 days. Shoot density, biomass and canopy height all declined after 38 days. Physiological parameters that responded significantly to the light deprivation were the amino acids which increased (from 20 to 80 mu mol g fresh wt.), the chlorophyll 8 to b ratio which decreased (from 2.5 to 2.1) and the values which became more negative (from -9 to -10). Changes in leaf physiology (e.g. amino acid content, chlorophyll content and delta(13)C) occurred before morphological changes (e.g, biomass, shoot, density, canopy height) or die-off, and were thus considered to be potential indicators of impending seagrass die-off during light deprivation. In conclusion, only long duration (>38 days) pulsed turbidity events would have a detrimental impact on H. pinifolia growing in the Gulf of Carpentaria and that by assessing specific physiological responses, seagrass loss during pulsed turbidity events can predicted. (C) 1999 Elsevier Science B.V. All rights reserved. Keywords: pulsed turbidity; survival; seagrass; Halodule; Halophila; light; deprivation; marina l eelgrass; zostera-marina; depth distribution;; heterozostera-tasmanica; physiological-responses; thalassia-testudinum;; sediment nutrients; water-quality; moreton bay; growth Permanent link  | Save citation:  RTF  PDF  LaTeX
Longstaff BJ, Loneragan NR, O'Donohue MJ, Dennison WC (1999) Effects of light deprivation on the survival and recovery of the seagrass Halophila ovalis (RBr) Hook. Journal of Experimental Marine Biology and Ecology 234(1):1–27 Abstract: Survival and recovery of the seagrass Halophiln ovalis (R.Br.) Hook during and after light deprivation was investigated to assist in the interpretation of recent losses of Halophiln spp. in Queensland, Australia. Light deprivation experiments were conducted in outdoor aquaria and in situ at two water depths. Halophiln ovalis plants were deprived of light for a maximum of 30 days, and recovery processes were investigated for up to 18 days following 15 days of light deprivation. Measurements of H. ovalis biomass, storage carbohydrate concentrations, chlorophyll a+b concentrations, stable carbon isotopes ratios (delta(13)C) and chlorophyll a fluorescence parameters (F-0, F-m and F-v/F-m) were made during and at the end of the light deprivation and recovery periods. Biomass declined after 3-6 days in the dark and complete plant death occurred after 30 days. During the recovery period, biomass continued to decline for a short duration of time before stabilising. Sugar concentrations declined rapidly for the first 2 days of light deprivation before stabilising, then increased rapidly during the recovery period, Chlorophyll a+b concentrations were sensitive to very small differences in light availability: concentration decreased in total darkness, remained unchanged at 0.1% of surface irradiance and increased at 0.5% of surface irradiance. Photochemical efficiency of photosystem II (F-v/F-m) remained unchanged during the light deprivation and recovery periods. The lack of response in delta(13)C during light deprivation indicated the cessation of carbon fixation. Decreased sugar utilisation after 2 days of light deprivation indicated a reduction in respiration and growth. Starch concentrations did not change during light deprivation, suggesting the inhibition of starch utilisation by anaerobic conditions within the plant. Plant death after 30 days was notably faster than previously reported for other species of seagrass. The rapid die-off may be due to a shortage of available carbohydrates or due to a build-up of the phytotoxic end products of anaerobic respiration. Overall, H. ovalis has a very limited tolerance to light deprivation when compared to larger species of seagrass. Consequently, the persistence of this species in coastal marine environments may be dependent upon the occurrence and duration of transient light deprivation events. (C) 1999 Elsevier Science B.V. All rights reserved. Keywords: chlorophyll alpha fluorescence; Halophila ovalis; light; seagrass;; storage carbohydrates; marina l eelgrass; zostera-marina; chlorophyll fluorescence;; photosynthetic responses; thalassia-testudinum; posidonia-oceanica;; aquatic vegetation; growth; intensity; reduction Permanent link  | Save citation:  RTF  PDF  LaTeX
Perry CJ, Dennison WC (1999) Microbial nutrient cycling in seagrass sediments. AGSO Journal of Australian Geology and Geophysics 17:227–231 Permanent link  | Save citation:  RTF  PDF  LaTeX
Udy JW, Dennison WC, Long WJL, McKenzie LJ (1999) Responses of seagrass to nutrients in the Great Barrier Reef, Australia. Marine Ecology-Progress Series 185:257–271 Abstract: Declines in seagrass biomass and growth have been widely reported in response to anthropogenic impacts. In contrast, the distribution and biomass of seagrass in the carbonate sediment around Green Island reef, part of Australia's Great Barrier Reef (GBR), has measurably increased during the past 50 yr, possibly due to increases in the availability of nutrients from local and regional anthropogenic sources. Using historical aerial photography, increases in seagrass distribution at Green Island have been mapped. The growth, morphological and physiological responses of 2 seagrass species (Halodule uninervis and Syringodium isoetifolium) to elevated sediment nitrogen (N; 100x control) and/or phosphorus (P; 10x control) were measured to investigate whether increased nutrients could account for the observed increase in distribution. Increases in the growth rate, amino acid composition and tissue nutrient content of both species occurred in response to elevated sediment N, but not P. Concentrations of the N-rich amino acids asparagine and glutamine increased 3- to 100-fold in seagrass leaves from N treatments. The delta(15)N values of leaves decreased in response to additions of nitrogen, probably due to increased discrimination against the N-15 isotope, because N availability was surplus to demand. The low delta(15)N value of seagrasses in the Green Island back reef suggests that their primary source of N is either from N-2 fixation or fertilisers and that the N from sewage is not a large component of their N budget. This study is the first to demonstrate N, rather than P, as the primary limiting nutrient for growth of seagrass in carbonate sediments and supports the hypothesis that the increase in the seagrass distribution and biomass at Green Island was caused by an increase in nutrient availability. We also hypothesise that seagrass distribution and biomass in many regions of the GBR may be limited by nutrients and that the lack of substantial seagrass meadows in the southern GBR could be due to these reefs receiving less nutrients from the mainland. Keywords: seagrass; Great Barrier Reef; nutrients; zostera-marina l; syringodium-filiforme; coral reefs;; physiological-responses; phosphorus limitation; thalassia-testudinum;; carbonate sediments; western-australia; sulfate-reduction;; nitrogen-fixation Permanent link  | Save citation:  RTF  PDF  LaTeX
1998
Ralph PJ, Gademann R, Dennison WC (1998) In situ seagrass photosynthesis measured using a submersible, pulse-amplitude modulated fluorometer. Marine Biology 132(3):367–373 Abstract: Assessments of photosynthetic activity in marine plants can now be made in situ using a newly developed, submersible, pulse-amplitude modulated (PAM) fluorometer: Diving-PAM. PAM fluorometry provides a measure of chlorophyll a fluorescence using rapid-light curves in which the electron-transport rate can be determined for plants exposed to ambient light conditions. This technique was used to compare the photosynthetic responses of seagrasses near Rottnest Island, Western Australia. Several fluorescence parameters were measured as a function of time of day and water depth; electron-transport rate (ETR), quantum yield, photochemical quenching and non-photochemical quenching and Photosystem II (PSII) photochemical efficiency (F-v:F-m ratio) were measured. Results indicate that recent light-history plays a crucial role in seagrass photosynthetic responses. Maximum ETR of Posidonia australis, Amphibolis antarctica and Halophila ovalis is influenced by the irradiance during the diurnal cycle, with low rates at dawn and dusk (<10 mu mol electron m(-2) s(-1)), highest rates in late morning (40 to 60 mu mol electron m(-2) s(-1)) and a mid-day depression. Maximum ETR and PSII photochemical efficiency varied widely between seagrass species and were not correlated. A comparison of photochemical to non-photochemical quenching indicated that seagrasses in shallow water receiving high light have a high capacity for non-photochemical quenching (e.g. light protection) compared to seagrasses in deep water. These results indicate that in situ measurements of photosynthesis will provide new insights into the mechanisms and adaptive responses of marine plants. Keywords: chlorophyll fluorescence; photoinhibition; temperature; responses;; yield; light Permanent link  | Save citation:  RTF  PDF  LaTeX
1997
Odonohue MJH, Dennison WC (1997) Phytoplankton productivity response to nutrient concentrations, light availability and temperature along an Australian estuarine gradient. Estuaries 20(3):521–533 Abstract: Phytoplankton productivity and the factors that influence it were studied in the Logan River and southern Moreton Bay, a large embayment on the east coast of Australia. Phytoplankton productivity, dissolved and total nutrient concentrations, and turbidity were determined throughout high and low rainfall periods to characterize light and nutrient influences on productivity. Turbidity and nutrient concentrations were highest at upriver sites, but productivity was highest at the river mouth and within the river plume. Phytoplankton productivity peaked after rainfall events (>150 mg C m(-3) h(-1)), commensurate with a decrease in dissolved nitrogen concentrations. Productivity responses to increased nutrient concentrations and light availability were determined in laboratory incubations. During summer, productivities at the bay sites were stimulated by nitrogen (N) enrichment, while productivities at upriver sites were stimulated by phosphorus (P) addition. Light stimulation of productivities was more pronounced at upriver sites than bay sites. The relative magnitude of nutrient and light stimulation of productivities indicate a predominance of light limitation upriver, significant N limitation within the Logan River plume, and little effect of light, N, or P at sites beyond the Logan River plume. Productivity decreased with seasonal decreases in temperature. Lower water temperatures in winter probably helped determine maximum rates of phytoplankton productivity. The combination of light and N limitation of productivity during summer, and temperature limitation during winter, account for low areal productivities (<0.6 g C m(-2) d(-1)), compared with other rivers and estuaries worldwide. Keywords: neuse river estuary; north-carolina; marine-environment; chesapeake; bay; limitation; dynamics; phosphorus; gracilaria; rhodophyta; delaware Permanent link  | Save citation:  RTF  PDF  LaTeX
Udy JW, Dennison WC (1997) Growth and physiological responses of three seagrass species to elevated sediment nutrients in Moreton Bay, Australia. Journal of Experimental Marine Biology and Ecology 217(2):253–277 Abstract: Seagrasses, marine angiosperms with high rates of primary productivity, are often limited by the supply of nutrients, particularly nitrogen (N) and phosphorus (P). We investigated growth and physiological responses of three seagrass species (Halodule uninervis (Forsk.), Zostera capricorni Aschers and Cymodocea serrulata (r.Br.) Aschers) to elevated sediment N (100X control) and/or P (10x control) in adjacent monospecific beds over a 3 month period from spring to early summer. Each species exhibited different growth and biomass responses to both N and P additions. Halodule uninervis growth and biomass increased in response to N and N + P additions, indicative of exclusive N limitation of growth. In contrast, growth and biomass of Z. capricorni increased in response to N + P additions only, indicative of balanced N and P limitation. Cymodocea serrulata growth and biomass were not affected by any of the nutrient additions. Physiological characteristics (amino acid composition, tissue nutrient content, delta N-15) of all three seagrass species responded to N additions (+ N and N + P). Total amino acid content of seagrass leaves increased by 2 to 4 fold in N additions compared with controls. Concentrations of the N-rich amino acids, glutamine and asparagine, increased by 10-1000 fold in N additions, suggesting that these amino acids may be a metabolic storage for N. Tissue N content of leaves, roots and rhizomes increased and delta N-15 of the leaves decreased in response to N additions. Although seagrass growth and biomass responses to nutrient additions were species specific, metabolic responses were similar for all species. This suggests physiological characteristics of seagrasses are useful for identifying saturating nutrient supply to an environment, but should not be used to determine whether nutrient availability is limiting the seagrass growth rate. (C) 1997 Elsevier Science B.V. Keywords: seagrass; nutrient; nitrogen; phosphorus; amino acid; zostera-marina l; halodule-wrightii aschers; phosphorus limitation;; syringodium-filiforme; thalassia-testudinum; cymodocea-nodosa;; light-intensity; chesapeake bay; florida bay; l eelgrass Permanent link  | Save citation:  RTF  PDF  LaTeX
Udy JW, Dennison WC (1997) Physiological responses of seagrasses used to identify anthropogenic nutrient inputs. Marine and Freshwater Research 48(7):605–614 Abstract: Fertilization experiments have established that seagrass growth in Moreton Bay can be limited by the supply of both N and P. In the present study, morphological and physiological characteristics (canopy height, shoot density, biomass, growth, tissue nutrient content, amino acid concentrations and delta(15)N ratios) of Zostera capricorni Aschers. in Moreton Bay, close to and distant from nutrient sources, were compared. Z. capricorni at the four sites close to nutrient sources (sewage, septic or prawn-farm effluent, or river discharge), had physiological characteristics representative of high nutrient availability and at the five sites distant from nutrient sources had physiological characteristics representative of low nutrient availability. Differences in sediment nutrient concentrations (NH4+ and PO43-), seagrass morphology and growth were not related to proximity to nutrient sources. However, the nutrient content of the seagrasses and their amino acid concentrations were consistently higher at sites close to a nutrient source. The amino acids glutamine and asparagine were the most responsive to elevated nutrient availability, and delta(15)N values of seagrasses reflected the source of N rather than the nutrient load. These results demonstrate that physiological characteristics of seagrasses can be used to identify the nutrient load and source affecting marine ecosystems. Keywords: zostera-marina l; syringodium-filiforme; carbonate sediments;; phosphorus limitation; thalassia-testudinum; dissolved phosphate;; light-intensity; eelgrass; growth; nitrogen Permanent link  | Save citation:  RTF  PDF  LaTeX
1996
Abal EG, Dennison WC (1996) Seagrass depth range and water quality in southern Moreton bay, Queensland, Australia. Marine and Freshwater Research 47(6):763–771 Abstract: Correlations between water quality parameters and seagrass depth penetration were developed for use as a biological indicator of integrated light availability and long-term trends in water quality. A year-long water quality monitoring programme in Moreton Bay was coupled with a series of seagrass depth transects. A strong gradient between the western (landward) and eastern (seaward) portions of Moreton Bay was observed in both water quality and seagrass depth range. Higher concentrations of chlorophyll a, total suspended solids, dissolved and total nutrients, and light attenuation coefficients in the water column and correspondingly shallower depth limits of the seagrass Zostera capricorni were observed in the western portions of the bay. Relatively high correlation coefficient values (r(2) > 0.8) were observed between light attenuation coefficient, total suspended solids, chlorophyll a, total Kjeldahl nitrogen and Zostera capricorni depth range. Low correlation coefficient values (r(2) < 0.8) between seagrass depth range and dissolved inorganic nutrients were observed. Seagrasses had disappeared over a five-year period near the mouth of the Logan River, a turbid river with increased land use in its watershed. At a site 9 km from the river mouth, a significant decrease in seagrass depth range corresponded to higher light attenuation, chlorophyll a, total suspended solids and total nitrogen content relative to a site 21 km from the river mouth. Seagrass depth penetration thus appears to be a sensitive bio-indicator of some water quality parameters, with application for water quality management. Keywords: western-australia; zostera-marina; cockburn sound; light; decline;; eelgrass; aschers; growth; photosynthesis; communities Permanent link  | Save citation:  RTF  PDF  LaTeX
Burke MK, Dennison WC, Moore KA (1996) Non-structural carbohydrate reserves of eelgrass Zostera marina. Marine Ecology-Progress Series 137(1-3):195–201 Abstract: The high minimum Light requirement of eelgrass Zostera marina L. suggests that this species has difficulty in maintaining a positive carbon balance except under high light conditions. The carbon balance of Z. marina can be studied by following seasonal changes in non-structural carbohydrate (NSC) reserves, however, little is known about the seasonal variation in NSC reserves in seagrasses or the influence of shading on NSC reserve content and distribution. Seasonal changes in eelgrass NSC reserves were measured in a shallow coastal lagoon, Chincoteague Bay, Maryland/Virginia, USA, near the southern edge of this species' distributional range. Concentrations of sugar varied seasonally in leaves, rhizomes and roots, with maximum concentrations occurring in the rhizomes. In contrast, starch concentrations did not vary with the season, but were highest in the roots. Seasonal peaks in rhizome NSC reserves parallel the spring and fall bimodal growth patterns observed for Z., marina in the region. Total NSC reserves change from an estimated 52 to 73 g m(-2) in June to 4 to 18 g m(-2) in January, or a decrease of 75 to 92%. Experimental shading for 3 wk in the spring reduced (p < 0.001) sugar but not starch concentrations in leaves (48%), rhizomes (40%) and roots (51%). In addition, shading reduced (p < 0.05) leaf biomass (34%), root and rhizome biomass (23%) and density (27%). Potential NSC reserve storage during shading was reduced by an estimated 66%. Spring appears to be an important time for both growth and storage of NSC reserves in Z. marina, and the NSC reserves are generally depleted throughout the remainder of the year. Turbidity during this springtime 'window of opportunity' may jeopardize subsequent survival as a result of inadequate NSC reserves to maintain a positive carbon balance during the rest of the year. Keywords: eelgrass; Zostera; seagrass; starch; sugar; shading; carbon balance;; biomass; column nitrate enrichment; lower chesapeake bay; thalassia-testudinum;; depth distribution; halodule-wrightii; ruppia-maritima; seagrasses;; growth; light; photosynthesis Permanent link  | Save citation:  RTF  PDF  LaTeX
Dawson SP, Dennison WC (1996) Effects of ultraviolet and photosynthetically active radiation on five seagrass species. Marine Biology 125(4):629–638 Abstract: Five seagrass species [Halophila ovalis (R.Br) Hook. f., Halodule uninervis (Forsk.) Aschers., Zostera capricorni Aschers., Cymodocea serrulata (R.Br) Aschers. (ed.) and Syringodium isoetifolium (Aschers.) Dandy] from Moreton Bay, Australia, were grown under increased (+25%) and ambient levels of ultraviolet (UV) radiation and photosynthetically active radiation (PAR), and various morphological and physiological responses were examined. Leaf fluorescence ratio (variable:maximum fluorescence) in conjunction with xanthophyll pigment content (violaxanthin, antheraxanthin and zeaxanthin) were used as a measure of photosynthetic efficiency. In addition, absorbance in the UV spectrum, chlorophyll content and chloroplast density were used as indicators of photosynthetic capacity. The seagrass species examined had varying degrees of sensitivity to UV radiation. Halophila ovalis and Halodule uninervis were the most sensitive species, exhibiting the largest decrease in photosynthetic efficiency and chloroplast density and the smallest increase in UV-blocking pigments in response to UV radiation. The more UV-tolerant species, Z. capricorni, C. serrulata and S. isoetifolium, were only significantly affected by increased levels of UV radiation, showing a gradual decline in photosynthetic efficiency and chloroplast density and the largest increases in UV-blocking pigment. UV sensitivity corresponded with leaf morphology, with thicker leaves (as in Z. capricorni, C. serrulata and S. isoetifolium) providing greater morphological protection for UV-sensitive organelles. Not al species were significantly affected by increasing PAR, with decreases in fluorescence ratio and increases in zeaxanthin content observed only in C. serrulata and S. isoetifolium. Sensitivity to PAR corresponded with morphological plasticity; species exhibiting a wide range of growth forms (e.g. Halophila ovalis, Halodule uninervis vis and Z. capricorni) were the least sensitive to increases in PAR. Seagrass depth-distributions in Moreton Bay appear to be influenced by species sensitivity to UV radiation and PAR, with other factors such as epiphytes, shading and nutrients also affecting species\' tolerance. All species were affected to some degree by UV radiation, thus future changes in UV intensity may have repercussions on the distribution of seagrasses. Keywords: uv-b radiation; chlorophyll fluorescence; morphological responses;; electron-transport; plant-sensitivity; light-intensity; growth;; irradiance; zeaxanthin; inhibition Permanent link  | Save citation:  RTF  PDF  LaTeX
Grice AM, Loneragan NR, Dennison WC (1996) Light intensity and the interactions between physiology, morphology and stable isotope ratios in five species of seagrass. Journal of Experimental Marine Biology and Ecology 195(1):91–110 Abstract: The effects of light intensity on stable isotope ratios, physiology and morphology of five seagrass species were investigated in an outdoor, light controlled experiment. Seagrasses were maintained in flowing seawater aquaria, with each seagrass species exposed to different light regimes (5, 15, 20, 30, 50, and 100% full sunlight) using shade screens. After 30 days exposure to the various light regimes the five species of seagrass showed markedly different delta(13)C signatures, with values ranging from -17.6 to -5.5 parts per thousand. Marked responses to light intensity were also shown by each species, with leaf delta(1)3C values becoming at least 3 to 4 parts per thousand less negative in full sunlight. Other common responses to light intensity were: higher productivities, higher C:N ratios, larger lacunal areas and more root biomass under full sunlight compared with lower light intensities. Less negative delta(13)C values at high light intensities could be primarily due to (a) increased uptake of C-13 from the external C source or (b) increased internal recycling of CO2 in the lacunae due to the increased lacunal size. The increase in size of lacunae may be related to the need to supply more oxygen to the increased root biomass occurring in seagrasses under high light conditions. In contrast to delta(13)C, the delta(15)N values of seagrass leaf tissue appeared to be affected by the site of collection, rather than the species of seagrass or light intensity. Higher delta(15)N values were found at the more eutrophic site (western Moreton Bay = 8.6 to 8.8 parts per thousand) than at the site further from anthropogenic influence (eastern Moreton Bay = 2.6 to 4.5 parts per thousand). Keywords: carbon; light; nitrogen; seagrass; stable isotope ratio; zostera-marina l; izembek lagoon; organic-matter; food web; carbon;; eelgrass; nitrogen; discrimination; plants; variability Permanent link  | Save citation:  RTF  PDF  LaTeX
Jones AB, Dennison WC, Stewart GR (1996) Macroalgal responses to nitrogen source and availability: Amino acid metabolic profiling as a bioindicator using Gracilaria edulis (Rhodophyta). Journal of Phycology 32(5):757–766 Abstract: The use of macroalgae as biological indicators of dissolved nutrient source and availability ill the water column was investigated. Total tissue nitrogen (N) content, pigments, and amino acids of the red alga Gracilaria edulis (Gmelin) Silva were compared to N source and availability in laboratory and field incubations to identify responses that would serve as bioindicators of N. Field-collected algae were preincubated (6-8 wk) in low-nutrient seawater to deplete their luxury reserves of N. Incubations were then conducted for periods of 3 d in laboratory aquaria (N-spiked seawater) and in the field using macroalgal incubation chambers. After incubation in different N sources (NH4+, NO3-, and urea) in laboratory aquaria, photosynthetic pigments (phycoerythrin and chlorophyll a) and total tissue N increased, in response to increasing [NH4+] but not to [NO3-] or [urea]. Incubation in two ranges of [NH4+], one from 0 to 80 μM and the other from 0 to 800 μM, in laboratory aquaria increased the total amino acid pool. Citrulline concentrations were the most responsive to [NH4+] (r(2) = 0.84). NH4+ source treatments produced increases in citrulline, phenylalanine, serine, and free NH4+ and decreases in alanine; NO3- treatments produced increases in glutamic acid, citrulline, and alanine; and urea treatments produced increases in free NH4+ and decreases in phenylalanine and serine. The observed variations in amino acid content facilitated the development of an index for each N source based on relative concentrations of various amino acids (i.e. metabolic profiling). Gracilaria edulis was incubated along a field N gradient in the Brisbane River (three sites) and Moreton Bay (four sites), Queensland, Australia. Both phycoerythrin and tissue N appeared to respond equally to NH4+ and NO3- availability in the field. N source indices, based on amino acid concentration, were effective predictors of both [NH4+] and [NO3-] over a wide range of concentrations along the field gradient. Macroalgal physiological responses, particularly amino acid content, to changes in source and availability of N appear to be useful as sensitive bioindicators of N. Keywords: amino acids; bioindicator; Gracilaria edulis; macroalgae; metabolic; profiling; nutrients; pigments; Rhodophyta; tissue nitrogen; water; quality; 2 red algae; biochemical-composition; chondrus-crispus; outdoor; cultures; nitrate uptake; growth; tikvahiae; light; phaeophyta; ammonium Permanent link  | Save citation:  RTF  PDF  LaTeX
1995
Goodman JL, Moore KA, Dennison WC (1995) Photosynthetic Responses of Eelgrass (Zostera marina L) to Light and Sediment Sulfide in a Shallow Barrier-Island Lagoon. Aquatic Botany 50(1):37–47 Abstract: Highly reducing sediments are prevalent in seagrass environments. Under anoxic conditions, hydrogen sulfide can accumulate as an end product of anaerobic respiration at levels which may be toxic to halophytes. The photosynthetic response of Zostera marina L. (eelgrass) to manipulations in sediment sulfide concentration and light regimes was examined in Chincoteague Bay in June 1991. Neutral density screens were used in a mesocosm experiment to decrease downwelling irradiance to 50 and 15% of insolation. Sediment sulfide levels were enriched using Na2S and lowered using FeSO4. Photosynthesis vs, irradiance (PI) relationships were determined experimentally at ten light levels throughout the 21 day experiment. Photoadaptation was detected in response to the previous 4 day light history of the plants, as maximum photosynthesis (P-max) decreased in response to lower daily light levels. Negative impacts of sulfide on eelgrass in this study were observed through reductions in P-max increases in the light intensity at which gross photosynthesis equals respiration, and decreases in the initial slope of the PI curve. The effects of eutrophication through reduced light and increased sediment sulfide on P-max were additive. Elevated sediment sulfide levels may contribute tb seagrass loss in stressed areas as the potential for utilization of available light is reduced. Keywords: seagrass thalassia-testudinum; salt-marsh sediments; nutrient; enrichment; hydrogen-sulfide; heterozostera-tasmanica;; posidonia-oceanica; depth distribution; sulfate reduction; coastal; lagoon; chesapeake bay Permanent link  | Save citation:  RTF  PDF  LaTeX
Horrocks JL, Stewart GR, Dennison WC (1995) Tissue nutrient content of Gracilaria spp (Rhodophyta) and water quality along an estuarine gradient. Marine and Freshwater Research 46(6):975–983 Abstract: Tissue nutrient content of Gracilaria spp. (Rhodophyta) was tested as a bioindicator of water column nutrient availability in the Logan River and southern Moreton Bay, south-eastern Queensland. Macroalgae were incubated for one to two weeks within flow-through incubation chambers suspended in the water column. Tissue nutrient content of Gracilaria spp, and water column nutrients were measured at five sites over a five-month period. Tissue nitrogen content (%N) was correlated with dissolved inorganic nitrogen (DIN) at a site 15 km upstream from the Logan River mouth (r(2) = 0.81), at the Logan River mouth (r(2) = 0.50), and at a Moreton Bay site 8 km from the Logan River mouth (r(2) = 0.71). Time-course analyses of water column nutrients and plant tissue content showed more significant correlations with nitrogen (N) than with phosphorus (P). Plant tissue nitrogen-to-phosphorus (N:P) molar ratios ranged between 19 and 23 whereas water column N:P ratios were between 2 and 6, suggesting low nitrogen availability relative to plant requirements and possible N limitation. In the laboratory, Gracilaria verrucosa was subjected to treatments of N, P or N + P nutrient additions. Deepening of the thallus colouration was observed after additions of N. Chlorophyll and phycoerythrin concentrations increased in treatments with N addition; however, owing to wide variability between phycoerythrin replicates, only chlorophyll increases were significant. The amino acid citrulline also increased with the addition of N and accounted for up to 16% of the total tissue N. Macroalgae may be more useful than traditional water quality sampling for integrating biologically available pulses of nutrients, especially for a limiting nutrient such as N in coastal marine ecosystems. Keywords: 2 red algae; biochemical-composition; tikvahiae mclachlan;; cyanidium-caldarium; nitrate uptake; florida keys; n-p; nitrogen;; growth; macroalgae Permanent link  | Save citation:  RTF  PDF  LaTeX
1994
Abal EG, Loneragan N, Bowen P, Perry CJ, Udy JW, Dennison WC (1994) Physiological and Morphological Responses of the Seagrass Zostera capricorni Aschers to Light-Intensity. Journal of Experimental Marine Biology and Ecology 178(1):113–129 Abstract: The responses of the seagrass Zostera capricorni Aschers. to changes in light intensity were examined in flowing seawater aquaria experiments. Plants were grown in six light regimes: full sunlight (100%), 50, 30, 20, 15, and 5% of full light over a 2-month period. Measurements of growth, biomass, pigments, stable isotopes and leaf anatomy were made at the end of the experiment. Plants survived under all light treatments, even below minimum light requirements of related seagrasses. However, the experimental light levels possibly do not correspond to light reaching seagrass leaves under natural conditions. Plants grown under high light conditions (50-100% light) had smaller shoots, higher biomass and productivity, less negative deltaC-13 values, lower leaf nitrogen content, less chlorophyll and more ultraviolet light absorbing pigment than plants grown under low light conditions (<20% light). Photoadaptation by ultraviolet light absorbing pigment(s) was noted, with more variability in ultraviolet light pigments than in chlorophyll levels. Increased CO2 demand and/or increased CO2 recycling in internal gas spaces may account for the less negative deltaC-13 values in high light treatments indicating less isotopic discrimination in seagrass leaves in high light. A saturation response of growth rates to light intensity was observed, with less substantial growth reductions at lower light intensities than observed in other seagrass shading experiments. Nutrient limitation in high light was inferred by a growth maximum at 50% light level, increased root biomass and lower leaf nitrogen content in high light treatments. Overall, a wide range of morphological and physiological photoadaptive responses not previously reported in Zostera capricorni was observed. Keywords: light; photoadaptation; seagrass; zostera; carbon isotope variability; ultra-violet radiation; great-barrier-reef;; oceanica l delile; marina l eelgrass; posidonia-oceanica;; thalassia-testudinum; depth distribution; izembek lagoon; gas-discharge Permanent link  | Save citation:  RTF  PDF  LaTeX
1993
Dennison WC, Orth RJ, Moore KA, Stevenson JC, Carter V, Kollar S, Bergstrom PW, Batiuk RA (1993) Assessing Water-Quality with Submersed Aquatic Vegetation. Bioscience 43(2):86–94 Keywords: tidal potomac river; upper chesapeake bay; macrophyte communities;; depth distribution; light; growth; decline; plants; sea; estuarine Permanent link  | Save citation:  RTF  PDF  LaTeX
1992
Murray L, Dennison WC, Kemp WM (1992) Nitrogen Versus Phosphorus Limitation for Growth of an Estuarine Population of Eelgrass (Zostera marina L). Aquatic Botany 44(1):83–100 Abstract: The relative importance of nitrogen (N) and phosphorus (P) limitation for growth and biomass accumulation in an estuarine population of eelgrass (Zostera marina L.) was examined by in situ additions of nitrogen (+N), phosphorus (+P) and nitrogen plus phosphorus (+N+P) to sediments at low and high loading rates. Nitrogen treatments resulted in no significant increases in leaf tissue N levels and only a small increase in the N content of root plus rhizome tissues. Phosphorus concentrations were, however, significantly (P < 0.05) higher in both leaf and root plus rhizome tissues with +P and +N+P enrichment. Eelgrass growth and biomass exhibited statistically significant (P < 0.05) increases in response to high +P. Similar increases in mean plant growth and biomass were observed with +N and +N+P enrichment, but large variabilities rendered these responses nonsignificant. Our results are in contrast with those reported for a previous sediment fertilization (+N+P) study at the same site and we attribute this difference to a change in the nutrient status of the study area. Comparison with other sediment fertilization experiments for both freshwater and marine plant species revealed a clear relationship between relative plant growth rates and tissue nutrient concentrations for both N and P enrichment. This relationship suggests a uniformity of submersed plant nutrition, wherein responses to changes in nutrient availability are regulated by alterations in both growth rates and tissue nutrient content. Keywords: seagrass syringodium-filiforme; chesapeake bay; nutrient limitation;; phytoplankton growth; thalassia-testudinum; carbonate sediments; depth; distribution; fresh-water; enrichment; ammonium Permanent link  | Save citation:  RTF  PDF  LaTeX
1990
Short FT, Dennison WC, Capone DG (1990) Phosphorus-Limited Growth of the Tropical Seagrass Syringodium-Filiforme in Carbonate Sediments. Marine Ecology-Progress Series 62(1-2):169–174 Permanent link  | Save citation:  RTF  PDF  LaTeX
Williams SL, Dennison WC (1990) Light Availability and Diurnal Growth of a Green Macroalga (Caulerpa-Cupressoides) and a Seagrass (Halophila-Decipiens). Marine Biology 106(3):437–443 Permanent link  | Save citation:  RTF  PDF  LaTeX
1989
Dennison WC, Marshall GJ, Wigand C (1989) Effect of 'brown tide' shading on eelgrass. Coastal Estuarine Studies 35:675–692 Permanent link  | Save citation:  RTF  PDF  LaTeX
1988
Cosper EM, Dennison WC, Milligan A, Carpenter EJ, Lee C, Holzapfel J, Milanese L (1988) An examination of the environmental factors important to initiating and sustaining 'brown tide' blooms. Coastal Estuarine Studies 35:317–340 Permanent link  | Save citation:  RTF  PDF  LaTeX
Dennison WC, Barnes DJ (1988) Effect of Water Motion on Coral Photosynthesis and Calcification. Journal of Experimental Marine Biology and Ecology 115(1):67–77 Permanent link  | Save citation:  RTF  PDF  LaTeX
1987
Cosper EM, Dennison WC, Carpenter EJ, Bricelj VM, Mitchell JG, Kuenstner SH, Colflesh D, Dewey M (1987) Recurrent and Persistent Brown Tide Blooms Perturb Coastal Marine Ecosystem. Estuaries 10(4):284–290 Permanent link  | Save citation:  RTF  PDF  LaTeX
Dennison WC (1987) Effects of Light on Seagrass Photosynthesis, Growth and Depth Distribution. Aquatic Botany 27(1):15–26 Permanent link  | Save citation:  RTF  PDF  LaTeX
Dennison WC, Aller RC, Alberte RS (1987) Sediment Ammonium Availability and Eelgrass (Zostera marina) Growth. Marine Biology 94(3):469–477 Permanent link  | Save citation:  RTF  PDF  LaTeX
1986
Dennison WC, Alberte RS (1986) Photoadaptation and Growth of Zostera marina L (Eelgrass) Transplants Along a Depth Gradient. Journal of Experimental Marine Biology and Ecology 98(3):265–282 Permanent link  | Save citation:  RTF  PDF  LaTeX
Marsh JA, Dennison WC, Alberte RS (1986) Effects of Temperature on Photosynthesis and Respiration in Eelgrass (Zostera marina L). Journal of Experimental Marine Biology and Ecology 101(3):257–267 Permanent link  | Save citation:  RTF  PDF  LaTeX
1985
Dennison WC, Alberte RS (1985) Role of Daily Light Period in the Depth Distribution of Zostera marina (Eelgrass). Marine Ecology-Progress Series 25(1):51–61 Permanent link  | Save citation:  RTF  PDF  LaTeX
1984
Smith RD, Dennison WC, Alberte RS (1984) Role of Seagrass Photosynthesis in Root Aerobic Processes. Plant Physiology 74(4):1055–1058 Permanent link  | Save citation:  RTF  PDF  LaTeX
1983
Mazzella L, Dennison WC, Alberte RS (1983) Photosynthetic Activity of Zostera marina L Epiphytes in Relation to Light Regime and Substratum. Biological Bulletin 165(2):508–509 Permanent link  | Save citation:  RTF  PDF  LaTeX
1982
Dennison WC, Alberte RS (1982) Photosynthetic Responses of Zostera marina L (Eelgrass) to Insitu Manipulations of Light-Intensity. Oecologia 55(2):137–144 Permanent link  | Save citation:  RTF  PDF  LaTeX
Smith RD, Dennison WC, Alberte RS (1982) Role of Shoot Photosynthesis in Root-Rhizome Respiration in Zostera marina L (Eel-Grass). Biological Bulletin 163(2):368–369 Permanent link  | Save citation:  RTF  PDF  LaTeX
1981
Dennison WC, Mauzerall D, Alberte RS (1981) Photosynthetic Response of Zostera marina (Eelgrass) to Insitu Manipulations of Light. Biological Bulletin 161(2):311–312 Permanent link  | Save citation:  RTF  PDF  LaTeX
Conference Proceedings
2006
Wang P, Linker L, Jasinski DA, Dennison WC, Shenk G, Batiuk R (2006) Forecast of Summer Anoxia in the Chesapeake Bay. In: Spaulding ML (ed) Estuarine and Coastal Modeling: Proceedings of the Ninth International Conference on Estuarine and Coastal Modeling held in Charleston, South Carolina, from October 31 to November 2, 2005. American Society of Civil Engineers, 874 pp Abstract: This paper presents a forecast model to predict summer anoxia in the Chesapeake Bay using preceding spring information of nitrogen and phosphorus loads, water temperature, algae concentration, and freshwater flows. It's based on a regression of over 20 years of observed data. The use of anoxic intensity, a DO-normalized anoxic volume, versus the traditional anoxic volume as the forecasting estimator is described. Anoxic volume can be influenced by partial mixing or other factors that sometimes causes a higher anoxic volume but with actually less intensity in the anoxic condition. This paper recommends using quadratic terms of separate nitrogen and phosphorus loads, and other conditions such as freshwater flows from the upper Bay and water temperature, as regressors. More than 18 regression equations with different combinations of explanatory variables were compared, and the importance of their effects on the anoxia forecast is discussed. Keywords: Chesapeake Bay; Forecasting; Nitrogen; Phosphorus; Water pollution Permanent link  | Save citation:  RTF  PDF  LaTeX
1999
Dennison WC, O' Neil JM, Jones AB, Costanzo SD, Hewson I, Prange JA (1999) Effect of Hydric Soil Disturbance on Ecological Health of Coastal Waters. Proceedings of the Australian Acid Sulfate Soils Conference Abstract: Soil disturbance in coastal regions could be linked to a variety of deleterious environmental impacts. The existing data are preliminary, but there is sufficient evidence to raise the issue to a higher priority for both research and management. Permanent link  | Save citation:  RTF  PDF  LaTeX
1998
Heil CA, Bird P, Dennison WC (1998) Macroalgal habitat preference of ciguatera dinoflagellates at Heron Island, A Coral Cay in the southeastern Great Barrier Reef, Australia. In: Reguera B, Blanco J, Fernandez ML, Wyatt T (eds) Harmful Algae. Proceedings of the 8th International Conference on Harmful Algal Blooms, Vigo, Spain. Xunta de Galicia and Intergovernmental Oceanographic Commission of UNESCO, p 52–53 Permanent link  | Save citation:  RTF  PDF  LaTeX
Jones AB, Dennison WC (1998) Photosynthetic capacity in coral reef systems: Investigations into ecological applications for the underwater PAM fluorometer. In: Greenwood JG, Hall NJ (eds) Proceedings of the Australian Coral Reef Society 75th Anniversary Conference, Heron Island, October 1997. School of Marine Science, The University of Queensland, Brisbane, p 67–79 Abstract: A submersible pulse amplitude modulated (PAM) fluorometer was used to determine the effects of desiccation, ultraviolet radiation, changes in solar radiation and nutrient availability on the photosynthetic apparatus of a variety of marine plants (zooxanthellae, benthic microalgae and macroalgae) at Heron Island, Great Barrier Reef, Australia. The PAM measures photosynthesis as irradiance-dependent photosystem II electron transport. There were a number of interspecific and intraspecific variations in electron transport rate (ETR) based on physiological and morphological differences, and the plant's response to changes in environmental conditions. The highest ETR was found in the zooxanthellae of the clam Tridacna maxima, and the lowest in the calcified green macroalga Halimeda opuntia. Factors such as water velocity, ultraviolet radiation, solar radiation (total irradiance and spectral changes), desiccation, nutrient availability and algal pigment content were hypothesised as influencing intraspecific changes in ETR. A series of experimental manipulations were conducted to test these hypotheses. Reef flat algae was shaded to 50% of incident solar radiation and 0% of ultraviolet radiation. Samples of macroalgae were collected from the reef flat and 15 m depth and allowed to desiccate to determine if different populations of the same species could adapt physiologically to different environmental conditions. Reef flat samples were collected and incubated in seawater enriched in nitrogen and phosphorus to test for nutrient limitation. Significant differences in the ETR of the plants tested highlighted the impacts of various environmental parameters on photosynthetic capacity. Samples from regions with higher water velocities on the reef flat had significantly higher ETRs. Screening of ultraviolet radiation increased the maximum ETR of certain species, while prolonged periods of shading reduced the maximum ETR of some species more quickly than others. Desiccation responses were the same between deep collected and reef flat populations, although increased light and temperature did reduce the maximum ETR of the deep collected samples. Fertilisation responses varied between species. The results indicate that PAM fluorometry can be used as a tool for in situ non destructive assessment of the effects of various ecological parameters on photosynthetic activity in marine plants. Permanent link  | Save citation:  RTF  PDF  LaTeX
Master's Theses
1979
Dennison WC (1979) Light Adaptations of Plants: A Model Based on the Seagrass Zostera marina L. Master's thesis. University of Alaska, Fairbanks, 66 pp Permanent link  | Save citation:  RTF  PDF  LaTeX
Books
2010
Longstaff BJ, Carruthers TJB, Dennison WC, Lookingbill TR, Hawkey JM, Thomas JE, Wicks EC, Woerner JL (2010) Integrating and Applying Science: A practical handbook for effective coastal ecosystem assessment. IAN Press, Camridge, MD, 244 pp Abstract: Vast areas of the globe's coastal zone have experienced significant declines in ecosystem health. Deteriorating water quality, loss and alteration of vital habitats, and reduced populations of fish and shellfish are some of the major changes recorded. Regardless of the differences between cultures, climate regions, and population pressures, integrated management and assessment is required to solve coastal environmental problems. Establishing and running an effective assessment program is a complex process that necessitates strategic collaboration and partnerships between many individuals and agencies. This book was written to make the process of running a coastal assessment program easier and the outcomes more effective. It provides a step‒by‒step approach from data collection and information management to synthesis and application and draws on the knowledge of a variety of coastal scientists and managers. The book is divided into four sections that represent the four major steps needed to apply data within an coastal assessment program: community engagement, community knowledge, environmental information, and data collection. Keywords: community engagement; community knowledge; environmental information; environmental data collection Permanent link  | Save citation:  RTF  PDF  LaTeX
2009
Dennison WC, Thomas JE, Cain CJ, Carruthers TJB, Hall MR, Jesien RV, Wazniak CE, Wilson DE (2009) Shifting Sands: Environmental and cultural change in Maryland's Coastal Bays. IAN Press, Cambridge, MD, 396 pp Abstract: The title of this book-Shifting Sands-refers to both the dynamic nature of the barrier islands forming the coastal lagoons of Maryland's Atlantic Ocean coastline and also the changing cultural landscape as more and more people discover these once-forgotten bays. The subtitle of the book-Environmental and cultural change in Maryland's Coastal Bays-reflects the way the book integrates natural and human influences. Shifting Sands is a richly illustrated, multi-authored introduction to Assawoman Bay, Isle of Wight Bay, St. Martin River, Sinepuxent Bay, Newport Bay, and Chincoteague Bay. This book leads the reader on a voyage of discovery, providing a user-friendly guide to the history, setting, context, and ecology of these waterways nestled behind Assateague, Fenwick, and Chincoteague Islands. Photographs, conceptual diagrams, maps, and graphs are used to showcase the key features of and major threats to these magnificent bays, watersheds, and islands, with recommendations for how to preserver them for future generations. Keywords: coastal bays; health; management; assessment; history; water quality; habitats Permanent link  | Save citation:  RTF  PDF  LaTeX
Petersen JE, Kennedy VS, Dennison WC, Kemp WM (2009) Enclosed Experimental Ecosystems and Scale: Tools for Understanding and Managing Coastal Ecosystems. Springer, 222 pp Abstract: The environmental challenges now facing humanity, ranging from climate change to urbanization to invasive species to agricultural and industrial pollutants are particularly acute in the coastal zone. Research in this region and in other aquatic ecosystems is complicated by interactions that occur over broad scales of time, space, and ecological complexity. Enclosed experimental ecosystems (mesocosms and microcosms) have become critical research tools because they provide a degree of control not achievable through field experiments. Yet to date, techniques for systematically extrapolating results from small-scale experimental ecosystems to larger, more open, more biodiverse, and more heterogeneous ecosystems in nature have not been well developed. This book is designed to provide scientists, resource managers and students with a comprehensive and practical guide and reference for improving the design and interpretation of research conducted in experimental ecosystems. Keywords: aquatic;coastal;ecology;ecosystem;enclosed ecosystem;estuarine;estuary;experimental ecosystem;mesocosm;microcosm;scale Permanent link  | Save citation:  RTF  PDF  LaTeX
2007
Lane H, Woerner JL, Dennison WC, Neill C, Wilson C, Elliott M, Shively M, Graine J, Jeavons R (2007) Defending Our National Treasure: Department of Defense Chesapeake Bay Restoration Partnership 1998-2004. Integration and Application Network, University of Maryland Center for Environmental Science, Cambridge, MD, 176 Abstract: Defending Our National Treasure: A Department of Defense Chesapeake Bay Restoration Partnership 1998–2004 provides an overview of major issues impacting the Chesapeake Bay, history of the Department of Defense’s involvement in Bay restoration efforts, current Department of Defense Chesapeake Bay restoration initiatives, specific case studies, and viewpoints of various key individuals dedicated to restoration. These topics are presented in a richly illustrated style including maps, photographs, conceptual diagrams, and figures to uniquely communicate information and make it accessible to a broad audience. Each section provides the essence of each topic rather than the complete and comprehensive treatment. For example, there are numerous documents describing Chesapeake Bay and Department of Defense initiatives (www.denix.osd.mil). Defending Our National Treasure provides the context and background for the issues impacting the Chesapeake Bay and describes the restoration activities conducted on the Department of Defense installations within the Bay watershed. Permanent link  | Save citation:  RTF  PDF  LaTeX
2006
Thomas JE, Saxby TA, Jones AB, Carruthers TJB, Abal EG, Dennison WC (2006) Communicating Science Effectively: A Practical Handbook for Integrating Visual Elements. IWA Publishing, London, 136 pp Abstract: This is a practical handbook on how to communicate science effectively. The first part is an introduction to the principles of science communication-what effective science communication is, why it is important, and how effective science communication can change societal paradigms and make one a better scientist. General principles relating to all science communication products include providing synthesis, visualization, and context, assembling self-contained visual elements such as photos, maps, conceptual diagrams and data, formatting content to define and simplify terms, and eliminating jargon and acronyms. Formatting of these visual elements is also discussed. This introduction is followed by chapters outlining techniques and principles for communicating in different media-desktop publishing (including posters and newsletters), presentations and websites. Techniques in these chapters include image, color, and font formats, resolution and design tips for different media. Finally, a case study is presented to illustrate how effective science communication has become an integral part of a successful environmental science, monitoring, planning, and implementation program. The book is accompanied by extensive internet resources, including interactive software tutorials for the different software programs commonly used in communication, discussion forums for science communication issues, and links to other websites of interest. This book will be a valuable resource for scientists working in research, management agencies, government and education. Although environmental scientists are the primary audience, the principles and techniques discussed are applicable to scientists from all disciplines. Keywords: science communication; handbook; visual, diagrams; images; research Permanent link  | Save citation:  RTF  PDF  LaTeX
2005
Abal EG, Bunn SE, Dennison WC (2005) Healthy waterways Healthy catchments: Making the connection in South East Queensland, Australia. Moreton Bay Waterways and Catchment Partnership, Brisbane, 240 pp Permanent link  | Save citation:  RTF  PDF  LaTeX
2004
Turner L, Tracey D, Tilden J, Dennison WC (2004) Where river meets sea: Exploring Australia's estuaries. Cooperative Research Centre for Coastal Zone, Estuary and Waterways Management, Brisbane, 294 pp Permanent link  | Save citation:  RTF  PDF  LaTeX
2001
Clarke L, Dennison WC, Bunn SE, Abal EG, Collier C, Ball B, Lloyd T, Greenfield P.F. (2001) Discover the waterways of south-east Queensland: waterways health and catchment management of south-east Queensland, Australia. South East Queensland Regional Water Quality Management Strategy, Brisbane, 155 pp Permanent link  | Save citation:  RTF  PDF  LaTeX
1999
Dennison WC, Abal EG (1999) Moreton Bay Study: A Scientific Basis for the Healthy Waterways Campaign. SE Queensland Water Quality Strategy, Brisbane, 245 pp Permanent link  | Save citation:  RTF  PDF  LaTeX
1998
Scott H, Dennison WC, Abal EG, Ball B, Lloyd T, Greenfield PF (1998) Crew Member's Guide to the Health of Our Waterways: ecological health and water quality management in the Moreton Bay catchment – Queensland Australia. Moreton Bay Catchment Water Quality Management Strategy Team, Brisbane, 97 pp Permanent link  | Save citation:  RTF  PDF  LaTeX
Tibbetts IR, Hall NJ, Dennison WC (1998) Moreton Bay and Catchment. School of Marine Science, The University of Queensland, Brisbane, 645 pp Permanent link  | Save citation:  RTF  PDF  LaTeX
Book Contributions
2010
Conner CS, Dennison WC, Thomas JE (2010) Chapter 4: Communication strategy: packaging and delivering the message for maximum impact. In: Longstaff BJ, Carruthers TJB, Dennison WC, Lookingbill TR, Hawkey JM, Thomas JE, Wicks EC, Woerner JL (eds) Integrating and Applying Science: A practical handbook for effective coastal ecosystem assessment. IAN Press, Cambridge, MD, p 45–58 Abstract: Drawing from the last chapter and its emphasis on the importance of communication, this chapter discusses ways to broadcast a message internally within a coastal assessment program and externally to the general public. Throughout the chapter, the steps involved in broadcasting the message (such as determining target audience, ways in which to relay the message, and how to create an appropriate timeline) will be explained in detail. Specifics such as how to choose a spokesperson and how to determine the look of the communication product will help create and project the most effective message to the audience. Additional tips on types of media that are available and the best way to prepare for interviews are also included. Permanent link  | Save citation:  RTF  PDF  LaTeX
Dennison WC, Thomas JE (2010) Chapter 2: Environmental leadership: achieving a sustainable future by fostering environmental champions. In: Longstaff BJ, Carruthers TJB, Dennison WC, Lookingbill TR, Hawkey JM, Thomas JE, Wicks EC, Woerner JL (eds) Integrating and Applying Science: A practical handbook for effective coastal ecosystem assessment. IAN Press, Cambridge, MD, p 19–32 Abstract: For every environmental campaign, a strong leader is needed for guidance and motivation. There have been a series of leaders or “champions” in the history of the world who have changed life on this planet. All of these leaders, no matter what area their specialty, have contained the following traits: knowledge of their field; passion for what they do; and an ability to successfully communicate their messages not only to their colleagues, but also to the broader community. This chapter discusses past champions and why they were so effective as well as discusses in detail the traits that are needed to become a successful champion and how to guide a successful coastal assessment program. Permanent link  | Save citation:  RTF  PDF  LaTeX
Dennison WC, Wicks EC (2010) Chapter 1: Environmental campaigns: achieving a shared vision using research, monitoring, and management. In: Longstaff BJ, Carruthers TJB, Dennison WC, Lookingbill TR, Hawkey JM, Thomas JE, Wicks EC, Woerner JL (eds) Integrating and Applying Science: A practical handbook for effective coastal ecosystem assessment. IAN Press, Cambridge, MD, p 7–18 Abstract: A coastal assessment program cannot simply draw from a few individuals; it takes contributions from an entire community and the creation of a shared vision. Keeping a balance among research, monitoring, and management is especially important and includes the dynamics of human interactions and strong communication between stakeholders and the broader community. In this chapter, we define an environmental campaign, which is part of a coastal assessment program, and describe some of the most important components for success. Permanent link  | Save citation:  RTF  PDF  LaTeX
Wicks EC, Longstaff BJ, Fertig BM, Dennison WC (2010) Chapter 5: Ecological indicators: assessing ecosystem health using metrics. In: Longstaff BJ, Carruthers TJB, Dennison WC, Lookingbill TR, Hawkey JM, Thomas JE, Wicks EC, Woerner JL (eds) Integrating and Applying Science: A handbook for effective coastal ecosystem assessment. IAN Press, Cambridge, MD, p 61–78 Abstract: Chapter 4 discussed how selecting an appropriate communication product can affect an audience and persuade opinions. This chapter discusses how using another tool, an indicator (Figure 5.1), not only can persuade opinions, but also can be used to evaluate the health of an ecosystem. It starts by introducing what an ecological indicator is and why it is important and then describes different kinds of indicators, the process of selecting an indicator, how indicators are used to aid in management decisions, and how to structure indicators. Selecting, developing, and communicating ecological indicators are perhaps the most important, yet challenging aspects of a coastal assessment program and, therefore, should be given appropriate effort and resources. Permanent link  | Save citation:  RTF  PDF  LaTeX
2009
Bricker SB, Dennison WC, Dunton KH, Ferreira JG, Hall MR, Herrera-Silveira JA, Longstaff BJ, Morales-Ojeda S, Onuf CP, Pastres R, Thomas JE, Wazniak CE (2009) The Coastal Bays in Context. In: Dennison WC, Thomas JE, Cain CJ, Carruthers TJB, Hall MR, Jesien RV, Wazniak CE, Wilson DE (eds) Shifting Sands: Environmental and cultural change in Maryland's Coastal Bays. IAN Press, Camridge, MD, p 175–210 Abstract: The title of this book-Shifting Sands-refers to both the dynamic nature of the barrier islands forming the coastal lagoons of Maryland's Atlantic Ocean coastline and also the changing cultural landscape as more and more people discover these once-forgotten bays. The subtitle of the book-Environmental and cultural change in Maryland's Coastal Bays-reflects the way the book integrates natural and human influences. Shifting Sands is a richly illustrated, multi-authored introduction to Assawoman Bay, Isle of Wight Bay, St. Martin River, Sinepuxent Bay, Newport Bay, and Chincoteague Bay. This book leads the reader on a voyage of discovery, providing a user-friendly guide to the history, setting, context, and ecology of these waterways nestled behind Assateague, Fenwick, and Chincoteague Islands. Photographs, conceptual diagrams, maps, and graphs are used to showcase the key features of and major threats to these magnificent bays, watersheds, and islands, with recommendations for how to preserver them for future generations. Keywords: coastal bays;health;management;assessment;history;water quality;habitats Permanent link  | Save citation:  RTF  PDF  LaTeX
Dennison WC (2009) Global Trajectories of Seagrasses, the Biological Sentinels of Coastal Ecosystems. In: Carlos M. Duarte (ed) Global Loss of Coastal Habitats: Rates, Causes and Consequences. Fundacion BBVA, 184 pp Permanent link  | Save citation:  RTF  PDF  LaTeX
Dennison WC, Cain CJ, Carruthers TJB, Hall MR, Jesien RV, Thomas JE, Wazniak CE, Wilson DE (2009) Conclusions and Recommendations. In: Dennison WC, Thomas JE, Cain CJ, Carruthers TJB, Hall MR, Jesien RV, Wazniak CE, Wilson DE (eds) Shifting Sands: Environmental and cultural change in Maryland's Coastal Bays. IAN Press, Camridge, MD, p 1–14 Abstract: The title of this book-Shifting Sands-refers to both the dynamic nature of the barrier islands forming the coastal lagoons of Maryland's Atlantic Ocean coastline and also the changing cultural landscape as more and more people discover these once-forgotten bays. The subtitle of the book-Environmental and cultural change in Maryland's Coastal Bays-reflects the way the book integrates natural and human influences. Shifting Sands is a richly illustrated, multi-authored introduction to Assawoman Bay, Isle of Wight Bay, St. Martin River, Sinepuxent Bay, Newport Bay, and Chincoteague Bay. This book leads the reader on a voyage of discovery, providing a user-friendly guide to the history, setting, context, and ecology of these waterways nestled behind Assateague, Fenwick, and Chincoteague Islands. Photographs, conceptual diagrams, maps, and graphs are used to showcase the key features of and major threats to these magnificent bays, watersheds, and islands, with recommendations for how to preserver them for future generations. Keywords: coastal bays;health;management;assessment;history;water quality;habitats Permanent link  | Save citation:  RTF  PDF  LaTeX
Wazniak CE, Carruthers TJB, Dennison WC, Hall MR, Thomas JE (2009) Ecosystem Health Assessment. In: Dennison WC, Thomas JE, Cain CJ, Carruthers TJB, Hall MR, Jesien RV, Wazniak CE, Wilson DE (eds) Shifting Sands: Environmental and cultural change in Maryland's Coastal Bays. IAN Press, Camridge, MD, p 15–20 Abstract: The title of this book-Shifting Sands-refers to both the dynamic nature of the barrier islands forming the coastal lagoons of Maryland's Atlantic Ocean coastline and also the changing cultural landscape as more and more people discover these once-forgotten bays. The subtitle of the book-Environmental and cultural change in Maryland's Coastal Bays-reflects the way the book integrates natural and human influences. Shifting Sands is a richly illustrated, multi-authored introduction to Assawoman Bay, Isle of Wight Bay, St. Martin River, Sinepuxent Bay, Newport Bay, and Chincoteague Bay. This book leads the reader on a voyage of discovery, providing a user-friendly guide to the history, setting, context, and ecology of these waterways nestled behind Assateague, Fenwick, and Chincoteague Islands. Photographs, conceptual diagrams, maps, and graphs are used to showcase the key features of and major threats to these magnificent bays, watersheds, and islands, with recommendations for how to preserver them for future generations. Keywords: coastal bays;health;management;assessment;history;water quality;habitats Permanent link  | Save citation:  RTF  PDF  LaTeX
Boward DM, Carruthers TJB, Chalmers RJ, Clearwater DH, Dennison WC, Hairston-Strang AB, Hall MR, Irani FM, Jesien RV, Knapp WM, Koch EW, Kyde KL, Luscher AE, Naylor MD, Orth RJ, Spaur CC, Tarnowski ML, Wicks EC, Zimmerman CS (2009) Habitats of the Coastal Bays & Watershed. In: Dennison WC, Thomas JE, Cain CJ, Carruthers TJB, Hall MR, Jesien RV, Wazniak CE, Wilson DE (eds) Shifting Sands: Environmental and cultural change in Maryland's Coastal Bays. IAN Press, Camridge, MD, p 345–390 Abstract: The title of this book-Shifting Sands-refers to both the dynamic nature of the barrier islands forming the coastal lagoons of Maryland's Atlantic Ocean coastline and also the changing cultural landscape as more and more people discover these once-forgotten bays. The subtitle of the book-Environmental and cultural change in Maryland's Coastal Bays-reflects the way the book integrates natural and human influences. Shifting Sands is a richly illustrated, multi-authored introduction to Assawoman Bay, Isle of Wight Bay, St. Martin River, Sinepuxent Bay, Newport Bay, and Chincoteague Bay. This book leads the reader on a voyage of discovery, providing a user-friendly guide to the history, setting, context, and ecology of these waterways nestled behind Assateague, Fenwick, and Chincoteague Islands. Photographs, conceptual diagrams, maps, and graphs are used to showcase the key features of and major threats to these magnificent bays, watersheds, and islands, with recommendations for how to preserver them for future generations. Keywords: coastal bays;health;management;assessment;history;water quality;habitats Permanent link  | Save citation:  RTF  PDF  LaTeX
2006
Soule ME, Mackay BG, Recher HF, Williams JE, Woinarski JCZ, Driscoll D, Dennison WC, Jones ME (2006) The role of connectivity in Australian conservation. In: Crooks KR, Sanjayan M (eds) Connectivity Conservation. Cambridge Univ. Press, Cambridge, p 649–675 Permanent link  | Save citation:  RTF  PDF  LaTeX
2004
Dennison WC, Carruthers TJB, Thomas JE, Glibert PM (2004) A comparison of issues and management approaches in Moreton Bay, Australia and Chesapeake Bay, USA. In: Wong MH (ed) Developments in Ecosystems Developments in Ecosystems volume 1: Wetlands Ecosystems in Asia: Function and Management. p 3–25 Permanent link  | Save citation:  RTF  PDF  LaTeX
2001
Carruthers TJB, Longstaff BJ, Dennison WC, Abal EG, Aioi K (2001) Measurement of light penetration in relation to seagrass. In: Short F, Coles R (eds) Global Seagrass Methods. Elsevier, p 369–392 Permanent link  | Save citation:  RTF  PDF  LaTeX
1999
McComb AJ, Dennison WC (1999) Seagrasses: angiosperms adapted to sea floors. In: Atwell BJ, Kriedemann PE, Turnbull CG (eds) Plants In Action. MacMillan Education Australia, South Yarra, p 587–591 Permanent link  | Save citation:  RTF  PDF  LaTeX
Udy JW, Dennison WC (1999) Seagrass and sediment nutrients: Species comparison and fertilisation responses of P. australis at Rottnest Island, Western Australia. The Seagrass Flora and Fauna of Rottnest Island, Western Australia. Western Australia Museum, Perth, p 73–88 Permanent link  | Save citation:  RTF  PDF  LaTeX
Walker DI, Dennison WC, Edgar G (1999) Status of Australian seagrass research and knowledge. In: Butler AJ, Jernakoff P (eds) Seagrass in Australia: Strategic review and development of an R&D plan. CSIRO Publishing, Collingwood, p 1–24 Permanent link  | Save citation:  RTF  PDF  LaTeX
1998
Abal EG, Dennison WC, O'Donohue MJH (1998) Seagrasses and mangroves in Moreton Bay. In: Tibbets IR, Hall NJ, Dennison WC (eds) Moreton Bay and Catchment. School of Marine Science, The University of Queensland, Brisbane, p 269–278 Permanent link  | Save citation:  RTF  PDF  LaTeX
Heil CA, O'Donohue MJH, Dennison WC (1998) Aspects of the winter phytoplankton community of Moreton Bay. In: Tibbets IR, Hall NJ, Dennison WC (eds) Moreton Bay and Catchment. School of Marine Science, The University of Queensland, Brisbane, p 291–300 Permanent link  | Save citation:  RTF  PDF  LaTeX
Heil CA, O'Donohue MJH, Miller CA, Dennison WC (1998) Phytoplankton community response to a flood event. In: Tibbets IR, Hall NJ, Dennison WC (eds) Moreton Bay and Catchment. School of Marine Science, The University of Queensland, Brisbane, p 569–584 Permanent link  | Save citation:  RTF  PDF  LaTeX
Jones AB, Dudley BJ, Dennison WC (1998) Factors limiting phytoplankton biomass in the Brisbane River and Moreton Bay. In: Tibbets IR, Hall NJ, Dennison WC (eds) Moreton Bay and Catchment. School of Marine Science, The University of Queensland, Brisbane, p 179–186 Permanent link  | Save citation:  RTF  PDF  LaTeX
O'Donohue MJH, Heil CA, Lowe S, Horrocks J, Abal EG, Costanzo SD, Dennison WC (1998) Assessing the impact of a flood event on Moreton Bay using marine plants as bioindicators of water quality. In: Tibbets IR, Hall NJ, Dennison WC (eds) Moreton Bay and Catchment. School of Marine Science, The University of Queensland, Brisbane, p 585–596 Permanent link  | Save citation:  RTF  PDF  LaTeX
Pillen TL, Ringeltaube P, Dennison WC (1998) Are expanding populations of the tropical green alga Caulerpa taxifolia a potential threat for Moreton Bay? In: Tibbets IR, Hall NJ, Dennison WC (eds) Moreton Bay and Catchment. School of Marine Science, The University of Queensland, Brisbane, p 327–328 Permanent link  | Save citation:  RTF  PDF  LaTeX
Udy JW, Dennison WC (1998) The use of the seagrass, Zostera capricorni, to identify anthropogenic nutrient sources in Moreton Bay. In: Tibbets I.R., Hall N.J., Dennison W.C. (eds) Moreton Bay and Catchment. School of Marine Science, The University of Queensland, Brisbane, p 213–228 Permanent link  | Save citation:  RTF  PDF  LaTeX
1996
Dennison WC, Kirkman H (1996) Seagrass survival model. In: Kuo J, Phillips RC, Walker DI, Kirkman H (eds) Seagrass Biology: Proceedings of an International Workshop. p 341–344 Permanent link  | Save citation:  RTF  PDF  LaTeX
Udy JW, Dennison WC (1996) Estimating nutrient availability in seagrass sediments. In: Kuo J, Phillips RC, Walker DI, Kirkman H (eds) Seagrass Biology: Proceedings of an International Workshop. p 163–172 Permanent link  | Save citation:  RTF  PDF  LaTeX
1990
Dennison WC (1990) Shoot density, Leaf production, Rhizome/root production, Chlorophyll content. In: Phillips RC, McRoy CP (eds) Seagrass Research Methods. UNESCO, Paris, p 61–64, p 77–80, p 81–82, p 83–86 Permanent link  | Save citation:  RTF  PDF  LaTeX

Science Communication Publications Browse all publications for Bill Dennison on IAN Press OR view individually:
2011
McKinney L, Tunnell W, Harwell M, Gentile J, Dennison WC, Kelsey RH, Thomas JE (2011) A vision for the Gulf of Mexico Report Card. IAN Press, Cambridge, MD, 4pp (Newsletter)
Integration and Application Network (2011) Healthy Darwin Harbour: Pathways and Partnerships. IAN Press, Cambridge, MD, 4pp (Newsletter)
Thomas JE, Carruthers TJB and Dennison WC (2011) Lessons learned from the Natural Resource Condition Assessment program. IAN Press, Cambridge, MD, 1pp (Poster)
McKinney L, Tunnell W, Harwell M, Gentile J, Kelsey RH and Dennison, WC (2011) Gulf of Mexico Report Card Initiative. IAN Press, Cambridge, MD, 14pp (Report)
Integration and Application Network (2011) Great Barrier Reef Report Card Summary - 2009 Baseline. Reef Water Quality Protection Plan Secretariat, 4pp (Report card)
Integration and Application Network (2011) Great Barrier Reef Report Card Regional Summaries - 2009 Baseline. Reef Water Quality Protection Plan Secretariat, 12pp (Report card)
Integration and Application Network (2011) Great Barrier Reef Technical Report Card - 2009 Baseline. Reef Water Quality Protection Plan Secretariat, 134pp (Report card)
Integration and Application Network (2011) Brisbane 2011: Living with floods and dancing with dugongs. IAN Press, Cambridge, MD, 56pp (Presentation)
Thomas JE, Calzarette J, Campbell JP, Carruthers TJB, Cohen D, Dennison WC, Donaldson L, Landsman A, Lehman M, Nortrup M and Wenschhof E (2011) Antietam National Battlefield Natural Resource Condition Assessment. IAN Press, Cambridge, MD, 160pp (Report)
Thomas JE, Banasik A, Campbell JP, Carruthers TJB, Dennison WC, Lehman M and Nortrup M (2011) Monocacy National Battlefield Natural Resource Condition Assessment. IAN Press, Cambridge, MD, 148pp (Report)
Thomas JE, Campbell JP, Carruthers TJB, Dennison WC, Gorsira B, Lehman M and Nortrup M (2011) Manassas National Battlefield Park Natural Resource Condition Assessment. IAN Press, Cambridge, MD, 144pp (Report)
Thomas JE, Calzarette J, Campbell JP, Carruthers TJB, Cohen D, Dennison WC, Donaldson L, Landsman A, Lehman M, Nortrup M and Wenschhof E (2011) Antietam National Battlefield Natural Resource Condition Assessment - Executive Summary. IAN Press, Cambridge, MD, 12pp (Report)
Thomas JE, Calzarette J, Campbell JP, Carruthers TJB, Cohen D, Dennison WC, Donaldson L, Landsman A, Lehman M, Nortrup M and Wenschhof E (2011) Antietam National Battlefield Natural Resource Condition Assessment Resource Brief. IAN Press, Cambridge, MD, 2pp (Brochure)
Thomas JE, Campbell JP, Carruthers TJB, Dennison WC, Gorsira B, Lehman M and Nortrup M (2011) Manassas National Battlefield Park Natural Resource Condition Assessment - Executive Summary . IAN Press, Cambridge, MD, 12pp (Report)
Thomas JE, Campbell JP, Carruthers TJB, Dennison WC, Gorsira B, Lehman M and Nortrup M (2011) Manassas National Battlefield Park Natural Resource Condition Assessment Resource Brief. IAN Press, Cambridge, MD, 2pp (Brochure)
Thomas JE, Banasik A, Campbell JP, Carruthers TJB, Dennison WC, Lehman M and Nortrup M (2011) Monocacy National Battlefield Natural Resource Condition Assessment - Executive Summary . IAN Press, Cambridge, MD, 12pp (Report)
Thomas JE, Banasik A, Campbell JP, Carruthers TJB, Dennison WC, Lehman M and Nortrup M (2011) Monocacy National Battlefield Natural Resource Condition Assessment Resource Brief. IAN Press, Cambridge, MD, 2pp (Brochure)
Carruthers TJB, Beckert KA, Dennison WC, Thomas JE, Saxby TA, Williams MR, Fisher T, Kumer J, Schupp C, Sturgis B, and Zimmerman C (2011) Assateague Island National Seashore Natural Resource Condition Assessment. IAN Press, Cambridge, MD, 182pp (Report)
Carruthers TJB, Beckert KA, Dennison WC, Thomas JE, Saxby TA, Williams MR, Fisher T, Kumer J, Schupp C, Sturgis B, and Zimmerman C (2011) Assateague Island National Seashore Natural Resource Condition Assessment - Executive Summary. IAN Press, Cambridge, MD, 12pp (Report)
Agardy T, Davis J, Sherwood K and Vestergaard O (2011) Taking Steps toward Marine and Coastal Ecosystem-Based Management - An Introductory Guide. United Nations Environment Programme, 68pp (Book)
Integration and Application Network (2011) Creating a Shared Vision for the Mackay-Whitsunday-Isaac Region. Mackay-Whitsundays-Isaac Healthy Waterways Alliance, 3pp (Newsletter)
Karrer L, Beldia II P, Dennison WC, Dominici A, Dutra G, English C, Gunawan T, Hastings J, Katz L, Kelty R, McField M, Nunez E, Obura D, Ortiz F, Quesada M, Sivo L, and Stone G (2011) Science-to-Action Guidebook. Conservation International, 20pp (Report)
Dennison WC, Udy, J (2011) South East Queensland Floods 2011. SEQ Healthy Waterways Partnership, 4pp (Newsletter)
Integration and Application Network (2011) Chesapeake Bay Report Card 2010. IAN Press, Cambridge, MD, 6pp (Report card)
Integration and Application Network (2011) Case studies of Regional Ecosystem Research. IAN Press, Cambridge, MD, 11pp (Report)
Integration and Application Network (2011) Innovations in environmental synthesis, reporting and governance. IAN Press, Cambridge, MD, 44pp (Presentation)
Crimp O, Dennison WC, Olley J, Saxton N, Layden I, McKew T, Hill A, Udy J, Walker A (2011) South East Queensland Floods 2011. SEQ Healthy Waterways Partnership, 4pp (Newsletter)
Kaufman L, Sandin S, Sala E, Obura D, Rohwer F, and Tschirky J (2011) Coral Health Index (CHI): measuring coral community health. Science and Knowledge Division, Conservation International, Arlington, VA, USA, 16pp (Report)
Dennison WC, Udy J, Schneider P, Filet P (2011) South East Queensland Floods 2011. SEQ Healthy Waterways Partnership, 3pp (Newsletter)
Boicourt KE and Johnson ZP (eds) (2011) Comprehensive Strategy for Reducing Maryland's Vulnerability to Climate Change, Phase II: building societal, economic, and ecological resilience. University of Maryland Center for Environmental Science, Cambridge, Maryland and Maryland Department of Natural Resources, Annapolis, Maryland, 80pp (Report)
2010
Integration and Application Network (2010) A Conceptual Basis for Monitoring Vital Signs: Shenandoah National Park. IAN Press, Cambridge, MD, 20pp (Brochure)
Integration and Application Network (2010) Expanding the diversity of the Mid-Atlantic Tributary Assessment Coalition. IAN Press, Cambridge, MD, 1pp (Poster)
Integration and Application Network (2010) Communicating science effectively to engage decision-makers. IAN Press, Cambridge, MD, 31pp (Presentation)
Integration and Application Network (2010) Living with the Sea: Local efforts buffer effects of global change. IAN Press, Cambridge, MD, 20pp (Report)
Samonte G, Bunce Karrer L, Orbach M (2010) People and Oceans: Managing marine areas for human well-being. IAN Press, Cambridge, MD, 20pp (Report)
Orbach M, Bunce Karrer L (2010) MMAs: What, why, and where. IAN Press, Cambridge, MD, 16pp (Report)
Integration and Application Network (2010) Conceptual Diagrams: Tools for Science Communication. IAN Press, Cambridge, MD, 4pp (Newsletter)
Integration and Application Network (2010) 2009 Chester River Report Card. IAN Press, Cambridge, MD, 4pp (Report card)
Integration and Application Network (2010) Proposal writing: A key to success. IAN Press, Cambridge, MD, 19pp (Presentation)
B.J. Longstaff, T.J.B. Carruthers, W.C. Dennison, T.R. Lookingbill, J.M. Hawkey, J.E. Thomas, E.C. Wicks, J. Woerner (2010) Integrating and Applying Science: A handbook for effective coastal ecosystem assessment. IAN Press, Cambridge, MD, 258pp (Book)
Integration and Application Network (2010) Integration and Application Network (IAN): 2010 Administrative Review. IAN Press, Cambridge, MD, 19pp (Presentation)
Dennison WC (2010) Chesapeake Bay health:What causes positive and negative trajectories?. IAN Press, Cambridge, MD, 16pp (Presentation)
2009
Dennison WC (2009) Closing the coastal charisma gap: how to integrate seagrasses into the public dialog on coastal ecosystems. IAN Press, Cambridge, MD, 24pp (Presentation)
Carruthers TJB, Kendrick G, Waycott M, Olyarnik S, Dennison WC, Duarte C, Orth RJ, Fourqurean J, Heck K, Hughes R, Kenworthy J, Short F, Williams S (2009) Global seagrass trajectories: a closer look in relation to future monitoring. IAN Press, Cambridge, MD, 20pp (Presentation)
Fertig BM, Carruthers TJB, Dennison WC, Altabet MA and Fertig EJ (2009) Variations of δ15N in eastern oysters (Crassostrea virginica) as a baseline to assess waste nitrogen sources. IAN Press, Cambridge, MD, 20pp (Presentation)
Wicks EC, Davis J, Dennison WC, Kelsey RH, Longstaff BJ, Nauman EG and Walls B (2009) Creating new opportunities for adaptive management: partnerships between government agencies and watershed organizations. IAN Press, Cambridge, MD, 19pp (Presentation)
Williams MR, Longstaff BJ and Dennison WC (2009) Novel Applications of the Chesapeake Bay Health Index. IAN Press, Cambridge, MD, 16pp (Presentation)
Woerner JL, Bishop T, Carruthers TJB, Dennison WC, Gurbisz C and Murray L (2009) Unlimited Access: Using collaborative products to make current scientific knowledge more accessible. IAN Press, Cambridge, MD, 1pp (Poster)
Thomas JE, Beckert K, Cain C, Carruthers TJB, Dennison WC1, Fisher T, Jesien R, Kumer J, Longstaff BJ, Radcliffe G, Schupp C, Sturgis B, Wazniak C, Wicks EC, Williams MR and Zimmerman C (2009) Assessing the Coastal Bays of Maryland and Virginia: A comparison of approaches. IAN Press, Cambridge, MD, 1pp (Poster)
Dennison WC and Carruthers TJB (2009) Tools for effective science communication. IAN Press, Cambridge, MD, 26pp (Presentation)
Integration and Application Network (2009) Rock Creek Park Natural Resource Condition Assessment. IAN Press, Cambridge, MD, 156pp (Report)
William C. Dennison, Jane E. Thomas, Carol J. Cain, Tim J.B. Carruthers, Matthew R. Hall, Roman V. Jesien, Catherine E. Wazniak, & David E. Wilson (2009) Shifting Sands: Environmental and cultural change in Maryland's Coastal Bays. IAN Press, Cambridge, MD, 418pp (Book)
Integration and Application Network (2009) Development of water transparency criteria for Florida seagrasses. IAN Press, Cambridge, MD, 4pp (Newsletter)
Integration and Application Network (2009) South Caucasus region transboundary report card. IAN Press, Cambridge, MD, 4pp (Report card)
Integration and Application Network (2009) South Caucasus region transboundary report card (Russian). IAN Press, Cambridge, MD, 4pp (Report card)
Integration and Application Network (2009) New Stream Health Indicator Being Developed. IAN Press, Cambridge, MD, 3pp (Newsletter)
Integration and Application Network (2009) 2008 Chester River report card. IAN Press, Cambridge, MD, 4pp (Report card)
Integration and Application Network (2009) 2008 Patuxent River Report Card. IAN Press, Cambridge, MD, 4pp (Report card)
Petersen JE, Kennedy VS, Dennison WC and Kemp WM (Eds.) (2009) Enclosed Experimental Ecosystems and Scale: Tools for Understanding and Managing Coastal Ecosystems. IAN Press, Cambridge, MD (Book)
Integration and Application Network (2009) Northern Great Plains Network: Using conceptual diagrams to aid communication. IAN Press, Cambridge, MD, 3pp (Newsletter)
2008
Integration and Application Network (2008) Oyster δ15N as a bioindicator of waste nitrogen and degraded water quality in a sub-estuary of Chesapeake Bay. IAN Press, Cambridge, MD, 1pp (Poster)
Integration and Application Network (2008) River Journeys. IAN Press, Cambridge, MD (Book)
Integration and Application Network (2008) Upstream land use affects water quality in Maryland's Coastal Bays. IAN Press, Cambridge, MD, 3pp (Newsletter)
Integration and Application Network (2008) Environmental report cards: A tool for better management,  monitoring, and research. IAN Press, Cambridge, MD, 1pp (Poster)
Integration and Application Network (2008) Chesapeake Bay 2007: Land Use and the Chesapeake Bay Report Card. IAN Press, Cambridge, MD, 4pp (Newsletter)
Beckert K, Fertig BM, O'Neil JM, Carruthers TJB, Wazniak C, Sturgis B, Hall M, Jones AB and Dennison WC (2008) Fine scale patterns of water quality in three regions of Marylands Coastal Bays: assessing nitrogen source in relation to land use. IAN Press, Cambridge, MD, 55pp (Report)
Integration and Application Network (2008) Reef Plan Monitoring: Marine Water Quality Impacts. IAN Press, Cambridge, MD, 3pp (Newsletter)
Integration and Application Network (2008) Watershed condition assessment for Rock Creek Park in the National Capital Region. IAN Press, Cambridge, MD, 54pp (Presentation)
Beckert K, Fertig BM, O'Neil JM, Carruthers TJB, Dennison WC and Fisher T (2008) Fine scale patterns of water quality in three regions of Maryland's Coastal Bays: assessing nitrogen source in relation to land use. IAN Press, Cambridge, MD, 32pp (Presentation)
Integration and Application Network (2008) Inventory and Monitoring Program, Pacific Island Network, National Park Service. IAN Press, Cambridge, MD, 4pp (Newsletter)
Integration and Application Network (2008) Ala Kahakai National Historic Trail. IAN Press, Cambridge, MD, 1pp (Poster)
Integration and Application Network (2008) Kaloko-Honokohau National Historical Park. IAN Press, Cambridge, MD, 1pp (Poster)
Integration and Application Network (2008) Pu'ukohola Heiau National Historic Site. IAN Press, Cambridge, MD, 1pp (Poster)
Integration and Application Network (2008) Pu'uhonua o Honaunau National Historic Park. IAN Press, Cambridge, MD, 1pp (Poster)
2007
Integration and Application Network (2007) A summer of poor water clarity, algal blooms, and fish kills. IAN Press, Cambridge, MD, 4pp (Newsletter)
Bricker S, Longstaff BJ, Dennison WC, Jones AB, Boicourt K, Wicks EC and Woerner JL (2007) National Estuarine Eutrophication Assessment: A Decade of Change. IAN Press, Cambridge, MD, 15pp (Presentation)
Lane H, Woerner JL, Dennison WC, Neill C, Wilson C, Elliott M, Shively M, Graine J and Jeavons R (2007) Defending our National Treasure: A Department of Defense Chesapeake Bay Restoration Partnership 1998-2004. IAN Press, Cambridge, MD, 176pp (Book)
Integration and Application Network (2007) 2006 Chesapeake Bay health report card. IAN Press, Cambridge, MD, 29pp (Presentation)
Integration and Application Network (2007) Synthesising research, management, and monitoring. IAN Press, Cambridge, MD, 1pp (Poster)
Integration and Application Network (2007) Supporting management through an annual cycle of ecological forecasting and assessment. IAN Press, Cambridge, MD, 1pp (Poster)
Fertig BM, Carruthers TJB and Dennison WC (2007) Linking Monie Bay watershed land use to nitrogen stable isotopes in tissues of the native eastern oyster, Crassostrea virginica. IAN Press, Cambridge, MD, 76pp (Report)
Integration and Application Network (2007) Protecting Palau's natural heritage. IAN Press, Cambridge, MD, 3pp (Newsletter)
Bricker S, Longstaff BJ, Dennison WC, Jones AB, Boicourt K, Wicks EC and Woerner JL (2007) Effects of nutrient enrichment in the Nation's estuaries: A decade of change. National Centers for Coastal Ocean Science, Silver Spring, MD, 328pp (Report)
Integration and Application Network (2007) Effects of nutrient enrichment in the Nation's estuaries: A decade of change. IAN Press, Cambridge, MD, 1pp (Poster)
Integration and Application Network (2007) Chesapeake Bay 2007: Summer Ecological Forecast. IAN Press, Cambridge, MD, 4pp (Newsletter)
Integration and Application Network (2007) Morro Bay: working together for a healthy ecosystem. IAN Press, Cambridge, MD, 3pp (Newsletter)
Integration and Application Network (2007) Morro Bay: working together for a healthy ecosystem. IAN Press, Cambridge, MD, 1pp (Poster)
Integration and Application Network (2007) Measuring the Health of our National Parks: Rock Creek Park. IAN Press, Cambridge, MD, 3pp (Newsletter)
Integration and Application Network (2007) Calculating the 2006 Chesapeake Bay report card scores. IAN Press, Cambridge, MD, 3pp (Newsletter)
Integration and Application Network (2007) Chesapeake Bay Habitat Health Report Card: 2006. IAN Press, Cambridge, MD, 6pp (Report card)
Integration and Application Network (2007) Biological indicators enhance water quality monitoring in Maryland's Coastal Bays. IAN Press, Cambridge, MD, 4pp (Newsletter)
Dennison WC, Nuttle W and Wicks EC (2007) Assessment of Coastal Management and Science Needs in South Florida. IAN Press, Cambridge, MD, 50pp (Report)
Integration and Application Network (2007) The role of benthic communities in the health of Maryland's Coastal Bays. IAN Press, Cambridge, MD, 4pp (Newsletter)
2006
Integration and Application Network (2006) National Capital Region Network Regional Overview. IAN Press, Cambridge, MD, 1pp (Poster)
Integration and Application Network (2006) Harmful algal blooms: Maryland status and trends newsletter. IAN Press, Cambridge, MD, 3pp (Newsletter)
Integration and Application Network (2006) Antietam National Battlefield. IAN Press, Cambridge, MD, 1pp (Poster)
Integration and Application Network (2006) Catoctin Mountain Park. IAN Press, Cambridge, MD, 1pp (Poster)
Integration and Application Network (2006) George Washington Memorial Parkway. IAN Press, Cambridge, MD, 1pp (Poster)
Integration and Application Network (2006) Chesapeake & Ohio Canal National Historical Park. IAN Press, Cambridge, MD, 1pp (Poster)
Integration and Application Network (2006) Harpers Ferry National Historical Park. IAN Press, Cambridge, MD, 1pp (Poster)
Integration and Application Network (2006) Manassas National Battlefield Park. IAN Press, Cambridge, MD, 1pp (Poster)
Integration and Application Network (2006) Monocacy National Battlefield Park. IAN Press, Cambridge, MD, 1pp (Poster)
Integration and Application Network (2006) National Capital Parks-East. IAN Press, Cambridge, MD, 1pp (Poster)
Integration and Application Network (2006) Prince William Forest Park. IAN Press, Cambridge, MD, 1pp (Poster)
Integration and Application Network (2006) Rock Creek Park. IAN Press, Cambridge, MD, 1pp (Poster)
Integration and Application Network (2006) Wolf Trap National Park for the Performing Arts. IAN Press, Cambridge, MD, 1pp (Poster)
Fertig BM, Carruthers TJB, Wazniak C, Sturgess B, Hall M, Jones AB, and Dennison WC (2006) Water quality in four regions of the Maryland Coastal Bays: assessing nitrogen source in relation to rainfall and brown tide. IAN Press, Cambridge, MD, 50pp (Report)
Le Tissier MDA, Buddemeier R, Parslow J, Swaney DP, Crossland CJ, Smith SV, Whyte HAY, Dennison WC, Hills JM and Kremer HH (eds) (2006) The role of the coastal ocean in the disturbed and undisturbed nutrient and carbon cycles: A management perspective. Land-Ocean Interactions in the Coastal Zone (LOICZ), 44pp (Report)
Integration and Application Network (2006) A global crisis for seagrass ecosystems?. IAN Press, Cambridge, MD, 27pp (Presentation)
Integration and Application Network (2006) Ecosystem health report cards: an approach to integrated assessment. IAN Press, Cambridge, MD, 1pp (Poster)
Thomas JE, Saxby TA, Jones AB, Carruthers TJB, Abal EG and Dennison WC (2006) Communicating Science Effectively: A Practical Handbook for Integrating Visual Elements. IWA Publishing, London (Book)
Longstaff BJ, Dennison WC, Batiuk R, Sylvester N, Haywood C, Conner C and Williams M (2006) Indicator and communication redesign effort: Progress and development of a spatial health index. IAN Press, Cambridge, MD, 28pp (Presentation)
Integration and Application Network (2006) A Conceptual Basis for Natural Resource Monitoring. IAN Press, Cambridge, MD, 36pp (Report)
Integration and Application Network (2006) 2006 Summer Ecological Forecast Media Briefing. IAN Press, Cambridge, MD, 34pp (Presentation)
Integration and Application Network (2006) An Eye Opening Approach to Integrated Environmental Assessments. IAN Press, Cambridge, MD, 1pp (Poster)
2005
Integration and Application Network (2005) Seagrasses of Southwest Australia. IAN Press, Cambridge, MD, 1pp (Poster)
Integration and Application Network (2005) Seagrasses of Southwest Australia: Estuaries. IAN Press, Cambridge, MD, 1pp (Poster)
Integration and Application Network (2005) Seagrasses of Southwest Australia: South Coast. IAN Press, Cambridge, MD, 1pp (Poster)
Integration and Application Network (2005) Seagrasses of Southwest Australia: West Coast. IAN Press, Cambridge, MD, 1pp (Poster)
Integration and Application Network (2005) Utilizing spatially intensive data in monitoring Maryland's Coastal Bays. IAN Press, Cambridge, MD, 1pp (Poster)
Integration and Application Network (2005) Developing a classification system for Caribbean seagrass communities. IAN Press, Cambridge, MD, 24pp (Presentation)
Integration and Application Network (2005) Bay Grass Restoration in Chesapeake Bay. IAN Press, Cambridge, MD, 4pp (Newsletter)
Integration and Application Network (2005) The role of educators in solving coastal environmental problems: imparting knowledge, power and passion in students. IAN Press, Cambridge, MD, 46pp (Presentation)
Zhang X, Wood RJ, Roman M, Longstaff BJ and Dennison WC (2005) Potential effects of nutrient reduction on the variability of plankton abundance and composition. IAN Press, Cambridge, MD, 1pp (Poster)
Orth, RJ and Dennison WC (2005) Aquatic grass: 2004 update and 2005 forecast. IAN Press, Cambridge, MD, 25pp (Presentation)
Integration and Application Network (2005) Summer Ecological Forecast. IAN Press, Cambridge, MD, 11pp (Presentation)
Integration and Application Network (2005) Ecosystem Assessment and Ecological Forecasting Project. IAN Press, Cambridge, MD, 1pp (Poster)
Integration and Application Network (2005) Zen and the art of science communication at Parks Canada. IAN Press, Cambridge, MD, 46pp (Presentation)
Integration and Application Network (2005) Chesapeake Bay Environmental Models. IAN Press, Cambridge, MD, 4pp (Newsletter)
Integration and Application Network (2005) Zen and the art of science communication at National Parks. IAN Press, Cambridge, MD, 46pp (Presentation)
2004
Integration and Application Network (2004) Restoration of aquatic grass communities of Chesapeake Bay: How should we proceed?. IAN Press, Cambridge, MD, 20pp (Presentation)
Jones AB, Carruthers TJ, Pantus F, Thomas JE, Saxby TA and Dennison, WC (2004) A water quality assessment of the Maryland Coastal Bays including nitrogen source identification using stable isotopes. IAN Press, Cambridge, MD, 60pp (Report)
Integration and Application Network (2004) Developing a global seagrass synthesis: Integrating ecophysiology, genetics, monitoring and management initiatives to understand and preserve seagrasses. IAN Press, Cambridge, MD, 55pp (Presentation)
Integration and Application Network (2004) New directions in environmental science: Moving into Pasteur's Quadrant. IAN Press, Cambridge, MD, 46pp (Presentation)
Integration and Application Network (2004) Conceptual diagrams: tools for science communication. IAN Press, Cambridge, MD, 1pp (Poster)
Wazniak C, Hall M, Cain C, Wilson D, Jesien R, Thomas JE, Carruthers TJB and Dennison WC (2004) State of the Maryland Coastal Bays 2004. IAN Press, Cambridge, MD, 48pp (Report)
Turner L, Tracey D, Tilden J and Dennison WC (2004) Where river meets sea: exploring Australia's estuaries. CSIRO Publishing (Book)
Integration and Application Network (2004) Proposal Writing: A Key to Success. IAN Press, Cambridge, MD, 19pp (Presentation)
Integration and Application Network (2004) Solving coastal environmental problems around the world and in the Chesapeake. IAN Press, Cambridge, MD, 47pp (Presentation)
Integration and Application Network (2004) Solving Environmental Problems: The Role of Science in Developing Spatially Explicit Ecosystem Health Assessments. IAN Press, Cambridge, MD, 55pp (Presentation)
Integration and Application Network (2004) Developing a Chesapeake Bay Report Card. IAN Press, Cambridge, MD, 1pp (Poster)
2003
Jones AB, Dennison WC and Pantus F (2003) Assessment of sewage and septic derived nitrogen in the Choptank and Patuxent Rivers. IAN Press, Cambridge, MD, 93pp (Report)
Integration and Application Network (2003) Zen and the art of science communication. IAN Press, Cambridge, MD, 49pp (Presentation)
Integration and Application Network (2003) Chesapeake Bay report card: Providing effective feedback for resource management. IAN Press, Cambridge, MD, 47pp (Presentation)
Integration and Application Network (2003) The art of science communication: using PowerPoint effectively. IAN Press, Cambridge, MD, 67pp (Presentation)
Integration and Application Network (2003) Nutrient limitation in coastal waters: The Moreton Bay, Australia case study. IAN Press, Cambridge, MD, 19pp (Presentation)
Integration and Application Network (2003) Assessing Nutrient Sources in Tidal Waters. IAN Press, Cambridge, MD, 17pp (Presentation)
Integration and Application Network (2003) University of Maryland Center for Environmental Science: History, Mission & Accomplishments. IAN Press, Cambridge, MD, 4pp (Newsletter)
2002
Integration and Application Network (2002) Conceptual Diagrams: A tool for science communication. IAN Press, Cambridge, MD, 67pp (Presentation)
Integration and Application Network (2002) Environmental problem solving in coastal regions. IAN Press, Cambridge, MD, 46pp (Presentation)
Integration and Application Network (2002) Submarine Springs and Sewage. IAN Press, Cambridge, MD, 1pp (Poster)
Integration and Application Network (2002) Balancing limitation and excess: ecophysiological implications for seagrass survival. IAN Press, Cambridge, MD, 28pp (Presentation)
Integration and Application Network (2002) Assessing ecosystem health in coastal waters. IAN Press, Cambridge, MD, 33pp (Presentation)
Integration and Application Network (2002) Vision for IAN. IAN Press, Cambridge, MD, 28pp (Presentation)

Media

Browse all media articles featuring Bill Dennison

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ABC News (Fri 13 Jan, 2012)
Bold Plan Proposed to Save Coastal Louisiana

The Boston Globe (Thu 12 Jan, 2012)
Bold plan proposed to save coastal Louisiana

The Statesman (Austin) (Thu 12 Jan, 2012)
Bold plan proposed to save coastal Louisiana

KSRO 1350AM (Santa Rosa) (Thu 12 Jan, 2012)
Bold plan proposed to save coastal Louisiana

KTRE 9 News (Thu 12 Jan, 2012)
Bold plan proposed to save coastal Louisiana

Anchorage Daily News (Thu 12 Jan, 2012)
Bold plan proposed to save coastal Louisiana

The Washington Post (Thu 12 Jan, 2012)
Facing land loss crisis, Louisiana proposes bold plan to save coast with $50B

Chesapeake Bay Journal (Fri 6 Jan, 2012)
Plan to make Baltimore Harbor swimmable, fishable by 2020 unveiled

Seafood Business (Thu 5 Jan, 2012)
Going Green: Comeback crabs - Ecological improvements aid Chesapeake Bay blue crab stock

Chesapeake Bay Action Plan (Wed 4 Jan, 2012)
2012: Changing the Dialogue About Chesapeake Restoration

NBC Washington (Fri 23 Dec, 2011)
Baltimore Aims to Make Inner Harbor Swimmable by 2020 - Planner: "I would definitely not consider swimming in the harbor right now"

WAMU (NPR) News (Thu 22 Dec, 2011)
Baltimore Aims To Make Inner Harbor Swimmable By 2020

Chesapeake Bay Action Plan (Mon 19 Dec, 2011)
3 Good Science News Stories

WJZ (Baltimore) Television (Wed 14 Dec, 2011)
Alliance Of Businesses & Local Govts. Working To Clean Inner Harbor Waters

The Baltimore Sun B'More Green Blog (Wed 14 Dec, 2011)
Harbor cleanup plan stirs hope - what now? Abell foundation chips in for water monitoring

WJZ (Baltimore) Television (Tue 13 Dec, 2011)
Report: Inner Harbor Most Polluted Water In Maryland

The Houston Chronicle (Wed 7 Dec, 2011)
Scientists working on report card for Gulf's health

Chesapeake Bay Action Plan (Thu 10 Nov, 2011)
Finally, some good news! Shrinking dead zones linked to nutrient reductions

The Baltimore Sun B'More Green Blog (Thu 15 Sep, 2011)
Storm that fouled Bay tests restoration efforts

The Baltimore Sun B'More Green Blog (Fri 9 Sep, 2011)
Noah's Bay - flooding adds to Chesapeake's woes

The Baltimore Sun (Fri 2 Sep, 2011)
Hurricane Irene leaves sewage spills in wake - Overflows a byproduct of inadequate upkeep, officials say

Charles Darwin University Newsroom (Fri 10 Jun, 2011)
CDU plays host to harbour studies expert

7.30 Report (Thu 27 Jan, 2011)
Scientists assess flood impact to Moreton Bay

Patch.com (Mon 17 Jan, 2011)
A River Geek's Pick of One of the Great Reads from 2010

Patch.com (Tue 14 Dec, 2010)
The Magic in a Bottle of Potomac River Water

The Annapolis Capital (Sat 20 Nov, 2010)
Digest: Experts launch bay 'action plan' blog

Bay Journal (Mon 1 Nov, 2010)
New USGS method improves ability to track nutrients flowing into Bay

WBOC (Salisbury) Television (Fri 1 Oct, 2010)
$491M in Federal Money Target Toward Bay Restoration

The Baltimore Sun (Thu 16 Sep, 2010)
Chesapeake Bay progress uneven, study shows

The Baltimore Sun (Thu 1 Jul, 2010)
Coastal bays maintain C+ rating

WJZ (Baltimore) Television (Wed 30 Jun, 2010)
Study Shows 2010 May Be Healthy Summer For Bay

The Baltimore Sun (Wed 23 Jun, 2010)
Bay 'dead zone' forecast smaller this summer

The Annapolis Capital (Wed 23 Jun, 2010)
Bay 'dead zone' could be smaller

University or Maryland's News 21 (Mon 14 Jun, 2010)
Chesapeake Bay Swim Attracts Hundreds in Balmy Conditions, But Course Includes a 'Dead Zone'

Bay Journal (Tue 1 Jun, 2010)
Scientists give Bay's health a C, up from last year

The Washington Post First Click Blog (Thu 20 May, 2010)
Quotables

The Baltimore Sun (Wed 19 May, 2010)
Bay's health improves slightly, scientists say

The Easton Star Democrat (Wed 19 May, 2010)
Report: Clarity increased in Choptank River watershed

The Baltimore Sun B'More Green Blog (Tue 18 May, 2010)
Chesapeake Bay's health improves slightly, scientists say

The Associated Press (Tue 18 May, 2010)
Chesapeake Bay gets C grade on health in report

The Annapolis Capital (Tue 18 May, 2010)
Grade for bay health: C

WJZ (Baltimore) Television (Tue 18 May, 2010)
Chesapeake Bay Gets C On Annual Health Report Card

The Baltimore Sun (Tue 18 May, 2010)
Bay's health improves slightly, scientists say

WYPR (NPR) Radio (Thu 15 Apr, 2010)
Return of an Underwater Forest (Audio)

The Annapolis Capital (Tue 30 Mar, 2010)
Heavy rainfall, snow may hurt bay

The Washington Post (Sat 13 Feb, 2010)
Rapid melting of record snowfall could harm waterways, aquatic life

Bay Journal (Mon 1 Feb, 2010)
Longtime Bay advocates say draft strategy falls short: Critics say stronger actions need to be taken to control pollution from agriculture and development

Northern Neck News (Wed 13 Jan, 2010)
Bay foundation doubts mandate enforcement

The Easton Star Democrat (Thu 31 Dec, 2009)
Group pushing new initiatives for Bay

The Baltimore Sun B'More Green Blog (Thu 31 Dec, 2009)
"Eagles" join fray over restoring Bay

WJZ (Baltimore) Television (Wed 30 Dec, 2009)
Bay Advocates Send Obama Restoration Strategy

Newschannel 8 (DC) (Wed 30 Dec, 2009)
Bay Advocates Dissatisfied by EPA's Proposal

The Associated Press (Wed 30 Dec, 2009)
Bay advocates send Obama restoration strategy

WBAL (Baltimore) Radio (Wed 30 Dec, 2009)
Bay Panel Wants Mandatory Pollution Control

The Maryland Gazette Newspapers (Wed 16 Dec, 2009)
Briefs: Bay 'dead zone' still bad in '09

The Washington Post (Wed 2 Dec, 2009)
Planet Panel - Yes, no, maybe so

The Annapolis Capital (Fri 27 Nov, 2009)
Bay 'dead zone' still bad in '09: But scientists have new knowledge of how it works

NPR's All Things Considered (Mon 9 Nov, 2009)
EPA Drafts Chesapeake Bay Cleanup Strategy

The Baltimore Sun (Wed 29 Jul, 2009)
Bay's 'dead zone' reported at normal size

The Associated Press (Wed 29 Jul, 2009)
Chesapeake Bay 'dead zone' reaches usual size

WJZ (Baltimore) Television (Wed 29 Jul, 2009)
Chesapeake Bay 'Dead Zone' Reaches Usual Size

The Baltimore Sun B'More Green Blog (Mon 27 Jul, 2009)
Bay 'dead zone' bigger than predicted

WJZ (Baltimore) Television (Fri 17 Jul, 2009)
Disappearance Of Underwater Grasses Causes Concern (Video)

United Press International (Tue 7 Jul, 2009)
Seagrass beds are dying worldwide

Reuters (Thu 2 Jul, 2009)
Loss of world's seagrass beds seen accelerating

Mongabay.com (Tue 30 Jun, 2009)
Coastal seagrass disappearing as quickly as coral reefs and rainforests

WMDT (Salisbury) Television (Tue 30 Jun, 2009)
MD Governor Addresses Bay Concerns In Ocean City

The Associated Press (Mon 29 Jun, 2009)
Study: Coastal seagrass increasingly being lost

WBOC (Salisbury) Television (Wed 10 Jun, 2009)
Environmentalists Release Report Card on Coastal Bays (Video)

The Baltimore Sun (Tue 9 Jun, 2009)
Coastal bays are degrading: String of fragile lagoons west of Ocean City given a C-plus in first report card

The Annapolis Capital (Sat 6 Jun, 2009)
Commentary: Tipping points for the bay

The Baltimore Sun (Tue 12 May, 2009)
O'Malley vows to speed rivers cleanup: Aggressive multistate effort would set deadlines to reduce pollution runoff to bay

The Annapolis Capital (Tue 12 May, 2009)
Chesapeake Bay showing signs of recovery: As officials consider new cleanup goals, optimism surfaces about pollution

WYPR (NPR) - Maryland Morning Radio Program (Tue 12 May, 2009)
Some Improvement in Maryland River Water Quality

WJZ (Baltimore) Television (Mon 11 May, 2009)
Governor Examines Chesapeake Tributary (Video)

WYPR (NPR) - Maryland Morning Radio Program (Wed 6 May, 2009)
Bountiful Bay Grasses? (Audio)

Bay Journal (Fri 1 May, 2009)
Report card gives Bay health a C- despite slight improvement: Project finds that best areas are getting better while worst areas are getting worse

Bay Journal (Fri 1 May, 2009)
Plan to cut Bay monitoring programs raises concerns: Proposal is part of move to shift more emphasis on actions taken upstream

The Baltimore Sun (Thu 30 Apr, 2009)
Bay grass rebound reported: Aerial surveys show 18-percent boost since 2007

The Baltimore Sun (Wed 15 Apr, 2009)
Septic system measure praised: Legislation seen as a boost for the Chesapeake

The Washington Times (Wed 15 Apr, 2009)
Bay gets C-minus

Environment News Service (Mon 13 Apr, 2009)
Chesapeake Bay Scores C-Minus on Health Report Card

The Maryland Gazette Newspapers (Tue 7 Apr, 2009)
Development muddies paradise on Patuxent River: River slightly healthier, but researchers warn against optimism

The Annapolis Capital (Mon 6 Apr, 2009)
Water quality failing in West, Rhode rivers

The Easton Star Democrat (Sun 5 Apr, 2009)
Chesapeake Bay health gets C-minus

The Washington Examiner (Fri 3 Apr, 2009)
Chesapeake Bay report sees bright spots despite overall stagnation

The Baltimore Sun (Fri 3 Apr, 2009)
Bay's health earns C-minus: Researchers say Chesapeake's vitality still poor

The Annapolis Capital (Fri 3 Apr, 2009)
County's rivers flunk health test: UM report card gives F to rivers, C- to bay

The Associated Press (Thu 2 Apr, 2009)
Report: Much of Chesapeake Bay remains unhealthy

The Baltimore Sun - Bay and Environment Blog (Thu 2 Apr, 2009)
Bay report cards - grading on a curve?

WJZ (Baltimore) Television (Thu 2 Apr, 2009)
Report: Chesapeake Bay Remains Unhealthy (Video)

WAMU (NPR) News (Thu 2 Apr, 2009)
Chesapeake Bay Continues to Suffer (Audio)

Capital News Service Television (Thu 2 Apr, 2009)
Chesapeake Grade (Video)

The Annapolis Capital (Tue 31 Mar, 2009)
Severn report card: C-minus - Bright spot found in underwater grasses

WJZ (Baltimore) Television (Mon 30 Mar, 2009)
Severn River Described As Being 'In Trouble' (Video)

The Baltimore Sun (Fri 20 Mar, 2009)
Bay's health not getting better, EPA says: Report for 2008 finds cleanup efforts inadequate

The Baltimore Sun - Bay and Environment Blog (Fri 20 Mar, 2009)
EPA's 'Bay barometer' - still too sunny?

The Annapolis Capital (Thu 19 Mar, 2009)
New report: Bay's health still in trouble: Assessment suggests stricter measures

Capital News Service (Thu 19 Mar, 2009)
Report: Bay Health 'Severely Degraded'

The Easton Star Democrat (Mon 16 Mar, 2009)
Shuttle blasts off with Bowie native aboard: Former Horn Point graduate student one of two science teachers on flight

The Baltimore Sun (Wed 11 Mar, 2009)
Teacher bound for space: Former Md. man joining shuttle crew for Wednesday night's launch

WTTG (Washington) Television (Tue 10 Mar, 2009)
Local Astronaut to Space (Video)

Bay Journal (Thu 1 Jan, 2009)
Scientists, policy leaders unite, argue for more aggressive cleanup: Citing lack of progress, group calls voluntary, collaborative effort 'fatally flawed.'

Bay Weekly (Thu 11 Dec, 2008)
Scientists in Wonderland: Now everybody knows the Chesapeake has a problem

The Baltimore Sun (Tue 9 Dec, 2008)
Group calls for better bay restoration effort

The Annapolis Capital (Tue 9 Dec, 2008)
Editorial: Experts call for action on bay - is anyone listening? Sometimes the most important thing is not what gets said but who says it.

WTOP Radio News (Mon 8 Dec, 2008)
Experts: Chesapeake Bay program has failed

The Baltimore Sun (Sun 28 Sep, 2008)
Tainted Waters: Despite a generation of efforts to clean up the Chesapeake, development and farming along Maryland's rivers still foul the bay

WYPR (NPR) Radio (Fri 29 Aug, 2008)
Examining the Future of the Bay

WTOP Radio News (Tue 5 Aug, 2008)
Climate change takes toll on waterways

The Annapolis Capital (Sat 2 Aug, 2008)
The Dead Zone

WTOP Radio News (Mon 28 Jul, 2008)
Water clarity murky in Chesapeake

The Baltimore Sun (Wed 16 Jul, 2008)
More corn seen increasing 'dead zones': Large acreage raises concern for bay, gulf

The Baltimore Sun (Mon 14 Jul, 2008)
Saving the shoreline, one parcel at a time: A conservation group is targeting miles of undeveloped land along the Chesapeake Bay and its tributaries for preservation

Bay Journal (Tue 1 Jul, 2008)
Ecological report cards getting good marks for attracting public's attention: Researchers are working to establish consistency in collecting and interpreting data

Bay Journal (Tue 1 Jul, 2008)
Scientists predict widespread low-oxygen conditions in Bay's mainstem

WBFF (Baltimore) Television (Thu 26 Jun, 2008)
Polluted Rivers (Video)

WJZ (Baltimore) Television (Sun 22 Jun, 2008)
This Summer Could Lead To More Dead Fish In Harbor

The Baltimore Sun (Thu 19 Jun, 2008)
Bad times forecast for bay and rivers

The Richmond Times Dispatch (Thu 19 Jun, 2008)
Bad summer forecast for bay - Report: Nitrogen levels up because of 2008's heavy rains Heavy rain has washed lots of nitrogen into the Chesapeake, a report says

The Annapolis Capital (Wed 18 Jun, 2008)
Forecast: Bay health will be poor this summer - 'Dead zone' will stretch from Bay Bridge to Calvert

WTOP Radio News (Wed 18 Jun, 2008)
Polluted Chesapeake to hurt crab, oyster seasons

Bay Weekly (Thu 22 May, 2008)
Low Marks for Our Watershed: To get its grades up, Chesapeake Bay's waterways need you

The Prince George's Gazette (Thu 1 May, 2008)
Patuxent River given D-minus: First overall health assessment faults suburban and urban growth

Bay Journal (Thu 1 May, 2008)
Reports reveal a degraded Chesapeake despite restoration efforts

The Baltimore Examiner (Tue 29 Apr, 2008)
Bay grass growth promising, but misses goal, survey says

The Washington Post (Sun 27 Apr, 2008)
Patuxent Gets D-Minus In First River Health Test

The Baltimore Examiner (Tue 22 Apr, 2008)
Can the Chesapeake Bay survive the garbage choking Maryland's rivers?

The Annapolis Capital (Tue 22 Apr, 2008)
Bad grades for Patuxent on report card

WYPR (NPR) Radio (Mon 7 Apr, 2008)
Chesapeake Bay Program Releases Its Latest Report Card

The Easton Star Democrat (Mon 7 Apr, 2008)
Bay's grade shows slight improvement: Choptank improves to D+, but drought may be biggest factor in better scores

The Annapolis Capital (Sun 6 Apr, 2008)
Editorial: Unfortunately, latest bad news on bay no surprise

The Richmond Times Dispatch (Fri 4 Apr, 2008)
Reports: Chesapeake Bay cleanup progress lags

The Baltimore Sun (Fri 4 Apr, 2008)
Pollution surveys offer grim news on bay tributaries: Two reports cite pollution, low oxygen levels

The Hampton Roads Daily Press (Fri 4 Apr, 2008)
New homes hurting Chesapeake Bay: "Report cards" say more people funnel more pollution into the bay, slowing the cleanup progress.

The Norfolk Virginian Pilot (Fri 4 Apr, 2008)
Efforts to clean up Bay falling short, report says

The Baltimore Examiner (Fri 4 Apr, 2008)
Bay tributary report cards poor

Environment News Service (Fri 4 Apr, 2008)
Chesapeake Bay Suffering, Restoration Efforts Treading Water

The Annapolis Capital (Thu 3 Apr, 2008)
Bad grades for bay on report card: Anne Arundel's rivers score D-

WJZ (Baltimore) Television (Thu 3 Apr, 2008)
Bay's Health Continues To Be A Concern

The Sarasota Herald Tribune (Tue 1 Apr, 2008)
New way to gauge Sarasota waters' ongoing health

The Easton Star Democrat (Sun 6 Jan, 2008)
From Bowie to the final frontier: Adventurer Richard Arnold to launch with space shuttle Discovery

The Associated Press (Sun 16 Dec, 2007)
Activists push for Chesapeake's future

The Baltimore Sun (Sun 9 Dec, 2007)
Troubled tributary: Runoff, growth turn the Choptank into Md.'s second-most polluted river

The Associated Press (Mon 3 Dec, 2007)
Environmental Report: Chesapeake Bay Health Worsening

The Diamondback (Fri 2 Nov, 2007)
Alumnus preps for blast off

Science Daily (Sat 20 Oct, 2007)
Coastal Habitats Are The Biosphere's Most Imperiled Ecosystems

WYPR (NPR) Radio (Fri 12 Oct, 2007)
Drought Brings Mixed Results To Chesapeake

WYPR (NPR) Radio (Tue 4 Sep, 2007)
Patapsco, Back Rivers Get Poor Environmental Marks

WYPR (NPR) Radio (Tue 28 Aug, 2007)
Environmental Reports Grade Severn, Patuxent Rivers

WYPR (NPR) Radio (Tue 21 Aug, 2007)
Environmental Report Cards for Corsica and Chester Rivers

The Hampton Roads Daily Press (Tue 12 Jun, 2007)
Chesapeake Bay's health still cause for concern: It's business as usual for the bay this summer, but that means conditions haven't improved, despite the work that's been done.

The (MD) Daily Record (Mon 11 Jun, 2007)
Bay's health unimproved: Environmentalists say if the forecast is correct, more will have to be done

The Associated Press (Mon 11 Jun, 2007)
Md. Agency Unveils Bay's Health Forecast: Chesapeake Bay Program Unveils Summer Forecast That Predicts Recurrence Of Low-Oxygen Zones

The Annapolis Capital (Mon 11 Jun, 2007)
Bay dead zone to be 'bad as usual'

Bay Journal (Tue 1 May, 2007)
Out of Shape: No matter how one looks at it, Bay's health fails to make the grade

Bay Journal (Tue 1 May, 2007)
Chesapeake Bay Report Card's goal is to challenge regions to strive harder

Bay Journal (Tue 1 May, 2007)
Chesapeake's SAV acreage down 25%; lowest level since 1989: Eelgrass beds in high-salinity areas took major hit

The College of William & Mary Flat Hat (Tue 1 May, 2007)
Chesapeake Bay Receives "D" minus on Health Report Card

The Baltimore Sun (Thu 19 Apr, 2007)
Bay is still hurting, 2 reports say: Quality of water called poor; loss of grasses noted

Science Daily (Thu 19 Apr, 2007)
Chesapeake Bay Ecosystem In Poor Shape, Says Researchers

The Annapolis Capital (Thu 19 Apr, 2007)
Bay cleanup not living up to expectations

WJZ Television (Baltimore) (Wed 18 Apr, 2007)
Report: Chesapeake Bay Is Not Healthy

The Associated Press (Wed 18 Apr, 2007)
Reports: Chesapeake Bay Health Pitiful

The Washington Post (Mon 19 Mar, 2007)
Warming Imperils Md. Species: Scientists Fear Loss Of Baltimore Oriole, Native Brook Trout

United Press International (Mon 19 Mar, 2007)
Birds and fish respond to climate change

The Baltimore Sun (Tue 13 Mar, 2007)
Officials pledge to shell out funds for oyster hatchery: O'Malley, Busch to seek $9 million in budget for Horn Point research

Environment Magazine (Thu 8 Feb, 2007)
Seagrasses in Dire Straits

Bay Journal (Mon 1 Jan, 2007)
Environmentally important underwater grass beds facing global crisis

The Indianapolis Star (Sun 10 Dec, 2006)
Declining seagrasses may be warning sign

Bay Weekly (Thu 7 Dec, 2006)
Way Downstream: Seagrasses

The Gulfport (MS) Sun Herald (Wed 6 Dec, 2006)
Seagrass mirrors all the ills of oceans: Marine scientists fear global crisis lies ahead

The Washington Post (Mon 4 Dec, 2006)
Science Notebook - Sea Grass Loss Said to Be Crisis

United Press International (Fri 1 Dec, 2006)
Sea grasses conservation efforts urged

Environment News Service (Fri 1 Dec, 2006)
Seagrass Ecosystems in Crisis

WYPR (NPR) - Maryland Morning Radio Program (Wed 15 Nov, 2006)
The Latest on the Health of the Chesapeake, and its Food Stock

The Associated Press (Mon 13 Nov, 2006)
Health of Chesapeake Bay gets low marks: Group cites minor improvements, issues 'D' on annual report card

Environment News Service (Fri 10 Nov, 2006)
Chesapeake Bay Summer Healthier Than Last Year

The Annapolis Capital (Sat 30 Sep, 2006)
Opinion - The next frontier: Ecological forecasting

Los Angeles Times (Sun 30 Jul, 2006)
A Primeval Tide of Toxins

The Washington Post (Sun 9 Jul, 2006)
Storms Leave the Bay Cloudy, With the Future No Brighter

The Annapolis Capital (Sat 1 Jul, 2006)
Toxic cocktail from heavy rainfall could devastate bay

Projects

Browse all projects for Bill Dennison

OR view individually:

Current Projects

Gulf of Mexico report card

Land Ocean Interactions in the Coastal Zone

Past Projects

Defending our National Treasure

Ecosystem Research and Coastal Management - Making the Connection on a Regional Scale

Global trajectories of seagrasses: Establishing a quantitative basis for seagrass conservation and restoration

Mesoamerican Reef Report Card

National Estuarine Eutrophication Assessment

Production of an Ecosystem Based Management Game

Science Communication Course

United Nations Environmental Programme - Ecosystem Based Management

Blog Posts

Browse all blog posts by Bill Dennison

OR view individually:

Brisbane 2011: Living with Floods and Dancing with Dugongs: Part 6- Global Initiatives in Response to Flooding

Brisbane 2011: Living with Floods and Dancing with Dugongs: Part 5- Preparing for Floods

Brisbane 2011: Living with Floods and Dancing with Dugongs: Part 4- The Brisbane River Renaissance

Brisbane 2011: Living with Floods and Dancing with Dugongs: Part 3- History of Flooding in Brisbane

Brisbane 2011: Living with Floods and Dancing with Dugongs: Part 2- A Learning Moment

Brisbane 2011: Living with Floods and Dancing with Dugongs: Part 1- Introduction

Coastal Louisiana Master Plan released

Australia reflections

Nutrient trading in Chesapeake Bay

Sabbatical reflections

Savai'i Island, Samoa; lava, blowholes, pigs, churches

Chesapeake citizens are well informed: New poll results of Maryland public perception of Chesapeake Bay restoration

Samoa; tsunamis, coral reefs, fishing, dredging

A visit to the Secretariat of the Pacific Regional Environment Programme, Samoa

Developing a Gulf of Mexico report card

Report card days of Christmas

Tim Carruthers moves to Samoa

Australian cities and waterways: Melbourne, Port Phillip Bay and the Yarra River

Australian cities and waterways: Sydney and Sydney Harbour

Australian cities and waterways: Brisbane, Moreton Bay and the Brisbane River

Australian cities and waterways: Connections, crossings, celebrations, and culture

Boggo Road Ecosciences Precinct; high tech laboratory on an old gaol site

Queenscliff, Bellarine peninsula and Victoria embayments

Communicating climate change via a melting ice bear

Seven attributes of a vibrant science group

Healthy Waterways Champion Award speech

Marine Botany lives on

Dugong Rock; Using iconic creatures in conservation

Flooding in Queensland: The story of the Paluma

The perspective from Australia's Top End; fishing, international waters, and invasive species

Darwin: Captain Wickham, Harriet the Tortoise, Alaskan similarities, and Darwinian art

Natural gas, live cattle, algal blooms & crocodiles: Darwin Harbour field trip

A virtual international collaboration producing conceptual diagrams

Developing a Swan River report card

A microcosm of the world's water quality problems: Peel-Harvey field trip

Swanlands: Western Australia estuaries

Sugarcane 101: Project Catalyst field trip

Sugar, Coca-Cola, WWF, clickers and scorecards

Reasons to be optimistic about sugarcane impacts on the Great Barrier Reef

Riparian Rhapsodies in Customs House

Walking tour of Brisbane (Part 3): Parliament, World War II and beyond

Walking tour of Brisbane (Part 2): Financial district, riverside and botanic gardens

Walking tour of Brisbane (Part 1): Parklands, City Hall and ANZAC

HMB Endeavour sets sail

The HMS Endeavour 'discovers' the Great Barrier Reef

Scientific discovery aboard the HMS Endeavour

Stoplight colors for environmental report cards

Creating a global symbol language

Dugong oil vat, sand mining and Geoff Moore

One Mile Harbour, Moreton Bay

Moreton Bay Research Station

Flood newsletter on seagrasses, turtles and dugongs

Mackay field trip #2: Sugarcane

Mackay field trip #1: Lagoons, champions and mangroves

"Rainbow Literature": Peer reviewed, colorful science communication products

New conceptual diagram worksheet developed

Dashboard books on fire: Communicating fire management creatively

TERN, TERN, TERN

TERN workshop

Storyboarding to generate a science newsletter

Launching the Healthy Waterways Alliance in Mackay

Dr. John Snow and Jack Maple, kindred spirits

Sea turtles, dugong and a major city skyline

Integrating science with people: Creating the corpus callosum connections

Discovering Southeast Queensland waterways and rediscovering Liz Clarke

Some Healthy Waterways history

Classifying environmental problems

Conceptual diagrams in a chapel

Discussion following Megan Ward seminar on Nanticoke Watershed Alliance: A New Model for Conservation

Discussion following Andrew Muller and Diana Muller seminar on Emerging hypoxia trends in the South River

International RiverFoundation

Celebrating Success: Healthy Waterways Awards

Flood newsletter on impacts to creeks, streambanks and paddocks

Experiential education: Changing the way we teach

Encountering Former Students

International WaterCentre field trip to North Stradbroke Island

South East Queensland 2011 flood newsletter

Lunch with Mayor Allan Sutherland in Redcliffe

Two Guys and a Tinny: Conducting estuarine assessments

Societal learning moments: The importance of timely, synthetic science communication

More Randy Alberte memories

Moreton Bay seagrasses after the flood

Queenslander!: The rallying cry for flood recovery

Queensland floods; 2011

Discussion following Bob Hirsch seminar on Are we making progress? Interpreting the nutrient flux records for the major rivers flowing to the Chesapeake Bay

Sabbatical in Queensland

Conceptionary in action: Learning through play

Bill Dennison speech to Latornell conference, Ontario, Canada: Part 8 - Communicating Science Effectively poster

Bill Dennison speech to Latornell conference, Ontario, Canada: Part 7 - O Canada!

Bill Dennison speech to Latornell conference, Ontario, Canada: Part 6 - Five step program for environmental report cards

Bill Dennison speech to Latornell conference, Ontario, Canada: Part 5 - Report card examples

Bill Dennison speech to Latornell conference, Ontario, Canada: Part 4 - Environmental Report Cards

Bill Dennison speech to Latornell conference, Ontario, Canada: Part 3 - History of Science Communication

Bill Dennison speech to Latornell conference, Ontario, Canada: Part 2 - Incorporating visual elements

Bill Dennison speech to Latornell conference, Ontario, Canada: Part 1 - Science Communication

Zanzibar seems like a dream

Notes from Zanzibar; Communicating science workshop

Notes from Zanzibar; arrival

Traveling to Zanzibar

Chesapeake Film Festival

Shari Wilson, Admiral of the Chesapeake Bay and Calliethos intellegente

Discussion following Don Weller seminar on Effects of riparian buffers on nitrate concentrations in watershed discharges: new models and management implications

Discussion following Margaret Palmer and Lisa Wainger seminar on Evidence-Based Restoration: Promoting Successful Restoration through Effective Monitoring and Adaptive Management

Remembering Randy Alberte

Sharing the iconic Jack Greer with the world

Discussion following Bob Wood's seminar on Climate forcing of fisheries production in Chesapeake Bay over the last century

Discussion following Bill Dennison's seminar on Challenges and advantages of using citizen scientists for environmental monitoring

Discussion following Walter Boynton's seminar on Where has all the nitrogen gone? Hot spots in the land and seascape

Communicating Science to Effect Social Change

How maps can lie: Chesapeake watershed stream health

Council for Environmental Deans & Directors summer conference; Boulder, Colorado

The Integration and Application Network 'tribe'

Ben Fertig's dissertation defense; 6 July 2010

Coastal Bays report card release

Discussion following Howard Townsend's seminar on Communicating complex scientific results for ecosystem-based management using cgi (computer generated image) animation

Annapolis walking tour

Joining Chesapeake Bay Scientific and Technical Advisory Committee

Visit with Grand River Conservation Authority

The Next Frontier: Ecological Forecasting

Great Barrier Reef report card workshop

Dr. Walter Boynton becomes Tidal Monitoring Analysis Workgroup chair

Chesapeake Bay report card release

Discussion following Kathy Boomer seminar on the role of watershed modeling in local land management decisions in Maryland communities

Reunited with Integration and Application Network alumni in Canada

Research Experience for Undergraduate students arrive at UMCES

IAN Press Launches eBook Format

Chesapeake Bay restoration: Are we headed in the right direction?

Launching Ricky Into Space

Discussion following Heath Kelsey seminar on beach and shellfish forecasts using integrated data from monitoring programs, remote sensing, and observing systems

IAN Science Communication Intern Program

Science Communication Course

Erasmus Mundus thesis defense in Faro, Portugal

Defining Science Application

Environmental report card grading system

Chesapeake literacy

Trip to NASA Goddard Space Flight Center; 29 March 2010

Discussion following Walter Boynton seminar on Corsica River estuary restoration

Discussion following Sara Powell seminar on Getting out of the Lake and into the Watershed: a study of volunteer monitoring efforts, water quality, and community outreach

Discussion following Bill Dennison seminar on Chesapeake Bay health: What causes positive and negative trajectories?

Is Science Communication an art?

Friends of the Bay go to Washington, D.C.

Colonial National Historic Park visit

6th anniversary of the IAN symbol libraries

Hello, my name is Chesapeake Bay, and I have a nutrient problem

Citizen Science Programs

Professional History

William C. Dennison PhD Vice President for Science Applications University of Maryland Center for Environmental Science

Dr. Bill Dennison is a Professor of Marine Science and Vice President for Science Applications at the University of Maryland Center for Environmental Science (UMCES). Dr. Dennison’s primary mission within UMCES is to coordinate the Integration and Application Network. The University of Maryland Center for Environmental Science is one of two research and service institutions in the 13-institution University System of Maryland. UMCES is comprised of three laboratories distributed across the watershed of Chesapeake Bay within Maryland: Appalachian Laboratory in Frostburg, Chesapeake Biological Laboratory on the western shore of Chesapeake Bay in Solomons and Horn Point Laboratory on the eastern shore of Chesapeake Bay near Cambridge as well as Maryland Sea Grant College in College Park, Maryland. UMCES also operates an Annapolis Liaison Office.

Bill Dennison rejoined UMCES in 2002 following a ten year stint at the University of Queensland in Brisbane, Australia. He originally started at UMCES (then the Center for Environmental and Estuarine Science) in 1987 as a Postdoctorate/Research Assistant Professor based at Horn Point Laboratory. In Australia, Bill developed an active Marine Botany group at the University of Queensland with strong links to the Healthy Waterways Campaign for Moreton Bay. Bill obtained his academic training from Western Michigan University (B.A., Biology & Environmental Science), the University of Alaska (M.S., Biological Oceanography), The University of Chicago (Ph.D., Biology), and State University of New York at Stony Brook at Stony Brook (Postdoc, Coastal Marine Scholar).

Beginnings

Converting to Marine Biology

Sea Semester

Alaska

Chicago and Woods Hole

Stony Brook, NY

In searching about for a postdoctoral position, I looked for an institutional position that would allow me to expand my research interests. I was lucky enough to obtain such a position (Coastal Marine Scholar) at the Marine Sciences Research Center at the State University of New York at Stony Brook (1984-1987). I quickly gravitated to the Carpenter/Capone lab, where Drs. Ed Carpenter and Doug Capone were investigating nitrogen cycling in marine ecosystems. I bought an old wooden boat (Adohr) to live aboard and serve as my diving platform. I began looking around at the seagrasses of Long Island and repeatedly encountered very turbid waters. Upon investigation, the turbidity was caused by very dense populations of a small, previously undescribed phytoplankton. This phytoplankton was dubbed the ‘brown tide’ because of the color it imparted to affected waters. The ‘brown tide’ received considerable media attention, largely because it induced massive shellfish mortality as well as seagrass declines. We assembled a team of researchers to investigate the ‘brown tide’, which was to occupy much of my effort at Stony Brook. In addition, I was able to travel to the Australian Institute of Marine Science with Doug and his research crew which included his wife, Dr. Linda Duguay. We worked in the laboratory of Drs. David Barnes and Bruce Chalker and went on research cruises to the Great Barrier Reef on the R/V Sirius and the Lady Baston. This was a wonderful opportunity—we were able to compare and contrast inshore, mid-shelf and outer shelf reefs. Our timing was fortutitious in that we were able to witness a large outbreak of crown-of-thorns (Acanthaster planci) and dive on the fore reefs of all of the reefs due to a seasonal lull in the prevailing winds. While Doug & Linda studied nutrient dynamics, I began investigating water motion effects with Dave Barnes. I also traveled around Australia, meeting up with future colleagues, Drs. Hugh Kirkman, Di Walker and Tony Larkum. Back at Stony Brook, I continued to investigate the recurring ‘brown tide’, as well as starting a project in the outer Bahama islands aboard the R/V Calanus with Doug Capone and Dr. Fred Short, another Peter McRoy graduate student. I met one of Doug's graduate students, Judy O'Neil, and we married several years later. Our interest in tropical ecosystems also led us to create a field course for Stony Brook undergraduates at La Parguera field station in the SW corner of Puerto Rico with our colleagues Drs. Bob Cowan and Sue Spanagle which we ran jointly for two years. Linda Duguay and Doug Capone in Australia Great Barrier Reef, Australia Great Barrier Reef, Australia Field class in Puerto Rico

Satellite image of Cambridge and Stonybrook Robert Moses Causeway Ed Carpenter and Doug Capone Back deck of Adohr Adohr from the water R/V Lady Baston & R/V Sirius at the Australian Institute of Marine Science pier Field class in Puerto Rico La Paguera Field Station, Puerto Rico

Chesapeake Bay

A Decade in Australia

Remembering my enjoyable visit to Australia, when an opportunity came along to take up a lectureship in Marine Botany at the University of Queensland, located in Brisbane, the capital city of Queensland, I jumped at the opportunity. I arrived in the Botany Department simultaneously with Professor George Stewart, which proved to be exceptionally good fortune. George was not only an excellent department chair, but he became a colleague on several ecophysiology projects using marine plants. Studying marine botany from within a Botany Department, instead of at a marine laboratory, provided unique opportunities. For example, Dr. Christa Critchley, who took over from George as department chair, helped our group develop expertise in measuring photosynthesis underwater with pulse amplitude fluorometry. Teaching field classes at Heron and Stradbroke Islands allowed for a good training ground for marine botanical students and research projects associated with the field classes often developed into thesis projects and larger programs. As a result of being in the right place at the right time, our Marine Botany group was able to flourish. I was inspired by the Brisbane Lord Mayor, Jim Soorley, who supported our research and worked to implement the necessary changes to improve ecosystem health of Moreton Bay. Prof. Paul Greenfield from the University of Queensland was my mentor in the Healthy Waterways program, as we developed a large multi-disciplinary and multi-institutional study. My first PhD student, Dr. Eva Abal, became a key colleague when she moved into the role of Scientific Coordinator of the Healthy Waterways campaign. Marine Botany 1992-1995 Marine Botany 1995-1998 Marine Botany 1998-2001 Investigate interactions of marine plants and environmental features Research for Health Waterways Research for Healthy Australian Estuaries

John Jell at Heron Island Eva Abal in the field Tony Larkum at One Tree Island Heron Island

Returning to Chesapeake Bay

My experience with the Healthy Waterways campaign in Australia convinced me that I wanted to devote my remaining career to solving, not just studying environmental problems. Simultaneously, the faculty of the University of Maryland Center for Environmental Science, led by Dr. Don Boesch, initiated an Integration and Application Network to address environmental problem solving focused on Chesapeake Bay. Thus, when a new position was created for a Vice President for Science Applications to energize the Integration and Application Network, it seemed a natural that I take on this effort (2002 – present).The goal of IAN is to inspire, manage and produce timely syntheses and assessments on key environmental issues, with a special emphasis on Chesapeake Bay and its watershed. IAN will then take these syntheses and assessments into the policy arena to develop solutions to environmental problems.

The initial phase of developing the Integration and Application Network was to form a suite of tools that can be used by scientists in various integration and application opportunities. Dr. Tim Carruthers came from Australia with me, and we have steadily built up a core staff, funded largely through grants and contracts. We have renovated a building on the Horn Point Laboratory campus to house the core IAN staff. We also renovated office space in Annapolis for the Annapolis Synthesis Center. A variety of active partnerships have developed with various agencies, universities, and non-governmental organizations. An IAN web site was created to share the tools developed through IAN activities. For example, symbol libraries were created to aid in the creation of conceptual diagrams, used in various science communication applications. These symbol libraries have become a global resource used by thousands of scientists. In addition, workshops and courses in science communication have been taught by IAN, internationally, nationally and locally. These courses culminated in a science communication handbook. The IAN web site also features real-time and archived web-cast seminars, enewsletters, printed newsletters, an image library, posters and presentations, discussion forum, workshop and conference proceedings.

The major focus of our activities is on Chesapeake Bay and its watershed. Developing an integrated assessment process for Chesapeake has been an ongoing effort. The IAN team has been expanded to include scientists based in Oxford, Maryland in a partnership with the NOAA Chesapeake Bay Office and scientists based in Annapolis, Maryland in a partnership with the EPA Chesapeake Bay Program. An annual communication cycle has been initiated with ecological forecasts in the spring, tracking conditions during the summer and analyzing the forecasts and then in the winter, providing an integrated assessment of the previous summer. In parallel efforts, we have developed strong, ongoing partnerships with colleagues in the Maryland Coastal Bays.

A lesser focus is on activities at national and international realms. I serve on the Scientific Steering Committee for the Land-Ocean Interactions in the Coastal Zone, using this organization to help us disseminate our tools internationally. I maintain some ongoing activities in Australia, serving as a reviewer of Swan River, Great Barrier Reef and Moreton Bay resource management activities. As well, I maintain as active interest in the International Riverfoundation which funds the annual Riverprize for the best river management program globally, awarded at the annual Riversymposium in Brisbane, Australia.

Former Students

I have been blessed with the experience of having had interesting, capable and hard working students. I am continually amazed at how much I learn from my students. One feature of the students that I have had is their passion for making a difference. They want to do good science, but moreover, they want their good science to help solve environmental problems. Another defining feature of their character is their ability to work as team and as part of other teams. We have had some incredible shared experiences together, experiencing nature, experiencing different cultures, experiencing the joys and sorrows of doing science together and working to do our bit in changing the world. Of the things that I have done and accomplished in my career, the role that I have had in providing opportunities for various students has been one of the most rewarding. I love hearing about what they are up to, what they have accomplished and what they are going to do next. It has been an honor and privilege to have had these committed, interesting and pleasant people as my students.