60 http://ian.umces.edu/seminarseries/ A monthly seminar series in Annapolis, MD to foster better interaction between the Chesapeake research, monitoring and management community, hosted by the Integration and Application Network. en-us ℗ & © Integration and Application Network Fostering interaction between Chesapeake research, monitoring and management communities Integration and Application Network A monthly seminar series in Annapolis, MD to foster better interaction between the Chesapeake research, monitoring and management community, hosted by the Integration and Application Network. Integration and Application Network ian@umces.edu no Jacqueline Grebmeier Chesapeake Bay Seminar Series - February 2009 The continental shelf and slope regions in the Pacific Arctic sector are extremely productive due to the input of nutrient-rich Pacific water on the northern Bering and Chukchi Sea shelves and into the Arctic Ocean. Benthic-dominated regions on these shallow shelves have high benthic infaunal biomass and sediment carbon cycling. Bivalves, polychaetes and amphipods dominate the infaunal organisms and this region serves as a major prey area for benthic-feeding marine mammals and seabirds, including walrus, gray whales and diving seaducks. Past studies in the region indicate food supply is the major factor influencing benthic carbon cycling, with colder water regions having some of the highest benthic carbon cycling rates, indicative of higher organic carbon export to the benthos. However, with the increasing influence of warmer, lower nutrient water transiting northward from the Bering Sea, a continued reduced seasonal sea ice coverage, and corresponding increases in seawater temperatures, it is likely that the changes being seen in the biological ecosystem will continue and possibly accelerate. A large-scale impact might well be a transitional change from a benthic-dominated northern Bering and Chukchi shelf region to a more pelagic-dominated system. Data will be presented on key biological factors influencing benthic carbon cycling at various time and space scales in the western Arctic region in order to evaluate both present impacts and possible future changes in benthic processes in this highly productive system. http://ian.umces.edu/mp3s/grebmeier_cbss_feb_2009.mp3 Thu, 19 Feb 2009 00:00:00 -0500 1:12:39 environment, ecology, management, restoration, research, monitoring, IAN Lee Cooper Chesapeake Bay Seminar Series - June 2008 The recent significant decline in Arctic sea ice has captured public interest in the challenges of mitigating and responding to climate changes that seem to be unambiguously underway at high latitudes. Despite the obvious physical differences between ice-covered seas and open water, predicting ecosystem response and biological changes that are likely to result is much more difficult. For example, it is thought that declining sea ice coverage will increase light penetration and increase primary production on arctic continental shelves, which might be globally significant because the continental shelves in the Arctic are the world\'s largest in extent. However, in comparisons between chlorophyll biomass in the Bering Sea for years with light versus heavy ice coverage, open water conditions do not lead to significantly higher water column chlorophyll biomass possibly because high winds significantly mix phytoplankton in open water and sea ice provides an attachment structure to hold sea ice algae close to the sea surface. The timing of seasonal sea ice retreat is also hypothesized to play a role in structuring the food web with better development of zooplankton populations in some circumstances. The northern Bering and Chukchi continental shelves currently have short, efficient food-chains that deposit organic material synthesized during the brief, but intense production period directly to the shallow sea floor without much exploitation by zooplankton. Specialized apex predators such as walrus, gray whales, bearded seals and diving sea ducks exploit the rich benthos as a food resource, but there is also evidence that fish are becoming more important in structuring the food web and zooplankton may also become more important in intercepting primary production too. The North Pacific Fisheries Management Council has also begun to assess how fisheries should be managed and what the potential conflicts will be for the existing benthic-based food-web as commercial exploitation of Bering Sea fisheries is poised to expand northward. I will present data on what is known about how the Bering and Chukchi Sea food webs and biological systems are changing in response to regime shifts and seasonal sea ice retreat. Our intent is to use these data as a starting point for developing a predictive capability to understand how the arctic biological system will respond to the stresses of climate change. http://ian.umces.edu/mp3s/cooper_cbss_jun_2008.mp3 Thu, 26 Jun 2008 00:00:00 -0400 52:23 environment, ecology, management, restoration, research, monitoring, IAN Lora Harris Chesapeake Bay Seminar Series - April 2008 Existing individual-based models of clonal plants rely on simple rules of rhizome spacing, branching angle, and branching rate to predict colonization of space by asexually reproducing ramets. These models have provided unanticipated explanations for the emergence of nonlinear patch growth observed in real populations. However, no efforts have attempted to link these models\' growth or morphological parameters with environmental conditions, relying instead on constant or stochastic values. In the case of seagrasses, widespread decline has prompted managers to ask for predictive tools that might provide better understanding of the landscape-level response of these clonal plants to water quality. The Virtual Eelgrass Meadow (VEM) was created to explore how the simple rules of a modular, clonal, architecture might be linked with environmental variables such as light, temperature, and nutrients to simulate eelgrass patch dynamics. Insights from VEM simulations suggest that changes to growth rates and resource allocation in response to the physical environment provide a mechanistic explanation for the morphological plasticity of ramets, which ultimately affects patch expansion rates. http://ian.umces.edu/mp3s/harris_cbss_apr_2008.mp3 Thu, 24 Apr 2008 00:00:00 -0400 1:05:04 environment, ecology, management, restoration, research, monitoring, IAN Byron Crump Chesapeake Bay Seminar Series - March 2008 Bacterioplankton are essential components of aquatic ecosystems, catalyzing critical biogeochemical reactions and serving as central members of planktonic food webs. Recent large-scale DNA sequencing projects show a staggeringly high genetic diversity in bacterioplankton communities, and yet several recent studies show predictable patterns in this diversity including spatial patterns related to environmental gradients and dispersal, and temporal patterns including seasonality and annual re-assembly. These biogeographic patterns reveal the tight connection between bacteria and their environment, and suggest that Metacommunity Theory and other ecological theories developed for macroscopic organisms may also apply to microscopic organisms. This talk will discuss these theories citing several examples of biogeographic patterns in bacterioplankton drawn from research on the Alaskan Tundra, a New England salt marsh estuary, and the anoxic zone of the Chesapeake Bay. http://ian.umces.edu/mp3s/crump_cbss_mar_2008.mp3 Thu, 27 Mar 2008 00:00:00 -0400 57:30 environment, ecology, management, restoration, research, monitoring, IAN Jeremy Testa Chesapeake Bay Seminar Series - February 2008 Regional, seasonal, and inter-annual variations of water quality, net O2 production, and pelagic-benthic coupling were examined in relation to changes in nutrient loading and climatic forcing for the Patuxent River estuary. Monthly rates of net biogeochemical production and physical transport of carbon, oxygen, and nutrients were calculated for six estuarine regions using a data-constrained salt- and water-balance model (box-model) and a time series of water quality and hydrologic data. Assuming fixed metabolic stoichiometry for O2, and carbon, we also derived estimates of particulate organic carbon (POC) sinking. Analyses of monthly mean rates for each estuarine volume revealed distinct regional and seasonal patterns in net O2 production, including spring peaks in surface layer rates and generally higher rates in the middle estuary than other regions. Rates of POC sinking, which also peaked during the spring bloom, were sufficient to support the majority of bottom layer nutrient regeneration and O2 consumption at annual time-scales. Computed rates of net O2 production and nutrient consumption in surface waters were generally enhanced by high river flow; however, muted effects of flow on bottom-layer respiration and nutrient regeneration suggest that much of the increased organic production in surface layers during high flow is transported to seaward regions. The box-modeling approach was also used to assess estuarine ecosystem responses to recent reductions in N and P loading from sewage treatment facilities under the variable climatic conditions of the last two decades. Reductions in nutrient concentrations, chlorophyll-a levels, and bottom layer O2 consumption rates in the upper estuary since 1990 are closely tied to reductions in point-source nutrient loading rates (by 40-60%). The absence of clear trends in water quality and net O2 production for the middle estuary appears to be attributable to persistently high diffuse-source nutrient loads, particularly during the high river flow conditions which characterized the mid- to late-1990s. Despite significant declines in the seaward transport of N and P from the upper to the lower estuary, chlorophyll-a concentrations, net O2 production, and turbidity have actually increased during this same time period. These surprising trends coincide with a trend of increasing net inputs of DIN from the Chesapeake Bay to the Patuxent, related to larger nutrient concentration decreases in the Patuxent relative to Chesapeake Bay. In addition, a contemporaneous reduction in grazing pressure on phytoplankton appears to be related to a top-down trophic cascade that has allowed algal biomass and productivity to increase, with total N concentrations remaining relatively constant. These analyses of water quality trends and ecosystem processes illustrate (1) the value of long-term monitoring data, (2) the need for regional scale nutrient management that includes integrated estuarine systems, and (3) the potential water quality impacts of altered coastal food-webs. http://ian.umces.edu/mp3s/testa_cbss_feb_2008.mp3 Thu, 28 Feb 2008 00:00:00 -0500 47:16 environment, ecology, management, restoration, research, monitoring, IAN Dr Ray Najjar Chesapeake Bay Seminar Series - October 2007 To better understand the implications of anthropogenic climate change for three major Mid-Atlantic estuaries (Chesapeake Bay, Delaware Bay, and the Hudson River Estuary), we analyzed the regional output of seven global climate models. The simulation given by the average of the models was generally superior to individual models, which differed dramatically in their ability to simulate 20th-century climate. The model average had little bias in its mean temperature and precipitation and, except in the Lower Chesapeake Watershed, was able to capture the 20th-century temperature trend. Weaknesses in the model average were too much seasonality in temperature and precipitation, a shift in precipitation\'s summer maximum to spring and winter minimum to fall, interannual variability that was too high in temperature and too low in precipitation, and inability to capture the 20th-century precipitation increase. All models warmed over the 21st century under the six greenhouse gas scenarios considered, with an increase of 4.7 ± 2.0° C (model mean ± 1 standard deviation) for the A2 scenario (a medium-high emission scenario) over the Chesapeake Bay Watershed by 2070-2099. Precipitation projections had much weaker consensus, with a corresponding increase of 3 ± 12% for the A2 scenario, but in winter there was a more consistent increase of 8 ± 7%. The projected climate averaged over the four best-performing models was significantly cooler and wetter than the projected seven-model-average climate. Precipitation projections were within the range of interannual variability but temperature projections were not. The implied research needs are for improvements in precipitation projections and a better understanding of the impacts of warming on streamflow and estuarine ecology and biogeochemistry. http://ian.umces.edu/mp3s/najjar_cbss_october_2007.mp3 Thu, 11 Oct 2007 00:00:00 -0400 57:13 environment, ecology, management, restoration, research, monitoring, IAN Carys Mitchelmore Chesapeake Bay Seminar Series - September 2007 Research in our laboratory encompasses both mechanistic and applied issues regarding the fate and effects of a range of chemical and biological stressors (pollutants) in the aquatic environment, from the Chesapeake Bay to tropical coral reefs. This seminar will focus on the projects pertinent to the Chesapeake Bay but also highlights some of the research that is being carried out on coral reef toxicology. To preempt this talk I would like to emphasize the words of one of the first well-known toxicologists; \'ALL substances are poisons, there is none which is not a poison, the right dose differentiates a poison from a remedy\', Paraceleus (16th century). So although the concentration and the duration of exposure to a pollutant in the Bay is important, we must also consider how (if at all) pollutant(s) can be taken up by organism\'s, it\'s fate and ultimate effect. Further complicating these issues is the myriad of multiple pollutants currently in the Bay and confounding effects of other chemical, biological and physical stressors. This seminar will address issues of metabolism and effects of organic contaminants, with an emphasis on oxidative stress, genotoxicity and thyroid hormone disruption. Targeted pollutants include, flame retardants (BDEs), crude oil and chemical dispersants, proposed ballast water treatment biocides and human bacterial pathogens. Organisms under study include, various estuarine/freshwater fish and invertebrates, native versus non-native oysters and tropical coral and anemone species. http://ian.umces.edu/mp3s/mitchelmore_cbss_sep_2007.mp3 Mon, 17 Sep 2007 00:00:00 -0400 1:02:50 environment, ecology, management, restoration, research, monitoring, IAN Michael Wilberg Chesapeake Bay Seminar Series - June 2007 American eels (Anguilla rostrata) have supported important local fisheries since the arrival of European settlers and are a highly prized fish in European and Asian markets. They are captured in a wide variety of ways and during almost all of their life stages. In recent years, however, the population appears to be declining in the northern part of their range and Chesapeake Bay. Consequently they were proposed to be listed on endangered species list. Determining whether American eels are declining and determining causes of decline has proved difficult because of their wide range and complex life history. American eels are widely distributed from South America to northern Canada and constitute a single population. American eels from the coasts of North and South America are thought to spawn in the same region - the Sargasso Sea in the middle of the Atlantic Ocean. Juveniles then migrate to the continent where they live most of their lives in freshwater rivers and lakes and brackish estuaries. Because of their wide distribution and stock dynamics, little is known of their overall population dynamics. In order to begin addressing the question of why American eels are declining, we have begun a study to determine the effects of exploitation on American eels in Chesapeake Bay. This seminar will describe efforts currently underway to understand American eel population dynamics. We are developing computer models that describe the portion of the eel life cycle in Chesapeake Bay. This model will include the life history complexities of American eels and will be “tuned” to data we are collecting on exploitation rates, age-structure of the population, and recruitment variability to explore causes of decline and improve management of this species. The Chesapeake Bay, in particular, provides an excellent opportunity to develop methods that can be applied to American eel management at a coast-wide level. http://ian.umces.edu/mp3s/wilberg_cbss_jun_2007.mp3 Thu, 14 Jun 2007 00:00:00 -0400 56:31 environment, ecology, management, restoration, research, monitoring, IAN Andrew Elmore Chesapeake Bay Seminar Series - May 2007 Headwater streams provide important ecosystem services such as drinking water, habitat for aquatic life, and biological uptake and increased processing of nutrients, which can reduce delivery of nitrogen and phosphorus to downstream coastal waters. Despite their known importance to humans, many streams have become 'missing' from developing landscapes due to coverage by impervious surfaces or direct conversion to storm drains, contributing to habitat degradation and loss of ecosystem services. Much of existing work has focused on understanding the consequences of riparian buffer degradation, but not the extent to which streams have become completely removed from the land surface. Using air photography and a digital representation of impervious surface area for the Gunpowder- Patapsco watershed in eastern Maryland, US, we provide the first analysis of stream burial across a range in catchments from 10 ha to 106 ha. We find that 20% of all streams are buried, with the smallest streams exhibiting 23% burial rates. Within the most densely urbanized landscapes, 70% of streams in catchments smaller than 240ha (1 mi2) are buried and burial rates only begin to decrease for streams in larger catchments. The threshold response seen in the data at a catchment size of 1 mi2 suggests that FEMA regulations of larger streams have been effective, yet may have shifted some development pressure to smaller streams. Only with continued understanding of the consequences of stream burial will we be able to properly regulate the destruction of small headwater streams. http://ian.umces.edu/mp3s/elmore_cbss_may_2007.mp3 Thu, 10 May 2007 00:00:00 -0400 49:31 environment, ecology, management, restoration, research, monitoring, IAN Johan Schijf Chesapeake Bay Seminar Series - April 2007 Green macroalgae of the genus Ulva (sea lettuce) are ubiquitous throughout most of the world’s coastal oceans and are highly tolerant of variations in salinity and temperature. Ulva is known to thrive in nutrient-polluted waters and nuisance blooms that cause noxious stench and widespread harm to benthic ecosystems have been studied and battled on several continents since the early 1900s. Seaweeds are also harvested and cultured for use as a nutritional supplement and for the production of food additives like alginate, carrageenan, iodine, and dietary fiber. In this regard, the propensity of Ulva and other macroalgae to rapidly adsorb large quantities of toxic heavy metals directly from seawater is a matter of serious concern. Conversely, this property as well as Ulva’s relatively simple physiology and position near the base of the food chain, potentially make it eminently suitable as a monitor organism for coastal metal pollution. Environmental scientists have moreover studied its use in engineering strategies for water purification and the remediation of contaminated sites. The seminar will describe approaches to developing a surface chemical model that is capable of predicting the extent of metal adsorption by Ulva lactuca as a function of environmental parameters like salinity and temperature. The model will be based on and tested with experiments employing state-of-the-art techniques including Inductively Coupled Plasma Mass Spectrometry (ICP-MS) and Extended X-ray Absorption Fine Structure (EXAFS). http://ian.umces.edu/mp3s/schijf_cbss_apr_2007.mp3 Thu, 12 Apr 2007 00:00:00 -0400 1:07:33 environment, ecology, management, restoration, research, monitoring, IAN Ben Fertig, Lisa Florkowski & Emily Benson Chesapeake Bay Seminar Series - March 2007 The three case studies presented here illustrate how ecological monitoring can be accomplished over a variety of spatial scales and complexities. In the simplest case study, that of Upper Saranac Lake, NY, monitoring and research are in the preliminary phases and focus exclusively on one ecological indicator, nitrogen stable isotope ratios, which can help determine the sources of anthropogenic nitrogen inputs. Spatially explicit monitoring with biological indicators in Maryland's Coastal Bays serves as an intermediate scope of spatial scale and indicator complexity. The Rock Creek National Park integrated assessment combines numerous ecological indicators from a variety of sources. Monitoring data is being collected on air quality, water quality, biodiversity, and ecosystem pattern and process. This assessment is a small part of a larger integrated assessment of the National Capital Region Network of the National Park Service. Taken together, these case studies demonstrate how research, monitoring, and management complement each other for integrated assessment on a variety of different scales and complexities. http://ian.umces.edu/mp3s/benson_fertig_florkowski_cbss_mar_2006.mp3 Thu, 08 Mar 2007 00:00:00 -0500 48:42 environment, ecology, management, restoration, research, monitoring, IAN Mark Brush Chesapeake Bay Seminar Series - February 2007 Using a combination of Chesapeake Bay Program monitoring data, high resolution spatial data from our towed Acrobat instrument platform, and high frequency time series data from the National Estuarine Research Reserve (NERR) system, dissolved oxygen dynamics are analyzed at three spatial scales relevant to management in the Chesapeake Bay: (1) the mainstem, (2) the York River estuary, and (3) nearshore, littoral systems at regional NERR sites. At the scale of the mainstem, lower Bay summertime hypoxia appears to be alleviated in some years by transient upwelling events outside the mouth of the bay and along the Delmarva Peninsula. Despite its presumed origins below the pycnocline on the inner shelf, this upwelled water appears to be relatively normoxic compared to lower bay waters, and it can intrude at least up to the mouth of the Rappahannock. As upwelling tends to be strongest in years with the highest freshwater flows - also when hypoxia is most severe - there appears to be a climatic connection which would tend to alleviate lower bay hypoxia in its worst years. At the scale of the York River, we have been using our Acrobat and a new vertical profiler to track development of hypoxia and its relation to the spring-neap tidal cycle. A high frequency study (every 2-3 days) over a spring-neap cycle in late 2005 captured the transition from well mixed, normoxic conditions to stratified, hypoxic conditions within a few days. While in situ oxygen consumption was likely somewhat responsible, the data suggest that a portion of this hypoxic water originated in the lower mainstem. At the scale of shallow littoral sites, early morning hypoxia can be a common occurrence and appears to be related to average temperature, turbidity, and chlorophyll-a. Perhaps more interesting however is the event-scale suppression of daily average oxygen concentrations in response to multiple days with low irradiance and slack winds. Net ecosystem metabolism at these sites is fundamentally tied to freshwater inputs, with maximal values at intermediate levels of flow. These patterns are consistent with monitoring results and predictions of a numerical simulation model developed for a shallow sub-estuary of Narragansett Bay, RI. The model is an innovative, intermediate complexity model and is suggested as an additional tool to complement more complex models in management of hypoxia. I will conclude by highlighting VIMS' new state-funded Chesapeake Bay Initiative, a monitoring program using state-of-the-art, high resolution sampling to quantify water quality concentrations, criteria attainment, and hypoxic/anoxic volume in Virginia's tributary estuaries. http://ian.umces.edu/mp3s/brush_cbss_feb_2007.mp3 Thu, 08 Feb 2007 00:00:00 -0500 53:07 environment, ecology, management, restoration, research, monitoring, IAN Jorge A. Herrera Silveira Chesapeake Bay Seminar Series - September 2006 http://ian.umces.edu/mp3s/herrera-silveira_cbss_sept_2006.mp3 Thu, 28 Sep 2006 00:00:00 -0400 54:24 environment, ecology, management, restoration, research, monitoring, IAN Jude Apple Chesapeake Bay Seminar Series - June 2006 The fundamental role of microbial communities in the functioning of aquatic systems is widely accepted, yet their biogeography (i.e., how species composition changes over space and time) remains poorly understood. A long standing assumption is that everything is everywhere (aka Baas-Becking Hypothesis). Recent studies, however, suggest that the phylogenetic composition of microbial communities may experience significant changes across ecosystems. In the present study, our objective is to identify transferable patterns in the biogeography of bacterioplankton communities and the environmental factors driving changes in community composition. We conducted longitudinal surveys in several large temperate estuaries, including Chesapeake Bay, Delaware Bay, Puget Sound/Snohomish River, and Gulf of Mexico/Atchafalaya River. Samples were collected every four salinity units along transects of the full salinity range (0-32). Shifts in bacterioplankton community composition were identified by denaturing gradient gel electrophoresis (DGGE) of PCR-amplified 16S ribosomal DNA and related to environmental parameters using multidimensional scaling (MDS) and canonical correspondence analysis (CANOCO). We observed compelling evidence that microbial communities in coastal and estuarine systems exhibit predictable biogeographic patterns, with changes in community composition well correlated with salinity, HMW DOM, and influenced by residence time in each system. http://ian.umces.edu/mp3s/apple_cbss_june_2006.mp3 Thu, 22 Jun 2006 00:00:00 -0400 54:00 environment, ecology, management, restoration, research, monitoring, IAN Lisa Wainger Chesapeake Bay Seminar Series - May 2006 With limited resources to spend on restoration, it is important to match the level and allocation of spending on these problems to expected societal benefits. We are developing decision support tools that offer a means to balance ecological and economic goals for ecosystems. To compare benefits, risks and costs associated with restoring sites, we use an approach that stresses the importance of location and the heterogeneity of effects due to location. We examine site characteristics and characteristics of the surrounding landscape that establish the cost-effectiveness of restoration based on 1) the relative value of ecosystem services at a particular location 2) the likelihood of management success and 3) costs of restoration. These data are combined to rate cost-effectiveness of options which can then feed into an optimization model to demonstrate where net benefits are maximized for a given level of spending. A case study on invasive species control will be presented to demonstrate techniques. http://ian.umces.edu/mp3s/wainger_cbss_may_2006.mp3 Thu, 11 May 2006 00:00:00 -0400 54:24 environment, ecology, management, restoration, research, monitoring, IAN Mary Booth Chesapeake Bay Seminar Series - April 2006 Nitrogen derived from agricultural fertilizer runoff in the Mississippi-Atchafalaya River Basin (MARB) is widely acknowledged as a primary cause of warm-season hypoxia in the Gulf of Mexico, often referred to as the “Dead Zone”. We mapped and modeled controls on spring nitrate flux for the Mississippi River Basin, relating current nitrate loading to N inputs and patterns of land use. As has been found previously, a small part of the MARB is disproportionately responsible for agricultural nitrate inputs to the Gulf, particularly in the crucial spring months preceding the development of hypoxia. However, patterns of land use and farming practices that drive fertilizer loading to surface waters have not arisen in a vacuum, but in response to an agricultural subsidy system that pays farmers to produce certain high fertilizer-input crops. Analysis of land use patterns suggests that shifts in subsidy payments to increase the proportion of land in conservation could reduce agricultural nitrogen inputs to the Gulf of Mexico, thereby bringing government agricultural policy more into line with stated objectives on Gulf restoration. http://ian.umces.edu/mp3s/booth_cbss_apr_2006.mp3 Thu, 13 Apr 2006 00:00:00 -0400 54:38 environment, ecology, management, restoration, research, monitoring, IAN David Kimmel Chesapeake Bay Seminar Series - March 2006 Chesapeake Bay is characterized by seasonal and interannual variability in species abundance and spatial distribution. These changes are the result of hydroclimatic variability driven by variability in the type and frequency of regional weather systems during the winter season. Strong variability in freshwater flow during winter and early spring impacts the Bay’s food web structure. To demonstrate this, winter climate patterns for the northeastern United States were classified using gridded, sea level pressure data for the period 1950-2002. The analysis revealed that the regional winter climatology can be characterized by 10 dominant synoptic-scale weather patterns. Interannual variability in these weather patterns is correlated to spring freshwater input. Weather patterns influence the timing, location, and magnitude of the spring phytoplankton bloom, which in turn, strongly influences the Bay’s food web. Both the bloom characteristics and hydrologic conditions determine spring zooplankton community composition and abundance, summer zooplankton abundance, summer gelatinous zooplankton composition and biovolume, and multi-species fisheries recruitment patterns. Characterizing and quantifying interannual climate variability provides a means to distinguish between climate forcing and the effects of land use and policy changes in influencing ecosystem conditions. http://ian.umces.edu/mp3s/kimmel_cbss_mar_2006.mp3 Fri, 17 Mar 2006 00:00:00 -0500 55:30 environment, ecology, management, restoration, research, monitoring, IAN Sujay Kaushal Chesapeake Bay Seminar Series - February 2006 Increased delivery of nitrogen due to land use change and human activities has led to increased eutrophication, decreased water quality, and habitat loss in many running waters and coastal waters around the world. Because of this, increasing interest has been placed on the potential for restoration of streams and rivers to remove nitrogen before delivery to coastal ecosystems. We tested whether geomorphic restoration of a degraded stream could increase rates of removal of nitrate (a common pollutant in many surface waters) through denitrification in a coastal watershed draining into the Chesapeake Bay using an in situ 15N tracer technique. Rates of denitrification were consistently greater in the restored reach of the stream as compared to the unrestored reach on an annual basis, and there were significant reductions in nitrate concentrations in ground and surface waters of the restored reach. Sandy riparian areas designed for frequent overland flooding showed higher rates of denitrification as compared to vegetated riparian areas, which were designed for less flooding, suggesting that this type of restoration technique worked best in improving water quality. Denitrification in saturated sediments in the hyporheic zone near the stream channel appeared to represent a considerable loss of nitrate-nitrogen, which has been previously difficult to quantify. Our work suggests that geomorphic restoration of streams and hyporheic zones may have the potential to significantly reduce the amount of nitrate pollution delivered from watersheds. Some future challenges to stream ecosystem restoration as a means to improve surface water quality will also be discussed such as: increasing organic nutrients in urban waterways, the ecological effects of “occult” carbon sources in suburban and urban streams, and the influence of large seasonal variations in stream salinity from road deicers. http://ian.umces.edu/mp3s/kaushal_cbss_feb_2006.mp3 Tue, 07 Feb 2006 00:00:00 -0500 56:10 environment, ecology, management, restoration, research, monitoring, IAN