Publications
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Peer-reviewed Publications |
1999 |
Purcell JE, White JR, Nemazie DA, Wright DA (1999) Temperature, salinity and food effects on asexual reproduction and abundance of the scyphozoan Chrysaora quinquecirrha. Marine Ecology-Progress Series 180:187–196
Abstract: Outbreaks of jellyfish are reported worldwide, yet the environmental factors that control the sizes of jellyfish populations are not well understood. The scyphomedusan Chrysaora quinquecirrha occurs in the mesohaline portion of Chesapeake Bay each summer. Population sizes of the medusae show dramatic annual variations that are correlated with salinity and temperature. We measured the total numbers of ephyrae and polyps produced by benthic polyps of C. quinquecirrha in laboratory experiments lasting 42 d, and found that temperature (15, 20, 25 degrees C) was not a statistically significant factor at low salinities (5 to 20 parts per thousand); however, ephyra production increased significantly with increasing temperature at high salinities (20 to 35 parts per thousand). Conversely, each 5 degrees C: decrease in temperature delayed strobilation (ephyra production) by about 1 wk. Salinity significantly affected the numbers of ephyrae and polyps produced in all experiments. Ephyra and polyp production was lower at both low (<11 parts per thousand) and high salinities (greater than or equal to 25 parts per thousand) than at intermediate salinities. Also, more ephyrae, but, not polyps, were produced with more available prey. Medusa numbers were 2 orders of magnitude lower in July 1996 when water temperatures, salinities, and zooplankton densities in Chesapeake Bay all were lower than in July 1995. The effects of these factors are important in understanding the changes caused by human activities in near-shore ecosystems, including effects of global warming, eutrophication, and reduction of commercial species.
Keywords: cnidaria; scyphozoa; medusa; scyphistoma; temperature; salinity;; zooplankton; production; strobilation; environmental factors; asexual; reproduction; aurelia-aurita l; chesapeake bay; western sweden; gullmar fjord; sea; nettle; l ephyrae; predation; medusae; scyphomedusae; ctenophores
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1996 |
Malone TC, Nemazie DA (1996) Toward a national agenda for research in the coastal zone: Where are we? Biological Bulletin 190(2):245–251
Abstract: In response to the complex challenges of understanding and managing the effects of human activities on coastal ecosystems, the research establishment has produced a plethora of reports and implemented a bewildering array of government-sponsored research and monitoring programs that are not cost-effective on regional or national scales. Consequently, the gap between national needs and the capacity of the nation's research institutions to respond is growing rapidly, and environmental policies are ambiguous at a time when coastal habitats and living resources are being lost or degraded at accelerating rates. A case is made that a grassroots effort is needed to develop cost-effect programs that are responsive to both local needs and national priorities.
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1994 |
Purcell JE, Nemazie DA, Dorsey SE, Houde ED, Gamble JC (1994) Predation Mortality of Bay Anchovy Anchoa-Mitchilli Eggs and Larvae Due to Scyphomedusae and Ctenophores in Chesapeake Bay. Marine Ecology-Progress Series 114(1-2):47–58
Abstract: We measured predation on bay anchovy Anchoa mitchilli eggs and larvae by abundant scyphomedusae Chrysaora quinquecirrha and ctenophores Mnemiopsis leidyi from gut contents, digestion rates, and densities of predators and prey during 9 d in July 1991 at 4 stations in Chesapeake Bay, USA, These predation rates were compared to egg and larval mortality rates measured concurrently in ichthyoplankton surveys. Daily predation by medusae and ctenophores was 19 +/- 13% (mean +/- SD) of the eggs over the 20 h stage duration, with medusae responsible for 26 to 100% of the predation. These gelatinous predators accounted for 21 +/- 17% of the total estimated daily egg-stage mortality. On average, medusae consumed 29 +/- 14% d(-1) of the larval hay anchovy, which was 41 +/- 35% of total estimated larval mortality. Predation on larvae by ctenophores was not detected. These predation effects are compared with those measured concurrently in free-drifting 3.2 m(3) mesocosms. We conclude that medusae, which had high feeding rates but low abundances, and ctenophores, which had low feeding rates but high abundances, were important predators of bay anchovy eggs and larvae in the mesohaline region of Chesapeake Bay.
Keywords: anchoa; chrysaora; mnemiopsis; fish eggs; fish larvae; scyphomedusae;; ctenophores; predation; mortality; feeding; chesapeake bay; port-phillip bay; mnemiopsis-leidyi; fish larvae;; chrysaora-quinquecirrha; british-columbia; ichthyoplankton;; zooplankton; growth; diet
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1993 |
Nemazie DA, Purcell JE, Glibert PM (1993) Ammonium Excretion by Gelatinous Zooplankton and Their Contribution to the Ammonium Requirements of Microplankton in Chesapeake Bay. Marine Biology 116(3):451–458
Abstract: Ammonium excretion rates of recently collected specimens of gelatinous zooplankton. the scyphomedusan Chrysaora quinquecirrha DeSor and the ctenophore Mnemiopsis leidyi A. Agassiz, were correlated with body mass and water temperature in measurements made from April to October 1989 and 1990. Rates ranged between 3.5 and 5.0 mug atoms NH4+-N (g dry wt)-1 h-1 for C. quinquecirrha and 3.0 to 4.9 mug atoms NH4-N (g dry wt) -1 h-1 for M. leidyi. Excretion rate equations and in situ data on the size distributions and biomasses of gelatinous zooplankters and water temperature were used to estimate the contribution of ammonium by medusae and ctenophores to mesohaline Chesapeake Bay waters on several dates during April to October 1989 and 1990. We then compared the estimated contributions to direct measurements of (NH4+)-N-15 uptake by microplankton. The maximum estimated regeneration by gelatinous zooplankton was 5.8 mug atoms NH4+ N m-3h-1 at night in August 1990, when medusae biomass was greatest. This represents about 4 % of the ammonium required by the microplankton. During the daytime on all dates, less than 1 % of the ammonium required by microplanktion was supplied by gelatinous zooplankton. Therefore, gelatinous zooplankton appear to play a minor role in the ammonium cycle of Chesapeake Bay.
Keywords: partially stratified estuary; chrysaora-quinquecirrha; food; availability; metabolic rates; phytoplankton; nitrogen; regeneration;; respiration; temperature; ctenophores
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1992 |
Purcell JE, Nemazie DA (1992) Quantitative Feeding Ecology of the Hydromedusan Nemopsis-Bachei in Chesapeake Bay. Marine Biology 113(2):305–311
Abstract: We determined feeding rates of the hydromedusan Nemopsis bachei L. Agassiz in the mesohaline region of Chesapeake Bay, USA during the spring of 1989 and 1990 from gut contents, digestion rates and abundances of medusae and zooplankton. The medusae consumed primarily copepodites of Acartia tonsa, selecting against naupliar stages. The peak abundance of N. bachei medusae was in April to May, when densities averaged more than 10 m-3. Medusa densities were similar in both years, but were greatest (maximum of 132 medusae m-3) along a southern transect sampled only in 1990. At peak densities, N. bachei medusae consumed 30% d-1 of the copepodite standing stocks, but they consumed < 1 % d-1 at the lower densities typical of late May or early June. The predation effects were generally greater than those reported for other hydromedusan species. But even at peak predation, N. bachei medusae could not have controlled or reduced A. tonsa copepod populations, which had a production rate of 85% d-1 at that time. Medusa feeding rates were highest at nighttime, and were correlated with prey density in the field, but not in the laboratory.
Keywords: chrysaora-quinquecirrha; copepod populations; food-intake; sea nettle;; ctenophores; growth; ingestion; predation
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Science Communication PublicationsBrowse all publications for Dave Nemazie on IAN Press OR view individually: |
2011 |
| 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) | |
2003 |
| Integration and Application Network (2003) University of Maryland Center for Environmental Science: History, Mission & Accomplishments. IAN Press, Cambridge, MD, 4pp (Newsletter) | |
Media
Browse all media articles featuring Dave Nemazie
OR view individually:
The Marc Steiner Show (Thu 21 Oct, 2010)
The Health of the Chesapeake Bay
WBOC (Salisbury) Television (Tue 17 Aug, 2010)
New Oyster Facility at UMCES
WBOC (Salisbury) Television (Tue 6 Jul, 2010)
Report Released on Oyster Disease
The Salisbury Daily Times (Fri 22 Jan, 2010)
Briefs: WET to hold annual banquet
NPR's Morning Edition (Mon 9 Nov, 2009)
Researchers Get Dirty To Clean Up Chesapeake
WBOC (Salisbury) Television (Thu 7 May, 2009)
Shortage of Pickers Could Help Crab Population (Video)
WBOC (Salisbury) Television (Thu 26 Mar, 2009)
Efforts to Rebuild Chesapeake Oyster Population Stalls (Video)
The Somerset Herald (Wed 28 Jan, 2009)
Somerset hopes for well funding: Possible stimulus would help water projects
The Salisbury Daily Times (Fri 16 Jan, 2009)
Task force's recommendations near end
The Salisbury Daily Times (Fri 21 Nov, 2008)
Tilghman may sign climate agreement
The Salisbury Daily Times (Wed 19 Nov, 2008)
Somerset tries to resolve water issues: Ammonia is in aquifer
The Somerset Herald (Thu 6 Nov, 2008)
Princess Anne Town Commissioners Government Briefing
The Somerset Herald (Wed 29 Oct, 2008)
Water approaches narrowed
The Salisbury Daily Times (Mon 27 Oct, 2008)
Drinking Water: Facilitator, panel focus on Somerset County shortage
The Somerset Herald (Sun 26 Oct, 2008)
State, county, facilitator to discuss water issues
The Somerset Herald (Fri 24 Oct, 2008)
Sanitary Commission, panel at odds over water: Removal of facilitator sought; Princess Anne officials to send letter opposing lawsuit
The Somerset Herald (Wed 22 Oct, 2008)
Princess Anne decries well dispute lawsuit: Town will send letter to governor
The Somerset Herald (Fri 17 Oct, 2008)
Lawsuit filed on well permits
The Salisbury Daily Times (Sun 28 Sep, 2008)
Sanitary Commission takes part in water supply talks
The Salisbury Daily Times (Tue 23 Sep, 2008)
County sanitary board, facilitator to meet
WMDT (Salisbury) Television (Thu 18 Sep, 2008)
New Environmental Task Force
The Salisbury Daily Times (Wed 17 Sep, 2008)
Facilitator to join Somerset water talks
The Salisbury Daily Times (Mon 18 Aug, 2008)
Wicomico gets 'green' task force: New Environmental Policy group made up of professionals, concerned citizens
The Maryland Gazette Newspapers (Fri 8 Aug, 2008)
Endangering Bay cleanup is shortsighted, critics warn: Lowered federal and state aid leaves Maryland behind in its efforts to stem pollution's fallout
ASM's Microbe World Video (Tue 6 Nov, 2007)
Save the Oysters: Non-native Species Podcast (Part 2)
ASM's Microbe World Video (Mon 15 Oct, 2007)
Save the Oysters
The Cecil Whig (Mon 24 Sep, 2007)
Little Insight Offered on Growth: State provides vague advice on populace problems
WBOC (Salisbury) Television (Wed 11 Jul, 2007)
More Salt in the Chesapeake a Threat to Oysters
The Cambridge Daily Banner (Fri 13 Oct, 2006)
Lab brings science to life
The Fredericksburg Freelance Star (Sat 15 Jul, 2006)
A nettle-some problem on Potomac
The Annapolis Capital (Sat 1 Jul, 2006)
Toxic cocktail from heavy rainfall could devastate bay
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