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1998 Progress Report: The Toxic Dinoflagellate, Pfiesteria piscicida, as a Potential Biosensor of Estuarine Stress
EPA Grant Number: R825551Title: The Toxic Dinoflagellate, Pfiesteria piscicida, as a Potential Biosensor of Estuarine Stress
Investigators: Burkholder, Joann M. , Rublee, Parke , Shumway, Sandra E.
Institution: North Carolina State University , Long Island University - Southampton College , University of North Carolina at Greensboro
Current Institution: North Carolina State University , Long Island University - Southampton College , University of North Carolina at Greensboro
EPA Project Officer: Rosenthal, Sheila
Project Period: May 19, 1997 through May 18, 2000 (Extended to May 18, 2001)
Project Period Covered by this Report: May 19, 1998 through May 18, 1999
Project Amount: $500,000
RFA: Harmful Algal Blooms (1997)
Research Category: Aquatic Ecosystems , Water Quality
Description:
Objective:The objectives of this project are to: (1) examine controlling influences of both inorganic and organic N and P on growth of Pfiesteria piscicida zoospores (toxic and nontoxic), when given food resources as dissolved or particulate (algal) carbon; (2) improve detection of Pfiesteria piscicida through development of a molecular probe for this species; and (3) assess Pfiesteria's acute and sublethal/chronic impacts on life stages of commercially/ecologically valuable shellfish species. Progress Summary:
Clones of P. piscicida, verified as capable of icthyotoxic activity, were essential for all aspects of this research, and have had to be replaced at ca. 6-month intervals because Pfiesteria loses toxicity in culture over time (also typical of various other toxic algae). We obtained two research-quality clones of toxic Pfiesteria piscicida from a fish kill site on the Neuse Estuary, NC (repeated twice this year). The clones were verified as capable of toxin production using our standardized fish bioassay process (required step since there is wide variability among P. piscicida cells in toxin production capability ranging from non-inducible, or apparently incapable of toxin production, to highly toxic).
In nutrient ecology research, within an experimental series we compared cell production of toxic (TOX-A functional type, actively toxic from fish-killing culture) vs. nontoxic zoospores (TOX-B, tested as capable of toxin production but without fish, fed algal prey for 3 months). The TOX-B (temporarily nontoxic) zoospores grew much faster (with higher grazing rates) on algal prey than the TOX-A zoospores, indicating that toxicity status (history of access to live fish) strongly influences response to algal prey. In a second experimental series, we confirmed direct uptake of 14C-acetate (dissolved organic carbon source) by P. piscicida toxic zoospores as well as uptake of 15N-urea. We also obtained direct uptake of 15N-nitrate by kleptochloroplastidic P. piscicida toxic zoospores. These data supported earlier observations in which we recorded apparent stimulation of (recently toxic) kleptochloroplastidic zoospore cell production by inorganic phosphate enrichment. Thus, when P. piscicida has functional chloroplasts retained from algal prey, it can "act" like a plant in showing direct stimulation by inorganic nutrient enrichments. The relationship between inorganic nutrient enrichment and kleptochloroplastidic zoospore cell production is not linear but, rather, a threshold effect, wherein high concentrations of nutrient (usually >100 mg nitrate or phosphate/L) can stimulate significantly increased cell production. Whether stimulation occurs also appears to depend on nutritional history of the prey; for example, P. piscicida fed N-starved algae showed a much stronger nitrate stimulation of cell production than zoospores fed N-enriched algae.
In molecular probe testing/refinement, we continued to test our fluorescent ribosomal DNA probe to P. piscicida from the Neuse Estuary on natural water samples from the Pocomoke Estuary and the Pamlico Estuary, and on isolates of various "lookalike" species. We also used our probe at the 1998 toxic Pfiesteria outbreak on the Neuse Estuary, and adapted it for semi-quantitative use (+ 200 cells/mL) to indicate that there were ca. 1,500 P. piscicida zoospores in the epicenter of the kill zone. We additionally developed a technique that can be used to check archived samples (preserved with acidic Lugol's solution and stored in darkness at 4 C) for P. piscicida zoospore abundance. In shellfish research, we set up an inland culture facility and used it to successfully maintain blue crabs, bay scallops, and northern quahogs. Replicated acute toxicity tests were conducted on adult bay scallops and blue crabs in the presence vs. absence of finfish (tilapia). P. piscicida was lethal to all three shellfish species, with adult bay scallops most sensitive to the toxins and blue crabs most resistant in these acute toxicity experiments. Note that these experiments had been planned for Year 1, but had to be delayed to September of Year 2 because emergency conditions encountered by Maryland required use of all available space in the biohazard III facility (needed for this research) for fish bioassay testing of Maryland samples. Expanded, custom-designed biohazard III facilities finally became available for this research in late summer 1998, but by that time, juvenile shellfish stages needed for certain aspects of the research were no longer available (spawning/early growth period missed). The delays created by the need for additional biohazard III space especially affected the nutritional ecology and shellfish research aspects of the project. Therefore, we needed to request a 1-year, no-cost extension.
Future Activities:During the next year, we will: (1) analyze the comparative ecology of the three functional types of Pfiesteria; (2) use PCR and fluorescent in situ hybridization (FISH) probed to assay for the presence of Pfiesteria piscicida in estuarine water samples collected from New York to northern Florida; and (3) assess the response of representative adult and pediveliger eastern oysters to zoospores of Pfiesteria piscicida. Journal Articles:
No journal articles submitted with this report: View all 19 publications for this project
Supplemental Keywords:estuaries, nutrients. , Ecosystem Protection/Environmental Exposure & Risk, Water, Scientific Discipline, Waste, RFA, Ecosystem/Assessment/Indicators, exploratory research environmental biology, Nutrients, Ecological Risk Assessment, algal blooms, Ecological Indicators, Environmental Microbiology, Ecological Effects - Human Health, Hydrology, Chemical Mixtures - Environmental Exposure & Risk, Ecological Effects - Environmental Exposure & Risk, Ecosystem Protection, Contaminated Sediments, Ecology and Ecosystems, nutrient kinetics, phytoplankton dynamics, water quality, aquatic ecosystem, estuarine food web, pfiesteria, phytoplankton, watershed management, harmful algal blooms, pfiesteria piscicida, dinoflagellates, dinoflagellate, contaminated sediment, algal growth, fish lesions, heterotrophic microbial prey, ecological exposure, nutrient transport, nutrient cycling, estuarine stress, estuaries, estuarine ecosystems, nutrient supply, biosensor, ecosystem stress, phytoplankton blooms
Progress and Final Reports:
1997 Progress Report
Original Abstract
1999 Progress Report
Final Report