The Ecology and Physiology of Pseudo-nitzschia Toxin Production in the Chesapeake Bay

EPA Grant Number: FP916343
Title: The Ecology and Physiology of Pseudo-nitzschia Toxin Production in the Chesapeake Bay
Investigators: Thessen, Anne E.
Institution: University of Maryland
EPA Project Officer: Michaud, Jayne
Project Period: January 1, 2004 through December 31, 2006
Project Amount: $86,536
RFA: STAR Graduate Fellowships (2004) RFA Text |  Recipients Lists
Research Category: Fellowship - Oceanography and Coastal Processes , Academic Fellowships , Aquatic Ecosystems


Some species of the algae Pseudo-nitzschia are known to produce the neurotoxin domoic acid (DA), which is responsible for amnesic shellfish poisoning in humans and domoic acid poisoning in marine birds and mammals. The earliest record of Pseudo-nitzschia in the Chesapeake Bay is from 1980. Historical data suggest that Pseudo-nitzschia abundances increased and spread throughout the Bay from 1998 to 2002. In the fall of 2002, I found toxic Pseudo-nitzschia in the Choptank River, a tributary of the Chesapeake Bay. Many species of algae produce chemicals that can be toxic to other organisms, but the triggers often are unclear. The objectives of this research project are to study: (1) the physiology of Pseudo-nitzschia toxin production with the goal of predicting what triggers it; and (2) the ecological and food web effects of Pseudo-nitzschia blooms and Pseudo-nitzschia toxin in the Chesapeake Bay.


The first working hypothesis is that Pseudo-nitzschia produce toxin during physiological stress as a way to excrete excess energy. Exposing Pseudo-nitzschia cultures to high light and low temperature conditions will cause an imbalance in energy going into the cell (light) and energy being processed (low temperatures slow down biological processes), resulting in an energy build-up within the cell. The second hypothesis is that DA is prevalent in the Chesapeake Bay environment at low levels and has many sublethal effects on organisms. To investigate this, I will take environmental samples from the water and living organisms and expose oysters to the toxin to look at changes in spawning and settling. The third hypothesis is that DA serves as a nitrogen source for other microbes. I plan to do a series of experiments to determine how DA degrades in turbid water and a series of growth experiments on its degradation products.

The research project will help explain DA production, explore new trophic links, possibly provide an explanation of why there have been no toxic events in Maryland, and be applicable to other systems with seasonal Pseudo-nitzschia problems. The results will contribute to the prediction and mitigation of harmful algae blooms and their effects.

Supplemental Keywords:

fellowship, Pseudo-nitzschia, neurotoxin, domoic acid, algae, toxin production, amnesic shelfish poisoning, Chesapeake Bay,, RFA, Health, Scientific Discipline, PHYSICAL ASPECTS, Water, Ecosystem Protection/Environmental Exposure & Risk, Health Risk Assessment, Oceanography, Risk Assessments, algal blooms, Physical Processes, Ecological Risk Assessment, Ecology and Ecosystems, marine ecosystem, marine food web, neurotoxin domoic acid, food web, marine biotoxins, Pseudo-Nitzschia species, coastal habitats, exposure, biotoxin risk, human exposure, algal toxins, Chesapeake Bay, diarrheic shellfish poisoning, marine toxins

Relevant Websites:

2004 STAR Graduate Fellowship Conference Poster (PDF, 1p., 5.95MB, about PDF)

Progress and Final Reports:

  • 2004
  • 2005
  • Final