The Impacts of Harmful and Toxic Phytoplankton and Prey Concentration on Zooplankton Grazer Production of Dissolved Organic Matter (DOM)

EPA Grant Number: F6E21170
Title: The Impacts of Harmful and Toxic Phytoplankton and Prey Concentration on Zooplankton Grazer Production of Dissolved Organic Matter (DOM)
Investigators: Henderson, Grace Kathleen
Institution: College of William and Mary
EPA Project Officer: Lee, Sonja
Project Period: September 1, 2006 through September 1, 2009
Project Amount: $111,172
RFA: STAR Graduate Fellowships (2006) RFA Text |  Recipients Lists
Research Category: Academic Fellowships , Aquatic Ecosystems , Fellowship - Oceanography and Coastal Processes


Estuarine and coastal systems are extremely sensitive to eutrophication and subsequent shifts in the phytoplankton composition favoring chronic occurrence of harmful and toxic phytoplankton. Harmful algal blooms (HABs), including toxic species, have been increasing in both frequency and range since the 1970s, and Chesapeake Bay has experienced an increase in the number of toxic diatom and dinoflagellate species over the past several decades. Concurrently with these phytoplankton composition changes, zooplankton grazing and nutrient release processes are expected to change. Only a small number of studies have focused on DOM production from zooplankton, which is one of the major pathways of DOM from phytoplankton to bacteria, and there have been no published studies on DOM production and composition as a result of grazing processes on harmful or toxic algal species.

The objective of this project is to explore the importance of mesozooplankton (copepods) and microzooplankton (heterotrophic ciliates and dinoflagellates) grazing on harmful and toxic algal species and the subsequent DOM release rate, magnitude, and composition.


I will conduct laboratory zooplankton grazing experiments using selected cultures of harmful or toxic algal species of increasing importance in Chesapeake Bay (and non-toxic algal species of the same or similar species), at varying concentrations to determine the release rate, quantity, and composition of DOM released from zooplankton. Concurrently in the field, I will determine in situ zooplankton grazing and release rates of DOM during two seasonal harmful and potentially toxic phytoplankton blooms.

Expected Results:

A decrease in ingestion or avoidance of harmful and toxic phytoplankton by grazers will most likely yield lower nutrient release rates. However, if the harmful or toxic algae have no detrimental effect on the zooplankton grazers, high concentrations of DOM may also be released via sloppy feeding and metabolism of the organic toxins during dense HABs. My results will provide information on nutrient cycling dynamics in estuaries and coastal oceans and help predict how nutrient budgets will change with enhanced eutrophication, and subsequent increases in the presence of harmful and toxic algal blooms.

Supplemental Keywords:

zooplankton, toxic phytoplankton, harmful algal blooms (HABs), grazing, biogeochemical cycling, dissolved organic matter, carbon, nitrogen, eutrophication, Chesapeake Bay,, RFA, Scientific Discipline, Water, Ecosystem Protection/Environmental Exposure & Risk, algal blooms, Biochemistry, Environmental Monitoring, Ecology and Ecosystems, marine ecosystem, dissolved organic matter, hydrography, dinoflagellates, nutrient enrichment, biogeochemical, HAB ecology, phytoplankton, phytoplankton population dynamics, carbon-specific growth rates, algal bloom detection, algal toxins, nitrogen

Progress and Final Reports:

  • 2007
  • 2008
  • Final