Ecophysiology Studies of Pseudo-Nitzschia Species

EPA Grant Number: R826306
Title: Ecophysiology Studies of Pseudo-Nitzschia Species
Investigators: Wells, Mark , Garrison, David L. , Goldman, Joel C. , Tjeerdema, Ronald S.
Institution: University of California - Santa Cruz
EPA Project Officer: Hiscock, Michael
Project Period: January 1, 1998 through December 31, 2001
Project Amount: $529,999
RFA: Harmful Algal Blooms (1997) RFA Text |  Recipients Lists
Research Category: Aquatic Ecosystems , Water Quality , Water , Ecosystems


Domoic acid-producing diatoms belonging to the genus Pseudo- nitzschia cause serious toxic algal blooms on the west coast of the United States that have resulted in deaths of seabirds in California water and humans poisonings in Oregon and Washington. Presently, little is known about the growth requirements of the individual species and the environmental conditions that promote toxicity. This project addresses the need for detailed information on how Pseudo-nitzschia species responds to various levels of macro- and micronutrients. These data are fundamental to developing the capability of predicting where and when these toxic blooms are likely to develop.

Based on published and unpublished findings on laboratory cultures and natural blooms of toxin producing Pseudo-nitzschia species, we identified the following specific hypothesis to be tested:

  • Production of domoic acid by toxigenic Pseudo-Nitzschia species varies as a function of silicate (Si)/nitrogen (N) limitation of the organism depending on their Si and N metabolic requirements,
  • Cellular production and release rates of domoic acid vary systematically with iron nutrient status of organisms, with rates being high under iron-deficient conditions and low in iron replete conditions,
  • Pseudo-Nitzschia species have a high iron requirement, so that toxic blooms in coastal waters are restricted to sites and times when iron concentrations in surface waters are high.


We will determine the macronutrient requirements of various Pseudo-nitzschia species, including both those now available in cultures and newly isolated clones from Monterey Bay. Both sequential batch and continuous cultures will be used to characterize the growth response, nutrient uptake kinetics, and domoic acid production under various macronutrient stress conditions. Iron uptake kinetics, intracellular iron content and iron use efficiencies will be measured at a variety of Fe availabilities. Domoic acid production and release rates under these micronutrient manipulations will be measured. The goal of these laboratory experiments is to assess the precise growth conditions which trigger domoic acid production by these toxigenic species.

Expected Results:

The proposed research will contribute significantly to management strategies for future domoic acid blooms in coastal waters of the Pacific and elsewhere. Being able to predict where and when blooms of toxigenic Pseudo-nitzschia species are likely to develop, would lead to considerably more efficient monitoring strategies and an enhanced ability to plan appropriate responses. If our hypotheses prove correct, serious toxic bloom problems may be restricted to specific regions of the coast system where micro- or macronutrient concentrations are sufficiently high to support the development of high-density blooms. These same conditions may also affect the levels of toxin produced by blooming species.

Publications and Presentations:

Publications have been submitted on this project: View all 13 publications for this project

Journal Articles:

Journal Articles have been submitted on this project: View all 3 journal articles for this project

Supplemental Keywords:

Marine, Ecological effects, Human health, Organism, Toxics, Organics, Indicators, Aquatic, Environmental chemistry, Biology, CA, RFA, Scientific Discipline, Water, Geographic Area, Ecosystem Protection/Environmental Exposure & Risk, Environmental Chemistry, Ecosystem/Assessment/Indicators, Ecosystem Protection, State, Oceanography, Ecological Effects - Environmental Exposure & Risk, algal blooms, Pacific Northwest, Biology, seabird deaths, aquatic, aquatic ecosystem, ecological effects, ecological exposure, bloom dynamics, estuaries, Pseudo-Nitzschia species, Oregon, harmful algal blooms, nutrient kinetics, Washington (WA), transport and concentration, iron deficient conditions, ecophysiology, California (CA), domoic acid producing diatoms, OR

Progress and Final Reports:

  • 1998
  • 1999
  • 2000 Progress Report
  • Final Report