Iron as a Driver of Harmful Algal Population Dynamics and Toxicity

EPA Grant Number: F5E20951
Title: Iron as a Driver of Harmful Algal Population Dynamics and Toxicity
Investigators: Lakeman, Michael B.
Institution: University of Washington
EPA Project Officer: Packard, Benjamin H
Project Period: September 1, 2005 through August 1, 2008
Project Amount: $110,506
RFA: STAR Graduate Fellowships (2005) RFA Text |  Recipients Lists
Research Category: Academic Fellowships


Human activities in coastal terrestrial systems have marked affects on downstream marine ecosystems, especially in estuaries, which lie on the cusp of the two. One such effect, which has recently been observed, is a shift from macronutrient limitation to iron limitation for phytoplankton productivity in estuaries. These enclosed bays are also the site of the greatest impacts of harmful algal blooms (HABs). The bloom-forming Raphidophyte taxon, produces reactive oxygen species (ROS), which have been linked with iron acquisition strategies. This project will investigate the linkages between iron limitation, population structure of Raphidophyte blooms and their toxicity due to ROS.

The central hypotheses that this research project will address are that prolonged, anthropogenically lowered iron availability in estuaries causes:

  1. changes in the population structure of resident phytoplankton
  2. and increased toxicity of Raphidophyte blooms.


By plating the Raphidophyte alga Heterosigma akashiwo on iron-limited media, a selection for clonal, spontaneously occurring low-iron tolerant mutants will occur. These mutant lines will be screened for altered profiles of reactive oxygen species production. Sub-cellular fractions of selected mutant and wild-type lines will be subjected to 2-dimensional protein electrophoresis, and differentially expressed proteins will be identified by mass-spectroscopy and homology-based proteomics. These proteins will be used to develop antibody markers specific for ROS production and/or low-iron adaptation. These functional markers will then be tested against field populations.

Expected Results:

One expectation of this project is to increase knowledge of the molecular mechanisms by which Raphidophyte algae produce ROS by identifying proteins correlated with ROS production. The developed functional markers will be able to be used to interrogate field populations for two important purposes;

  1. following the changes in functional characteristics of phytoplankton populations in response to altered iron availability,
  2. and determining the potential toxigenicity of blooms of Raphidophyte algae.

Supplemental Keywords:

HABs, harmful algal blooms, phytoplankton, Raphidophytes, Heterosigma akashiwo, Chattonella, red tide, population dynamics, microevolution, evolution, intraspecific variation, intraspecific diversity, coastal development, deforestation, eutrophication, nutrient limitation, micronutrient limitation, iron, iron limitation, estuaries, phycotoxins, ROS, reactive oxygen species, superoxide, hydrogen peroxide, proteomics, homology-based proteomics, functional markers, molecular markers,, RFA, Scientific Discipline, Water, ECOSYSTEMS, Ecosystem Protection/Environmental Exposure & Risk, Aquatic Ecosystems, algal blooms, Environmental Monitoring, Ecological Risk Assessment, Ecology and Ecosystems, marine ecosystem, marine food web, estuaries, Pseudo-nitzschia, phytoplankton, trophic transfer of phycotoxins, benthic algae, trophic interactions, algal bloom detection, algal toxins, domoic acid producing diatoms, marine toxins

Progress and Final Reports:

  • 2006
  • 2007
  • Final