Grantee Research Project Results

The Effect of Atrazine on Dimethyl Sulfur in Marine Phytoplankton

EPA Grant Number: F07E71122
Title: The Effect of Atrazine on Dimethyl Sulfur in Marine Phytoplankton
Investigators: Spiese, Christopher E.
Institution: The State University of New York
EPA Project Officer: Hahn, Intaek
Project Period: September 1, 2007 through September 1, 2010
RFA: Minority Academic Institutions (MAI) Fellowships for Graduate Environmental Study (2003) RFA Text |  Recipients Lists
Research Category: Academic Fellowships , Fellowship - Aquatic Ecology and Ecosystems , Fellowship - Oceanography

Objective:

Dimethyl sulfide (DMS) is thought to play a key role in climate regulation, as its oxidation leads to the formation of cloud condensation nuclei in the atmosphere. Although DMS is produced by marine phytoplankton from dimethylsulfoniopropionate (DMSP), its role in the cell is poorly understood. This study aims to look at DMS and its potential as an antioxidant compound – one that prevents damage caused by free radicals in the cell. It will examine this role by testing cellular responses to chemical stress induced by atrazine. Atrazine is a triazine herbicide that is the second most commonly used herbicide in the United States, and as such has the potential to impact estuaries and the coastal zone, where most of the oceanic primary productivity occurs.

Approach:

This project will focus primarily on laboratory cultures of axenic marine algae. Three classes of marine algae will be tested: diatoms, prymnesiophytes, and dinoflagellates. Atrazine will be the primary focus, but other chemical stressors of environmental importance will be used, such as paraquat, and cupric ion (Cu2+). All of these compounds are known to cause oxidative stress in photosynthetic organisms. Laboratory studies will focus on changes to the cellular concentrations of DMS, DMSP, and dimethyl sulfoxide (DMSO). Oxidative stress will be measured by quantifying both ascorbic acid and lipid peroxidation.

Expected Results:

It is anticipated that under stress, the cellular DMSP concentration should drop, as sulfur is transferred from the DMSP pool to DMS. Sulfur in the DMS pool will be transferred to the DMSO pool as radicals are scavenged. Enzyme activities such as DMSP lyase, which converts DMSP to DMS, and DMSO reductase, which converts DMSO to DMS, should also increase. As stress increases and cellular lysis occurs, there will be a shift in the dissolved sulfur pools toward the more oxidized sulfur species such as DMSO, dimethyl sulfone, and methane sulfonic acid.

Supplemental Keywords:

Atrazine, dimethyl sulfide, DMS, DMSP, dimethyl sulfoxide, DMSO, marine algae, estuaries,

Progress and Final Reports:

2008

2009

Final Report