Occurrence of Current-use Pesticides in Suisun Bay and Potential Effects on Phytoplankton

Science Center Objects

Suisun Bay is an area identified as critical habitat for the threatened Delta Smelt. Several important changes in the pelagic food web of this area have been documented over the last two decades indicating that food for Delta Smelt and other threatened fishes is in short. 

Satellite view showing locations of sites sampled during study.

Locations of sites sampled during study. (Public domain.)

There is evidence that primary productivity of diatoms is inhibited in Suisun Bay, and that ammonia may be causing that inhibition. An ongoing study is measuring nutrients, primary production, nutrient uptake by phytoplankton, and phytoplankton biomass and species composition in Suisun Bay during the spring to determine if there is inhibition and, if so, to determine what is causing the inhibition. But other contaminants in the water of Suisun Bay, such as current-use pesticides, may be contributing to this inhibition.

The objectives of this study are to characterize the mixtures of current-use pesticides present in Suisan Bay waters, determine their primary geographic sources, and assess the potential toxicity to phytoplankton in collaboration with toxicologists at AQUA-Science.

This study will consist of five tasks: (1) extraction and processing of water samples collected weekly for 10 weeks, (April 4 through June 13) from 3 sites, for a total of 30 environmental samples; (2) analyze samples for pesticides using two analytical methods; (3) analyze QA/QC samples and evaluate the results; (4) participate in TIE work with scientists from AQUA-Science by analyzing spiked water samples for pesticides; and (5) present final pesticide data and QA/QC results in spreadsheet format to cooperator following approval of the data by the CAWSC water quality specialist. The environmental sample and QA/QC results will also be entered into NWIS.