HA10 Environmental Toxicology, Environmental Assessment
D135-136
8:00 AM - 12:00 PM, Thursday
() Assessing Water Quality Effects of Aquatic Weed Control Methods using Biological and Chemical Endpoints.
David, N1, Hayworth, J1, Greenfield, B1, Siemering, G1, 1 San Francisco Estuary Institute, Oakland, CA, US
ABSTRACT- The Aquatic Pesticide Monitoring Program, funded by the State Water Resources Control Board, is evaluating the potential environmental impacts on water bodies treated for the control of aquatic plant growth in California. The impacts of pesticides and mechanical controls on biological and chemical characteristics of lakes and reservoirs were assessed utilizing different indicator tools. For assessing organism diversity and biotic integrity, benthic and epiphytic macroinvertebrates and phytoplankton were monitored. Phytoplankton species were highly variable between sites and sampling events. However, changes in phytoplankton richness and density showed no correlation with pesticide applications. Confounding factors, such as changes in nutrient concentrations and seasonal changes, could not be ruled out. Epiphytic invertebrate metrics indicated a contaminant-tolerant assemblage before and after the chemical treatment. However, several years of data would be necessary before definite conclusions can be made. No significant changes in nutrient concentrations, dissolved oxygen, or turbidity were associated with chemical applications. Additionally, changes in water quality were monitored for several mechanical treatment methods. Immediate environmental effects of mechanical harvesting, shredding, and crushing or grinding of invasive plant species were assessed by measuring conventional water quality parameters and nutrient concentrations in the treated water bodies. In mechanical harvester evaluations, comparison with reference sites and pre-treatment data indicated a slight increase in total phosphorus, ortho-phosphate, and turbidity at the experimental sites. As another quantitative assessment tool, fish species that were removed with the harvested plant material were identified and counted. Accidental fish mortality was primarily observed in juvenile bluegill sunfish (Lepomis macrochirus), and the overall removal rate was 0.074 fish per square meter.
Key words: weeds, aquatic, pesticides, harvesting