UNDERSTANDING AND PREDICTING THE IMPACT OF AGRICULTURE ON THE ENVIRONMENTAL INTEGRITY OF MANAGED WATERSHEDS
Location: Water Quality and Ecology Research
Title: Effects of an atrazine, metolachlor, and fipronil mixture on Hyalella azteca (Saussure) in a modified backwater wetland
Submitted to: Bulletin of Environmental Contamination and Toxicology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: August 3, 2009
Publication Date: August 22, 2009
Citation: Lizotte Jr., R.E., Knight, S.S., Shields Jr., F.D., Bryant, C.T. 2009. Effects of an atrazine, metolachlor, and fipronil mixture on Hyalella azteca in a modified backwater wetland. Bulletin of Environmental Contamination and Toxicology. 83(6):836-840. DOI:10.1007/s00128-009-9850-1.
Interpretive Summary: Natural wetlands occurring in a flood plain near rivers can be modified to be used as best management practices to improve and sustain river water quality. A study was done in a modified natural flood plain wetland near the Coldwater River in northern Mississippi to improve our understanding of how well this wetland could decrease effects of three commonly used agricultural pesticides, atrazine, metolachlor and fipronil on aquatic animals. The study showed the flood plain wetland was capable of efficiently decreasing the effects of all three pesticides and preventing them from entering the Coldwater River and possibly affecting aquatic animals. These results are of interest to regulatory and other agencies and the pesticide industry as an additional tool to improve and sustain river water quality and overall environmental quality.
We examined the toxicity mitigation efficiency of a hydrologically modified backwater wetland amended with a mixture of three pesticides, atrazine, metolachlor, and fipronil, using 96 h survival bioassays with Hyalella azteca. Significant H. azteca 96 h mortality occurred within the first two hours of amendment at the upstream amendment site but not at any time at the 700 m downstream site. H. azteca survival varied spatially and temporally in conjunction with measured pesticide mixture concentrations. Estimated 96 h pesticide mixture LC50 values (µg L-1) ranged from 5.911-6.073, 3.280-3.462, 0.386-0.403, and 0.018-0.024 for atrazine, metolachlor, fipronil, and fipronil-sulfone (metabolite).