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(615) The Effects of Fipronil in an Estuarine Mesocosm.
Fulton, Michael*,1, Pennington, Paul1, DeLorenzo, Marie1, Wirth, Ed1, Key, Pete1, Bearden, Dan1, Sivertsen, Scott1, Shaddrix, Brian1, Walse, Spencer2, Ferry, John2, 1 National Ocean Service, Charleston, SC, USA2 University of South Carolina, Columbia, SC, USA
ABSTRACT- Fipronil is a phenylpyrazole insecticide that produces toxicity by blocking the GABA receptor in the central nervous system. The use of fipronil is increasing in the coastal zone, and although not intensively investigated, laboratory studies have shown that some aquatic invertebrates are extremely sensitive to fipronil. The goal of this study was to evaluate the sensitivity of selected estuarine species in a mesocosm system simulating a saltmarsh ecosystem. Twelve mesocosm units were constructed. Each unit was designed to allow for tidal flux and consisted of a stream channel and two elevated marsh components. Seawater, sediments, flora and fauna were collected from an uncontaminated site and established in the systems. Test species included sheepshead minnows (Cyprinodon variegatus), grass shrimp (Palaemonetes pugio), clams (Mercenaria mercenaria), and oysters (Crassostrea virginica). Four treatments with three replicates each were utilized and consisted of a single dose of fipronil at 0, 150, 355 and 5,000 ng/L. Endpoints measured included 28 day survival in all species, growth in fish, clams and oysters and reproduction in fish. Additionally, caged grass shrimp were added at weekly intervals to assess survival at discrete time points. An LC50 of 357 ng/L was estimated for grass shrimp at 28 days and significant grass shrimp mortality was observed in this species at the two highest fipronil concentrations. Significant mortality was observed in caged grass shrimp for six weeks after dosing in the highest treatment and for two weeks in the 355 ng/L treatment. No significant mortality was observed in fish, clams or oysters. Additional findings and the significance of these results will be discussed.
Key words: mesocosm , estuarine, insecticide, toxicity
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