Assessing the risk to green sturgeon from application of imidacloprid to control burrowing shrimp in Willapa Bay, Washington--Part II: controlled exposure studies.
The activities of 2 species of burrowing shrimp have a negative impact on the growth and survival of oysters reared on intertidal mudflats in Willapa Bay and Grays Harbor, Washington (USA). To maintain viable harvests, oyster growers proposed the application of the neonicotinoid insecticide imidacloprid onto harvested beds for the control of burrowing shrimp. In test applications, water column concentrations of imidacloprid were relatively low and dissipated rapidly. The foraging activities of the green sturgeon (listed in the US Endangered Species Act) could result in exposure to higher, more sustained imidacloprid concentrations within sediment porewater and from the consumption of contaminated shrimp. Controlled experiments were conducted using surrogate white sturgeon to determine acute and chronic effect concentrations, to examine overt effects at more environmentally realistic concentrations and durations of exposure, and to assess chemical depuration. The 96-h median lethal concentration was 124 mg L(-1) , and the predicted 35-d no-observed-adverse-effect concentration was 0.7 mg L(-1) . No overt effects were observed following environmentally relevant exposures. Imidacloprid half-life in plasma was greater than 32 h. Measured concentrations of imidacloprid in porewater were significantly lower than the derived acute and chronic effect concentrations for white sturgeon. Exposure risk quotients were calculated using the effect concentrations and estimated environmental exposure. The resulting values were considerably below the level of concern for direct effects from either acute or chronic exposure to an endangered species.
Washington Cooperative Fish and Wildlife Research Unit, School of Aquatic and Fishery Sciences, University of Washington, Seattle, Washington, USA.
John A
JA
Frew
Washington Cooperative Fish and Wildlife Research Unit, School of Aquatic and Fishery Sciences, University of Washington, US Geological Survey, Seattle, Washington, USA.
Christian E
CE
Grue
D000818:Animals; D061006:Bays; D002851:Chromatography, High Pressure Liquid; D003445:Crustacea / Q000502:physiology*; D004781:Environmental Exposure; D004784:Environmental Monitoring; D004797:Enzyme-Linked Immunosorbent Assay; D005399:Fishes / Q000378:metabolism; D019015:Geologic Sediments / Q000737:chemistry; D006207:Half-Life; D007093:Imidazoles / Q000097:blood*; D007306:Insecticides / Q000097:blood*; D000073943:Neonicotinoids; D009574:Nitro Compounds / Q000097:blood*; D018570:Risk Assessment; D053719:Tandem Mass Spectrometry; D013696:Temperature; D013997:Time Factors; D023382:Toxicity Tests, Acute; D014861:Washington; D014874:Water Pollutants, Chemical / Q000097:blood*
D007093:Imidazoles; D007306:Insecticides; D000073943:Neonicotinoids; D009574:Nitro Compounds; D014874:Water Pollutants, Chemical; C082359:imidacloprid
Burrowing shrimp; Effects characterization; Green sturgeon; Imidacloprid; Willapa Bay