Plasma cholinesterase activity as a biomarker for quantifying exposure of green sturgeon to carbaryl following applications to control burrowing shrimp in Washington State

Willapa Bay (Washington State, USA) has been 1 of the rare intertidal locations where large-scale pesticide applications occur. Until recently, carbaryl was applied to control burrowing shrimp that decrease commercial oyster productivity. The bay is a critical habitat for green sturgeon (Acipenser medirostris), an anadromous species listed as threatened under the US Endangered Species Act. However, the hazard that carbaryl poses is unknown. Surrogate seawater-acclimated white sturgeon (A. transmontanus) were exposed to 0gL(-1), 30gL(-1), 100gL(-1), 300gL(-1), 1000gL(-1), and 3000gL(-1) carbaryl for 6h, and brain acetylcholinesterase (AChE) and plasma butyrylcholinesterase (BChE) activities were measured. Enzyme recovery was measured in an additional cohort exposed to 1000gL(-1) carbaryl for 6h. Activity of AChE was reduced (p0.001) at concentrations100gL(-1) with recovery in the 1000gL(-1) cohort by 72h. Surprisingly, BChE activity was greater than controls at concentrations300gL(-1) (p>0.05), a finding confirmed in additional fish exposed to 3000gL(-1) for 6h (+30%, p < 0.001) with apparent recovery by 48h. Plasma samples were collected from free-living green sturgeon before and 4d to 5d after application of carbaryl in Willapa Bay. Activity of BChE after application was reduced 28% (p<0.001), indicating exposure to the pesticide. However, the lack of congruence between BChE and AChE activity in captive white sturgeon exposed to carbaryl indicates that further studies are needed to better understand the risk carbaryl exposure poses to green sturgeon. Environ Toxicol Chem 2016;35:2003-2015. (c) 2015 SETAC