Effect of Bifenthrin and Reduced Salinity Exposure on Larval Sheepshead Minnows (Cyprinodon variegatus) and Grass Shrimp (Palaemon pugio) Aquaculture and Fisheries Studies

In 2016 America’s coastal counties were home to more than 40 percent of the total population despite accounting for less than 10 percent of the country’s landmass. Large-scale changes in land use lead to proportional increases in impervious ground cover, ultimately resulting in increased input of stormwater runoff into adjacent waterways. Stormwater runoff reduces salinity and increases contaminant loads as rainwater washes pollutants, including pesticides such as bifenthrin, into receiving waters. The present study examined bifenthrin toxicity and the potential combined effect of reduced salinity for larval sheepshead minnows (Cyprinodon variegatus) and grass shrimp (Palaemon pugio). LC50 values were established in salinities of 20, 10, and 5 psu as 0.431, 0.415, 0.377 µg/L and 0.00650, 0.00640, 0.000109 µg/L for larval C. variegatus and P. pugio, respectively. Salinity did not significantly affect bifenthrin toxicity to larval C. variegatus, but mortality rates increased to 90% when larval P. pugio were exposed to 0.0015 µg/L of bifenthrin in 5 psu compared to 20 psu. Given that stormwater input is increasing as a result of increasing impervious cover, it is critical to understand how exposure to bifenthrin in low-salinity regimes affects estuarine organisms.