Response of estuarine benthic invertebrates to field applications of insecticide

摘要

The response of estuarine invertebrates to the neonicotinoid insecticide imidacloprid following field applications in Willapa Bay, Washington (U.S.A.) was examined using Principal Response Curve (PRC) Analysis. A total of 60 analyses was conducted to examine responses of six taxonomic assemblages (polychaetes, non-juvenile polychaetes only, mollusks, non-juvenile mollusks only, crustaceans, and all invertebrates combined). Eight trials were conducted among five sites over the course of three years. Five of the eight featured a liquid formulation of imidacloprid and three a granular formulation. Both the response and treatment effects were significant (p 0.05) among 49 of the analyses, but pre-treatment differences in the abundance and composition of the assemblages at test and control plots often confounded interpretation of results. In the majority of analyses, the response of the treated assemblage relative to the control assemblage remained relatively stable over time, indicating a neutral treatment effect. Only six of the 60 PRCs indicated a negative effect from imidacloprid application. Five of the six were assemblages of mollusks and one was an assemblage of crustaceans. Polychaetes were never negatively affected. The low frequency of a negative effect was likely due to imidacloprid exposures that were limited to low concentrations and short time periods, low toxicological susceptibility to imidacloprid for many taxa, and natural resilience to disturbance and extreme environmental events. The long-term use of imidacloprid to suppress burrowing shrimp in Willapa Bay would likely increase the diversity of benthic invertebrates.