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Interactive Effects of Mosquito Control Insecticide Toxicity, Hypoxia, and Increased Carbon Dioxide on Larval and Juvenile Eastern Oysters and Hard Clams

Author(s): Garcia, R.N.; K.W. Chung; P.B. Key; L.E. Burnett; L.D. Coen; M.E. DeLorenzo


Publication Type: Journal Article

Journal Title: Archives of Environmental Contamination and Toxicology

Date of Publication: 2014

Reference Information: 66(3): 450-462

Keywords: bivalve molluscs; toxicity; mosquito control insecticides; Hypoxia; pH

Abstract: Mosquito control insecticide use in the coastal zone coincides with the habitat and mariculture operations of commercially and ecologically important shellfish species. Few data are available regarding insecticide toxicity to shellfish early life stages, and potential interactions with abiotic stressors such as low oxygen and elevated CO2 (low pH) are less understood. Toxicity was assessed at 4 days and 21 days for larval and juvenile stages of the Eastern oyster, Crassostrea virginica, and the hard clam Mercenaria mercenaria, using two pyrethroids (resmethrin and permethrin), an organophosphate (naled), and a juvenile growth hormone mimic (methoprene). Acute toxicity (4 d LC50) values ranged from 1.59 to >10 mg/L. Overall, clams were more susceptible to mosquito control insecticides than oysters. Naled was the most toxic compound in oyster larvae, while resmethrin was the most toxic compound in clam larvae. Mortality for both species generally increased with chronic insecticide exposure (21 d LC50 values ranged from 0.60 to 9.49 mg/L). Insecticide exposure also caused sublethal effects, including decreased swimming activity after 4 d in larval oysters (4 d EC50 values of 0.60 to 2.33 mg/L) and decreased growth (shell area and weight) in juvenile clams and oysters after 21 d (detected at concentrations ranging from 0.625 to 10 mg/L). Hypoxia, hypercapnia and a combination of hypoxia and hypercapnia caused mortality in larval clams and increased resmethrin toxicity. These data will benefit both shellfish mariculture operations and environmental resource agencies as they manage the use of mosquito control insecticides near coastal ecosystems.