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 increased CO2 (low pH), are less understood. Toxicity was assessed at 4 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-day 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, whereas resmethrin was the most toxic compound in clam larvae. Mortality for both species generally increased with chronic insecticide exposure (21-day LC50 values ranged from 0.60 to 9.49 mg/L). Insecticide exposure also caused sublethal effects, including decreased swimming activity after 4 days in larval oysters (4-day EC50 values of 0.60 to 2.33 mg/L) and decreased growth (shell area and weight) in juvenile clams and oysters after 21 days (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.

Pharmaceuticals and personal care products (PPCPs) such as caffeine and sulfamethoxazole have been detected in the estuarine environment. The present study characterized effects of a maternal exposure of these compounds on the development of the daggerblade grass shrimp Palaemonetes pugio from embryo to juvenile life stage. Ovigerous females were exposed to either caffeine (20 mg/L), sulfamethoxazole (60 mg/L), or a mixture of both (20 mg/L caffeine and 60 mg/L sulfamethoxazole). Embryos were then removed from the females and the effects of the PPCPs on hatching, metamorphosis, juvenile growth, and overall mortality were determined. No significant effect was observed on gravid female survival after 5 d of exposure to caffeine, sulfamethoxazole, or the mixture; however, development of the embryos on the female shrimp was delayed in the mixture. Caffeine and sulfamethoxazole in the mixture significantly reduced embryo survival. There was a significant effect of caffeine, sulfamethoxazole, and the mixture on embryo hatching time. Exposure to sulfamethoxazole alone significantly delayed larval metamorphosis. Exposure to caffeine and sulfamethoxazole separately led to significantly smaller length of juvenile shrimp. Maternal exposure to caffeine and sulfamethoxazole, individually and in mixture, resulted in negative effects on P. pugio offspring survival and development; however, the concentrations tested in the present study were well above maximum detected field concentrations. These results may be incorporated into PPCP risk assessments to protect sensitive estuarine ecosystems more effectively.