Employing molecular, chemical and physiological techniques using Crassostrea virginica to assess ecosystem health along coastal South Carolina and North Carolina, United States.

Natural and anthropogenic environmental impacts can introduce contaminants into sensitive habitats, threatening ecosystems and human health. Consistent monitoring of coastal areas provides critical environmental assessment data. Sediments and Eastern Oyster (Crassostrea virginica) tissues were collected at fourteen South Carolina (SC) and four North Carolina (NC) sites as part of the National Oceanic and Atmospheric Administration's Mussel Watch environmental monitoring program. Cellular and molecular techniques were employed to measure C. virginica stress response, specifically, Lipid Peroxidation (LPx), Glutathione (GSH), and qPCR techniques. Gene specific primers targeted for detecting oxidative stress and cellular death were developed in C. virginica to gauge response to current environmental conditions using gill and hepatopancreas (HP) tissue. In order to validate gene specific markers as additional assessment tools, a 96 h zinc (Zn) laboratory exposure was performed. Cellular biomarker data revealed tissue specific responses. Hepatopancreas data showed C. virginica exhibited stress through the lipid peroxidation assay amongst sampling sites, however, response was managed through glutathione detoxification. Gill tissue data had significantly lower levels of cellular biomarker response compared to hepatopancreas. Molecular biomarkers targeting these cellular stress pathways through qPCR analysis show upregulation of Metallothionein in hepatopancreas and gill tissue with a concurrent > 2-fold upregulation in the detoxification marker Superoxide Dismutase (SOD) at three NC sites. SC sites displayed higher stress levels through LPx assays and down-regulation in GPx gene activity. Laboratory zinc exposure revealed no significance in cellular biomarker results, however, molecular data showed gills responding to zinc treatment through upregulation of Metallothionein, SOD and Cathepsin L, indicating an acute response in gills. Collectively, chemical, cellular and molecular methods clarify sentinel stress response of biological impacts and aid in evaluating environmental health in coastal ecosystems. This combined methodological approach provides a detailed analysis of environmental conditions and improves land-use management decisions.

Toxicity of fipronil and its enantiomers to marine and freshwater non-targets.

Fipronil is a phenylpyrazole insecticide used in agricultural and domestic settings for controlling various insect pests in crops, lawns, and residential structures. Fipronil is chiral; however, it is released into the environment as a racemic mixture of two enantiomers. In this study, the acute toxicity of the (S,+) and (R,-) enantiomers and the racemic mixture of fipronil were assessed using Simulium vittatum IS-7 (black fly), Xenopus laevis (African clawed frog), Procambarus clarkii (crayfish), Palaemonetes pugio (grass shrimp), Mercenaria mercenaria (hardshell clam), and Dunaliella tertiolecta (phytoplankton). Results showed that S. vittatum IS-7 was the most sensitive freshwater species to the racemic mixture of fipronil (LC50 = 0.65 microg/L) while P. pugio was the most sensitive marine species (LC50 = 0.32 microg/L). Procambarus clarkii were significantly more sensitive to the (S,+) enantiomer while larval P. pugio were significantly more sensitive to the (R,-) enantiomer. Enantioselective toxicity was not observed in the other organisms tested. Increased mortality and minimal recovery was observed in all species tested for recovery from fipronil exposure. These results indicate that the most toxic isomer of fipronil is organism-specific and that enantioselective toxicity may be more common in crustaceans than in other aquatic organisms.