John Wiley & Sons, Ltd.

The acute toxicity of chemically and physically dispersed crude oil to key arctic species under arctic conditions during the open water season

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The acute toxicity of physically and chemically dispersed crude oil and the dispersant Corexit 9500 were evaluated for key Arctic species. The copepod Calanus glacialis, juvenile Arctic cod (Boreogadus saida), and larval sculpin (Myoxocephalus sp.) were tested under conditions representative of the Beaufort and Chukchi Seas during the ice‐free season. Toxicity of three water accommodated fractions (WAF) of Alaska North Slope (ANS) crude oil was examined with spiked, declining exposures. A dispersant‐only test was conducted with the copepod, C. glacialis. Each preparation with oil [WAF, breaking wave WAF (BWWAF), chemically enhanced WAF (CEWAF)] produced distinct suites of hydrocarbon constituents; the total concentrations of oil was lowest in WAF and highest in CEWAF preparations. The relative sensitivity for the different species and age classes was similar within WAF type. Median lethal concentrations (LC50) values based on TPH ranged from 1.6 to 4.0 mg/L for WAF and BWWAF treatments, and from 22 to 62 mg/L for CEWAF. For Corexit 9500 exposures, LC50 values ranged from 17 to 50 mg/L. The differences in the relative toxicity among the accommodated fractions indicated that the majority of petroleum hydrocarbons in the CEWAF are in less acutely toxic forms than the components that dominate the WAF or BWWAF. Further evaluation showed that the parent PAH compounds, specifically naphthalene, were highly correlated to acute toxicity. Environ Toxicol Chem © 2013 SETAC

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