Acute and chronic toxicity of the water accommodated fraction (WAF) and chemically enhanced WAF (CEWAF) of crude oil in the rock pool copepod Tigriopus japonicus

Abstract

We determined the toxicity of the water accommodated hydrocarbon fraction (WAF), two chemically enhanced WAFs (CEWAFs; CEWAF-C, Crude oil + Corexit 9500 and CEWAF-H, Crude oil + Hiclean) of crude oil and two dispersants (Corexit 9500 and Hiclean) to the rock pool copepod Tigriopus japonicus. In the acute toxicity test, Corexit 9500 was the most toxic of all the chemicals studied. The nauplius stages of T. japonicus were more susceptible to the toxic chemicals studied than the adult female. The toxicity data using the nauplius stages were then considered as a baseline to determine the spiking concentration of chemicals for chronic toxicity tests on thecopepod. In an experiment over two generations (F0 and F1), results of the chronic toxicity test, survival, sex ratio, developmental time and fecundity of the copepod exposed to several toxic chemicals showed various responses with different concentrations of chemicals. All chemicals used in this study resulted in an accumulation of toxicity. The lowest-observed-adverse-effect (LOAE) concentrations of WAF, CEWAF-H, CEWAF-C, Hiclean and Corexit 9500 were observed to be 50%, 10%, 0.1%, 1% and 1%, respectively. As a result, the two-generation toxicity tests were the most sensitive in this study and biochemical or molecular biological traits would be required for a moresensitive and precise assessment to further study.d Hiclean) to the rock pool copepod Tigriopus japonicus. In the acute toxicity test, Corexit 9500 was the most toxic of all the chemicals studied. The nauplius stages of T. japonicus were more susceptible to the toxic chemicals studied than the adult female. The toxicity data using the nauplius stages were then considered as a baseline to determine the spiking concentration of chemicals for chronic toxicity tests on thecopepod. In an experiment over two generations (F0 and F1), results of the chronic toxicity test, survival, sex ratio, developmental time and fecundity of