The acute and chronic toxicity of the dispersants Corexit 9527 and 9500, water accommodated fraction (WAF) of crude oil, and dispersant enhanced WAF (DEWAF) to Hydra viridissima (green hydra)

The acute and chronic toxicities of the dispersants Corexit 9527 and Corexit 9500 to green hydra (Hydra viridissima) were determined. The mean (SE) 96 h LC50 values for Corexit 9527 and Corexit 9500 were 230 (4.8) ppm and 160 (2.3) ppm. The 7-day no-observed-effect-concentration (NOEC) and lowest-observed-effect-concentration (LOEC) values based on population growth rates were <15 and 15 ppm for Corexit 9527 and 13 and 43 ppm for Corexit 9500. The mean (SE) 96 h LC50 values for water accommodated fraction (WAF) of Bass Strait crude oil, Corexit 9527 dispersant enhanced WAF (DEWAF) and Corexit 9500 DEWAF were 0.7 (0.1) ppm total petroleum hydrocarbons (TPH), 9.0 (0.5) and 7.2 (0.1) ppm TPH. The NOEC and LOEC values based on 7-day population growth rates were: 0.6 and >0.6 ppm TPH for WAF,<0.6 and 0.6 ppm TPH for Corexit 9527 DEWAF, and 2 and 4 ppm TPH for Corexit 9500 DEWAF.