Acute toxicity of selected organic pollutants to saltwater (mysid Siriella armata) and freshwater (cladoceran Daphnia magna) ecotoxicological models.

The acute toxicity of three organophosphate pesticides (diazinon, chlorpyrifos, pirimiphos-methyl) two chlorinated biocides (endosulfan, pentachlorophenol) and a nonsteroidal anti-inflammatory drug (diclofenac) was tested on <24 h neonates of saltwater mysidacea (Siriella armata) in laboratory acute toxicity test. The 50 and 10 % lethal effective concentrations (LC(50) and LC(10)), NOEC and LOEC values were calculated. The three organophosphate pesticides showed an apparently biphasic dose-response profile, supporting that its mechanism of action in crustaceans differ from other organic compounds. The biphasic pattern of response was confirmed using the common aquatic ecotoxicological model Daphnia magna. According to the 96-h LC(50) values for S. armata, the ranking of toxicity was chlorpyrifos (0.13 µg/L) < pirimiphos-methyl (1.3 µg/L) < endosulfan (3.2 µg/L) < diazinon (4.03 µg/L) < pentachlorophenol (262.2 µg/L) < diclofenac (2919 µg/L). In general, mysids resulted at least one order of magnitude more sensitive than model daphnia, which stresses the need for using marine species for the derivation of seawater quality standards.