ACUTE TOXICITY STUDIES OF SURFACTANTS TO DAPHNIA-MAGNA AND DAPHNIA-PULEX

Several experiments were designed to examine the acute toxicity of surfactants to Daphnia. Specific tests were designed to develop comparisons between existing acute toxicity data for fish and similar data for Daphnia, and to provide data on the effects of various environmental factors on resultant toxicity of surfactants to Daphnia. Acute toxicity data for a series of homologous linear alkyl benzene sulfonates (LAS) demonstrate increases of up to one order of magnitude in toxicity for each increase of two alkyl carbons. LC 50's obtained with Daphnia magna are similar to those obtained with bluegills, L. Macrochirus. Comparative tests with D. magna and D. pulex indicate no statistical differences in 48-hr LC 50 values for three anionic and two nonionic surfactants. A 50 mg/L concentration of suspended, naturally-occurring kaolin significantly reduced the toxicity of longer chain length LAS homologs and had no effect on nonionic surfactant toxicity. In tests with variable hardness concentrations, the acute toxicity of LAS to D. magna is a combined function of both culture and test water hardness. The toxicity of a nonionic surfactant to D. magna was higher in soft water and was not affected by culture water hardness levels. Unlike previously published data for fish, the results of acute toxicity tests with D. magna cultures previously exposed to 0.4 mg/L LAS for periods up to seven generations indicated no significant difference in LAS susceptibility compared to simultaneously tested unexposed controls. © 1979 Springer-Verlag New York Inc.