The Sensitivity ofCeriodaphnia dubia andDaphnia magna to seven chemicals utilizing the three-brood test

Abstract

This paper reports the sensitivity ofCeriodaphnia dubia andDaphnia magna to ethanol, acetone, phenol, 4-chlorophenol, trichloromethane, diethanolamine and chlorobenzene, utilizing the three-brood test. The endpoints examined include survival at 48 h and at the end of the three-blood test, total progeny, number of broods, mean brood size, and dry weight. The final calculated result was the LC₅₀/EC₅₀ or that concentration of the test solution that reduced the variable in question to 50% of that of the controls. Total progeny, number of broods and mean brood size provided results of the same order of magnitude for each compound for a specific organism. Dry weight proved to be a poor endpoint. The response ofC. dubia to six compounds failed to provide a determinable EC₅₀ due to a lack of significance of the regression equation. In the case ofD. magna, only five of the seven compounds provided a determinable result for dry weight. Compared to the results based on total progeny, number of broods and mean brood size, dry weight results in the absolute sense forD. magna were less sensitive for ethanol, phenol, 4-chlorophenol, more sensitive for trichloromethane, and about the same for diethanolamine as were the results for total progeny. For both cladocerans, progeny was the most sensitive endpoint for ethanol. For the other six compounds, survival at the end of the three-brood test provided LC₅₀/EC₅₀ results of the same order of magnitude as progeny, number of broods and mean brood size. Finally, it was of interest to discover the differences, if any, between these two cladocerans and place their response in relation to those other organisms that have been so tested. The three brood test results forD. magna prove this organism to be most sensitive to four out of the seven compounds.