Chronic Toxicity Testing with Daphnia magna in Three Generations

Abstract

This work shows the informativeness and predicted value of multigenerational testing on Daphnia magna Straus on exposure of 75 days in comparison with standard bioassays for chronic toxicity on exposure of 21–24 days. D. magna were exposed in water polluted with strontium chloride (1 and 2 mg Sr/L). No acute toxicity (death within 96 hours) and chronic toxicity (mortality and fertility within 24 days) were observed. In 50 days of the experiment, mortality of crustaceans was more than 30%, and fertility decreased by 2 times (P < 0.05). In 75 days of the experiment, mortality of the experimental daphnia was above 90%, and most of the individuals did not reproduce. The effects intensified in subsequent generations F2 and F3. In the third generation, the number of juveniles in 24 days of exposure (2 mg Sr/L) was only 9% of the control value (P = 0.03); then the juveniles did not appear. We also noted an increase in the number of abortive eggs and dead juveniles in generations F2 and F3 compared with F1. The totality of the observed effects testifies the delayed toxic effect of strontium. Delayed mortality and reduced fertility of the remaining individuals in a series of generations threaten the existence of the population of organisms. Therefore, chronic toxicity testing using D. magna is a method for detecting and predicting loss of biodiversity in the environment.