TOXICITY OF SEDIMENT IN CHAGANG SEWAGE ENTRANCE OF DONGHU LAKE ON GOBIOCYPRIS RARUS

Donghu Lake is a typical shallow lake in the northeast of Wuhan city. It has been badly polluted by point and area sources and becomes severely eutrophic since 1950s. Anterior studies have shown that high concentration of nutrients, heavy metal and organic contamination existed both in water and sediment. In order to repair the ecological environment, more attention is being paid to inner contamination after outer contamination is controlled. In the present study, toxicity of the sediment collected from a main sewage entrance of Donghu Lake was studied, using Gobiocypris rarus as experimental animal because this species is sensitive to many poisons and has been widely used in toxicology in China. In this study, 96h acute toxicity test and embryoyolk sac stage larva toxicity test were made on the elutriate phase of sediment. The result showed that high concentration of elutriate had obvious toxicity effect on embryo, yolksac larva and young of G. rarus . Dose2effect relations between the concentration of elutriate and hatching rate, abnormality rate, survival rate and growth were analyzed. As the concentration of the elutriate increasing, decreasing of hatching rate and survival rate, increasing abnormality rate, as well as delay on growth were observed. It was proved that toxicity test on embryo2yolk sac stage was more sensitive than the 96h acute toxicity test . The no observed effect concentration (NOEC), the lowest observed effect concentration (LOEC) and the maximum acceptable toxicant concentration (MATC) for embryo2yolk sac stage were 12.5 %, 25 % and 17.68 %, respectively, while the median lethal concentration (LC50) for young was 69.1 %. These results suggested that the embryoyolk sac stage larva toxicity test of Gobiocypris rarus was a rapid, exact and sensitive test method and could be used in sediment toxicology in the future. Moreover, test on sundried sediment revealed that the NOEC was 100 %, which was 8 times higher than that of fresh sediment. This result implies that toxicity of sediment could be reduced by solar radiation photodegradation. In the end, the authors suggest that Donghu Lake should be reconnected with the Yangtze River to let the water level fluctuate seasonally. It would be in favor of controlling pollution and repairing ecological environment because the exist of hydrofluctuation land is helpful for solar radiation photodegradation and growth of aquatic plants.