Bioaccumulation And Transfer Of Nonylphenol In Chlorella Pyrenoidosa And Daphnia Magna

Nonylphenol(NP) is a typical environmental endocrine disruptors, widely exists in the Pearl River Estuary, and has harmful effects on aquatic ecosystems. In aquatic ecosystems, the microalgae is the first trophic level and extremely sensitive to the poisons in the water. Zooplanktons feed on microalgae, are important parts of the material circulation and energy flow in aquatic ecosystems. This paper aimed to study the enrichment and delivery effects of nonylphenol between Chlorella Pyrenoidosa and Daphnia magna in the Pearl River Estuary.The results showed that:(1) The 96 h-EC50 of NP for Chlorella Pyrenoidosa was 3.13 mg·L-1. The influence of NP on the cell density and chlorophyll content of Chlorella Pyrenoidosa showed clear dose-effect and time-effect change, both representing certain inhibition effect. Within 96 h, the algal density decreased by 3.81% to 50.4%, the content of chlorophyll a decreased by 8.5% to 23.6%, comparing with control group. In the toxicity test of NP on Daphina magna, the acute and chronic toxic effects of NP on Daphina magna were studied in this article. The 48 h-LC50 of NP on Daphnia magna was 37.41 μg·L-1, belonging to high toxic substances. NP could reduce the survival rate, intrinsic rate, generation period and average length of Daphnia magna. With the increase of NP concentration, inhibitory effect was gradually enhanced.(2) Chlorella pyrenoidosa had a rapid and high ability to enrich NP, in the bioconcentration test of NP between Chlorella Pyrenoidosa and Daphnia magna, the bioconcentration factor(BCF) of C. pyrenoidosa for NP ranged from 418.9 to 8429.12 within 24 h, and the accumulation amount ranged from 132.33 μg·g-1 to 826.38 μg·g-1(dry weight). Daphnia magna could enrich NP, within 15 d, the accumulation amount of NP ranged from 4.05 μg·g-1~29 μg·g-1(dry weight). NP in the water could significantly inhibit the survival and grazing process of Daphnia magna, at 15 d, the survival rate of Daphnia magna was 3.33%, and the grazing rate was 1.9×103 cells·h-1·ind-1.(3) NP in the body of Daphnia magna could be obtained through ingesting Chlorella pyrenoidosa with NP. Accumulation amount of NP in the Daphnia magna fed with Chlorella pyrenoidosa exposed NP ranged from 25.99 μg·g-1 to 29 μg·g-1(dry weight), which was less than the accumulation amount of NP in Chlorella pyrenoidosa. Accumulation amount of NP decreased when NP was trasferred from Chlorella pyrenoidosa to Daphnia magna, biological amplification effect did not exist in this process. NP in Chlorella pyrenoidosa could significantly inhibit the survival and grazing process of Daphnia magna. With the extension of feeding time, the inhibitory effect was gradually enhanced. The survival rate and grazing rate of feeding group were significantly inhibited by NP compared with the control. With the extension of time, inhibitory effect gradually increased. At 15 d, the survival rate of Daphnia magna was 6.67%, and the grazing rate was 1.8×103 cells·h-1·ind-1. This study could reveal the adverse effect of NP for hydrobios and help envaluate the long-term ecological risk of NP in aquatic ecosystems.