In order to investigate the toxic effects of suspended particulate matter and microcystins complexes on Daphnia magna,the most frequently detected variants of microcystin,MC-LR,was selected and the suspended particulate matter(SPM)and MC-LR complexes were prepared.The acute toxicity of MC-LR adsorbed SPM(SPM-MC-LR)on Daphnia magna was also studied.The results showed that the adsorption process of MC-LR by SPM fitted well with the pseudo-second-order kinetic model and Freundlich isothermal adsorption model,and a maximum adsorption capacity of 1720µg/g was determined.This multimolecular layer adsorption dominated by chemical adsorption was relatively easy to occur.SPM-MC-LR influenced the immobilization rate(the maximum immobilization rate reached 93.77%)and the activity of antioxidant enzymes of Daphnia magna,with positively dose and time dependent manner.However,when the MC-LR content reached 73.52 and 94.53µg/g on the SPM surface,the oxidative stress triggered in the Daphnia magna would inhibit the activities of antioxidant enzymes.As a result,the activities of SOD and CAT after 48h exposure to SPM-MC-LR were decreased by 21.44%,26.51%and 6.2%,18.27%in comparison to that after 24h exposure,respectively.Compared with single MC-LR,the presence of SPM may enhance the toxicity of MC-LR toward Daphnia magna.
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