[Eutrophication and pollution level of microcystin in Dianshan Lake].

A survey was conducted in Dianshan Lake to study the eutrophication indexes including total phosphorus (TP), total nitrogen (TN), pH, temperature, diaphaneity and chlorophyll-a level and dominant algae in seasons. The impacts of temperature, light, nitrogen and phosphorus on growth of and microcystin LR production by Microcystis aeraginosa strain under laboratory conditions were studied. Relationship between algal cell density and concentration of microcystin LR were studied. Results suggest that water in Dianshan Lake was eutrophicated. The suitable seasons for algae growth are the end of spring and summer. The annual average of TP and TN were 1.93 mg/L and 0.18 mg/L respectively. And 93.5 and 92.2 percent of TP and TN were higher than the criteria for the third class water body. Significant impact from agriculture was indicated since the peak of algae laged one month after the maxium use of fertilizer. The dominant algae in Dianshan Lake were cyanobacteria, bacillariophyta, cryptophyta and euglenophyta. Microcystis, anabaena and synedra, which excrete toxins and indicate water pollution, and are dominant algae species in summer. M. aeraginosa strain had a biggest growth rate at temperature of 25 degrees C and light intensity of 3 0001x, while microcystin LR production contents reached maximum at 20 degrees C and 5000lx respectively. The optimum TP and TN concentrations for growth of and toxin production by M. aeraginosa were found to be 650 micromol/L and 6.5 micromol/L respectively. TP is suspected to be the limiting factor for the growth of algae both in field and laboratory conditions. Positive correlations between total microcystin LR concentrations and algae cell density or M. aeraginosa cell densities are found. The algae cell density can be used to predict the level of algal toxins in water.

[Survey on the contamination of microcystin-LR in water supply of Shanghai city].

OBJECTIVE: To study the pollution level of microcystin-LR in water supply of Shanghai city and the removal efficacy for microcystin-LR through routine water treatment technique. METHODS: High performance liquid chromatogram (HPLC) was applied to determine the concentration of microcystin-LR in source water, water samples after various water treatment procedures and tap water. RESULTS: The concentration of microcystin-LR varied with sampling seasons and sites and reached peak during summer and fall. The maximum of microcystin-LR was 2.38 microg/L in source water. Coagulation plus chlorine disinfection were found to be effective for the removal of microcystin-LR, while the remove rate through filtration was not significant. And it could also be detected in tap water as high as 1.27 microg/L. CONCLUSION: The source waters of Shanghai city were polluted by cyanobacteria toxins represented by microcystin-LR. The source water in suburb was more polluted. Routine water treatment techniques can not remove the toxins effectively.

[Study on DNA damage induced by microcystin-LR].

OBJECTIVE: To investigate whether microcystin-LR (MC-LR) at doses which were not cytotoxic can induce DNA damage and compare its effect on HL-7702 and KB cell lines. METHODS: Cytotoxin and DNA damage were detected by MTT and comet assay, respectively. RESULTS: As doses ranged from 10 to 100 micro/L, MC-LR showed no significant impact on viability of these two cell lines. However, DNA damage induced by MC-LR occurred at the dose of 30 microg/L in HL-7702 cell and significantly increased with dose. MC-LR did not induce DNA damage in KB cell. CONCLUSION: MC-LR has potential genotoxicity, DNA damage induced by MC-LR is more significant in hepatocyte with bile acid transportation system than other cell lines.