Effect Of Rain Water And River Water On Cyanobacteria In Taihu Lake

Rain and river water are the main sources of inputing nutrient in Taihu lake. On the Laboratory controlling conditions, the impact of rainwater and different kinds of river water on cyanobacteria (Microcystis sp.) growth were investigated.The results are as follows:1 The influence of precipitation on the growth of cyanobacteria:Under the processing of different rainwater proportion, Chla content in cyanobacteria achieves maximum of each process on the second day, and significantly higher than of CK, but substantially drops in the next days. Cyanobacteria Chla content decreased with the increase of rainwater proportion. The results show in a short time that rainwater significantly stimulates cyanobacteria growth, and the effect of that is weakened by the increase of rainwater proportion.On the first days of nutritive salt regulation on different proportions of rainwater experimental treatments, cyanobacteria Chla content is significantly higher in the rainfall treatment with the regulation of nitrogen and phosphorus than not with them, and cyanobacteria Chla content in low rainfall proportion treatment is higher than high rainfall proportion. In the late period, algae Chla content in the treatment of rainwater with phosphorus is higher than with nitrogen, and is also higher in the low rainwater proportion treatment with phosphorus than high rainwater proportion treatment with phosphorus.2 The influence of rainwater pH on the growth of cyanobacteria:In low rainwater pH conditions, Cyanobacteria chlorophyll fluorescence is inhibited, Cyanobacteria growth is slowed, and cyanobacteria death rate is higher than cell division rate. but increases at low pH, but rainwater nutritive salt can significantly promote Cyanobacteria growth, and ease the stress of rainwater on Cyanobacteria acid.Cyanobacteria in the process of growth will affect the environment pH. In the low pH conditions in the rainwater, the Cyanobacteria can not adjust pH to 7.0, but after adding nutritive salt to the low pH rain, Cyanobacteria can regulate the pH to between 8.0 and 9.0.Regardless of pH level of rain, rainwater pH has a great impact on the cyanobacterial NPQ, leading to NPQ is significantly lower than control sample, which indicates that the cyanobacteria tolerance in hard light is reduced, and photosynthetic organs are more vulnerable to injury in the hard light.3 The influence of river water on the growth of cyanobacteria:Industrial waste river water more significantly affects the growth of cyanobacteria than lake water, long time treatment results in Fv '/Fm'and NPQ decreasing, effects the potential quantum efficiency of cyanobacteria in PSⅡlight, weakens cyanobacteria tolerance in hard light, and the photosynthetic organ is more vulnerable to damage under strong light. ETR-PAR response the initial slope (a) of the curve basic parameters, maximum electron transport rate(ETRmax) compared to its initial value decreases significantly, while the increasing of half-saturation light intensity (Ek) inhibits ETR-PAR response curve growth. The agricultural nonpoint source river water, sewage river water and lake water has no significant difference.