Ecotoxicological Studies On The Effects Of Eutrophication And Cyanobacteria On Planktonic Rotifers

The occurrence of toxic cyanobacterial blooms in eutrophic lakes, reservoirs, and recreational waters has become a worldwide problem. Such blooms are undesirable because they damage water quality, decrease dissolved oxygen and cause odor smelt. In addition, the cyanotoxins produced by cyanobacteria can be harmful to various aquatic organisms, also posing a health hazard to humans. In China, cyanobacteria blooms frequently occur in many shallow eutrophic lakes. However, there have been very few studies to evaluate the effects of eutrophication and cyanobacteria blooms on the planktonic rotifers. In this thesis, field investigations were conducted in the shallow eutrophic Lakes Chaohu and Taihu (Meiliang bay) to assess the effects of eutrophication and cyanobacteria blooms on the rotifer community and the relationships between rotifer and other aquatic organisms. In addition, the effects of Microcystis aeruginosa, a dominant species in cyanobacterial blooms, on the experimental populations of two common freshwater rotifers, Brchionus calyciflorus and B. rubens, were evaluated under different environmental conditions in laboratory experiments. The main results and conclusions are as follows.Rotifer assemblage in the shallow, eutrophic Lake Chaohu was investigated monthly from September 2002 to August 2003. Forty-nine species belonging to 18 genera and 14 families were recorded. The annual mean of the rotifer density was 453.6 ind./L, with the highest density of 1816.7 ind./L in June. The eutrophication of the lake has resulted in the great change in rotifer species composition. The indicator...