Effects of algal bloom (AB) on sediment microorganisms with special functions at different AB stages in Chaohu Lake

Algal bloom (AB) is a serious water environment problem in China, but it is still unclear how AB affects microorganisms with special functions (such as nitrogen-, phosphorus-, sulfur- and iron-related bacteria) at different AB stages. Samples of water and sediment were taken in the AB region and free algal bloom (FAB) region of Chaohu Lake at different AB stages, and the numbers of N-, P-, S- and Fe-related bacteria were determined by culture-dependent methods. Results showed that during the whole experiment, numbers of N-, P-, S-, and Fe-related bacteria in the AB region were significantly higher than those in the FAB region, especially at the AB outbreak stage. In the FAB region, numbers of above bacteria showed little variation with time. In the AB region, however, numbers of N-, S-, and Fe-related bacteria evidently changed as 'Λ'-type with AB process. They presented an upward trend at the AB formation stage and the initial stage of AB outbreak, and then showed a downward trend. Numbers of P-related bacteria also showed a similar trend as the above bacteria, but they kept high level for long time at the AB outbreak stage. This study indicated that AB produced different effects on microorganisms with special functions at different AB stages.