Bacterial and cyanobacterial diversities determined by T-RFLP analyses in the Jiaozhou Bay

The methods of DAPI staining epifluorescence microscopy and T-RFLP analysis were used to analyze the microbial abundance and diversity in surface seawater sampled from 12 stations inside and outside of the Jiaozhou Bay during a survey on 12 and 13 September 2004. The abundance of total microbes is in the range of 10 6~10 7 cells/cm 3, similar to those of most semi-enclosed bays in the temperate areas in the world. The highest microbial densities occur in the northeastern part of the Jiaozhou Bay, around the mouths of Loushan and Licun Rivers and the Hongdao aquacultural farming areas, suggesting that the degree and characteristics of pollutions, along with geographical and hydrological effects, may be important determinants affecting the abundance and distribution of bacteria in the Jiaozhou Bay. Bacterial communities inside and outside of the Jiaozhou Bay can be grouped into three classes based on T-RFLP patterns and cluster analyses. Stations at the water channel of the bay mouth and outside, such as D1, D3, D5, D6 and D7, are grouped together to stand for the outside bacterial community interacting with the environment outside of the Jiaozhou Bay. Stations of the innermost side of the Jiaozhou Bay, such as A3, A5, B2 and Y1, are grouped together to stand for the residential bacteria community. Stations C1, C3 and C4 are grouped together and may stand for the transitional bacterial assemblage between the residential community and the outside community. However, there is no such a defined relationship for the case of cyanobacterial diversity, indicating the fact that cyanobacteria are more flexible and adaptable to all kinds of conditions.