Ecological effect of blue-green algae on sustainable reproduction of choleraic vibrio in the estuaries of Zhejiang

Field observations on ecology of \%Vibrio cholerac biotype eltor pribram\% and the factors governing its survival and reproduction in the waters with frequent occurrence of cholera in the estuaries of Qiantang River were carried out during four seasonal representative months from April 1997 to February 1998 The results obtained show that there were pronounced differences in ecological environments between the waters of cholera frequent occurrence regions and a comparing region, in the former phytoplankton abundance was high, with a range of 10\+5 cell/dm\+3 to 10\+7 cell/dm\+3, and diversity was also high, 35 species only for blue\|green algae were found during spring Moreover, heterotrophic bacteria abundance of the former was also high, from 10\+5 to 10\+6 cell/cm\+3, among which \%Flavobacterum, Pseudomonas\% and \%Bacillus\% were dominant genus, vibrio abundance ranged from 10\+1 to 10\+2 cell/cm\+3; while in the latter phytoplankton abundance was low, ranging from 10\+2 to 10\+3 cell/dm\+3, the number of species was also low, only 4~7 species of blue\|green algae were observed. Furthermore, the abundance of heterotrophic bacteria (10\+2~10\+4 cell/cm\+3) was two orders of magnitude lower in the latter than in the former, and the vibrio was not found in the latter during the four seasonal observations