Abstract
The annual changes in bacterial community were studied as related to those of phytoplankton in Maizuru Bay, Japan from May 1985 to April 1986. Five phytoplankton blooms were observed through the year Dominant algal species for three blooms were diatoms, Cerataulina pelagica, Asterionella japonica and Leptocylindrus danicus, and for the other two, dinoflagellate Prorocentrum micans and Raphidophycean Chattonella marina, respectively. The analysis of the bacterial community revealed that in these blooming periods the diversity of bacterial flora decreased. In particular the bacteria of genus Vibrio were not found in the bloom of phytoplankton A positive correlation was found between abundance of free-living bacteria and chlorophyll a concentrations. The results suggest that phytoplankton in the blooming period influences the bacterial flora and the bacterial concentration is closely related to the abundance of phytoplankton.