Characters of variation and impacting factors of biomass of heterotrophic bacterioplankton in Jiaozhou Bay in summer

Characters of variation and impacting factors of the biomass of heterotrophic bacterioplankton in Jiaozhou Bay in summer were studied in 2001.The biomass was larger and showed a day-night variation in surface waters is more obvious than in bottom waters with an average of 8.99×109 cell/dm3 and 5.23×109 cell/dm3 respectively.The largest biomass occurred in low tide period and the smallest occurred both in surface and bottom waters in high tide.The main impacting factors on the day-night variation of the biomass were grazing pressure by zooplankton,the supply of DOC from phytoplankton,the temperature of water and the sunlight irradiation.Mean-while,the dominative effectting factor of the daily variation of the biomass was the dynamic of sea water.