Chlorophyll specific growth rate and grazing mortality rate of phytoplankton in the shelf water of the Bering Sea in summer

• Main Authors: Tsuneo Odate, Sei-Ichi Saitoh
• Format: Report
• Language: English
• Published: Faculty of Fisheries, Hokkaido University/Faculty of Fisheries, Hokkaido University 2001
• Subjects: Bering Sea shelf; phytoplankton growth; grazing mortality; dilution methods; Bering Sea; Polar bioscience
• Online Access: https://nipr.repo.nii.ac.jp/?action=repository_uri&item_id=6172; http://id.nii.ac.jp/1291/00006172/; https://nipr.repo.nii.ac.jp/?action=repository_action_common_download&item_id=6172&item_no=1&attribute_id=18&file_no=1

Chlorophyll specific growth rate and grazing mortality rate due to microzooplankton were estimated based on the dilution methods, using surface waters collected at four stations in the continental shelf area of the Bering Sea in summer. Growth rates and grazing mortality rates of phytoplankton communities were ranged between 0.06d^<-1> and 0.56d^<-1> and between 0.04d^<-1> to 0.33d^<-1>, respectively. The high growth rate seems to have resulted from continuous supply of nutrients caused by gentle stratification, which is a favorable condition of the water column for phytoplankton growth. Growth and grazing mortality rates were almost the same at one station, where the most typical summer concentration of chlorophyll a was observed (less than 1μgl^<-1>), suggesting that the major grazer seems to be microzooplankton in the Bering Sea shelf in summer. On the other hand, the lowest growth rate was obtained in near St. Laurence Island, where higher chlorophyll concentrations more than several μgl^<-1> occurred. In this water passive sinking of cells seems to become one of controlling factor of phytoplankton abundance.