SIGNIFICANCE OF SEDIMENTATION FOR THE TERMINATION OF PHAEOCYSTIS BLOOMS

The role of sedimentation for the termination of Phaeocystis blooms is exemplified through case studies from the literature as well as from anecdotal evidence. Scenarios of high and low sedimentation following Phaeocystis blooms exist. Mass sedimentation was found in the Barents Sea and the Ross Sea, but vertical flux below the euphotic zone was insignificant in a north Norwegian fjord and the Weddell Sea. In general, no regular and recurring pattern of sedimentation events can be expected during Phaeocystis blooms. Factors influencing the fate of senescent Phaeocystis blooms are probably water depth, turbulent energy supply, aggregate formation, release of flagellated cells from colonies, microbial degradation, zooplankton grazing as well as lysis of colonies and cells. The role sedimentation plays for the termination of Phaeocystis blooms seems to be determined by the physical and biological characteristics of the specific ecosystem where the bloom occurs. In general, Phaeocystis-dominated ecosystems tend to endorse pelagic rather than benthic mineralization.