GRAZING BY THE COPEPOD COMMUNITY DOES NOT CONTROL PHYTOPLANKTON PRODUCTION IN THE SUB-ARCTIC PACIFIC-OCEAN

The copepod community of the subarctic Pacific Ocean is dominated by large-bodied species. Peak reproduction is during fall and winter. It has long been thought that the resultant grazing capacity, in place at the onset of the spring increase in phytoplankton production, prevents the accumulation of phytoplankton stock to ''spring bloom'' concentrations. In this paper, grazing by the copepod community is compared to phytoplankton production during the spring to determine if ingestion rates are sufficient to balance or control phytoplankton production. Feeding rates on phytoplankton were measured for the dominant copepod species, Neocalanus plumchrus, N flemingeri, N cristatus, Eucalanus bungii, and some smaller species, during spring cruises in 1983, 1984, 1987 and 1988, by two independent methods. Feeding rates of individual organisms were applied to appropriate abundance measurements to determine the grazing contribution of each species. Community grazing rate was calculated by summing the grazing contributions of all species. For 1987 and 1988, community grazing rates were compared to phytoplankton production rates measured during the same periods. The copepod community ingested between 6 and 15% of the daily phytoplankton production. Direct grazing on phytoplankton by the copepod community does not prevent the accumulation of phytoplankton production to ''bloom'' concentrations in the subarctic Pacific Ocean.