Springtime microprotozoan abundance and biomass in the southeastern Bering Sea and Shelik of Strait, Alaska

Abstract

We surveyed springtime biomass and abundance of the >20 nm microprotozoa in surface waters of the SE Bering Sea and Shelikof Strait, Alaska. This study was part of the Fisheries Ocean- ography Coordinated Investigations (FOCI) program examining processes which affect the recruit- ment variability of walleye pollock (Theragra chalcogramma). Microprotozoa are a potential prey resource for larval pollock which has not been previously examined. In both areas, the >20 (im micro- protozoa were predominantly dinoflagellates and ciliates. At the time of sampling (May 1990 in Sheli- kof Strait and April 1992 in the SE Bering Sea), the spring diatom bloom was under way in Shelikof Strait, but not in the SE Bering Sea. Heterotrophic dinoflagellates dominated the microprotozoan assemblage in Shelikof Strait, but not in the SE Bering Sea. In the SE Bering Sea. total microprotozoan abundances ranged from 300 to 6233 organisms 1 ' and biomass from 0.58 to 9.73 jig C I1. In Shelikof Strait, abundance and biomass were higher, ranging from 850 to 14 960 organisms 1' and from 1.29 to 70.73 jig C I ', respectively. These biomass levels are comparable to those reported from other coastal and oceanic regions. Microprotozoan biomass levels were sufficient to support the estimated metabolic needs of first-feeding larval walleye pollock. It remains to be shown whether larval pollock use this resource.