Species Composition and Abundance of Zooplankton in the Nearshore Beaufort Sea in Winter-Spring

Abstract

Zooplankton samples collected in winter-spring 1978-79 and in spring 1980 from under the sea ice at two sites near Prudhoe Bay, Alaska, were analyzed for species composition and abundance. Sixty-eight categories, including 48 species and 20 other categories where identification was made to genus or other higher taxonomic rank, were identified. Calanoid copepods were dominant under the ice. As spring progressed, however, other organisms, including cyclopoid and harpacticoid copepods, hydrozoans, amphipods, larvaceans, and larval stages of planktonic and benthic invertebrates, became more numerous. Some of these organisms, such as cyclopoid and harpacticoid copepods, probably lived in the sea ice in early spring and were released into the water column as the ice melted. A correlation matrix identified three groups of zooplankton. Group one, consisting of Pseudocalanus spp., had large fluctuations in numbers throughtout the spring. Group two, consisting of benthic copepods, polychaetes, and the amphipod Halirages mixtus, became abundant when the ice began to melt. The third group, composed of all other species, had a more uniform abundance during early spring, but declined in numbers as the ice melted.

Key words: western Beaufort Sea, zooplankton, copépodes, Pseudocalanus, cyclopes, harpaticoides, glace marine