ARCTIC Species Composition and Abundance of Zooplankton

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. Sixtyeight categories, including 48 species and 20 other categories where identifica-tion 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 Pseudoculunus spp., had large fluctuations in numbers throughout the spring. Group two, consisting of benthic copepods, polychaetes, and the amphipod Hulirages mixius, became abundant when the ice began to melt. The third group, composed of ail other species, had a more uniform abundance during early spring, but declined in numbers as the ice melted. Key words: western Beaufort Sea, zooplankton, copepods, Pseudoculunus, cyclopoids, harpacticoids, sea ice RÉSUMÉ. Des échantillons de zooplancton recueillis sous la glace marine prks de la baie Prudhoe, en Alaska, au cours de l’hiver de 1978 et du printemps de 1979 furent analysés afin d’en déterminer les espkces et leur nombre. Soixante-huit catégories furent relevées, y compris 48 espkces et 20 autres catégories identifiées par genre ou par rang taxonomique supérieur. Les copépods Culanus figuraient en nombre supérieur sous la glace. Cependant, a mesure que le printemps avançait, d’autres organismes augmen