UNDER-ICE ZOOPLANKTON OF THE WESTERN WEDDELL SEA (16th Symposium on Polar Biology)

Species composition, abundance, and seasonal dynamics of the under-ice zooplankton collected during the USA-Russia ISW-1 Expedition, from the end of February to the middle of May in 1992, in the western rim of the Weddell Sea Gyre are presented. Zooplankton were collected by a diver with plankton landing net directly from the under-ice surface (0 m layer) and at 5-m depth. Larvae and postlarvae of Euphausia superba (Euphausiidae), Oithona similis, Stephos longipes, Paralabidocera antarctica, Pseudocyclopina belgicae, Microcalanus pigmaeus and Ctenocalanus citer (Copepoda) were most abundant in both layers. Differences in the stage composition and abundance of these species between two layers (0 and 5 m) were found. E. superba, S. longipes, P. antarctica and P. belgicae were numerous near the under-ice surface and scarce at 5 m. O. similis density was greater at 5 m than at 0 m. M. pigmaeus and C. citer were comparatively greater in number at 5 m. Seasonal changes inabundance and stage structure of euphausiids and copepods are discussed. A delay in seasonal development of E. superba, S. longipes, P. antarctica and P. belgicae comparing is shown