COMPOSITION AND BIOMASS OF SUMMER METAZOAN PLANKTON IN THE 0-200 M LAYER OF THE ATLANTIC SECTOR OF THE ANTARCTIC

Composition of the metazoan plankton was studied during R.V. ''Dmitry Mendeleev'' cruise 43 (February to April, 1989) in the Atlantic sector of the Southern Ocean. Samples were collected from ten stations at si x locations. Four of the locations were in open oceanic waters along t he 15-degrees-W longitude. Two others were in the Bransfield Strait an d in inshore waters near Elephant Island. At three locations at 15-deg rees-W sampling was conducted twice or thrice. At all stations three d ifferent sampling gears were used to collect different size groups of zooplankton: series of hauls were performed by 200 1 water-bottle, mes oplankton net and macroplankton trawl for depths from 200 m to the sur face. The average biomass of zooplankton in open oceanic waters was 20 .55 g.m-2 wet weight. Copepoda Calanoida dominated composing 54.8% of the total plankton, followed by Euphausiacea (19.8%), Ctenophora (9.7% ) and Copepoda Cyclopoida (7.2%). Biomass of any other taxonomic group was less than 1 g.m-2. The relative biomass of Calanoida had a tenden cy to decrease southward along 15-degrees-W from 86.1 to 68.1 % in Feb ruary and from 81.8 to 23.6% in March-April. The relative biomass of E uphausiacea increased in the same manner from 2.3 to 17.8% in February and from 3.7 to 41.6% in March-April. The average biomass of calanoid s from February to March-April decreased from 77.3 to 31.2% and that o f euphausiids increased from 6.2 to 33.8%. The contribution of copepod s and euphausiids to the production of the plankton community in the A ntarctic is discussed.