THE COMPOSITION, ABUNDANCE, BIOMASS AND DIVERSITY OF THE EPIPELAGIC ZOOPLANKTON COMMUNITIES OF THE SOUTHERN BELLINGSHAUSEN SEA (ANTARCTIC) WITH SPECIAL REFERENCE TO KRILL AND SALPS

Zooplankton was sampled in the southern Bellingshausen Sea with RMT 18 gear during austral summer 1994. A total of 121 zooplankton species were found. Although zooplankton diversity was high in oceanic and ner itic waters, abundances and biomass were among the lowest recorded for Antarctic epipelagic zooplankton. Copepods and chaetognaths dominated numerically, while chaetognaths and krill Euphausia superba dominated in biomass wet weight. Salpa thompsoni occurred in low densities (med ian 0.1 to 0.4/1000 m(3)), although during the same period a mass deve lopment was recorded from the South Shetland Island region. Density va lues for Euphausia crystallorophias were in the same range as reported from the southern Weddell Sea. Krill, Euphausia superba, biomass was lower than generally found in the Antarctic Peninsula and Elephant Isl and region. A distinct spatial separation for size groups was observed for salps, Euphausia crystallorophias and krill. Small salp size grou ps dominated in the East Wind Drift zone and larger ones further north under the influence of West Wind Drift waters. Larger size classes of E. crystallorophias concentrated in nearshore areas. Krill was smalle r in neritc and larger in oceanic waters. The overall krill length fre quency distribution was similar to that reported from the South Shetla nd Island region for the same period. The recruitment index for E. cry stallorophias and Thysanoessa macrura age group 1+ indicated a very su ccessful year-class 1992/93 in the region (R(1) = 0.412 and R(1) = 0.6 09, respectively), while krill showed the opposite, a poor recruitment of the 1992/93 year class (R(1) = 0.076). Spawning was late during th e 1994 season for E. crystallorophias and E. superba; no larvae were f ound in the area. These findings are discussed in the light of recentl y described correlations between winter sea-ice conditions and krill s pawning and recruitment success, and lead to the conclusion that recru itment of the 1993/94 krill year-class will be poor.