Zooplankton communities in the Southern Weddell Sea (Antartica)

Abstract

Standardized abundances of 40 frequently occurring macrozooplankton taxa collected by double-oblique bongo net hauls between the surface and 200 m depth were submitted to an agglomerative hierarchical cluster analysis, to characterize surface zooplankton communities in the southern and eastern Weddell Sea. The sensitivity of the analysis concerning reduction of the number of considered taxa (especially stages of species) was tested. Dominant taxa in the entire area over the whole period were copepods Metridia gerlachei and Calanoides acutus. Calanus propinquus, Appendicularia spp. and calyptopis-1 larvae of krill, Euphausia superba were abundant at 73°S/19°W. Euphausia crystallorophias and larval fish Pleuragramma antarcticum dominated at 77°S/40°W on the southern shelf. The cluster analysis revealed marked similarities between the southern shelf community and the January community further to the northeast. E. crystallorophias, and larval Pleuragramma antarcticum are thought to be transported in surface layers of the coastal current to the southwest. Oceanic species such as Thysanoessa sp. and E. superba are probably not transported in the same way. Possible mechanisms for the maintenance of the community structures are discussed. A simplified method of characterizing communities, based on analysis of euphausiids, is presented.