MESOSCALE DISTRIBUTION PATTERNS OF MACROZOOPLANKTON COMMUNITIES IN PRYDZ BAY, ANTARCTICA JANUARY TO FEBRUARY 1991

Previous large-scale surveys of the Prydz Bay region (Antarctica) have identified the continental shelf edge of Prydz Bay as an area of rapid transition between 3 major zooplankton communities. One of these communities is dominated by the Antarctic krill Euphausia superba. This community was located mainly along the continental shelf edge, usually between the offshore main oceanic community dominated by copepods and chaetognaths, and the neritic community dominated by E. crystallorophias. In January to March 1991, the Prydz Bay continental shelf area was the subject of a more intensive mesoscale survey to more accurately define the distribution patterns of the 3 zooplankton communities in that area. Cluster analysis and non-metric multidimensional scaling were used to define the communities, their distribution patterns, indicator species and species affinities. The composition of the communities were much the same as previously defined. E. superba again exhibited a distinct dissociation from all other species. However, the distribution pattern of the krill-dominated community was different from those previously observed. That community did not separate the copepod- and E. crystallorophias-dominated communities in Prydz Bay and apparently was displaced to the west. Temperature was strongly correlated with the zooplankton community distribution patterns, suggesting that temperature has more influence at the mesoscale level than at larger scales. Sea ice patterns, chlorophyll a abundance and salinity were also correlated, to a lesser extent, with the community distribution patterns.