Macrozooplankton community structure off East Antarctica (80-150 degrees E) during the Austral summer of 1995/1996

Zooplankton data from routine 0-200 m oblique trawls and targeted trawls we re analysed using cluster analysis and non-metric multidimensional scaling to define the communities in Eastern Antarctica (80-150 degrees E), their d istribution patterns, indicator species, and species affinities. Three comm unities were defined based on routine trawls. The Main Oceanic Community co mprising herbivorous copepods, chaetognaths, and the euphausiid Thysanoessa macrura dominated the area west of 120 degrees E. The area east of 120 deg rees E was dominated by Salpa thompsoni. The third community located in the neritic zone was dominated by Euphausia crystallorophias. Antarctic krill Euphausia superba did not form a distinct community in its own right, unlik e previous observations in Prydz Bay. Krill were distributed throughout mos t of the survey area but generally in higher abundances towards the shelf b reak. Overall, krill abundance was low compared with previous net surveys i n Prydz Bay. Three main types of assemblages were identified based on targe t trawls. The first group was dominated by krill (mean 1149 individuals per 1000 m(3)) which represented > 99% of Group 1 catches in terms of numbers and biomass. Group 2 comprised the bulk of target trawls and comprised a wi de diversity of species typical of the main oceanic community, with a mean abundance approximately half of that observed in the routine trawls. The th ird group comprised trawls in the neritic zone dominated by E. crystallorop hias. No salp-dominated aggregation was found. While E. superba did not dom inate a distinct community geographically as seen in previous Prydz Bay sur veys, it did dominate discrete layers or aggregations, showing that both ho rizontal and vertical separation of communities exist. (C) 2000 Elsevier Sc ience Ltd. All rights reserved.