Meso-zooplankton abundance, distribution and community composition in the eastern Great Australian Bight

Abstract

Seasonal meso-zooplankton abundance, distribution and community composition were examined in the eastern Great Australian Bight (EGAB) in 1999 and 2000. Meteorological and oceanographical conditions in the region change markedly with season, with an upwelling circulation dominating the area during summer/autumn, and downwelling prevailing in winter. Highest zooplankton densities occurred in summer in both years of the study, and corresponded to areas of elevated chlorophyll a concentration and cool sea surface temperature, indicative of coastal upwelling. Copepods and cladocerans dominated the zooplankton community, regardless of season. However, a clear difference in zooplankton community composition was identified between the different seasons. During summer/autumn in the EGAB, zooplankton with opportunistic reproductive strategies were significantly more abundant than during winter/spring. It appears that the elevated chlorophyll a concentrations in the EGAB during the summer/autumn upwelling season underpinned the clear seasonal differences in zooplankton community composition observed in this study.