Oceanographic influence on coastal zooplankton assemblages at three IMOS National Reference Stations in Western Australia

Abstract

Knowledge about the coastal zooplankton of the south-eastern Indian Ocean is limited, with few studies having compared assemblages across the latitudinal range of the western seaboard of Australia. The dominant oceanographic feature in this region is the Leeuwin Current, which transports warm, lower-salinity, tropical waters southward along the shelf-edge. This study examined data collected by Australia’s Integrated Marine Observing System at three coastal National Reference Stations located at 22°S 114°E, 32°S 115°E and 34°S 122°E. Spatial and temporal patterns in zooplankton abundance, composition and diversity were investigated, and differences in assemblage structure, particularly with respect to copepods, were related to oceanographic conditions. Clear dissimilarities among copepod assemblages were observed, becoming weaker in winter owing to enhanced connectivity of species driven by alongshore and cross-shelf transport in the Leeuwin Current. Both physical and biogeochemical factors were significant in structuring copepod assemblages, with seawater density, incorporating temperature and salinity, exerting the greatest influence. The results suggest that both broad-scale latitudinal gradients and mesoscale events contribute to variation in zooplankton assemblages in these waters. This study provides the first detailed comparison of zooplankton assemblages among the north-west, south-west and southern coastal waters of Western Australia, and enhances understanding of the processes influencing zooplankton distribution and structure.

Intertidal macroalgal and epiphytic polychaete distributions strengthen marine ecoregions of Western Australia

“…(tropical realm) and South-West Australia (temperate realm) (Forbes 1856, Ekman 1953, Briggs 1995, Bailey 1998, Sherman and Duda 1999, Adey and Steneck 2001, Spalding et al 2007, Hayden et al 2009. Differences in the distribution patterns of marine assemblages between those realms are also found for other groups, e.g., coastal zooplankton (McCosker et al 2020), shallow-water barnacles (Jones 2003), and fishes (Alan et al 2001, Fox and Beckley 2005, Last et al 2011, and seem to be stable across geological times (Cowman et al 2017, Kocsis et al 2018.…”