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Influence of oceanographic conditions on coastal zooplankton assemblages at three IMOS National Reference Stations in Western Australia

McCosker, Erin (2016) Influence of oceanographic conditions on coastal zooplankton assemblages at three IMOS National Reference Stations in Western Australia. Masters by Coursework thesis, Murdoch University.

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Despite the importance of zooplankton in providing vital information about ocean-climate forcing in marine systems, knowledge of the planktonic zoogeography of the south-east Indian Ocean is limited. The dominant oceanographic feature in this region is the anomalous poleward flowing Leeuwin Current, which transports warm, tropical waters south along the Western Australian coast, and follows a trajectory that crosses thirteen degrees of latitude, from the tropical north to the temperate south. This study examined two years of data collected by Australia’s Integrated Marine Observing System at three unique locations in Western Australian coastal ocean waters between 22°S and 34°S. Spatial and temporal patterns in zooplankton abundance, composition and diversity were investigated, with a focus on copepods, and differences in assemblage structure were related to oceanographic conditions. Clear distinctions in copepod assemblages were observed, becoming weaker in winter due to enhanced connectivity driven by alongshore and crossshelf transport of species in the Leeuwin Current. Both physical and biogeochemical factors were revealed to be significant in shaping copepod assemblages, with seawater density, an indication of water mass, exerting the greatest influence. The results suggest that both broad scale latitudinal gradients and mesoscale events contribute to variation in dissimilarities of zooplankton assemblages in these waters. This study provides the first detailed comparison of zooplankton assemblages in the northwest, southwest and southern coastal waters of Western Australia, and enhances understanding of the processes influencing zooplankton distribution and structure.

Item Type: Thesis (Masters by Coursework)
Murdoch Affiliation(s): School of Veterinary and Life Sciences
Supervisor(s): Beckley, Lynnath and Davies, C.
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