University of Tasmania
Browse

File(s) under permanent embargo

New evidence links changing shelf phytoplankton communities to boundary currents in southeast Tasmania

journal contribution
posted on 2023-05-17, 20:44 authored by Buchanan, PJ, Kerrie SwadlingKerrie Swadling, Ruth Eriksen, Wild-Allen, K
Southern Tasmanian shelf waters are host to the seasonal interplay of Australia’s two poleward boundary currents; the East Australian Current (EAC) and the Leeuwin Current (LC). While the behaviour and properties of the LC remain underexplored, strong research focus has allowed insight into how an intensifying EAC has created greater subtropical influence, leading to changes in the physical and biological oceanography of the region. In this cool temperate setting seven species of dinoflagellates, all in the genus Ceratium, which are more typically associated with warm waters of eastern Australia, were observed. This coincided with the seasonal increase in the EAC’s southward penetration beginning in October. Despite the seasonal peak in EAC activity, temperature-salinity plots, nutrient, chlorophyll a and phytoplankton concentrations all indicate the presence of subantarctic waters on the shelf and in coastal waters in summer. Our results are consistent with the description of the EAC as an erratic, eddy-driven current; this itself allowing the periodic influx of subantarctic waters across the shelf. In winter, temperature- salinity plots and nutrient concentrations indicate that the LC was present in southern shelf waters. In addition to its high nitrate signature, the LC displayed low silicate properties in southern Tasmania. Chlorophyll a concentrations revealed a distinct spring bloom event and an extended, productive summer, typical of temperate and subantarctic systems, respectively. This suggests the region is a transitional state between classic seasonal primary production cycles for temperate and subantarctic waters. This paper links changes in southern Tasmanian microphytoplankton communities to shelf ventilation by the EAC, the LC and subantarctic waters, and provides new insight into the oceanography of the region. Consequently, this study provides an awareness of potential phytoplankton perturbations that may be applied to other coastal cool temperate marine environments.

History

Publication title

Reviews in Fish Biology and Fisheries

Volume

24

Pagination

427-442

ISSN

1573-5184

Department/School

Institute for Marine and Antarctic Studies

Publisher

Kluwer Academic Publ

Place of publication

Van Godewijckstraat 30, Dordrecht, Netherlands, 3311 Gz

Rights statement

Copyright 2013 Springer Science+Business Media Dordrecht

Repository Status

  • Restricted

Socio-economic Objectives

Assessment and management of terrestrial ecosystems

Usage metrics

    University Of Tasmania

    Exports

    RefWorks
    BibTeX
    Ref. manager
    Endnote
    DataCite
    NLM
    DC