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

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Buchanan, PJ and Swadling, KM and Eriksen, RS and Wild-Allen, K (2013) New evidence links changing shelf phytoplankton communities to boundary currents in southeast Tasmania. New evidence links changing shelf phytoplankton communities to boundary currents in southeast Tasmania, 23. ISSN 1573-5184 (In Press)

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Abstract

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

Item Type: Article
Keywords: Phytoplankton Ocean warming Ceratium Leeuwin Current East Australian Current Range extension Primary production regimes
Journal or Publication Title: New evidence links changing shelf phytoplankton communities to boundary currents in southeast Tasmania
ISSN: 1573-5184
Identification Number - DOI: 10.1007/s11160-013-9312-z
Additional Information:

Copyright 2013 Springer

Date Deposited: 03 Dec 2013 23:18
Last Modified: 18 Nov 2014 04:56
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