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Climate change cascades: Shifts in oceanography, species's ranges and subtidal marine community dynamics in eastern Tasmania

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Johnson, CR and Banks, S and Barrett, NS and Cazassus, F and Dunstan, PK and Edgar, GJ and Frusher, SD and Gardner, C and Haddon, M and Helidoniotis, F and Hill, KL and Holbrook, NJ and Hosie, G and Last, PR and Ling, SD and Melbourne-Thomas, J and Miller, KJ and Pecl, GT and Richardson, AJ and Ridgway, K and Rintoul, SR and Ritz, DA and Ross, DJ and Sanderson, JC and Shepherd, SA and Slotwinski, A and Swadling, KM and Taws, N (2011) Climate change cascades: Shifts in oceanography, species's ranges and subtidal marine community dynamics in eastern Tasmania. Journal of Experimental Marine Biology and Ecology, 400 (1-2). pp. 17-32. ISSN 0022-0981

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Abstract

Several lines of evidence show that ocean warming off the east coast of Tasmania is the result of intensification
of the East Australian Current (EAC). Increases in the strength, duration and frequency of southward incursions
of warm, nutrient poor EAC water transports heat and biota to eastern Tasmania. This shift in large-scale
oceanography is reflected by changes in the structure of near shore zooplankton communities and other
elements of the pelagic system; by a regional decline in the extent of dense beds of giant kelp (Macrocystis
pyrifera); by marked changes in the distribution of near shore fishes; and by range expansions of other northern
warmer-water species to colonize Tasmanian coastal waters. Population-level changes in commercially
important invertebrate species may also be associated with the warming trend.
Over-grazing of seaweed beds by one recently established species, the sea urchin Centrostephanus rodgersii, is
causing a fundamental shift in the structure and dynamics of Tasmanian rocky reef systems by the formation of
sea urchin ‘barrens’ habitat. Formation of barrens represents an interaction between effects of climate change and
a reduction in large predatory rock lobsters due to fishing. Barrens realize a loss of biodiversity and production
from rocky reefs, and threaten valuable abalone and rock lobster fisheries and the local economies and social
communities they support. This range-extending sea urchin species represents the single largest biologically
mediated threat to the integrity of important shallow water rocky reef communities in eastern Tasmania.
In synthesizing change in the physical ocean climate in eastern Tasmania and parallel shifts in species'
distributions and ecological processes, there is evidence that the direct effects of changing physical conditions
have precipitated cascading effects of ecological change in benthic (rocky reef) and pelagic systems. However,
some patterns correlated with temperature have plausible alternative explanations unrelated to thermal
gradients in time or space. We identify important knowledge gaps that need to be addressed to adequately
understand, anticipate and adapt to future climate-driven changes in marine systems in the region.

Item Type: Article
Journal or Publication Title: Journal of Experimental Marine Biology and Ecology
Page Range: pp. 17-32
ISSN: 0022-0981
Identification Number - DOI: 10.1016/j.jembe.2011.02.032
Additional Information:

The definitive version is available at http://www.sciencedirect.com

Date Deposited: 26 Aug 2011 03:06
Last Modified: 18 Nov 2014 04:21
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