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An extreme climatic event alters marine ecosystem structure in a global biodiversity hotspot


Extreme climatic events, such as heat waves, are predicted to increase in frequency and magnitude as a consequence of global warming but their ecological effects are poorly understood, particularly in marine ecosystems1,2,3. In early 2011, the marine ecosystems along the west coast of Australia—a global hotspot of biodiversity and endemism4,5—experienced the highest-magnitude warming event on record. Sea temperatures soared to unprecedented levels and warming anomalies of 2–4 °C persisted for more than ten weeks along >2,000 km of coastline. We show that biodiversity patterns of temperate seaweeds, sessile invertebrates and demersal fish were significantly different after the warming event, which led to a reduction in the abundance of habitat-forming seaweeds and a subsequent shift in community structure towards a depauperate state and a tropicalization of fish communities. We conclude that extreme climatic events are key drivers of biodiversity patterns and that the frequency and intensity of such episodes have major implications for predictive models of species distribution and ecosystem structure, which are largely based on gradual warming trends.

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Figure 1: The 2011 heat wave in the southeast Indian Ocean.
Figure 2: The ecological structure of marine communities before and after the heat wave of 2011.
Figure 3: The response of macroalgae and fish to the marine heat wave of 2011.
Figure 4: Changes in seaweed canopy cover and tropicalization index for fish communities following the marine heat wave of 2011.


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This research was supported by Australian Research Council grants to T.W. Blended sea surface temperature anomalies were provided by the National Weather Service and the NOAA Operational Model Archive Distribution System. J. Zinke commented on the manuscript and provided assistance with the HadISST1 data.

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T.W. conceived the research programme and secured financial support. D.A.S. and T.W. contributed equally to the conceptualization and development of the paper. D.A.S. wrote most of the paper, with assistance from T.W., and carried out most analyses, with assistance from T.W. and T.J.L. Fieldwork was orchestrated by T.W. and conducted by T.W., F.T., T.d.B., M.S.T., S.B., T.J.L. and D.A.S. Analysis of temperature data was carried out by C.S.R. and T.W., with assistance from D.A.S. All authors discussed the results.

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Correspondence to Thomas Wernberg or Dan A. Smale.

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The authors declare no competing financial interests.

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Wernberg, T., Smale, D., Tuya, F. et al. An extreme climatic event alters marine ecosystem structure in a global biodiversity hotspot. Nature Clim Change 3, 78–82 (2013).

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