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Response of Western Australian coral reefs to climate and environmental change

Increased levels of atmospheric CO2 is not only causing global warming and associated mass coral bleaching, but is also lowering the oceans’ pH and hence carbonate ion concentration, upon which corals depend to calcify their skeletons. Locally, increased pollution from for example runoff from degraded river catchments or dredging, can also severely impact coral growth due to the effects of high sediment and nutrient loads on coral reefs.  Research at UWA is thus directed at developing a holistic understanding of how increasing sources of stress and their interactive effects are impacting coral reefs now, and into the future.

The coral reefs of Western Australia are found in the warm tropical waters of the Kimberley down to the temperate zones of south-western Australia, providing a unique opportunity to study the effects of climate change across a large latitudinal gradient. There is also a wide diversity of coral reef environments, with those in the Kimberley being subject to an extreme conditions with repeated exposure and warming due to the large (>10m) tidal ranges, whilst in contrast the Ningaloo Reef, one of the World’s largest fringing reefs is subject to persistent wave driven action as well as regional forcing from the offshore Leeuwin current. In the south-west of Australia the coral reefs of Abrolhos Islands and especially the nearby Rottnest Island exist at the southernmost limits of tropical reefs. These relatively pristine reefs therefore provide a unique ‘natural laboratory’ within which the effects of increased temperatures and reduced seawater pH can be studied under realistic conditions.

The specific projects include the:

• Determination of in-situ rates of coral calcification combined with measurement seasonally changing reef-water parameters (eg. seawater temperature, pH¬, W, light, nutrients) that control the sensitivity of corals and other marine calcifiers (eg. coralline algae and plankton) to the combined forces of ocean acidification and global warming?
• Application of geochemical proxies to interrogate the physiological controls (e.g. internal pH and saturation state of the calcifying fluid using boron isotopes) that aragonitic (eg. corals) impose during calcification, the energetics of these processes, and how are they linked to changes in their ambient marine environment?
• Use of long-term coral proxy records to determine the causes and effects of changes in the marine environment that are occurring on timescales from years, decades to centuries. This research is aimed at determining the longer-term response of the oceans and marine calcifiers generally to the effects of climate and environmental change has occurred over the last century using geochemical proxies  records of pH¬-W,  and temperature preserved within long-lived coral skeletons.
• Development of a new science-based quantitative framework to facilitate ‘best practice’ adaptive management to optimise the sustainability of our coral reefs for future generations.

Collaborator/s

  • Professor Jim Falter, Professor Ryan Lowe,
  • Research Associate Juan Pablo D’Olivo,
  • Research Associate Verena Schoepf,
  • ARC Postdoctoral Fellow Julie Trotter at The University of Western Australia