SCIENCE AT THE SHINE DOME canberra 6 - 8 may 2009

Career awards

Thursday, 7 May 2009

JAEGER MEDAL

Professor Malcolm McCulloch FAA
Australian National University

Malcolm McCulloch was awarded a PhD from Caltech and then returned to Australia to take-up a research fellowship at the Australian National University (ANU). At the ANU he was responsible for establishing a new range of geochemical approaches providing insights into the origin and evolution of the Earth's crust and mantle. For the past decade his research has focused on the growing problem of environmental and climate change in the Great Barrier Reef. From 300 to 400 year old coral skeletons he has shown how European settlement and intensive land-use practices has led to a five to ten fold increase in sediment and nutrient fluxes entering the reef. This has provided important quantitative evidence to support joint federal–state protective measures. More recently his research on the affects ocean acidification from rapidly increasing levels of atmospheric CO2 in coral reefs has the potential to severely reduce the ability of corals to form coral reefs.

Coral reefs and environmental change

Coral reef ecosystems are highly sensitive to the impacts of climate and environmental change. Rapidly increasing CO2 emissions will result in a doubling of atmospheric levels by later this century. This is not only causing global warming but is also directly changing the chemistry of the world’s surface oceans by reducing the oceans pH and carbonate-ion concentration upon which coral calcification is dependent. Furthermore intensive land-use practices and growing urbanisation of coastal zones, is leading to increased supplies of sediment and nutrients to inshore regions, placing many coral reefs at risk. Collectively these forces can lead to a phase shift from coral to algal dominated reefs. How are coral reefs such as Australia’s iconic Great Barrier Reef responding? The challenge is to ascertain both the extent and trajectory of change prior to largely irreversible phase shifts. Unfortunately long-term observation records of parameters such as coral cover are largely absent, and in any case would be very difficult to interpret due to the highly dynamic nature of coral reefs. An alternative approach described here is to use the chemical signals preserved within the carbonate skeleton of corals as proxies for ocean temperature, sediment nutrient and in recent developments seawater pH. Such long-term (300 to 400 years), coral-based records show a five to tenfold increase in inshore sediment fluxes and more than 0.3 units decrease in seawater pH, the latter being significantly larger than anticipated from global emissions alone. Such quantitative, scientifically-based data provides much needed guidelines to ensure the resilience of coral reef systems to the combined forces of global climate change and direct
human impacts.