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Coral expert and isotope geochemist Professor Malcolm McCulloch was the only WA academic to receive an Australian Laureate Fellowship recently. Australia’s most prestigious research fellowship will enable him to advance global understanding of the coral reefs that store vital signals on changes in ocean chemistry, sea levels and climate.

Tiny coral polyps – cylinders of tissue encased in a calcium carbonate base – are the building blocks of Australia’s spectacular and expansive reefs. Each polyp is a wonder, accommodating photosynthesising single-celled algae that gather sunlight by day and provide the polyp with oxygen, amino acids and other organic compounds.

The algae paint the cabbage corals fluorescent green and orange, the brain corals pink and staghorns brown, blue, purple and green. They also provide the energy that enables corals to extract calcium carbonate from seawater and this becomes the building material for coral reefs.

By day the polyps retract and the reef becomes a sunlight-absorbing photosynthetic carpet; by night they resume the business of feeding themselves.

Whereas the cues for coral spawning in the Great Barrier Reef are a full moon and warm water in November, on Western Australia’s coastline coral spawning happens after the full moon in April when the warm Leeuwin Current washes the reefs. The corals wait for perfect conditions to release – on the same night – their colourful clouds of sperm and eggs that create the next generation of reef corals.

But what happens if the ocean’s chemistry undergoes change as it absorbs more carbon dioxide and if the resulting acidification robs the polyps of a critical component necessary for manufacturing their calcium carbonate skeletons?

This is the very topical area of study being explored by UWA’s Premier’s Fellow, Winthrop Professor Malcolm McCulloch, whose trail-blazing research has seen him elected a Fellow of the prestigious Royal Society and awarded an Australian Research Council Laureate Fellowship.

After undertaking PhD studies at the California Institute of Technology followed by an appointment at the Australian National University studying the Great Barrier Reef, the coral reef expert returned to his home state in 2009 to take up an appointment with UWA’s School of Earth and Environment and the Oceans Institute.

While the climate change debate generates its own heat, Professor McCulloch dons scuba gear, gathers core samples of coral and uses the raft of laboratory equipment that his research team employs at UWA to directly chart changes in the ocean.

“We are already seeing the effects of increased carbon dioxide from the atmosphere being dissolved in the ocean and making it more acidic,” says Professor McCulloch. “This is an aspect of climate change that cannot be disputed because the uptake of carbon dioxide into seawater is a very well understood process and can be accurately measured.

“We also know that acidification is slowing the growth of corals. We can trace the history of acidification using isotopes. We can also measure the rate of coral growth and chart the fact that it has slowed in the last 20 years.”

To date most of Professor McCulloch’s research on Australian corals has been centred on the Great Barrier Reef where he produced the first studies demonstrating direct links between reef degradation and run-off from cattle stations and cane plantations, and between climate change and ocean acidification.

“By studying corals that live for more than several hundred years, we are able to document the increase in sediments being swept into the ocean by floods. That increase began soon after colonial settlement and was the result of introducing cattle to the catchments of North Queensland, together with land clearing and soil erosion. Whenever there is a major flood event – especially after a period of drought – we can quantify increased sediment flows into the ocean by the chemical signals in corals.”

Earlier studies and reports of the run-off were disputed by the agricultural industry; however, information gathered from long-lived corals by Professor McCulloch and his team was indisputable.

“It provided the scientific evidence that prompted the Federal and Queensland Governments to increase efforts to preserve catchments and these are ongoing. Initially there was a voluntary scheme involving cane plantations and cattle farms, but this has now been strengthened to make catchment protection a legislative requirement with penalties.

“What has become a thread through my research has been using corals to tell us what is happening in the ocean.”

Professor McCulloch is now exploring a very different scenario off Western Australia’s north-west coast which he describes as “a new frontier for scientists”.

“We know very little about these reef systems,” he says. “In the Kimberley they exist in an extraordinary tidal range that creates a lot of sediment movement. They also experience extremes: being exposed at low tides and adapting to unusually hot water temperatures. They could provide clues as to how corals generally may cope with the expected extremes of global warming and rapidly changing environments.

“We are also continuing our ocean acidification and climate change work in what is generally a far more pristine environment and it will be interesting to compare our findings with research we’ve done in the Great Barrier Reef.”

Professor McCulloch grew up in the coastal community of Busselton, where his early dreams of studying our planet were hatched. Undergraduate and Masters degrees in physics led to an interest in mass spectrometry that saw him studying at California Institute of Technology in Pasadena. He went on to explore the origins of magma and the Earth’s evolution, but it wasn’t until he was introduced to the ancient reefs of the Huon Peninsula in Papua New Guinea that his fascination with coral began.

The terraced vertical cliffs of the peninsula provide scientists with an incomparable opportunity to trace the relationship between reef development and sea-level changes over more than 100,000 years. Coral samples from drill-cores can be dated using mass spectrometry.

“These reefs were exposed by tectonic uplift and by sea level change and they were the starting point of my current research,” he says.

Professor McCulloch’s international stature in this important arena of research has been acknowledged by the Royal Society, the world’s oldest scientific academy.

In welcoming him to its ranks, the former President Martin Rees said that Fellows followed in the footsteps of distinguished scientists of the calibre of Isaac Newton and Robert Boyle. “They embody the spirit of enquiry, dedicated to ‘the relief of man’s estate’ on which the Royal Society was founded,” he said.

During his term as President of the Royal Society, Lord Rees emphasised that mainstream science was in agreement that human-induced climate change is happening and we need to worry. He joined others in advocating that scientists – not by choice selfpromoters of their work – become more engaged in communicating their findings in response to wellorchestrated campaigns by climate sceptics.

“The Royal Society has been more proactive in recent years and I think university scientists have a responsibility to explain the climate change arguments and facts,” says Professor McCulloch. “Sure there are uncertainties, but we need to explain the nature of those uncertainties.

“Most people understand that while there are debates about detail, there is a definite and clear scientific consensus that the data indicate a world starting to change in a way that is outside normal variation. Getting that message out through UWA research is something we are trying to do on campus – not just in relation to climate change but to scientific research across the board.”

Professor McCulloch is not surprised that increasing numbers of students are attracted to research in marine science. “Australia undoubtedly has the world’s best reefs,” he says, “so we have a great responsibility to understand and look after them. I believe we are world leaders in marine science and we need to lead by example and provide new tools for studying the marine environment.

“While we know that ocean acidification is happening, what we don’t know is how different marine ecosystems will respond. This is cutting-edge area of research that will provide very interesting avenues for study for both undergraduate and postgraduate students.”

Professor McCulloch is part of UWA’s Oceans Institute, which brings together and acts as a focus for the marine research being undertaken on the UWA campus. His 2009 Premier’s Fellowship helped to fund a new UWA node of the Australian Research Council’s Centre of Excellence in Coral Reef Studies which has a global perspective and takes advantage of expertise in the ARC Centre of Excellence at James Cook University and the University of Queensland.

The distinguished isotope geochemist was awarded the Jaeger Medal in Earth Science by the Australian Academy of Sciences. He is also a Fellow of the Academy, and of the Geological Society of Australia, the Geochemical Society and the American Geophysical Union.

Published in Uniview Vol. 31 No. 3 Spring 2012