Massive corals Western Australia

Extracting a coral core at Rowley Shoals. Image: Eric Matson.

Massive corals are being used by marine scientists to unravel the effects of climate and environmental change on coral reefs in Australia's remote north-west. Often referred to as the Methuselah's of coral reefs because they can be older than 500 years, these massive corals grow by adding a new layer to their surface each year, which creates a reliable calendar that stores a wealth of information about the past environment experienced by the colony. It is the old skeletal material contained deep within the coral that allows researchers to compare present day growth rates with those pre-dating the industrial revolution and hence examine the consequences of climate change on coral reefs.

The team of scientists, led by Eric Matson and Dr Tim Cooper from AIMS, returned in late 2009 from Rowley Shoals, approx 300km west of Broome. The cores the team collected were up to 350 years old, meaning the corals were growing about the time when the first Dutch sailors in square-riggers were exploring the west coast of Australia.

Coral reefs are confronting a serious crisis in the face of a changing climate. "Since the industrial revolution, levels of atmospheric carbon dioxide have risen from approximately 280 ppm to current day levels of 390 ppm," said Dr Cooper. "As a consequence, seawater temperatures have risen over the past 200 years and evidence is emerging that part of this extra CO2may be absorbed by the oceans making them more acidic," he said. "These processes have already had a measurable effect on coral growth rates in some parts of the world, including the GBR, but virtually nothing is known about the climate history or growth rates of corals on reefs along Australia's west coast," said Dr Cooper.

Specialised commercial diving equipment was needed to carefully remove a biopsy of coral skeleton with only minimal stress to the massive corals. "The only living part of massive corals is a thin layer of tissue 0.5-1 cm thick that deposits the coral skeleton beneath it as the coral grows upwards" said Mr Matson. "We use a hydraulic drill with a diamond-studded bit to remove the core and the hole is plugged when we're finished to promote a quick recovery from the procedure," he said. "The coral will continue growing and show no effects that a sample of skeleton has been removed from it," said Mr Matson.