Coral sample study links reef health to water quality

Posted 13 September 2016

Great Barrier Reef coralsCores drilled from corals dating back thousands of years are providing important insights into the positive and negative impacts of human settlement on the Great Barrier Reef.

By studying coral samples, Queensland researchers have confirmed that human activity since European settlement has affected the frequency of coral deaths and composition of the reef.

But studies have also shown that efforts to reduce sediment runoff and improve water quality are building the reef’s resilience for the future.

“The research has found clear evidence of a significant change in coral community composition since European settlement in the 1800s, as well as frequent links between the timing of previous coral mortality incidents and sediment runoff events,” said Queensland's Minister for the Great Barrier Reef Dr Steven Miles.

“There was also evidence linking coral deaths to past anomalies in sea surface temperatures over the past century, with data suggesting there has been an increase in mortality from the mid-1990s to the present.”

Miles said latest research showed more than 90% of the reef was affected by the last summer's bleaching, but there were some positive signs.

“I understand the preliminary results on this research, which are yet to be published, are showing there are signs of corals recovering faster in areas with better water quality, compared with areas of poorer water quality,” he said.

“Studies of coral reef condition over 30 years by the Australian Institute of Marine Science’s long-term monitoring programs have shown that when water quality is good coral reefs recover well from acute disturbance events such as cyclones, storms and floods.”

The University of Queensland's School of Earth Sciences was one of a number of organisations dating and analysing coral and reef cores taken from along the Great Barrier Reef.

The university's Professor Gregg Webb said the cores provided important insights into coral growth rates and climate impacts over time.

“The historical perspectives on water quality and community structure gained from geochemical and ecological analysis of dated corals in cores help distinguish natural from human induced changes in coral reef systems,” he said.

“This can define shifting baselines and ongoing trends that may help identify tolerances and tipping points to better target attempts at restoration.”