Coral bleaching biggest threat to reefs, says Deakin expert

FISH living in coral reefs cope better with ocean acidification than previously thought, a Deakin University study has found.

Lead researcher Associate Professor Timothy Clark from Deakin’s Waurn Ponds campus described the comprehensive study as a “game changer”, with the findings revealing fish behaviour remains normal as ocean acidifies.

“Contrary to previous studies, we have demonstrated that forecasted ocean CO2 levels for the end of this century have a negligible impact on the behaviour and sensory systems of coral reef fish,” Associate Professor Clark said.

“The negative effects of CO2 emissions are well established, with global warming already having devastating effects on coral reef ecosystems because of coral bleaching during heatwaves.

“CO2 emissions are also the cause of ocean acidification, which can be detrimental to calcifying organisms like oysters and corals at vulnerable life stages.”

Associate Professor Clark said the new study does not align with reported results from earlier high-profile studies of coral reef fish.

“Previous research has reported that fish become attracted to the smell of predators in acidified waters. But by measuring multiple behaviours in multiple species and making our data freely available, we have comprehensively and transparently shown that end-of-century ocean acidification has negligible direct impacts on the behaviour of fish in coral reefs.”

Associate Professor Clark and his research found “consistently normal” behaviours in fish that were acclimated to elevated C02.

But he cautioned that even though the new findings suggested that ocean acidification may not cause population declines, climate change posed serious risks to reef habitats through coral bleaching during heatwaves.

“Despite our new results, coral reefs and their fish communities remain in grave danger because of increasing atmospheric CO2.

“We are confident that our paper will have a pronounced impact on the entire field of ocean acidification biology.”

The findings authored by Associate Professor Clark, Graham Raby, Dominique Roche, Sandra Binning, Ben Speers-Roesch, Fredrik Jutfelt and Josefin Sundin have been published in Nature and be found online via nature.com.