The ongoing impact of climate change and acidification of the world’s oceans is leading to a battle between coral and algae with both set to lose out, according to a new report released by the University of Queensland (UQ).
UQ’s Dr Kristen Brown said that conventional wisdom found that algae would aggressively take over areas of coral habitat, but new experiments have suggested otherwise.
“Coral and macroalgae principally compete through direct physical or chemical mechanisms, and more algae can mean an increase in coral bleaching and mortality,” Dr Brown said.
“So far, our warming and acidifying oceans have led to a shift in competitive advantage between macroalgae and coral, generally in favour of algal species,” she said.
“But in our experiments – using the branching coral Acropora and the green algae species Halimeda – we looked even further into the future, to see if macroalgal competitive mechanisms will increase at the expense of the coral.
The experiment began at UQ’s Heron Island Research Station on the southern Great Barrier Reef, with scuba divers retrieving coral and algal fragments from the reef slope.
The specimens were then brought back to the research station, where they were incubated in 24 tanks for two months under different climate change scenarios simulating mid-late century conditions.
“We then performed multiple physiological measurements in the lab to determine how competition with algae under these stressful conditions might affect the growth of coral reefs,” Dr Brown said.
“And the results were clear – the combined effects of ocean warming and acidification reduced survivorship, calcification and photosynthesis of coral.
“Coral reefs are among the most threatened ecosystems on Earth, with an estimated 50 per cent of reef-building corals lost in the last few decades due to human influences.