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Coral Babies Won’t Disperse from Warm Reefs

Rising ocean temperatures due to climate change will see reefs retaining and nurturing more of their own coral larvae, leaving large reef systems less interconnected and potentially more vulnerable.

“We found that at higher temperatures more coral larvae will tend to stay on their birth reef,” says Dr Joana Figueiredo from the ARC Centre of Excellence for Coral Reef Studies (Coral CoE) at James Cook University. “This is good news in an otherwise cloudy picture for isolated reefs, because in the future they will be able to retain more of their own larvae and recover faster from severe storms or bleaching events,” she adds.

But the news is not so good for the Great Barrier Reef. Prof Sean Connolly of the Coral CoE says that while more coral larvae will stay close to their parents, fewer will disperse longer distances, leaving reefs less connected. “The loss of connectivity can make reef systems such as the Great Barrier Reef more vulnerable,” he said. “So interconnected reef systems that depend on the recruitment of coral larvae may take more time to recover after a disturbance, such as a cyclone, because fewer larvae will disperse from other reefs to the disturbed reef.”

Connolly says that weaker connections between reefs mean that warm-adapted corals in the northern Great Barrier Reef may take longer to expand their ranges to the south.

Similarly for isolated reefs, Dr Saki Harii from the University of the Ryukyus in Japan says that “while isolated reefs can retain more of their own larvae, this also leaves them with fewer possibilities to change their species composition to adjust to climate change”.

Prof Andrew Baird of the Coral CoE says the implications of the research present management with both challenges and opportunities. “The stronger link between adults and recruits means an even greater benefit if we reduce local threats such as dredging and fishing methods that can damage corals,” he says before warning: “This does not reduce the need for global action on climate change”.

The research has been published in Nature Climate Change.