Warming Oceans Lead to Coral Reef Babies Staying Home

New research suggests that rising ocean temperatures are causing coral reefs to retain and nurture more of their own larvae, which in turn leaves large reef systems less interconnected.

Writing in the journal Nature Climate Change, an international team of researchers suggest that their find could have significant implications for understanding the future of coral reefs.

"The loss of connectivity can make reef systems such as the Great Barrier Reef more vulnerable," study co-author Sean Connolly, from the ARC Centre of Excellence for Coral Reef Studies (Coral CoE) at James Cook University, said in a statement.

"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 said.

It's not all bad news though. Lead study author Joana Figueiredo, also from Coral CoE, said the find is promising for isolated reef systems.

"We found that at higher temperatures more coral larvae will tend to stay on their birth reef," she said. "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."

The researchers noted that weaker connections between reefs means that corals that live in warm waters, such as those in the Caribbean, may take longer to expand their ranges to the north.

Isolated reefs, much like warm-water reefs, face considerable challenges, however.

"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," said Saki Harii, from the University of the Ryukyus in Japan.

Andrew Baird of the Coral CoE said the research presents marine ecosystem managers with both challenges and opportunities.

"Our results demonstrate that global warming will change patterns of larval connectivity among reefs," he said. "On a positive note, 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."

However, Baird noted: "This does not reduce the need for global action on climate change."