Resilience of Great Barrier Reef Offers Lessons on Ecosystem Recovery

Diversity of coral forms shows rich underwater life found on healthy coral reefs. (Peter J. Mumby)

(CN) – A new study finds that despite major disturbances to corals in recent years, there are still 100 reefs on the Great Barrier Reef capable of stimulating regional recovery of the ecosystem as it battles predators and the effects of climate change.

Australia’s Great Barrier Reef, which is made up of more than 3,800 individual reefs, has recently faced multiple large-scale disturbances including unprecedented coral bleaching events and massive outbreaks of the coral-consuming crown-of-thorns starfish.

While the challenges the massive coral ecosystem faces threaten its immediate health and long-term survival, a small portion of its reefs are uniquely situated to both withstand major disturbances and promote the recovery of other reefs, scientists report Tuesday in the journal PLOS Biology.

“Finding these 100 reefs is a little like revealing the cardiovascular system of the Great Barrier Reef,” said co-author Peter Mumby, a professor at the University of Queensland in Australia.

“Although the 100 reefs only make up 3 percent of the entire GBR, they have the potential to supply larvae to almost half (45 percent) of the entire ecosystem in a single year.”

These reefs fulfill three critical criteria for promoting coral recovery.

First, the reefs are in cool areas and are rarely damaged by coral bleaching, which means that corals on these reefs are fairly healthy and can supply larvae to other reefs.

Since larvae travel along ocean currents, reefs should be located in areas that enable them to supply larvae to as many reefs as possible.

Crown of Thorns starfish competing to feed on live coral. (JSLUCAS75 via Wikipedia)

Finally, these reefs do not spread crown-of-thorns starfish larvae.

“The presence of these well-connected reefs on the Great Barrier Reef means that the whole system of coral reefs possesses a level of resilience that may help it bounce back from disturbances, as the recovery of the damaged locations is supported by the influx of coral larvae from the non-exposed reefs,” said lead author Karlo Hock.

Hock, a postdoctoral research fellow at the University of Queensland, added these reefs are not capable of single-handedly saving the Great Barrier Reef.

“Unfortunately, these findings by no means suggest that the Great Barrier Reef corals are safe and in great condition, and that there are no reasons for concern,” he said.

“Indeed, the fact that the study only identified around a hundred of these reefs across the entire 2,300-km (about 1,429 miles) length of the massive Great Barrier Reef emphasizes the need for both effective local protection of critical locations and reduction of carbon emissions in order to support this majestic ecosystem.”

Mumby believes conservation efforts must aim to boost the benefits presented by these reefs.

“While more research is needed to determine to what extent the Great Barrier Reef will benefit from replenishment by these 100 reefs, given the scale of the recent disturbances, the importance of supporting such natural recovery mechanisms is likely to increase in future as climate change makes various disturbances more intense and unpredictable,” he said.

“Saving the Great Barrier Reef is possible but requires serious mitigation of climate change and continued investments in local protection. We talk to management agencies frequently and our results can inform where they target on-the-ground actions.”

 

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