Coral reefs in the Arabian Gulf 'talk' to each other to repair areas under stress

A study by the American University of Sharjah found how corals move larvae to maintain areas in need

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Coral reefs in the Arabian Gulf talk to each other to help repair areas under stress.

Researchers from the American University of Sharjah discovered a connectivity phenomenon allows corals to transport larvae from areas where it is abundant to regions in need of supply.

That may be enough to maintain areas facing degradation and help them recover.

Coral is made up of thousands of tiny animals that float freely in the ocean during their larval, or immature, stage.

But once they settle down, they anchor themselves to a reef for the rest of their lives.

"We have noticed that there is great potential for 'self-recruitment', where the larvae settle on their parental reef, and for 'inter-regional connectivity', where larvae move from one region to other, for example, moving from Kuwait to Bahrain and onwards to the UAE," said Georgenes Cavalcante, a research fellow at the university who was involved in the study.

Any further increase in temperatures puts them at risk

The mechanism helped to resupply degrading reefs along the UAE coast, from Abu Dhabi to Ras Al Khaimah, he said.

Coral communities exist in all eight nations on the Arabian Gulf. But they are under huge pressure because of climate change.

"Global warming is affecting coral communities throughout the world," said Mr Cavalcante.

“In the Arabian Gulf, the warming effect is particularly relevant as the corals in the region are already subject to extremely high temperatures.

“Any further increase in temperature, therefore, puts them at immediate risk.”

The team plans to study what happened in other years, since the flow of larvae depends on water circulation patterns.

A brain coral off the breakwater near Marina Mall in Abu Dhabi. Corals are vital for the marine ecosystem. Antonie Robertson / The National
A brain coral off the breakwater near Marina Mall in Abu Dhabi. Corals are vital for the marine ecosystem. Antonie Robertson / The National

“Such a strategy will give us a better representation of the different oceanographic conditions present in the Gulf and improve our knowledge of the locations with more potential to serve as a source [areas that supply larvae] or sink [area of recruitment] region,” said Mr Cavalcante.

The team did not say specifically how the phenomenon works, but a 2018 study by the Woods Hole Oceanographic Institution in the US provided a clue.

Researchers found that corals chose their home based on the sounds made by animals living nearby. The sounds are loud in healthy reefs.

In that study, more larvae chose to settle in healthy sites.

Coral communities around the world are at risk because of bleaching events, which are becoming more frequent.

They occur when the water is too warm, causing coral to expel algae living in their tissues, which give them their colour and provide 90 per cent of their energy.

If the water temperature remains high, coral do not let the algae back in, and the coral dies.

It was revealed this month that the Great Barrier Reef has lost more than half of its corals since 1995.

In 2015, a global coral bleaching event lasted for 36 months causing many reefs to die off.

Coral communities in the Gulf, which are used to enduring high heat, were the last to be affected by the event but by 2017, reef bottom temperatures in the region reached record levels and vast areas died off.

In total, 94.3 per cent of corals in the southern Gulf bleached and about 67 per cent of corals died between April and September 2017, according to a study by New York University Abu Dhabi and the Environment Agency Abu Dhabi.

“Given the increasing frequency of mass bleaching in the Gulf and the above global rates of regional warming, the capacity for recovery and the prognosis for the future of Gulf reefs are not optimistic," said the study.

Efforts are under way to save and bolster coral reefs in the region, including a project in Fujairah that will plant 1.5 million corals across 300,000 square metres of the emirate's coast.