‘Mother’ coral reefs are breathing life into their neighbours

Coral reef

A life source for other reefs?

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Meet the Gaias of the coral world. “Mother” reefs are spreading life to their neighbours via swift ocean currents.

This activity was spotted from space, after Dionysios Raitsos at Plymouth Marine Laboratory in the UK and his colleagues studied satellite images of ocean currents in the Red Sea from 1992 to 2012.

“We could see how currents were dragging huge water masses carrying fish eggs, larvae and coral larvae from one area to another,” says Raitsos. “We used satellite data to identify the most important ‘mother’ reefs, which we found were population donors.”

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Identifying and protecting mother reefs, both in the Red Sea and elsewhere, could be the most effective way to conserve more distant reefs that are “receivers” rather than propagators of marine life, he says.

Some currents were so strong and fast that they could sweep larvae between the flanks of the Red Sea – an average distance of around 280 kilometres – in just two weeks. This allows life to spread, says Raitsos, because larvae and eggs can survive for that long.

Key routes

The researchers discovered the main “thoroughfares” for eggs and larvae using a computer model of the Red Sea. They placed millions of virtual particles at 19 reef locations along the sea’s 1500-kilometre eastern coastline, then tracked how far they travelled.

They found that material from reefs halfway down the coast travelled much further – 700 kilometres both north and south – than that from reefs elsewhere, especially compared with material at the southern tip of the Red Sea. This identified the central reefs as the ones that seeded the others.

To check that this tallied with the direction of real biological material, they analysed a database of clownfish genealogy along the eastern coastline held by collaborators at the King Abdullah University for Science and Technology in Thuwal, Saudi Arabia. They found that the pattern of clownfish gene flow matched the general flow of material from the mother reefs. “They overlapped nearly perfectly,” says Raitsos.

“Using satellite data, these researchers successfully predicted the genetics of clownfish in the Red Sea, and identified conservation hotspots that are key sources of larvae in the region,” says Steve Simpson at the University of Exeter, UK.

Journal reference: Scientific Reports, DOI: 10.1038/s41598-017-08729-w

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