Coral found growing at record depth

The discovery of a type of coral growing at a world-record depth has raised hope for the recovery reefs damaged by warming oceans.

Scientists from the Museum of Tropical Queensland in Australia report the successful collection of 4000 samples of mesophotic corals – species which typically grow in tropical and subtropical regions starting at 30 metres below the surface – during an expedition to the Gambier islands of French Polynesia.

Until now, mesophotic corals have not been found deeper than 150 metres. However, oceanographer Michel Picon and colleagues logged a sample at 172 metres – a substantial increase.

‘’I’ve been waiting for this kind of discovery for over 40 years,” says Picon.

The discovery extends the known environmental tolerances of the coral species, but also has potentially positive implications for shallow reef rehabilitation prospects. 

In previous research Picon and colleagues established that many shallow water coral species are also represented at least in upper mesophotic environments.

Looking at Australia’s Great Barrier Reef, the researchers found that of corals that characterise the near-surface reefs, “78% of genera, and all families extended below 30 metres depth, with 13% of species, 41% of genera, and 78% of families extending below 45 metres”.

The latest discovery of one particular species, Leptoseris hawaiiensi, growing deeper than 170 metres bolsters the theory that deep-water ecosystems may hold the key to reef recovery strategies.

“Those results represent robust foundations to test the capacity for mesophotic corals to act as a refuge consequently to the deterioration of the shallow reefs impacted by global changes, as well as their ability to play a role in the restoration of those reefs,” Picon says.

The Gambier islands expedition was conducted under aegis of a France-based multi-institute collaboration called Under The Pole.

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