Coral bleaching 'lifeboat' could be just beneath the surface

May 24, 2016
Leptoseris coral-dominated Mesophotic Coral Ecosystem in the 'Au'au Channel, offshore of Maui, Hawai'i, depth of 70m. Credit: Credit NOAA's Hawai'i Undersea Research Laboratory.

A report commissioned by the United Nations and co-authored by the University of Sydney's UNESCO Chair in Marine Science offers a glimmer of hope to those managing the impact of bleaching on the world's coral reefs, including the Great Barrier Reef.

Coral bleaching has affected virtually the entire Great Barrier Reef and many other coral reef systems globally, a result of the continuing rise in global temperatures and exacerbated by the summer's major El Niño event.

The 35 authors of the United Nations Environmental Programme report - including the University's Professor Elaine Baker in the School of Geosciences - say as the world's surface reefs are being threatened, part of the ecosystem may survive in these barely known deeper environments, known as mesophotic (MCEs).

Shallow from the water's surface to 30-40 metres depth are the tip of the iceberg that comprises the ocean's extensive coral ecosystem. MCEs are intermediate depth reefs starting at about 40 metres depth and continuing to around 150 metres. The report being launched today - 'Mesophotic Coral Ecosystems A lifeboat for coral reefs?' - looks at the role MCEs could play in the preservation of shallower reefs.

The report asks if MCEs can provide a refuge for the species under threat in shallower reef ecosystems and whether they can provide the stock to re-populate shallow reefs if they continue to decline.

In shallow waters, the Caribbean coral Montastraea cavernosa exhibits a boulder-like morphology, shown at 5m. Credit: John Reed

"Mesophotic coral ecosystems are a seed bank for some organisms," said Professor Baker.

"More research needs to be done to firmly establish the role of MCEs in preserving our reefs; they aren't a silver bullet but they may be able to resist the most immediate impacts of climate change—thereby providing a refuge for some species and potentially helping to replenish destroyed surface reef and fish populations.

"It may be that the cooler, deeper water in MCEs could be more hospitable to many species than the warmer surface water," she said. "They also are less prone to waves and turbulence, therefore potentially offering a more stable environment."

The review brought together information on the geology, biology, distribution and socio-economic aspects of mesophotic reefs in order to examine their potential resilience.

The report found some deep mesophotic coral ecosystems may be less vulnerable to the most extreme ocean warming, but others may be just as vulnerable as their shallow counterparts and cannot be relied on to act as "life boats".

The report was set to be launched at the second session of the United Nations Environment Assembly UNEA-2 in Nairobi, reef media roundtable, on Tuesday 24 May from 15:30 to 16:15 Kenyan time / by 11.15pm Australian Eastern Standard time.

The full and UN media release will be available via UNEP/UNEA-2 as well as from the University of Sydney.

Explore further: Care about coral reefs? Protect the 'lawnmowers'

More information: sydney.edu.au/science/geoscien … eso-coral-report.pdf

Related Stories

Care about coral reefs? Protect the 'lawnmowers'

May 20, 2016

Coral reefs provide protection for islands, billions of dollars in economic value, and a dazzling array of biodiversity. Keeping reefs healthy is an important job, and one particular group of herbivorous fish and invertebrates ...

Researchers study sediment record in deep coral reefs

December 2, 2015

A University of Miami (UM) Rosenstiel School of Marine and Atmospheric Science-led research team analyzed the sediments of mesophotic coral reefs, deep reef communities living 30-150 meters below sea level, to understand ...

Coral death stops fish from learning predators

May 10, 2016

In a world first study researchers have found that coral bleaching and death can have dramatic repercussions for how small reef fish learn about and avoid predators. The new results are published in the journal Proceedings ...

New study of largely unstudied mesophotic coral reef geology

July 7, 2014

A new study on biological erosion of mesophotic tropical coral reefs, which are low energy reef environments between 30-150 meters deep, provides new insights into processes that affect the overall structure of these important ...

Recommended for you

New research could predict La Nina drought years in advance

November 16, 2017

Two new studies from The University of Texas at Austin have significantly improved scientists' ability to predict the strength and duration of droughts caused by La Niña - a recurrent cooling pattern in the tropical Pacific ...

0 comments

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.