Seagrass could help coral reefs

23 June 2012 Last updated at 10:01 ET

Research headed by a Swansea University marine biologist has offered potential solution to endangered coral reefs around the world's oceans.

Dr Richard Unsworth's team included scientists from Oxford University and James Cook University in Australia.

They found varieties of seagrass which may reduce the acidity of water around reefs, protecting them from erosion.

Corals are worm-like creatures of around a centimetre length which live in colonies numbering millions.

Calcium carbonate released by the corals forms a protective reef around the entire group.

The survival of these corals has been threatened by carbon dioxide in the atmosphere over the last 40 years, as it has raised the acidity of the oceans, rotting the reefs in the same way as fruit and fizzy drinks can erode tooth enamel.

But now Dr Unsworth believes he has found varieties of seagrass which can photosynthesise carbon dioxide so quickly and efficiently that they actually turn the surrounding water more alkaline.

"Highly productive tropical seagrasses often live adjacent to or among coral reefs and photosynthesise at such rates you can see the oxygen they produce practically bubbling away," he said.

"We wanted to understand whether this could be a major local influence on seawater and the problems of ocean acidification."

"Rising atmospheric carbon dioxide in the air, primarily from human fossil fuel combustion, reduces ocean pH and causes wholesale shifts in seawater carbonate chemistry.

"Over long term time scales, this change in seawater carbonate chemistry is likely to cause coral reefs to start to disappear as the rate of erosion starts to exceed growth rates."

Dr Unsworth said not only are coral reefs intrinsically valuable in their own right, but they provide natural fishing lagoons and sea defences for millions of people, mostly living on small islands in the South Pacific.

The team's findings are published in this month's edition of the science journal, 'Open Access Environmental Research Letters', and Dr Unsworth is due to give a presentation on 10 July at the 12th coral preservation symposium in Cairns, Australia.

But he warned that unless action is taken to protect them, then seagrass itself could be under threat from human activity such as over-fishing, chemical pollution and climate-change.

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