Coral reefs grow quickly in 'muddy' waters

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A new study has shown rapid coral reef growth in conditions that were previously thought to have been detrimental to reef growth.

The study by a team from the University of Exeter has established that the Middle Reef — part of Australia's Great Barrier Reef — has grown more rapidly than many other reefs that have lower levels of sediment stress.

The water in which the Middle Reef grows is persistently 'muddy' from sediment — believed to have a detrimental effect on marine biodiversity - and the research has shown that it has continued to grow rapidly towards sea level at rates averaging nearly 1cm per year — a greater rate than those growing in clear water reefs on the Great Barrier Reef and elsewhere. In fact the periods of most rapid growth coincided with the times that sediment was actually at its peak.

Researchers believe that in the case of the Middle Reef, the sedimentation has actually aided its development, as it rapidly covers coral skeletons after their death, preventing destruction by fish, urchins and other biological eroders, thus promoting coral framework preservation and rapid reef growth.

Professor Chris Perry of Geography at the University of Exeter said: "Our research challenges the long-held assumption that high sedimentation rates are necessarily bad news in terms of coral reef growth. It is exciting to discover that Middle Reef has in fact thrived in these unpromising conditions. It is, however, important to remain cautious when considering what this means for other reefs. Middle Reef includes corals adapted to deal with high sedimentation and low light conditions. Other reefs where corals and various other reef organisms are less well adapted may not do so well if sediment inputs increased.

"Our research calls for a rethink on some of the classic models of reef growth."

The results of the study were published in the journal Geology.

The study was conducted by a team from the University of Exeter (UK), James Cook University, Townsville, Queensland (Australia), and the NERC Radiocarbon Laboratory, Scotland (UK). It was funded by the Leverhulme Trust and Natural Environment Research Council (NERC).

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