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Without calcium, coral reefs may stop growing

U. QUEENSLAND (AUS) — Many Caribbean coral reefs don’t have enough calcium carbonate and have either stopped growing or are on the threshold of eroding away, new evidence suggests.

Coral reefs form some of the planet’s most biologically diverse ecosystems, and provide valuable services to humans and wildlife, however their ability to maintain their structures and continue to grow depends on the reef’s ability to both produce and accumulate calcium carbonate.

Researchers have found that the amount of new carbonate being added by Caribbean coral reefs is now significantly below rates measured over recent geological timescales—as much as 70 percent lower in some habitats.

The research, published in Nature Communications, is the first evidence that these ecological changes are now also affecting the growth potential of reefs themselves.

Professor Peter Mumby from the University of Queenland’s School of Biological Science says this discovery could affect millions of people who benefit from reef structures.

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“Reef structures provide benefits such as being fishery habitats for seafood, they are used for recreational diving adventures, and often provide a natural barrier to storm surge,” Mumby explains. “Our new findings imply that the benefits people receive from reefs will deteriorate considerably unless we take greater care of them.”

Scientists have long known that reef ecosystems are in decline and that the amount of live coral on reefs is dwindling. Though, calcium carbonate is mostly produced by corals themselves, they are also fighting against the loss of carbonate through various erosional processes.

“Our estimates of current rates of reef growth in the Caribbean are extremely alarming. Our study goes beyond only examining how much coral there is, to also look at the delicate balance of biological factors which determine whether coral reefs will continue to grow or will erode,” says Professor Chris Perry of the University of Exeter, who led the research.

“Our findings clearly show that recent ecological declines are now suppressing the growth potential of reefs in the region, and that this will have major implications for their ability to respond positively to future sea level rises.”

“It is most concerning that many coral reefs across the Caribbean have seemingly lost their capacity to produce enough carbonate to continue growing vertically, whilst others are already at a threshold where they may start to erode.”

“At the moment there is limited evidence of large-scale erosion or loss of actual reef structure, but clearly if these trends continue, reef erosion looks far more likely. Urgent action to improve management of reef habitats and to limit global temperature increases is likely to be critical to reduce further deterioration of reef habitat.”

Source: University of Queensland

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