Written by DIVE Magazine Wednesday, 30 January 2013 12:29
A study published this week reveals that reef growth rates have dropped by as much as 70 per cent in shallow waters and up to 25 per cent in deeper waters.
A multinational team led by Exeter University measured corals at 19 sites in the Bahamas; Belize; Grand Cayman and Bonaire. The study, published in the journal Nature Communications, found that in shallow waters of around 5m (16.25ft) in depth, reef growth rates today were between 60 and 70 per cent lower compared to the regional averages of the distant past.
The fall was smaller – around 25 percent – in deeper waters of around 10m (32.5 ft).
Many reefs may have lost their ability to produce enough carbonate to grow vertically, according to the study. Some are already below the threshold by which enough carbonate is produced to maintain the skeletal reef structure, and thus are at risk of erosion.
The estimates 'are extremely alarming,' said Chris Petty, an Exeter University professor. '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.'
Previous research has estimated that coral cover is declining by as much as two per cent per year in parts of the Indian Ocean and the Pacific. In the Caribbean, cover has shrunk by around 80 per cent on average since the mid-1970s.
According to a June 2012 update of the 'Red List' compiled by the International Union for Conservation of Nature (IUCN), 33 per cent of reef-building corals are at risk of extinction.
Habitat destruction, pollution and more recently global warming are the factors blamed in the decline.