Survey of 19 colonies finds many may soon begin to shrink

By Rachel Ehrenberg

Web edition: January 28, 2013

Enlarge

CORAL IN CRISIS

Slowing growth threatens the survival of many Caribbean coral reefs (shown).

Credit: Chris Perry

Reefs in the Caribbean are experiencing a budget crisis: Corals’ production of calcium carbonate — their bony material that creates reefs — is way down, a 16-month-long investigation finds. Shallow-water reefs are in especially bad shape, with growth rates that are 30 to 40 percent of historical values. Many of these shallow sites also lack Acropora species, which are key reef-building corals that typically produce a lot of carbonate. These degraded reefs also have a lot of smothering seaweed and few critters to graze upon it, the study of 19 sites found.

The new analysis, published January 29 in Nature Communications, suggests that when the amount of live coral in a reef drops below about 10 percent, erosion begins to outpace growth of new reef structures. Many Caribbean coral reefs are approaching this tipping point, the team led by Chris Perry of the University of Exeter in England found. Ongoing assaults such as warming waters and ocean acidification may further hinder reefs’ efforts to get their budgets back in the black.