carbonate budget

Regional-scale dominance of non-framework building corals on Caribbean reefs affects carbonate production and future reef growth

Abstract

Coral cover on Caribbean reefs has declined rapidly since the early 1980's. Diseases have been a major driver, decimating communities of framework building Acropora and Orbicella coral species, and reportedly leading to the emergence of novel coral assemblages often dominated by domed and plating species of the genera Agaricia, Porites and Siderastrea. These corals were not historically important Caribbean framework builders, and typically have much smaller stature and lower calcification rates, fuelling concerns over reef carbonate production and growth potential. Using data from 75 reefs from across the Caribbean we quantify: (i) the magnitude of non-framework building coral dominance throughout the region and (ii) the contribution of these corals to contemporary carbonate production. Our data show that live coral cover averages 18.2% across our sites and coral carbonate production 4.1 kg CaCO3 m−2 yr−1. However, non-framework building coral species dominate and are major carbonate producers at a high proportion of sites; they are more abundant than Acropora and Orbicella at 73% of sites; contribute an average 68% of the carbonate produced; and produce more than half the carbonate at 79% of sites. Coral cover and carbonate production rate are strongly correlated but, as relative abundance of non-framework building corals increases, average carbonate production rates decline. Consequently, the use of coral cover as a predictor of carbonate budget status, without species level production rate data, needs to be treated with caution. Our findings provide compelling evidence for the Caribbean-wide dominance of non-framework building coral taxa, and that these species are now major regional carbonate producers. However, because these species typically have lower calcification rates, continued transitions to states dominated by non-framework building coral species will further reduce carbonate production rates below ‘predecline’ levels, resulting in shifts towards negative carbonate budget states and reducing reef growth potential.

 

Date
2015
Data type
Scientific article
Theme
Research and monitoring
Geographic location
Bonaire

Densities of the sea urchin Diadema antillarum before and after mass mortalities on the coral reefs of Curacao

The sea urchin Diadema antillarum commonly occurs on Caribbean reefs in densities sufficiently high to influence characteristics such as community composition and reef growth. We observed an outbreak of mass mortality in this species reducing population densities by 98 to 100 %. Mortality spread from the Curacao harbour mouth along the coast, most rapidly advancing in the down-current direction. Our calculations show a pronounced effect on the carbonate budget of the reef. Recovery of Diadema populations may be facilitated by parthenogenesis. There is continuing recruitment on affected reefs, a possible location of the parent population being up-current unaffected reefs of Bonaire.

Date
1984
Data type
Scientific article
Theme
Research and monitoring
Geographic location
Curacao