Ronald L. Shimek, Ph. D.

This month, I will discuss an interesting article on coral growth rates...

Carricart-Ganivet, J. P. 2004. Sea Surface temperature and the growth of the West Atlantic reef-building coral Montastraea annularis. Journal of Experimental Marine Biology and Ecology. 302: 249-260.

Abstract:

Relationships were analyzed between sea surface temperature (SST) and annual growth characteristics (density, extension rate and calcification rate) of the Caribbean reef-building coral Montastraea annularis. Colonies were collected from 12 localities in the Gulf of Mexico and the Caribbean Sea. Calcification rate and skeletal density increased approximately 0.57 g/cm2/year for each 1°C increase in SST. Zero calcification was projected to occur at 23.7°C (74.7°F) in corals from the Gulf of Mexico and at 25.5°C (77.9°F) in corals from the Caribbean Sea. The 24°C (75.2°F) annual average isotherm marks the northern limit of the distribution of M. annularis. Montastraea annularis populations of the Gulf of Mexico are isolated from those of the Caribbean Sea, and results indicate that corals from the Gulf of Mexico are adapted to growth at lower minimum and average annual SST. Corals from both the Gulf of Mexico and the Caribbean Sea, growing at lower SSTs and having lower calcification rates, extend their skeletons the same or more than those growing at higher SSTs. They achieve this by putting more of their calcification resources into extension and less into thickening, i. e. by sacrificing density.

Comments:

This article clearly shows the dependence of two populations from one species of reef forming corals on suitable, and high, temperatures. Growth ceases at temperatures below 74.7°F for individuals from the Gulf of Mexico and below 77.9°F at individuals from the Caribbean Sea. Above those temperatures, calcification increases with increasing temperature to at least 29°C (84.2°F). The authors had no higher temperature data points, but their data showed increasing growth rates up to the 29°C value. It is likely this species is tolerant of higher temperatures. The data in the paper also show that coral specimens collected from sites that were relatively near to one another (on opposite sides of the Yucatan Peninsula) were from two genetically distinct populations.