Effects of seawater pCO2 changes on the calcifying fluid of scleractinian corals

Increased atmospheric concentrations of CO2 due to anthropogenic emissions of inducing changes in the carbonate chemistry of the ocean and a decrease in ocean pH. This process of acidification is expected to be harmful calcifying organisms such as coccolithophores, mollusks, echinoderms and corals. A sharp decline in the abundance of corals, for example, expected later this century, with consequent disastrous effects on reef ecosystems. Despite the growing importance of the issue, little progress has been made ​​regarding the modeling of the impact of acidification on coral calcification. Here is a model of a coral polyp that simulates the carbonate system in four distinct compartments: sea water, the tissue of the polyp, coelenteron, and calicoblastic layer. The calcium carbonate precipitation takes place in the layer below metabolically controlled calicoblastic polyp tissue. The model conforms to a state of activity as observed by direct measurements of microsensors in the calcifying fluid. Simulation experiments reveal disruption of CO2 reduced calcification rates in the high pCO2 despite strong control of the metabolism of calcifying fluid. CO2 diffusion through the tissues in calicoblastic layer increases with increasing seawater pCO2 leading to reduced aragonite saturation in the fluid of calcification of the coral polyps. Our modeling study provides important insights into the complexity of the process of calcification at the organism and helps to quantify the effect of ocean acidification on corals.

Hohn S. and A. Merico, 2012. Effects of seawater pCO2 changes in the fluid of scleractinian coral calcification. Biogeosciences Discussions 9 (3) :2655-2689. Article.