Evidence has shown that the changing carbonate saturation state, triggered by the rise in atmospheric CO2, may have a negative influence upon the calcification of scleractinian corals. However, such decreases have to date not been recognized in cores taken from coral skeletons. This proposal will explore the question of whether corals are able to adapt their growth to reduced saturation conditions to help solve this dilemma by using corals growing in marginal environments, which exhibit wide ranges in calcium carbonate saturation. Environments, such as Florida Bay, contain a small but apparently robust community of survivor corals maintaining extension rates comparable to corals on the nearby reef tract in spite of large and documented changes in saturation state. The PIs plan to use large colonies of the genus Solenastrea sp. that grow in Florida Bay to conduct a unique experiment in which they will allow the natural environment to manipulate the saturation state. Every two months over an 18 month period, calcification will be measured together with other physiological parameters. Superimposed upon this natural variation, the PIs will impose changes in saturation aimed at unraveling the competing influences of salinity and saturation state on calcification and extension. Finally, they will examine the density and geochemical record within the coral skeleton in order to determine what influences the changing pCO2 and whether past changes in pCO2 can be read from the skeletal record.
