Science Serving Maryland's Coasts

Elsa Chen, Skidmore College

Class Year: 

Project Title: 

Investigation of Interspecies Differences in Sr/Ca SST Reconstructions for Diploria and Orbicella Corals


Coral strontium to calcium ratio (Sr/Ca) measurements can be used to generate reconstructions of past climate, providing information that allows us to not only place current global conditions within a historical context but also improve predictive models. Most field studies use only one species for a coral-based climate reconstruction, but there is a growing recognition of the need for replication in these studies to explore potential species and growth effects and increase confidence in the models. We sampled two species, Diploria strigosa and Orbicella annularis, for two different time periods, 1355-1360 and modern (>1930s), to examine potential interspecies differences in how they record climate. After sampling with a microdrill at an average rate of 12 samples a year, the samples were diluted with 2% nitric acid to create ~20 ppm Ca solutions, which were then analyzed with an Inductively-Coupled Plasma Optical Emissions Spectrometer. The data did not contain regular seasonal cycles as expected for Sr/Ca in pristine coral material, most likely as a result of diagenesis and sampling of non-thecal material. A large Sr/Ca spike in January-February, 1360 found in both species may be a result of an environmental perturbation affecting both corals, such as an upwelling of Sr-rich waters.