THE SR CA-TEMPERATURE RELATIONSHIP IN CORALLINE ARAGONITE - INFLUENCEOF VARIABILITY IN (SR/CA)SEAWATER AND SKELETAL GROWTH-PARAMETERS/

This paper provides an evaluation of two of the most likely pitfalls o f Sr/Ca thermometry, i.e., the effect of biogenic cycling of Sr vs. Ca in the surface ocean and the effect of variable extension rate on Sr incorporation in coralline aragonite. We also report calibration of th e Sr/Ca-temperature relationship for three coral species, Porites loba ta, Pocillopora eydouxi, and Pavona clavus, collected from the Hawaiia n and Galapagos islands. Analyses of seawater samples show significant spatial and depth variability in the Sr:Ca ratio. The uncertainty int roduced by this effect is estimated to be <0.2-degrees-C for corals lo cated in tropical oligotrophic waters, and potentially larger for cora ls located in upwelling areas. Sr/Ca analyses along two different grow th axes of a Galapagos Pavona clavus, with annual extension rates of a pproximately 6 and 12 mm/y, respectively, indicate an offset of 1-2-de grees-C, with higher Sr/Ca values associated with slower extension rat es. The offset observed between the two growth axes may be the result of variations in extension and/or calcification rate.