Isotopic and elemental records in a non-tropical coral (Cladocora caespitosa): Discovery of a new high-resolution climate archive for the Mediterranean Sea

A 95-year annual record of skeletal Sr / Ca, Mg / Ca, δ18O and δ13C is reported for a non-tropical, slow-growing coral (Cladocora caespitosa) collected in the north-western Mediterranean Sea. Significant correlations were found for Sr / Ca vs. Mg / Ca, Sr / Ca vs. δ18O and for δ18O vs. δ13C, indicating the possibility of using this non-tropical species as a climatic and paleoclimatic biomarker. The Sr / Ca and Mg / Ca ratios as well as the δ18O composition in corals were compared against the Sea Surface Temperature (SST) data of IGOSS (Integrated Global Ocean Service System Products) for the north-western Mediterranean region. The Sr / Ca ratios show a significant correlation with the SST, according to the following equation: Sr / Ca (mmol/mol) = 11.25 (± 0.38) − 0.079 (± 0.026) SST (°C). The δ18O data do not appear to fit with the SST interval used, since the regression obtained is non-significant. This implies that other factors apart from temperature, such as the δ18Oseawater, are affecting the coral δ18O. The relationship between Mg / Ca ratio and SST is not statistically significant. This is probably due to the heterogeneities in magnesium content found among the coral microstructures (calcification centres, surrounding fibres and dissepiments), along with other factors, such as the presence of microborings and/or organic matter. The annual record indicates a history of SST variation that is consistent with the instrumental measurements, and strongly suggests the feasibility of using this non-tropical coral as a new proxy for the Mediterranean Sea.