The non-tropical coral Cladocora caespitosa as the new climate archive for the Mediterranean: high-resolution (~weekly) trace element systematics

High-resolution (similar to weekly) laser ablation ICP-MS trace element analyses (B, Sr, U, Mg, Ba) are reported for the scleractinian coral Cladocora caespitosa, collected from the Northern Adriatic Sea. Geochemical ratios (Sr/Ca, B/Ca, Mg/Ca, U/Ca, Ba/Ca) were measured in a 38-mm long (similar to 10 years' growth) external coralline portion (wall region) and generally exhibit a close relationship with the in situ measured (weekly-fortnightly) data on sea surface temperature (SST), available for the last 6 years. In particular, B/Ca ratios tuned to fine-scale variations in SST show a high degree of correlation (r = -0.856, n = 136) with SST, and indicate that coral calcification only occurs above a minimum temperature threshold of 14-16 degrees C. In addition, the ranges of trace element variability are larger than those typically recorded in tropical corals, consistent with the large seasonal variations in SST of the Adriatic. This study thus demonstrates the feasibility of extracting and exploiting high-resolution geochemical records from non-tropical corals such as C. caespitosa as a proxy for SST.