Boron and carbon isotope, and B/Ca data for a Siderastrea siderea coral core CIM_C_2-2-1/CIM_C_2-2-2 from the Gulf of Mexico

Massive scleractinian corals provide unique opportunities to reconstruct past climatic and chemical changes in the ocean, where there is no additional information. Regular pH measurements and carbonate chemistry observations of the ocean are still sparse but are essential to monitor the health of our oceans. Boron isotopes and B/Ca measured from coral skeletal material can be used to reconstruct the pH and the carbonate chemistry of their environment. The results from boron isotope measurements show an acidifying Gulf of Mexico over 160 years (1845-2005) and declining δ13C. A coral core was drilled in 2005 from a living Siderastrea siderea coral close to Havana, Cuba. The coral core was cut, slabbed and X-rayed at the Leibniz Center for Tropical Marine Research, Bremen. Yearly samples were drilled over two polyps with a Proxxon drill and 1 mm diamond-coated drill bit. Boron Isotopes were measured from the yearly samples for every 3rd year (if there was enough coral skeletal material) at the MARUM facilities in Bremen with a Thermo Fisher Neptune MC-ICP-MS. δ13C was measured on monthly samples on the Thermo Fisher Finnigan MAT 251 and Finnigan Mat 253plus isotope ratio mass spectrometer also at MARUM. Trace elements-Calcium ratios where measured at ZMT on a Plasma Quant MS Elite Inductively Coupled Plasma - Mass Spectrometer with monthly samples. The age model for the dataset was interpolated using the Arand software Ager and Timer (Howell et al., 2006). Outliers were identified with the detection method provided by Chen and Liu (1993).