Seawater carbonate chemistry and zooxanthellate coral Cladocora caespitosa boron isotopic and elemental systematics during experiments, 2011

• Main Authors: Trotter, Julie, Montagna, Paolo, McCulloch, Malcolm T, Silenzi, Sergio, Reynaud, Stéphanie, Mortimer, Graham, Martin, Sophie, Ferrier-Pagès, Christine, Gattuso, Jean-Pierre, Rodolfo-Metalpa, Riccardo
• Format: Dataset
• Language: English
• Published: PANGAEA 2011
• Subjects: Alkalinity; total; standard deviation; Aragonite saturation state; Bicarbonate ion; Boron/Calcium ratio; Boron hydroxide/Bicarbonate ratio; Calculated; see reference(s); Carbon; inorganic; dissolved; Carbonate ion; Carbon dioxide; partial pressure; DATE/TIME; DISTANCE; EPOCA; European Project on Ocean Acidification; Experimental treatment; Measured; Partial pressure of carbon dioxide (water) at sea surface temperature (wet air); pH; pH meter (Metrohm; 826 pH mobile); Salinity; Site; Species; Temperature; Ocean acidification
• Online Access: https://doi.pangaea.de/10.1594/PANGAEA.767603; https://doi.org/10.1594/PANGAEA.767603

Boron isotopic and elemental systematics are used to define the vital effects for the temperate shallow water Mediterranean coral Cladocora caespitosa. The corals are from a range of seawater pH conditions (pHT ~ 7.6 to ~ 8.1) and environmental settings: (1) naturally living colonies harvested from normal pH waters offshore Levanto, (2) colonies transplanted nearby a subsea volcanic vent system, and (3) corals cultured in aquaria exposed to high (700 µatm) and near present day (400 µatm) pCO2 levels. B/Ca compositions measured using laser ablation inductively coupled mass spectrometry (LA-ICPMS) show that boron uptake by C. caespitosa cultured at different pCO2 levels is independent of ambient seawater pH being mainly controlled by temperature-dependent calcification. In contrast, the boron isotope compositions (delta11Bcarb) of the full suite of corals determined by positive thermal ionisation mass spectrometry (PTIMS) shows a clear trend of decreasing delta11Bcarb (from 26.7 to 22.2 %o) with decreasing seawater pH, reflecting the strong pH dependence of the boron isotope system. The delta11Bcarb compositions together with measurements of ambient seawater parameters enable calibration of the boron pH proxy for C. caespitosa, by using a new approach that defines the relationship between ambient seawater pH (pHsw) and the internally controlled pH at the site of calcification (pHbiol). C. caespitosa exhibits a linear relationship between pHsw and the shift in pH due to physiological processes (deltapH = pHbiol - pHsw) giving the regression deltapHClad = 4.80 - 0.52* pHsw for this species. We further apply this method ("deltapH-pHsw") to calibrate tropical species of Porites, Acropora, and Stylophora reported in the literature. The temperate and tropical species calibrations are all linearly correlated (r2 > 0.9) and the biological fractionation component (deltapH) between species varies within ~ 0.2 pH units. Our "deltapH-pHsw" approach provides a robust and accurate tool to reconstruct palaeoseawater pHsw for ...