Quantifying the pH `vital effect' in the temperate zooxanthellate coral Cladocora caespitosa: Validation of the boron seawater pH proxy

• Published in: Earth and Planetary Science Letters
• Main Author: Martin, Sophie
• Other Authors: Ecogéochimie et Fonctionnement des Ecosystèmes Benthiques (EFEB), Adaptation et diversité en milieu marin (AD2M), Station biologique de Roscoff Roscoff (SBR), Université Pierre et Marie Curie - Paris 6 (UPMC)-Centre National de la Recherche Scientifique (CNRS)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Centre National de la Recherche Scientifique (CNRS)-Centre National de la Recherche Scientifique (CNRS)-Station biologique de Roscoff Roscoff (SBR), Université Pierre et Marie Curie - Paris 6 (UPMC)-Centre National de la Recherche Scientifique (CNRS)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Centre National de la Recherche Scientifique (CNRS)-Centre National de la Recherche Scientifique (CNRS), ARC Discovery DP0986505, ARC Centre of Excellence in Coral Reef Studies, Marie Curie International Outgoing Fellowship, OMP project for P. Montagna, Prince Albert II of Monaco Foundation, International Atomic Energy Agency (IAEA-NAML, Monaco), European Community 211384
• Format: Article in Journal/Newspaper
• Language: English
• Published: HAL CCSD 2011
• Subjects: boron; Cladocora caespitosa; seawater pH; pCO(2); Mediterranean; ocean acidification; [SDV]Life Sciences [q-bio]; [SDE]Environmental Sciences; Ocean acidification
• Online Access: https://hal.science/hal-01255972; https://doi.org/10.1016/j.epsl.2011.01.030

International audience 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 (pH(T) similar to 7.6 to similar 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 mu atm) and near present day (400 mu atm) pCO(2) levels. BiCa compositions measured using laser ablation inductively coupled mass spectrometry (LA-ICPMS) show that boron uptake by C caespitosa cultured at different pCO(2) levels is independent of ambient seawater pH being mainly controlled by temperature-dependent calcification. In contrast, the boron isotope compositions (delta(11)B(carb)) of the full suite of corals determined by positive thermal ionisation mass spectrometry (PTIMS) shows a clear trend of decreasing delta(11) B(carb) (from 26.7 to 22.2%.) with decreasing seawater pH. reflecting the strong pH dependence of the boron isotope system. The delta(11)B(carb) 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 (pH,) and the internally controlled pH at the site of calcification (pH(biol)). C. caespitosa exhibits a linear relationship between pH(sw) and the shift in pH due to physiological processes (Delta pH = pH(biol) - pH(sw)) giving the regression Delta pH(clad) = 4.80 - 0.52 x pH(sw) for this species. We further apply this method (''Delta pH-pH(sw)'') to calibrate tropical species of Porites, Acropora, and Stylophora reported in the literature. The temperate and tropical species calibrations are all linearly correlated (r(2)> 0.9) and the biological fractionation component (pH) between species varies within similar to 0.2 pH units. Our ``Delta ...