Seawater carbonate chemistry and coral calcifying fluid pH and calcification

• Main Authors: Comeau, Steeve, Cornwall, Christopher Edward, McCulloch, Malcolm T
• Format: Dataset
• Language: English
• Published: PANGAEA 2017
• Subjects: Acid-base regulation; Acropora yongei; Alkalinity; total; standard error; Animalia; Aragonite saturation state; Benthic animals; Benthos; Bicarbonate ion; Biomass/Abundance/Elemental composition; Boron/Calcium ratio; Calcification/Dissolution; Calcification rate of calcium carbonate; Calcifying fluid; dissolved inorganic carbon; pH; Calcite saturation state; Calculated using seacarb; Calculated using seacarb after Nisumaa et al. (2010); Carbon; inorganic; dissolved; Carbonate ion; Carbonate system computation flag; Carbon dioxide; Cnidaria; Coast and continental shelf; Containers and aquaria (20-1000 L or < 1 m**2); Fugacity of carbon dioxide (water) at sea surface temperature (wet air); Indian Ocean; Laboratory experiment; OA-ICC; Ocean Acidification International Coordination Centre; Partial pressure of carbon dioxide (water) at sea surface temperature (wet air); Pocillopora damicornis; Ocean acidification
• Online Access: https://doi.pangaea.de/10.1594/PANGAEA.892497; https://doi.org/10.1594/PANGAEA.892497

Evaluating the factors responsible for differing species-specific sensitivities to declining seawater pH is central to understanding the mechanisms via which ocean acidification (OA) affects coral calcification. We report here the results of an experiment comparing the responses of the coral Acropora yongei and Pocillopora damicornis to differing pH levels (8.09, 7.81, and 7.63) over an 8-week period. Calcification of A. youngei was reduced by 35% at pH 7.63, while calcification of P. damicornis was unaffected. The pH in the calcifying fluid (pHcf) was determined using delta 11B systematics, and for both species pHcf declined slightly with seawater pH, with the decrease being more pronounced in P. damicornis. The dissolved inorganic carbon concentration at the site of calcification (DICcf) was estimated using geochemical proxies (B/Ca and delta 11B) and found to be double that of seawater DIC, and increased in both species as seawater pH decreased. As a consequence, the decline of the saturation state at the site of calcification (Ωcf) with OA was partially moderated by the DICcf increase. These results highlight that while pHcf, DICcf and Ωcf are important in the mineralization process, some corals are able to maintain their calcification rates despite shifts in their calcifying fluid carbonate chemistry.