The impact of seawater saturation state and bicarbonate ion concentration on calcification by new recruits of two Atlantic corals

• Published in: Coral reefs 2011-06, Vol.30 (2), p.321-328
• Main Authors: de Putron, S. J., McCorkle, D. C., Cohen, A. L., Dillon, A. B.
• Format: Article
• Language: English
• Subjects: Acidification; Alkalinity; Animal and plant ecology; Animal, plant and microbial ecology; Biological and medical sciences; Biomedical and Life Sciences; Carbon dioxide; Cnidaria. Ctenaria; Coral reefs; Dissolved inorganic carbon; Environmental conditions; Freshwater & Marine Ecology; Fundamental and applied biological sciences. Psychology; Invertebrates; Larvae; Life Sciences; Mineralization; Ocean acidification; Oceanography; Oceans; Organic contaminants; Sea water ecosystems; Seawater; Synecology
• ISSN: 0722-4028; 1432-0975
• DOI: 10.1007/s00338-010-0697-z

Rising concentrations of atmospheric CO 2 are changing the carbonate chemistry of the oceans, a process known as ocean acidification (OA). Absorption of this CO 2 by the surface oceans is increasing the amount of total dissolved inorganic carbon (DIC) and bicarbonate ion (HCO 3 − ) available for marine calcification yet is simultaneously lowering the seawater pH and carbonate ion concentration ([CO 3 2− ]), and thus the saturation state of seawater with respect to aragonite (Ω ar ). We investigated the relative importance of [HCO 3 − ] versus [CO 3 2− ] for early calcification by new recruits (primary polyps settled from zooxanthellate larvae) of two tropical coral species, Favia fragum and Porites astreoides . The polyps were reared over a range of Ω ar values, which were manipulated by both acid-addition at constant pCO 2 (decreased total [HCO 3 − ] and [CO 3 2− ]) and by pCO 2 elevation at constant alkalinity (increased [HCO 3 − ], decreased [CO 3 2− ]). Calcification after 2 weeks was quantified by weighing the complete skeleton (corallite) accreted by each polyp over the course of the experiment. Both species exhibited the same negative response to decreasing [CO 3 2− ] whether Ω ar was lowered by acid-addition or by pCO 2 elevation—calcification did not follow total DIC or [HCO 3 − ]. Nevertheless, the calcification response to decreasing [CO 3 2− ] was nonlinear. A statistically significant decrease in calcification was only detected between Ω ar  =