Meeting Abstract
Ocean acidification (OA) is characterized by dramatic changes in ocean carbonate chemistry. In particular, seawater pH and saturation state with respect to aragonite (Ω) decrease, and seawater pCO2 and DIC increase. While OA is generally understood to be harmful to calcifying organisms, overall responses of to OA vary greatly across taxa, making it difficult to predict how organisms will fare under continued environmental change. Cold-water scleractinian corals (CWC) generally tend to dwell in waters with relatively low pH and Ω. In addition, CWCs lack photosynthetic symbionts, which allows for the isolation of calcification processes from photosynthesis.
In this study, we investigated the calcification response of the orange cup coral, Balanophyllia elegans, to changes in shifting carbonate system parameters. In experimental treatments, dissolved inorganic carbon (DIC) and pH were manipulated independently, with seawater set at nine different conditions: one at ambient DIC and pH, four at stable pH with varied DIC, and four at stable DIC with varied pH. Net calcification rates were determined using alkalinity anomaly. Large variations in calcification rate were seen at stable pH when DIC was varied, and vice versa. Aragonite saturation state was found to most closely control calcification.
Our findings agree with previous research1 on tropical coral that has found aragonite saturation state to be the dominant parameter controlling calcification in scleractinian coral. However, results also suggests that CWCs have the may calcify at lower saturation states than tropical coral.
1Schneider, K., Erez, J.. The effect of carbonate chemistry on calcification and photosynthesis in the hermatypic coral Acropora eurystoma. Limnology and Oceanography. 51(3), 2006, 1284-1293.
