Evidence That High pCO2 Affects Protein Metabolism in Tropical Reef Corals

Early life stages of the coral Seriatopora caliendrum were used to test the hypothesis that the depression of dark respiration in coral recruits by high pCO(2) is caused by perturbed protein metabolism. First, the contribution of protein anabolism to respiratory costs under high pCO(2) was evaluated by measuring the aerobic respiration of S. caliendrum recruits with and without the protein synthesis inhibitor emetine following 1 to 4 days at 45 Pa versus 77 Pa pCO(2). Second, protein catabolism under high pCO(2) was evaluated by measuring the flux of ammonium (NH4+) from juvenile colonies of S. caliendrum incubated in darkness at 47 Pa and 90 Pa pCO(2). Two days after settlement, respiration of recruits was affected by an interaction between emetine and pCO(2), with emetine reducing respiration 63% at 45 Pa pCO(2) and 27% at 77 Pa pCO(2). The interaction disappeared 5 days after settlement, when respiration was reduced 27% by emetine under both pCO(2) conditions. These findings suggest that protein anabolism accounted for a large proportion of metabolic costs in coral recruits and was affected by high pCO(2), with consequences detected in aerobic respiration. Juvenile S. caliendrum showed net uptake of NH4+ at 45 Pa pCO(2) but net release of NH4+ at 90 Pa pCO(2), indicating that protein catabolism, NH4+ recycling, or both were affected by high pCO(2). Together, these results are consistent with the hypothesis that high pCO(2) affects protein metabolism in corals.