Physiological and ecological performance differs in four coral taxa at a volcanic carbon dioxide seep

Around volcanic carbon dioxide (CO2) seeps in Papua New Guinea, partial pressures of CO2 (pCO(2)) approximate those as predicted for the end of this century, and coral communities have low diversity and low structural complexity. To assess the mechanisms for such community shifts in response to ocean acidification, we examined the physiological performance of two hard corals that occur with increased or unaltered abundance at a seep site (mean pH(Total) = 7.8, pCO(2) = 862 mu atm) compared to a control site (mean pH(Total) = 8.1, pCO(2) = 323 mu atm), namely massive Porites spp. and Pocillopora damicornis, and two species with reduced abundance, Acropora millepora and Seriatopora hystrix. Oxygen fluxes, calcification, and skeletal densities were analyzed in corals originating from the seep and control site. Net photosynthesis rates increased considerably in Porites spp. and A. millepora and slightly in P. damicornis at increased pCO(2), but remained unaltered in S. hystrix. Dark respiration rates remained constant in all corals investigated from both sites. Rates of light calcification declined in S. hystrix at high pCO(2), but were unaffected by pCO(2) in the other three coral taxa. Dark and net calcification rates remained unchanged in massive Porites and P. damicornis, but were drastically reduced at high pCO(2) in A. millepora and S. hystrix. However, skeletal densities were similar at both seep and control sites in all coral taxa investigated. Our data suggest that the pCO(2)-tolerant corals were characterized by an increased ability to acclimatize to ocean acidification, e.g. by maintaining net calcification. Thus, robust corals, such as Porites spp. and P. damicornis, are more likely to persist for longer in a future high pCO(2) world than those unable to acclimatize. (C) 2015 Elsevier Inc. All rights reserved.