Calcification responses of symbiotic and aposymbiotic corals to near-future levels of ocean acidification

[摘要] Increasing the acidity of ocean waters will directly threaten calcifying marine organisms such asreef-building scleractinian corals, and the myriad of species that rely on corals for protectionand sustenance. Ocean pH has already decreased by around 0.1 pH units since the beginning ofthe industrial revolution, and is expected to decrease by another 0.2–0.4 pH units by 2100. Thisstudy mimicked the pre-industrial, present, and near-future levels of pCO₂ using a precisecontrol system (± 5% pCO₂), to assess the impact of ocean acidification on the calcification ofrecently settled primary polyps of Acropora digitifera, both with and without symbionts, andadult fragments with symbionts. The increase in pCO₂ of ~100 μatm between the pre-industrialperiod and the present had more effect on the calcification rate of adult A. digitifera than theanticipated future increases of several hundreds of micro-atmospheres of pCO₂. The primarypolyps with symbionts showed higher calcification rates than primary polyps without symbionts,suggesting that: (i) primary polyps housing symbionts are more tolerant to near-future oceanacidification than organisms without symbionts, and (ii) corals acquiring symbionts from theenvironment (i.e., broadcasting species) will be more vulnerable to ocean acidification thancorals that maternally acquire symbionts.

[学科分类] 地球化学与岩石