Coral reef calcifiers buffer their response to ocean acidification using both bicarbonate and carbonate

• Published in: Proceedings of the Royal Society B: Biological Sciences
• Main Authors: Comeau, S., Carpenter, R. C., Edmunds, P. J.
• Format: Article in Journal/Newspaper
• Language: English
• Published: The Royal Society 2013
• Subjects: Rus’; Ocean acidification
• Online Access: http://dx.doi.org/10.1098/rspb.2012.2374; https://royalsocietypublishing.org/doi/pdf/10.1098/rspb.2012.2374; https://royalsocietypublishing.org/doi/full-xml/10.1098/rspb.2012.2374

Central to evaluating the effects of ocean acidification (OA) on coral reefs is understanding how calcification is affected by the dissolution of CO 2 in sea water, which causes declines in carbonate ion concentration [CO 3 2− ] and increases in bicarbonate ion concentration [HCO 3 − ]. To address this topic, we manipulated [CO 3 2− ] and [HCO 3 − ] to test the effects on calcification of the coral Porites rus and the alga Hydrolithon onkodes , measured from the start to the end of a 15-day incubation, as well as in the day and night. [CO 3 2− ] played a significant role in light and dark calcification of P. rus , whereas [HCO 3 − ] mainly affected calcification in the light. Both [CO 3 2− ] and [HCO 3 − ] had a significant effect on the calcification of H. onkodes , but the strongest relationship was found with [CO 3 2− ]. Our results show that the negative effect of declining [CO 3 2− ] on the calcification of corals and algae can be partly mitigated by the use of HCO 3 − for calcification and perhaps photosynthesis. These results add empirical support to two conceptual models that can form a template for further research to account for the calcification response of corals and crustose coralline algae to OA.