Colony-specific calcification and mortality under ocean acidification in the branching coral Montipora digitata.

Ocean acidification (OA) threatens calcifying marine organisms including reef-building corals. In this study, we examined the OA responses of individual colonies of the branching scleractinian coral Montipora digitata . We exposed nubbins of unique colonies (n = 15) to ambient or elevated p CO 2 under natural light and temperature regimes for 110 days. Although elevated p CO 2 exposure on average reduced calcification, individual colonies showed unique responses ranging from declines in positive calcification to negative calcification (decalcification) to no change. Similarly, mortality was greater on average in elevated p CO 2 , but also showed colony-specific patterns. High variation in colony responses suggests the possibility that ongoing OA may lead to natural selection of OA-tolerant colonies within a coral population. [ABSTRACT FROM AUTHOR]