Chemistry

Ecology

Porites

Coral reef

Geology

Coral

Organic chemistry

Seawater

Biology

Carbonate

Ecosystem

Ocean acidification

Environmental science

Oceanography

Aragonite

Reef

Proceedings of the National Academy of Sciences

Significance Ocean acidification (OA) threatens coral reef futures by reducing the concentration of carbonate ions that corals need to construct their skeletons. However, quantitative predictions of reef futures under OA are confounded by mixed responses of corals to OA in experiments and field observations. We modeled the skeletal growth of a dominant reef-building coral, Porites , as a function of seawater chemistry and validated the model against observational data. We show that OA directly and negatively affects one component of the two-step growth process (density) but not the other (linear extension). Combining our growth model with Global Climate Model output, we show that skeletal density of Porites corals could decline by up to 20.3% over the 21st century solely due to OA.

Ocean acidification affects coral growth by reducing skeletal density