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.
Photo Credit: Lauren Valentino (NOAA)