CO₂ emissions into the atmosphere have promoted the absorption rate by the ocean, lowering the pH and causing its acidification. This change in pH affects all marine biota, particularly reef-building corals. Estimations of the ocean acidification-OA effects on marine environments indicate that coral reefs' structure will collapse, so it is important to establish mitigation strategies based on the most probable effects of pH reduction on corals. This study aimed to determine the effects of on corals near the Colombian Caribbean city of Cartagena, taking as model organisms of the species Porites astreoides and P. porites.

For each species, the effect of OA on bleaching, survival, and calcification was determined using artificial systems with concentrations of 700 ± 50 ppm (pH 7.879 ± 0,004) and 950 ± 50 ppm (pH 7.789 ± 0,007). The results showed that under concentrations of 700 ± 50 ppm pCO₂, the bleaching of P. astreoides increased by 24.92% and its survival decreased by 80.56%, while at 950 ± 50 ppm pCO₂, bleaching increased in 32.78% and survival decreased by 87.5%. In the case of P. porites, at 700 ± 50 ppm pCO₂, bleaching increased by 29.42% and survival decreased by 30.56% and at 950 ± 50 ppm pCO₂, bleaching increased in 37.32% and survival decreased by 13.39%. In both species, calcification was reduced more than 90% at 700 ppm pCO₂ and their skeleton began to disolve at 950 ppm pCO₂. This study represents the first effort to determine OA effects on Colombian Caribbean's marine biota.