Coral calcification and carbonate production in the eastern tropical Pacific: The role of branching and massive corals in the reef maintenance

Hermatypic corals have the potential to construct calcium carbonate (CaCO₃ ) reef-framework, maintain habitats tridimensionality and contribute to both the biogeochemical and the geo-ecological functionality of coral reefs. However, in the past decades, coral reef growth capacity has been affected by multiple and cumulative anthropogenic stressors, threating the reef functionality and their ecosystem goods and services provision to humankind. This study evaluated temporal changes in geobiological growth characteristics as a function of live coral cover, calcification rate (extension rate and skeletal density) and coral carbonate production at Islas Marias archipelago from the eastern tropical Pacific, using historical data obtained in 2007 (López-Pérez et al., 2015, Marine Ecology, 37, 679) and data obtained through field and laboratory research between 2015 and 2018. Overall, live coral cover decreased (82%), where Pocillopora spp. corals reduced from 26% in 2007 to 4% in 2018, in contrast, Pavona spp. declined from 4.1% to 3.7% over the same period. Coral carbonate production ranged between 1.78 and 10.65 kg CaCO₃ m^-2 yr^-1 , with a significant difference (threefold) between reef zones (shallow vs deep), highlighting the higher carbonate production at deep-reef sites. Coral cover, carbonate production and sclerocronological characteristics showed a decrease rate (between 30 and 60%) associated with thermal anomaly events such as La Niña (2010-2011) and El Niño (2014-2016), with positive sights of recovery (twofold) during the following years 2017-2018. This study provides evidence that massive Pavona and branching Pocillopora corals are key reef-building species at Islas Marias archipelago, due to their capability of sustaining live coral coverage and carbonate through thermal disturbance periods. Revealing, that corals at mid-water depths (>10 m) may significantly contribute to the long-term stability of biogenic reef-framework, and geo-ecological functionality of the eastern tropical Pacific reefs.