Carbonate Budget in the reef-patch of La Entrega, Oaxaca. Southern Mexican Pacific

Background. Coral reefs provide several important geo-ecological functions essential for the sustainability of coastal human communities. However, during the last 50 years, reef ecosystems are experiencing rapid degradation caused by natural and anthropogenic disturbances. One consequence of the above has been the reduction in the carbonate production rate and the structural complexity of these systems. Particularly, the loss of key coral species in the construction of reefs has compromised the functionality of the ecosystem. Objective. In this study we used an adaptation of the ReefBudget methodology to measure the calcium carbonate budget in the reef of La Entrega, Oaxaca, Mexico. Methods. Six transects were carried out to estimate the abundance of eroding fish (25 x 4 m), sea urchins (25 x 2 m) and the composition of the benthos. Results. When carrying out the corresponding calculations, it was found that in La Entrega 13.72 kg m-2 year-1 (commonly referred as “G”) are produced, the endobioerosion (including erosion by sponges) calculated was 5.65 G. The sea urchin erosion is 0.12 G and that of fish is 0.73 G; the resulting net carbonate budget was 7.21 G. The accretion rate (vertical reef growth) at La Entrega reef was 7.07 mm yr-1. We consider it important to mention that the reef patch at La Entrega is relatively small (approximately 324 x 233 m) compared to formations in the Caribbean or Indo-Pacific regions. Conclusions. Net production at La Entrega is higher than estimated for most Caribbean reefs (2-4 G) but lower than that of the Indo-Pacific (5-14 G). Differences in the balance between regions are mainly associated with differences in the abundances of builder species in each region. According to what was modeled in this work, the La Entrega reef patch presents a sufficient accretion rate to deal with a possible rise in sea level under the RCP 4.5 and 2.6 scenarios (4 and 7 mm, respectively).