Internal bioerosion in massive corals associated with reef communities in the northeastern tropical Pacific: The effect of intrinsic and extrinsic factors

Abstract

The development and maintenance of the physical structure of coral reefs depends on the balance between production (accretion) and removal (erosion) of CaCO₃ produced mainly by reef-building corals. This calcareous material may be removed from the coral skeleton by means of physical, chemical, or biological agents, with the latter being the most influential. Despite being important, bioerosion studies on coral reefs from the Pacific coast of Mexico are scarce. In this study, we determined the volume and percentage of CaCO₃ removed through bioerosion from the main massive coral species, Pavona gigantea, Porites lobata, and Porites panamensis, in the Islas Marietas and Isla Isabel National Parks (Mexico). We also evaluated the effect of extrinsic (morphology, sex, and age) and intrinsic (depth and location) factors on bioerosion. The buoyant weight technique was used to estimate internal bioerosion parameters and CaCO₃ skeletal density. At the species level, P. gigantea showed volume of bioerosion values of 71.31 ± 32.35 cm³ (27.28 ± 18.05% of internal bioerosion); Po. lobata, 26.60 ± 24.87 cm³ (16.87 ± 16.31%); and Po. panamensis, 29.6 ± 14.61 cm³ (31.127 ± 29.43%). At the genus level, Pavona exhibited the highest bioerosion and skeletal density values (1.61 g·cm^–3). Regarding morphology, bioerosion was higher in massive corals, but regarding age, it was higher in adult colonies (10–26 years). Islas Marietas National Park showed the highest values for volume and percentage of bioerosion. The results suggest that coral reefs on the Pacific coast of central Mexico are undergoing a high degree of inconspicuous erosion by internal bioeroders and its variability is controlled by both intrinsic and extrinsic factors. If this effect continues to rise, it could threaten the long-term maintenance of coral communities, modifying the carbonate flux equilibrium and the ecological functionality of coral reef ecosystems.