Three-dimensional morphological variation and physical functionality of Caribbean corals

Reef functionality depends on the coral community's species composition, abundance, and on the capacity of corals to build carbonate structures. Nevertheless, the coral's contribution to functionality remains hidden in species morphological variation displayed. Here, we use three-dimensional (3D) models to estimate the morpho-functional space of 14 Caribbean coral species by combining information from five morphological traits (sphericity, convexity, packing, first moment of surface area, and first moment of volume). Based on a principal component analysis, we selected the trait that captured most of the coral morphological variation to address the effect of colony size on structural complexity, shelter volume, and efficiency of resource use in terms of colony volume and calcium carbonate (CaCO3) investment. At the species level, structural complexity increased as a function of coral colony size in branching, digitate, and columnar coral species. Shelter volume increased with colony size in all species; however, branching species such as Acropora palmata not only provide more shelter volume than species with simpler morphologies, but they do so more efficiently, investing less colony volume and CaCO3 mass for attaining the same shelter volume. Tracking changes in coral morphologies and colony size can improve our ability to predict functional repercussions from modifications to coral assemblages that are caused by, for example, disease outbreaks or environmental disturbances.