Spatial distribution of damage affects the healing, growth, and morphology of coral

Many predators and herbivores do not kill their prey, but rather remove or damage tissue. Prey are often able to heal or regenerate this lost tissue. If the prey are modular organisms (e.g., some plants and cnidarians), regeneration is frequently influenced by other modules interconnected to damaged ones. For example, many coral predators remove tissue from colonies consisting of many polyps, and these polyps often share resources with their neighbors. Thus, the distribution of tissue loss on a coral colony could affect the coral's response. I hypothesized that spatially aggregated damage might be slow to heal due to competing demands on nearby polyps. To explore the spatial patterns of corallivory and their implications, I conducted: (1) field surveys documenting the spatial distribution of lesions on corals; (2) field experiments testing the effect of the distance between lesions on coral tissue healing, skeletal growth, and morphology; and (3) field surveys relating corallivore presence to coral growth and morphology. In the field surveys, lesions were aggregated at multiple spatial scales, and most lesions had other lesions within 2 cm. When lesions were near one another, coral tissue regeneration was depressed, although there was no effect on whole colony growth. After a year, however, linear extension was lower in the neighborhood of the lesions. Additionally, gastropod corallivores (Coralliophila violacea) with low movement decreased coral growth and increased coral topographical complexity. These results suggest that corallivores that create clusters of coral damage have a greater effect on coral growth and recovery from damage than corallivores that spread damage throughout the colony.