PREDICTING REGENERATION OF PHYSICAL DAMAGE ON A REEF-BUILDING CORAL BY REGENERATION CAPACITY AND LESION SHAPE

We present a relationship that predicts regeneration of physical damag e on reef-building corals as a function of regeneration capacity and l esion shape. The great abundance of lesions on colonies in the field a nd the characteristics of the regeneration process indicate that the a bility of corals to regenerate damage is limited. Regeneration, the ex tension of new coral tissue over a damaged area, slows down exponentia lly. We hypothesized that regeneration is a function of (1) a species specific regeneration capacity and (2) the amount of tissue that direc tly borders a lesion. A corollary is that there should be a maximum am ount of tissue that can be recovered for a certain amount of border. C onsequently, there is a maximum lesion size that can be completely reg enerated by the surrounding tissue depending on the shape of the lesio n. We studied the regeneration process in field experiments and made c ircular lesions of 4 different size classes (83, 183, 243 and 406 mm(2 )) on colonies of the main reef-building coral of the Caribbean, Monta strea annularis. Lesion size decreased rapidly at the onset of the reg eneration process but the rate of regeneration slowed to zero and the curve representing lesion size with time approached an asymptote. This asymptote represents the size of the area which is not recovered by t he regenerating tissue at the end of the regeneration process. The val ue of this asymptote increased with increasing lesion area, indicating Limited regeneration capacity. Larger lesions regenerated more tissue than smaller lesions, but this difference was absent when the regener ated surface area was standardized to initial lesion perimeter. This i ndicates that the lesion perimeter is the primary factor determining t he amount of area that will be regenerated. M. annularis could regener ate a maximum of 4.7 mm(2) of new tissue per mm of lesion perimeter le ngth. Circular lesions larger than 130 mm(2) will not be regenerated. The dependence of regeneration on lesion perimeter results in lesion s hape being of major importance for the degree of regeneration of physi cal damage (e.g. long narrow lesions may be closed, while circular les ions of much smaller size may never be closed). A relationship is pres ented that predicts percentage regeneration on the basis of lesion sha pe, with shape being defined as the ratio of initial lesion surface ar ea to initial perimeter length. This function predicts regeneration of physical damage in M. annularis for any size and shape of lesion.