MARINE BfOLOGY AND ECOLOGY

In corals, extant damage to colonies depends on the balance between injury and recovery rates. Sclerochronology- the study of scleractinian coral growth rings- provides information about these historical processes, since corals preserve traces of previous injuries and annual bands representing regrowth. Cross-sections of two Caribbean coral species, Porites astreoides (Ellis and Solander) and Siderastrea siderea Le Sueur, were examined to determine the size-frequency and incidence of partial mortality and the rate at which these injuries recover. Each year’s injuries were divided into four size classes, and subsequent changes in lesion size were developed into probabilities of switching size classes each year. Matrix models, composed of a matrix of transition probabilities and a vector added annually to account for new damage, predicted a dynamic equilibrium of extant damage to corals that matches field censuses well. A census of corals was carried out at two (P. astreoides) or five (5’. siderea) sites. In 23 of 28 comparisons, values of extant damage were within the 95 % confidence intervals of model predictions. Discrepancies arose because the model underestimated small lesions in P. astreoides. Scleroch-ronology may fail in this instance because small, rapidly-recovering injuries do not leav