The Fate of Coral Feeding Scars Following Predation by Individual Crown-of-Thorns Seastars

Aggregated crown-of-thorns seastars (Acanthaster spp., COTS) in outbreak populations create large feeding scars that often result in complete coral colony mortality. In contrast, feeding scars produced by individual COTS may retain living coral tissue remnants, but the responses of these remnants post predation remain unknown. We tracked the fate of discrete feeding scars left after predation by individual Acanthaster cf. solaris from a low-density population at One Tree Reef on the Great Barrier Reef. We found that the average feeding scar size did not differ by season, despite variation in coral genera and colony sizes preyed on. Most scars (72%) were left with remnants around their perimeter. The scars were initially colonised by turf algae, with some crustose coralline algae (CCA) present by 10 weeks post-predation. By 22 weeks, 26% of scars showed signs of regenerating coral tissue. Regeneration occurred predominantly in Montipora. In contrast, Acropora scars remained covered by turf or CCA. COTS appear to consume a relatively consistent amount of coral tissue per feeding event; consequently, remnant extent is primarily determined by colony size and whether a colony exceeds the typical amount of tissue consumed during a single feeding event. Thus, coral survival after COTS predation appears to be governed by two interacting processes: the likelihood that a remnant is left following predation and the regenerative capacity of that remnant. These findings demonstrate that predation by low-density COTS does not necessarily result in coral colony mortality and highlights sublethal predation and live tissue survival as important components of coral persistence and recovery. This may help maintain coral community diversity by limiting fast-growing taxa, consistent with the intermediate disturbance hypothesis, and is an important consideration in COTS management.