Predicted disappearance of coral‐reef ramparts: a direct result of major ecological disturbances

Abstract

SummaryTwo coral cays near La Parguera, Puerto Rico, have large, exposed coral ramparts composed almost entirely of loose pieces of elkhorn coral Acropora palmata (88% of horizontal transects, 98% of vertical transects). The total volume of elkhorn coral in the ramparts of the two cays was estimated at 3600 and 12 800 m3. The present volume of living elkhorn coral on these two reefs was estimated at 7 and 14 m3 and previous volumes at 11 000 and 34 900 m3. White‐band disease was found on 8.5% of living elkhorn colonies. Lang’s boring sponge Cliona langae covered 10.8% of the total transect area, overgrowing both dead and living corals. White‐band disease and coral‐reef bleaching have drastically reduced the populations of elkhorn coral, thus, skeletal coral materials to replenish the plate ramparts are severely reduced, disrupting the process of forming and maintaining these coral reef ramparts. We predict that the next series of major storms striking these prominent cay ramparts will remove them. These disappearances will represent a quick, obvious and permanent consequence of global disturbances. Loss of cay ramparts will modify the environments on and around Atlantic coral reefs. Ramparts may be similarly lost from Indo‐Pacific reefs. The lack of any other indisputable definitive indicators of long‐term, major disturbances on coral reefs makes the distinct loss of coral‐reef ramparts an important physical sign.