Did the community structure of a coral reef patch affected by a ship grounding recover after 15 years? Merging historical and recent data sets

Abstract

Shifts in dominance from coral to other benthic groups in coral reefs have raised concerns about the persistence of coral reefs and their ability to provide ecosystem services. Acute disturbances such as ship groundings offer the opportunity to examine the dynamics of successional processes in coral reefs, since understanding them is a prerequisite for their proper management. In this study, we investigated whether a ship grounding area in a reef located in a marine protected area in Cancún, Mexico, showed signs of recovery 15 years after the incident. We evaluated the reef's composition and structure by taking samples at three different scales (reef scale, 1 m2, and 0.01 m2). In these samples, we analysed coral density and recruitment, the abundance of five functional algal groups, and the abundance of the grazer sea urchin Diadema antillarum. If recovery had already occurred, we expected the impacted sector to have a community composition and structure similar to that of a contiguous, non-impacted sector. Using historical information, we found indications of a long-term phase shift, with Porites astreoides being the dominant coral species some time ago and at all scales of analysis; this species also showed intense recruitment. In agreement with previous studies of Caribbean reefs, architectural complexity was low. The algal cover was similar in impacted and non-impacted sectors though the density of sea urchins differed between them. Fifteen years after the ship grounding and despite the enforcement of the prohibition of tourism and fishing activities at the site, the impacted sector does not show signs of recovery. On the contrary, like other reefs in the Caribbean Sea, the non-impacted sector is becoming degraded due to the loss of reef builder key species and the increase of the algae-covered area, mirroring the path observed in the impacted sector.