Improving Restoration Approaches for Acropora palmata: Lessons from the Fortuna Reefer Grounding in Puerto Rico

Detached Acropora palmata  fragments (n=1857) generated by the M/V Fortuna Reefer  grounding off Mona Island, Puerto Rico were secured to reef substrates or dead standing A. palmata  skeletons using stainless steel wire. After 10 years, only 6% (n=104) of the fragments were alive, of which half (n=54) exhibited extensive branching (mean = 5 branches, 89 cm length), and a substantial increase in height (mean = 39 cm). Most surviving fragments were 20-100 cm (original length when first restored), secured to the reef and oriented upright. Fragments died or were lost in the first three years from wire breakage (23%), overgrowth by bioeroding clionid sponges (16%) and other factors (5%). Over the next 7 years, another 50% died due to gastropod predation, additional wire breakage and detachment during storms, and continued overgrowth by Cliona . Fragments attached to A. palmata  skeletons initially grew rapidly and produced new branches, but most were subsequently dislodged due to bioerosion and breakage of the skeleton to which they were attached. Low fragment survival is attributed to 1) wire failure and inability of corals to overgrow wire, 2) limited fragment fusion, 3) attachment of fragments to inappropriate substrates, and 4) progressive mortality of large, older basal portions of detached colonies that failed to grow. Natural stressors unrelated to the restoration including diseases, predators, and bioeroding sponges have increased over time within and outside the grounding site and are also impacting fragment survival. Restoration may be a viable means to promote recovery of acroporid populations if the use of uncoated wire to attach fragments is avoided; fragments are placed on suitable substrates with live tissue in direct contact with the substrate to promote fusion, and efforts to mitigate disease and corallivory are undertaken.