Improving scientific decision-making in the restoration of ship-grounding sites on coral reefs

When ships contact reefs they break and crush coral rock, kill corals and other sessile organisms, open bare space for colonization, and eliminate topographic (habitat) complexity. We explored the ecology of ship groundings and the scope of restoration possibilities. Our guiding hypothesis was that high-relief areas damaged by ship groundings would not recover to their original community structure without restoration, but instead would converge on an alternate community state similar to natural hardground communities. To test this hypothesis, ship-grounding sites in the Florida Keys National Marine Sanctuary (FKNMS) were surveyed repeatedly and compared to surveys of undamaged reference sites at the same depths. In a study of the 1984 MV Wellwood ship-grounding, many univariate parameters of the community structure of the ship-grounding site in 1995–1996 resembled a nearby natural hardground reference site more closely than they resembled the spur-and-groove habitat adjacent to the spur-and-groove that had been flattened by the accident. The Wellwood site was also more similar to another hardground reference site, a century-old ship grounding at Pickles Reef, than it was to the original spur-and-groove community configuration. The Wellwood study suggests that damaged spur-and-groove habitat will not recover rapidly to its former state and that it may not recover at all without substantial restorative engineering. In contrast, the MV Elpis grounding site, which damaged an existing hardground community, was statistically indistinguishable from adjacent hardground sites less than 10 yrs after the incident. If these results can be generalized, when a ship grounding occurs in a hardground habitat, the community may recover on a decadal time scale. Substrate stabilization and coral transplantation will likely speed this natural recovery. Consideration of ecological setting is important in the design of restoration projects, ensuring preservation of the resource for future generations.