Improving decision making in coral reef restoration

Precht, William; Swanson, W; Aronson, Richard

Information from both ship-damaged and undamaged coral reefs can be used to evaluate the need for implementing restoration as well as providing a scientific basis for restoration design. We used the guiding hypothesis that high relief reef 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 those found in natural hardground (reef pavement) communities. This is due to the fact that 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. To test this hypothesis, grounding sites in the Florida Keys National Marine Sanctuary (FKNMS) were surveyed repeatedly and compared to surveys at three types of reference sites at the same depths. One such study addressed the 1984 M/V Wellwood grounding site and two undamaged reference sites- Molasses Reef spur-and-groove and Conch Reef hardground. Results from this study strongly supported our guiding hypotheses. Many univariate parameters of the community structure of the Wellwood ship-grounding site resembled the natural hardground more closely than they resembled the spur-and-groove area adjacent to the spur-and-groove that had been flattened by the accident. Another hardground reference site evaluated was a century-old ship grounding at Pickles Reef. This site was also more similar to the Wellwood site than to the original spur-and-groove community configuration. Thus, the Wellwood grounding study suggests that damaged spur-and-groove habitat will not recover rapidly to its former state, and may not recover at all without substantial restoration efforts. Those restoration efforts must include the reestablishment of both structure and topographic complexity. Conversely, a study of the M/V Elpis grounding site in the FKNMS which damaged an existing hardground community, was statistically indistinguishable from adjacent and reference hardground sites less than 10 years after the incident. If these results can be generalized, when a ship grounding occurs in a hardground habitat, it is likely that the community may recover within decadal-scale time frames. Rehabilitation measures, including substrate stabilization and coral transplantation will likely assist in speeding the direction and rate of this natural recovery. We suggest that better reef restoration efforts can be designed by modeling projects on local, unimpaired reefs of similar habitat type and on what we have learned from earlier projects. This information can then be used to plan and design restoration projects that will have an increased probably of performing and functioning like their unimpaired counterparts. This consideration of ecological setting is important in evaluating and understanding the functions of natural reefs and the performance of restoration projects. We contend that this will, in turn, lead to better management and protection of the resource for the future generations. Abstract provided by author.

Improving decision making in coral reef restoration

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