Assessment of juvenile coral populations at two reef restoration sites in the Florida Keys National Marine Sanctuary: Indicators of success?

Two major ship groundings in 1989 damaged reef habitats in the northern Florida Keys National Marine Sanctuary, the MV Alec Owen Maitland and the MV Elpis. Both sites underwent structural restoration in 1995, involving the emplacement of exogenous structures to stabilize loose rubble and fill in lost reef framework. These two projects of the same age and similar location, but differing in depth and structure design, provide an opportunity to evaluate restoration success in terms of the re-establishment of coral populations via in situ recruitment. In fact, coral assemblages differ markedly in density, size distribution, and diversity between the two sites. Within the Maitland site, coral recruitment is positively associated with rough limerocks embedded in the concrete restoration structure, but the coral assemblage is dominated by a single species, Porites astreoides. At the Elpis site, the juvenile coral assemblage has substantial representation by four taxa and has estimated juvenile density 50% greater than Maitland. These differences are associated with differences in the benthic algal assemblages at the two sites. It is hypothesized that differences in algal assemblage may result from differing structure designs (e.g., differing material, surface texture, and/or surface orientation) and may mediate differential coral recruitment success at the two sites.