Use of photogrammetric techniques to monitor coral reef recovery following a major ship grounding

Photogrammetric techniques were used in a detailed study of benthic coral reef communities following a major physical disturbance, the grounding of the freighter Wellwood on Molasses Reef, in Key Largo National Marine Sanctuary, Florida. The sessile reef communities of the Wellwood site and the adjacent unimpacted reef areas were studied with non-destructive samplings of permanently located quadrats to document the recruitment of organisms and reef recovery in the impacted area. The grounding site was rapidly colonized by an algal community that was soon dominated by a fine algal turf composed of filamentous red algae. Although algal diversity and total algal abundance quickly returned to the levels of the nearby unimpacted reef, there remained a significant number of differences in the species composition and in the abundance of individual species. More conspicuously, the major benthic invertebrates of the community, particularly the important reef-building hard corals, recruited into the impacted area much more slowly, if at all, than the algae. By the end of the study, there was still a substantial number of major differences between the algal community of the impacted area and the unimpacted reef. The advantages of the techniques used in this study included: a minimal impact on a protected reef community, a large sample size for adequate statistical analysis, and high precision and quality-control.