Research Product

In situ measurement of scleractinian coral size and structural complexity in has been elusive. Three-dimensional (3D) colony surface area has been measured in the laboratory but the techniques are inappropriate for underwater field surveys. Recent field studies have demonstrated the potential of 3D colony surface area measurements for evaluating coral condition. This potential would be enhanced by an ability to accurately estimate 3D coral surface area from rapid underwater field measurements. Here we apply non-destructive photographic methods to document size and structure of corals in the field. Multiple images of a single colony were used to generate a scaled 3D computer reconstruction of colony morphology that can be accurately measured for colony dimensions and 3D surface area. Methods were applied to 23 colonies of two stony coral species, Diploria clivosa and D. strigosa, photographed in situ at the Florida Keys and Dry Tortugas. Accuracy of the technique was examined by comparison with a laser-scanned laboratory colony, and precision was documented through repetitive model construction. Surface areas and volumes calculated from digitally reconstructed corals were compared to colony dimensions and to size classes assigned in the field. These comparisons provided a means to estimate coral surface area and volume from simple field measurements and demonstrated that surface area of Diploria colonies closely approximated hemispheric surface area. Further application of this technique to additional coral taxa will advance methodology for assessment of coral and coral reef condition as well as for understanding surface-related physiological processes of coral.