MEPS 200:177-189 (2000)  -  doi:10.3354/meps200177

ABSTRACT: Corals vary in their ability to resist breakage from mechanical force. Biomechanical theory predicts that resistance to mechanical injury should be determined by the morphological properties of coral colonies. However, a general model to predict resistance of corals to mechanical impact from structural characteristics has been lacking. In order to determine whether resistance can be predicted from colony structure, I use a suite of 6 variables‹skeletal density, branch thickness, branch spacing, branch length, colony height and colony (projected) area‹to quantitatively describe the structure of colonies from 12 species of scleractinian coral. Experimental analysis of the resistance of colonies from each species, which range from massive and tabular growth forms to various branching models, showed that damage susceptibility varied widely. Resistance ranged from very high for species such as Leptoria phrygia, Porites cylindrica and Porites spp. in which there was no reduction in colony area as a result of mechanical stress, to low in species such as Pocillopora damicornis, Seriatopora hystrix and Montipora sp. which suffered over 60% damage. Regression tree analysis revealed a strong relationship between resistance and colony morphology, producing a model which accounted for 76% of the variation in resistance using only 4 of the structural variables: colony height, branch thickness, branch spacing and colony area. Skeletal density and branch length were relatively unimportant in determining susceptibility to breakage. The regression tree model showed potential for development as a predictive tool in reef management, as it was able to predict susceptibility to breakage of corals using 4 easily measured morphological variables with 57% reliability (estimated by cross-validation).

KEY WORDS: Coral · Skeletal density · Structure · Disturbance · Biomechanics · Morphology · Reef management