Investigating the spatial distribution of growth anomalies affecting Montipora capitata corals in a 3-dimensional framework.

Diseases have caused significant reductions in coral populations throughout the global ocean. Despite a substantial effort to thoroughly characterize the epizootiology and etiology of coral diseases, little is known about the distribution and spatial clustering of disease lesions on affected coral colonies. This study investigated spatial clustering of the coral disease, growth anomaly (GA), which exhibits high levels of prevalence and severity in Montipora capitata and other corals at Wai'ōpae, southeast Hawai'i Island. Like many other coral diseases, the patterns of disease spread and transmissibility of GA remains unknown. We utilized cutting-edge 3D reconstruction techniques to map the precise spatial distribution of GAs on affected coral colonies. Three statistical measures, Ripley's K, Moran's I, and the Kolmogorov-Smirnov test were used to determine if the GA lesions were distributed in a non-random pattern. Each measure showed the GA lesions exhibited distinct spatial clustering on all ten affected colonies analyzed in this study. Our study is not only the first 3D analysis of intra-colony disease clustering, but also provides a novel approach for investigating and quantifying levels of disease clustering in order to improve our understanding of coral disease epizootiology, transmission, and etiology.