Abstract

We surveyed corals in American Samoa for presence of lesions. We did 19 SCUBA and additional snorkel dives on six and seven sites on Tuituila and Ofu-Olosega, American Samoa. We photographed and took 70 samples from 49 corals comprising 29 species. Corals were fixed, decalcified, and sectioned on microscope slide to examine cellular architecture. Grossly, the most common lesions in corals were bleaching, growth anomalies, and tissue necrosis. On histology, depletion of zooxanthellae from coral tissue was most often seen followed by tissue necrosis associated with algae or fungi, hyperplasia of gastrovascular canals, or uncomplicated tissue necrosis. Two grossly bleached corals had evidence of pathologic lesions associated with invasion by ciliates (protozoa). One coral had evidence of primary infection with a fungus that manifested grossly as growth anomaly. One coral had evidence of skeletal enlargement associated with polychaete infestation. Incidental lesions included presence of bacterial aggregates or crustacea in normal tissues of several coral species. A gross diagnosis (e.g., bleaching) could have several different causes. This phenomenon underlines the importance of conducting microscopic exams on coral lesions to better define what the underlying causes of grossly visible changes. This study also provided the first baseline survey of corals in this region for pathogens and the first evidence that ciliates may, in some instances, be responsible for bleaching of selected coral colonies. This study also extended the documented range of growth anomalies in acroporid corals. Future surveys should concentrate on systematically evaluating the spatial distribution of major lesions to allow for better comparisons among sites.