A significant increase in the incidence of coral disease has been observed world-wide over the last decade and may play a significant role in the demise of critical reef-building species. Dark Spot Syndrome (DSS) typically affects the reef-building coral Siderastrea sidereal and manifests as black, brown or purple lesions of varying size, shape and location. These lesions can result in tissue death and can cause underlying skeletal changes. To date, the cause of DSS remains unknown. Thus, investigation is needed at a level of resolution not possible with light microscopy. Transmission (TEM) and scanning (SEM) electron microscopy allows detection of ultrastructural tissue and skeletal changes, including variability in organelle morphology, membrane integrity, and micron-scale crystalline structure of the coral skeleton.
In addition to intracellular effects, ultrastructural analysis may reveal microbial activity and initial tissue effects not resolvable by histology. For example, we have recently reported on previously unrecognized bacterial populations within the epidermal tissue of the reef-building coral, Montastraea cavernosa (Blackwelder et al. 2006; Renegar et al., in prep). The primary objective of this study is the investigation of the cellular characteristics, possible pathogenic microbes, and skeletal variability of diseased and healthy S. siderea using TEM and SEM. This work will be collaborative with researchers at the University of Mississippi currently investigating DSS. An additional objective is identification and isolation of epidermal bacteria observed undergoing active phagocytosis by amoebocyte cells in M. cavernosa using current methods of genetic analysis in collaboration with Dr. Kim Ritchie at Mote Marine Laboratory. Four NSU Oceanographic Center graduate students will participate at the author level in all aspects of this study. This study will contribute to the need for detailed knowledge of coral disease etiology and advances the goal of effective protection of current coral reef condition.