Symbiodinium - Symbiodinium and Coral Bleaching

Symbiodinium and Coral Bleaching

The study of Symbiodinium biology is driven largely by a desire to understand global coral reef decline. A chief mechanism for widespread reef degradation has been stress-induced coral bleaching caused by anomalously high seawater temperature (Fig. 4). Bleaching is defined as the disassociation of the coral and the symbiont and/or loss of chlorophyll within the alga, resulting in a precipitous loss in the animal’s brown pigmentation. Many Symbiodinium-cnidarian associations are affected by sustained elevation of sea surface temperatures, but may also result from exposure to high irradiance levels (including UVR), extreme low temperatures, low salinity, and other factors. The bleached state is associated with decreased host calcification (Colombo-Pallotta et al. 2010), increased disease susceptibility and, if prolonged, partial or total mortality. The magnitude of mortality from a single bleaching event can be global in scale, and these episodes are predicted to become more common and severe as temperatures worldwide continue to rise. The physiology of a resident Symbiodinium species often regulates the bleaching susceptibility of a coral. Therefore a significant amount of research has focused on characterizing the physiological basis of thermal tolerance and in identifying the ecology and distribution of thermally tolerant symbiont species.