The photophysiology of symbiotic dinoflagellates ( Symbiodinium) under varying light and thermal conditions and the implications for coral bleaching

Coral reefs are complex ecosystems full of extraordinary biodiversity. Reef building corals are reliant upon a symbiosis with intracellular dinoflagellates of the genus Symbiodinium. A considerable threat to coral reefs is the breakdown of this symbiosis, known as bleaching. Coral bleaching is characterized by the ghostly white tissue appearance resulting from loss of algal density. Over the past 20 years, there has been an increase in the frequency and magnitude of worldwide bleaching, which is strongly correlated with elevated seawater temperature, and exacerbated by increased irradiance. Bleaching has been linked to photosynthetic stress within the algae.; The capacity for photoacclimation to light at 100 or 600 mumol photons•m -2•s-1 and the subsequent response to thermal stress was examined in four genetically distinct cultures of Symbiodinium (ITS2: A1, A1.1, B1, and F2). Cultures were maintained at the above light levels for at least one month prior to thermal investigation. Temperatures were ramped from the control temperature 26°C up to 32°C over 72hrs, where they remained for up to 10 days. Cultures were then monitored with chlorophyll fluorescence and protein techniques to monitor changes in photosynthesis. (Abstract shortened by UMI.)...