Meeting Abstract
Coral reefs are susceptible to climate change through coral bleaching, which is often caused by increases in ocean temperatures and light. Perturbation causes symbiotic algae, Symbiodinium spp., that live within the coral to become stressed and lost. Bleaching begins with perturbation of photosynthesis, but the actual site of damage is not clear. Using fluorescent microscopy, the relative chlorophyll fluorescence of individual symbionts can be measured in control and perturbed colonies of Sarcothelia sp., Sympodium sp., and Phenganax parrini. Individual colonies were removed from culture conditions (27 ºC and 110 μmol photons m-2 s-1) and images of three stolons per colony were obtained. The control colonies were returned to culture conditions while the perturbed colonies were placed in an incubator (30 ºC and 140 μmol photons m-2 s-1). After the 30 minutes, images of the same three areas of both colonies were again acquired. For each stolon, the fluorescence of the same symbionts were measured in the before and after images. This allowed for changes in the fluorescence of individual symbionts to be tracked over time. Merely measuring colonies significantly increased the fluorescence of some symbionts. Incubation under higher temperature and light levels for 30 minutes consistently increased chlorophyll fluorescence, suggesting greater reduction of photosystem II due to blockage of downstream electron transport. This effect was stronger in colonies of Sarcothelia sp. than in colonies of P. parrini, which corresponds to reactive oxygen species production by these colonies and to their general susceptibility to perturbation.
