Abstract
Endosymbiotic algae in reef-building corals are often exposed to extreme light fluctuation. The ripples on the surface water can concentrate light up to 9000 μmol photons m-2s-1. Recent reports suggest that photoinhibition of endosymbionts can induce the dissociation of coral-algae symbiosis, also known as Coral Bleaching. We investigated the effects of light fluctuation on symbiotic algae in hospite of a shallow inhabiting coral, Acropora digitifera. Pulse amplified modulated (PAM) fluorescence measurements showed less dynamic photoinhibition under fluctuating light treatments (1 hour repetition of 3 sec of 1300 μmol photons m-2s-1 and 7 sec of 155 μmol photons m-2s-1) compared to that measured under the constant light (500 μmol photons m-2s-1). The results suggest potential stress-amelioration by ripple-induced light fluctuation in shallow inhabiting reef-building corals. Future experiments will focus on the effects of higher-frequency light fluctuation (sub-second fluctuation) on dynamic photoinhibition in symbiotic algae.
