Photoinhibition of photosynthesis on a coral reef

Photoinhibition of macroalgae in the epilithic algal community (EAC) of coral reefs was studied using chlorophyll fluorescence techniques at One Tree Island, Great Barrier Reef, Australia. F-v/F-m (variable to maximum fluorescence, darkened samples) of shallow macroalgae declined by 50% on fine summer and winter days, recovering in late afternoon. Within a species, thalli from low-light habitats were more photoinhibited (2h at 1400 mu mol m(-2) s(-1)) than those from high-light habitats. The sensitivity of Lobophora variegata (Phaeophyta) and Chlorodesmis fastigiata (Chlorophyta) increased with depth (1 versus 20 m). However, shallow Halimeda tuna (Chlorophyta) plants growing between corals were more photoinhibited than those from deep, open areas.