UV-B radiation and high light induced oxidative damage in Phormidium corium may cause bleaching to associated coral reefs.

Effect of UV-B and photosynthetic active radiation (PAR) flux at 30 degrees C in Phormidium corium (Agardh) Gomont, a cyanobacterium isolated from coral, Ponies lutea (Milne-Edwards and Haime) on the Kavaratti reef of the Lalcshawdeep Island, (11 degrees N; 71 degrees E), India had been examined. Exposure of P. corium to UV-B and PAR decreased photosynthetic efficiency and increased oxidative damage measured as F-v/F-m ratio and lipid peroxidation of cell membrane. Data indicate little activity of superoxide dismutase (SOD) and ascorbate peroxidase (APX) in response to the UV-B and PAR treatment. Activity to quench reactive oxygen species (ROS) was much less in P. corium as compared to other cyanobacteria and higher plants. Though mycosporine like amino acids (MAAs) increased significantly as a result of UV-B treatment, PAR caused decrease in the MAAs content, thus neutralizing the beneficial effect of MAAs. Present study suggest that one of the factors of bleaching of coral reefs off the Lalcshawdeep Island, may be due to oxidative damage caused to it by production of ROS as P. corium lacks efficient antioxidant system.