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

Abstract

Effect of UV-B and photosynthetic active radiation (PAR) flux at 30^oC in <i style="">Phormidium corium </i>(Agardh) Gomont,<i style=""> </i>a cyanobacterium isolated from coral, <i style="">Porites lutea</i> (Milne-Edwards and Haime) on the Kavaratti reef of the Lakshawdeep Island, (11^o N; 71^oE), India had been examined.&nbsp;&nbsp; Exposure of <i style="">P. corium</i> 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 <i style="">P. corium</i> 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 Lakshawdeep Island, may be due to oxidative damage caused to it by production of ROS as <i style="">P. corium </i>lacks efficient antioxidant system.