THE EFFECT OF UV RADIATION ON CYANOBACTERIAL MAT COMMUNITY STRUCTURE

31 pagesCyanobacteria are thought to have evolved during the early Precambrian, 2.5-3.8 billion years ago, when there were very high levels of UV radiation reaching the Earth's surface due to a lack of absorbing gases int he atmosphere. Oxygenic cyanobacteria were one of the few photosynthetic organisms that could survive under these harsh conditions. Cyanobacteria today have also been found to employ UV tolerant strategies to cope with the damaging effects of UV radiation. In this study three cyanobacterial mats were investigated to determine if UV had an effect on the mats in the field and subsequently on clonal isolates cultured from these mats in the lab. UV exclusion experiments, using UV blocking and UV transmitting filters, were carried out in the field over a two-month period. Protein and pigment analysis on the core samples collected from the field UV treatments showed no significant difference between the treatments. However, samples collected of new settlement cell material on ceramic tiles, did show a significant different between the two UV treatments. UV exclusion experiments run using two strains of clonal isolates of Lebtolyngbya sp. cultured from Mushroom Spring did show a highly significant detrimental effect of UV on growth measured by dry weights. In addition, the two strains, one cultured from the UV(-) field material and one cultured from the UV(+) material, were effected differently by UV radiation in the lab UV exclusion experiment. The isolate cultured from the UV(+) mat material was less effected by UV radiation, as measured by dry weight accumulation over time. This may imply the use of a unique UV tolerant strategy employed by this strain