Ecophysiology of Cyanobacteria in the Polar Regions

Abstract Cyanobacteria, the main primary producers in the polar regions, are subjected to extreme environmental conditions. The major stress conditions include low temperatures, freezing/melting, desiccation/rehydration, salinity, and visible and ultraviolet radiation. Their occurrences differ in periodicity (days to years), amplitude (range), synchronicity with other stress conditions, and irregularity (like liquid water availability), thus resulting in unique combinations of severe stress factors. In response, cyanobacteria developed very effective adaptation/acclimation mechanisms. They include passive (stress avoidance) and active (stress tolerance) strategies. The stress avoidance strategies result in escape from the stress conditions, by movement to more favorable conditions, production of resting stages, or consortia formation. The stress tolerance strategies are induced by stress perception. Some of the reactions occur during almost any stress, while others are stress-specific. Therefore, polar cyanobacteria represent unique model organisms for the study of adaptation/acclimation mechanisms to reveal the possible diversity of adaptation/acclimation reactions to cold environments.