Cyanobacteria in Polar and Alpine Ecosystems

Abstract

Cyanobacteria are commonly found in freshwaters, soils and glacial environments in polar and alpine regions. Studies to date indicate these cold-dwelling phototrophs are psychrotolerant rather than psychrophilic, with temperature optima for growth that lie well above the temperature ranges of their ambient environment. Cyanobacterial mats occur at the bottom of lakes, ponds and streams and within meltwater habitats on glaciers and ice shelves. They can accumulate large biomass stocks and may account for the dominant fraction of total ecosystem productivity in such environments. Certain taxa in these benthic communities are known to produce cyanotoxins, including microcystins. Planktonic cyanobacteria are also found in many high latitude lakes, specifically picocyanobacteria, but they are conspicuously absent or poorly represented in polar seas, probably as a result of their minimal growth rates in extreme cold. Cyanobacteria also occur in a variety of nonaquatic habitats in the cold regions, including on and within rocks, and as a major constituent of soil crusts in polar and alpine deserts. The nitrogen-fixing capabilities of some cyanobacteria make them especially important for the natural enrichment of soils that have been newly exposed after glacial retreat. The evolution and biogeography of cyanobacterial ecotypes in the cold biosphere is a current focus of genomic analysis and pole-to-pole comparisons, and these studies are providing insights into how microbial ecosystems survived prolonged periods of cold and freeze-up on early Earth.