Subglacial lakes under Iceland's Vatnajökull ice cap provide unique habitats for microbial life because they receive heat and chemical inputs from subglacial volcanic activity, influencing the chemistry of lower lake waters and sediments. Active psychrophilic, autotrophic bacteria have been discovered in the lake below the Grímsvötn volcanic caldera. A low-diversity microbial community has also been found in the east Skaftárketill and Kverkfjallalón subglacial lakes, where bacteria include Geobacter and Desulfuosporosinus species that can use sulfur and iron for anaerobic respiration. In the western Skaftá lake, the anoxic bottom waters appear to be dominated by acetate-producing bacteria rather than methanogens.