Diversity and Abundance of Methanogenic Archaea in Near-Saturated Hypersaline Lakes of Different Chemical Composition in the Kulunda Steppe

This study analyzes the diversity and abundance of methanogenic archaea in the bottom sediments of five hypersaline lakes in the Kulunda Steppe with comparable high salinity (~300‰) but with different chemical composition (chloride, chloride–sulfate, soda) and pH values (7.7 to 10.2). A specific association of different methanogens with lakes of different chemical types was revealed: methyl-reducing Ca. Methanohalarchaeum developed in neutral chloride lakes, methyl-reducing Methanonatronarchaeum developed in alkaline chloride lakes, methylotrophic Methanosalsum developed in chloride–sulfate and soda lakes, and hydrogenotrophic Methanocalculus was found only in the soda lake. This is the first demonstration that methyl-reducing methanogens of the family Methanonatronarchaeaceae can be highly abundant (up to 10.8% of all archaea) and be the only methanogens in native chloride lake sediments at moderate temperatures.