Diverse morphologies found in living microbial mats and associated microbialites—A field report from the alkaline and hypersaline Nuoertu Lake, Badain Jaran Desert, N-China

Abstract

During recent sampling of the alkaline and hypersaline Lake Nuoertu in the Badain Jaran Desert, Inner Mongolia, PR China, various living microbial mat morphologies, along with associated lithified microbialites and stromatolitic tufa were discovered. Our fieldwork confirmed preliminary findings from the late 1990s that linked carbonate formations to subterranean freshwater discharge into the alkaline lakes of the Badain Jaran desert. This field report provides an overview of the microbialite morphologies, including phyto-microbialites, columnar and domical-linked as well as hemispherical roll-up structures, their redox stratification and water quality measurements at several lake sites and one groundwater spring. Environmental DNA data of differently pigmented mat layers reveal a well-defined vertical microbial zonation with cyanobacteria and aerobic heterotrophs dominating the top layer and deeper anaerobic layers characterised by anoxygenic purple sulphur bacteria and sulphate reducing bacteria, as well as sulphur bacteria and fermenters in strictly anoxic zones. This work serves as a preliminary report, highlighting the newly documented alkaline environment that hosts a key living microbialite community in China.