Microbial communities of urban soils in the Norilsk agglomeration

Arctic cities are an important and relevant object of research due to the unique combination of extreme natural and climatic conditions and anthropogenic impact. Microbial communities are sensitive indicators of changes occurring as a result of anthropogenic impact, including urbanization, the consequences of which in the Arctic zone are poorly studied and poorly predictable. The aim of this study was to assess the microbiological potential of urban soils of the Norilsk agglomeration (Norilsk, Kayerkan, Oganer and Talnakh) to perform ecological functions based on the study of some microbiological parameters. The number of saprotrophic and oligotrophic bacteria, microscopic fungi (plating method), microbial biomass and respiration (substrate induced respiration method), functional diversity of microbial communities (MicroRespTM technique), and the sanitary and hygienic state of soils were studied. It was revealed that urban soils were characterized by low microbial biomass (from 107 to 159 μg C g–1) compared to the background, but sufficient microbial respiration (from 0.28 to 0.64 μg C g–1h–1), which indicates their high activity. An increase in the number of culturable bacteria and microscopic fungi was noted in urban soils and, in some areas, an increase in the functional diversity of microbial communities compared to the background. Microorganisms capable of decomposing easily accessible compounds — carbohydrates and carboxylic acids — prevailed in the community, but the proportion of microorganisms utilizing difficult-to-decompose compounds was also high (up to 20%). The sanitary and hygienic condition of urban soils of the agglomeration was assessed as moderately hazardous. An increase in the number of coliform bacteria, enterobacteria and opportunistic microfungi has been noted, which is generally characteristic of urban ecosystems and is not critical. The identified patterns suggest that urban green infrastructure can form niches for the microorganisms that can effectively perform ecological functions despite stressful conditions. In this case, issues of an integrated environmental approach to solving the problems of landscaping and improvement of Arctic cities, selecting a range of plants and technologies for the care and maintenance of green infrastructure are becoming increasingly relevant, which will contribute to the formation of sustainable and healthy urban ecosystems.