Microbial Communities as Environmental Indicators in Urban Waters

Abstract:

Xi'an was the birthplace of cultural civilization and the capitals for 13 dynasties in ancient China. It is known for the eight rivers surrounding the city, including the Chan, Ba, Feng, and Zao Rivers in the urban areas. More than 100 water samples for the 16s rDNA and water quality were collected in April, May, August, and December of 2020 from around 155 kilometers of river segments extending from their source areas in the Qin Mountain to the outlets into the Wei River in the north. Multiple statistical analyses showed there were clear dynamic differences of microbial communities from various sampling periods and heterogeneity in their spatial distribution along the rivers, implied the impacts of natural environments such as the seasonal variation of hydrologic and hydraulic conditions and human-induced factors such as sewage discharges and non-point sources from urban stormflow and agriculture as well. Through the LEfSe test, the differentially abundant microbial communities at phylum and class levels between the Chan, Ba, Feng, Zao, and the Wei Rivers for the sampling period and between various sampling periods in the same river segment were identified. The GIS-based presentation of microbial communities showed that pathogenic bacterias such as Lentisphaerae, Fusobacteria, Spirochaetes, Dependentiae, and Elusimicrobia existed at various locations of the rivers with different abundance for different sampling periods, indicating contaminations of urban water environments by industrial and pharmaceutical wastes and a serious threat to the healthiness of eco-environments in the region.