Structure of microbial communities in benthic biofilms of glacier-fed streams from Patagonia, Argentina.

VEGA EVELYN NATHALIE; BASTIDAS NAVARRO, MARCELA; MARTYNIUK, NICOLÁS; MODENUTTI, BEATRIZ

Berlin

Congreso; 36th Congress of the International Society of Limnology; 2022

International Society of Limnology

Glacier-fed streams are highly dynamic environments and constitute an important ecological component of the glacial ecosystem. The glacier retreat produces physicochemical and hydrological changes that affect the microbial communities in downstream habitats. Here, we studied the microbial community structure in three streams of the Upper Manso River (Patagonia, Argentina). We analyzed environmental variables, the bacterial communities composition by 16S ribosomal (r)RNA genes sequences, and the presence of nitrogen functional genes (by PCR conventional) in biofilms of the different streams in two sampling occasions (summer and autumn). Streams differ in glaciality influence, Negro stream have upper influence, following for Nalcas, Blanco and Cesares streams. Was estimated by the combined effect of suspended solids, water temperature, conductivity, and streambed stability. The dominant phyla were Proteobacteria, Cyanobacteria, Bacteroidetes and Actinobacteria. At summer Cyanobacteria predominance in Negro stream and Proteobacteria in the rest. At autumn Cyanobacteria predominance in Negro and Cesares streams, and Proteobacteria in the rest. The presence of the following functional genes was detected: Nif H, Amo A bacteria, nrf A and nir S in both seasons, nir S gene only present in Negro stream at summer. Ordination analysis (PCA) showed clear segregation between replicates and clear separation Negro stream respect to the rest. The environmental variables that most explain the structure of the bacterial community are: nitrite, total dissolved phosphorus, conductivity, dissolved organic carbon, total suspended solids and total dissolved nitrogen. Our results showed that the glacial influence affect in bacterial community structure and could impact in nitrogen cycle.