Bacteria communities in the proglacial lake Ventisquero Negro (Patagonia; Argentina)

MODENUTTI B.; M. BASTIDAS NAVARRO; N. MARTYNIUK; V. DÍAZ VILLANUEVA; E. BALSEIRO

Congreso; SAME 14; 2015

Climate change affects glaciers all over the world causing glacial recession with the formation of new lakes. These proglacial lakes are characterized by heavy glacial clay inputs that cause a turbidity-induced attenuation of photosynthetically active radiation (PAR), therefore they can be expected as environments with light limitation for primary producers. The aim of this study was to assess temporal shifts in bacterial abundance, diversity and respiration, in the proglacial lake of Ventisquero Negro located in Mountain Tronador (41° S, Patagonia, Argentina). Samplings were conducted during four successive austral summers (2012/15). We measured nutrient concentrations, bacteria abundances assessing different components of bacterial community structure using next-generation sequencing of the 16S rRNA gene. In addition we conducted experiments measuring oxygen consumption by bacteria community. Results showed that chlorophyll a concentrations were low (0.571±0.33 µg L-1) due to the light limitation imposed by the high turbidity due to total suspended solids. Dissolved organic carbon (DOC) concentrations were low (0.43± 0.16 mg L-1) and the fluorescent excitation?emission matrices (EEMs) analyses revealed the predominance of protein-like components over humic-like components. Higher bacteria respiration rates were attained in coincidence with the presence of one protein-like component in the dissolved organic matter fluorescence analysis, while no relationship was observed between bacteria respiration and chlorophyll a. Community analysis using the 16S rRNA gene identified a total of 2135 OTUs consisting mainly of Proteobacteria, Firmicutes, Actinobacteria and Bacteroidetes.