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

B. MODENUTTI,; BASTIDAS NAVARRO, M.,; NICOLÁS MARTINIUK; E. BALSEIRO,

Uppsala

Congreso; SAME 14; 2015

SAME

Climatechange affects glaciers all over the world causing glacial recession with theformation of new lakes. These proglacial lakes are characterized by heavyglacial clay inputs that cause a turbidity-induced attenuation ofphotosynthetically active radiation (PAR), therefore they can be expected asenvironments with light limitation for primary producers. The aim of this studywas 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 wereconducted during four successive austral summers (2012/15).  We measured nutrient concentrations, bacteriaabundances assessing different components of bacterial community structureusing next-generation sequencing of the 16S rRNA gene. In addition we conductedexperiments 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 totalsuspended 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 predominanceof protein-like components over humic-like components. Higher bacteriarespiration rates were attained in coincidence with the presence of one protein-like component in the dissolvedorganic matter fluorescence analysis, while norelationship was observed between bacteria respiration and chlorophyll a.  Community analysis using the 16S rRNA geneidentified a total of 2135 OTUs consisting mainly of Proteobacteria,Firmicutes, Actinobacteria and Bacteroidetes.