Effects of different dissolved organic carbon sources on bacterial community in a North-Patagonian Andean wetland

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

Turín

Congreso; SIL; 2016

SIL

Dissolved organic carbon (DOC) in aquatic ecosystems comprises a complex mix of compounds of different origin. In North Patagonian Andes, Nothofagus pumilio (lenga) determines the upper limit of the temperate forest and constitutes an important source of organic input for the catchment area. In addition the wetlands of the area, locally called mallín, develop benthonic algal communities (Spirogyra sp and Zygnema sp) that provide autochthonous DOC. The objective here was to analyze the metabolism, and genetic and functional diversity of bacterioplankton in relation to different sources of DOC (algal exudates and lenga leachates) in a mountain wetland (Mallín Los Patos). We conducted laboratory experiments in three different seasons (autumn, spring and summer) in which lake water with a bacterial inoculum was enriched with exudates or leachates. We measured nutrient concentrations, bacteria abundances, and we assessed bacterial community structure using next-generation sequencing of the 16S rRNA gene and microplates EcoplateTM. In addition, we performed bacterial respiration and DOC-decay experiments, and changes in dissolved organic matter (DOM) using spectrofluorometric analysis (excitation-emission matrix spectra, EEMs analysis). DOM characterization showed in both exudates and leachates one peak of protein-like origin and two corresponding to humic-like compound. P content was higher in leachates, with a lower C:P ratio than exudates (197.4 ± 80.1 and 503.95± 105.8, respectively). The enrichments with either DOC sources (exudates and leachates) stimulated the bacterial metabolism (higher respiration and DOC consumption rates), but leachates exhibited the highest increase in the C consumption rate likely due to its lower C:P ratio. Both enrichments seemed to developed diverse bacterial communities, since different physiological groups were stimulated in each treatment.