Abundances and activities of prokaryotic community in water of an Arctic river

The spatial and temporal distribution of microbial biomass and metabolic rates were investigated in water samples collected along the Pasvik River (Arctic Norway) from 9 stations during two sampling campaigns (May and July 2014). Water samples were analyzed for physico-chemical parameters, viable bacterial abundance (VCs), prokaryotic abundance (PA), microbial enzymatic and respiratory activity. All data were statistically analyzed. VCs were generally homogeneous in May and July. PA showing enhanced abundance in July and higher values in the outer than in inner stations. Microbial respiration was higher in July than in May. Pearson's correlation coefficients showed that physical and chemical parameters affected both the PA and functionality. Respiration was significantly related to Temperature, suggesting its stimulation on the oxidation process. ANOSIM analysis showed seasonal significant differences (R=0.231, p=0.002), with temperature accounting for 11.4% of total variability. Psychrophilic microorganisms of the Pasvik river appear to be quite plastic to acclimate to seasonal changes of the cold habitat in which they live, modifying their abundance and metabolism, although further research is needed for a deepen knowledge of this Arctic ecosystem.