Bacterial Diversity in a Dynamic and Extreme Sub-Arctic Watercourse (Pasvik River, Norwegian Arctic)

Microbial communities promptly respond to the environmental perturbations, especiallyin the Arctic and sub-Arctic systems that are highly impacted by climate change, and fluctuationsin the diversity level of microbial assemblages could give insights on their expected response. 16SrRNA gene amplicon sequencing was applied to describe the bacterial community composition inwater and sediment through the sub-Arctic Pasvik River. Our results showed that river water andsediment harbored distinct communities in terms of diversity and composition at genus level. Thedistribution of the bacterial communities was mainly affected by both salinity and temperature insediment samples, and by oxygen in water samples. Glacial meltwaters and runoff waters frommelting ice probably influenced the composition of the bacterial community at upper and middleriver sites. Interestingly, marine-derived bacteria consistently accounted for a small proportion ofthe total sequences and were also more prominent in the inner part of the river. Results evidencedthat particular conditions occurring at sampling sites (such as algal blooms, heavy metalcontamination and anaerobiosis) may select species at local scale from a shared bacterial pool, thusfavoring certain bacterial taxa. Conversely, the few phylotypes specifically detected in some sitesare probably due to localized external inputs introducing allochthonous microbial groups.