Search

Polar marine environments host a complex assemblage of cold-adapted auto- and heterotrophic microorganisms that affect water biogeochemistry and ecosystem functions. However, due to logistical difficulties, remote regions like those in close proximity to glaciers have received little attention, resulting in a paucity of microbiological data. To fill these gaps and obtain novel insights into microbial structure and function in Arctic regions, a survey of microbial communities in an area close to the Blomstrandbreen glacier in Kongsfjorden (Svalbard Archipelago; Arctic Ocean) was carried out during an early summer period. An Unmanned Autonomous Vehicle designed to safely obtain seawater samples from offshore-glacier transects (PROTEUS, Portable RObotic Technology for Unmanned Surveys) was equipped with an automatic remotely-controlled water multi-sampler so that it could sample just beneath the glacier, where access from the sea is difficult and dangerous. The samples were analysed by image analysis for the abundance of total prokaryotes, viable and respiring cells, their morphological traits and biomass; by flow cytometry for autotrophic and prokaryotic cells (with high and low nucleic acid contents) as well as virus-like particle counts; by BIOLOG ECOPLATES for potential community metabolism; and by fluorimetry for potential enzymatic activity rates on organic polymers. Contextually, the main physical and chemical (temperature, salinity, pH, dissolved oxygen and nutrients) parameters were detected. Altogether, besides the PROTEUS vehicle's suitability for collecting samples from otherwise inaccessible sites, the multivariate analysis of the overall dataset allowed the identification of three main sub-regions differently affected by the haline gradient (close to the glacier) or terrigenous inputs coming from the coast. A complex microbiological scenario was depicted by different patterns of microbial abundance and metabolism among the transects, suggesting that ice melting and Atlantic water inflow differently supported microbial growth. [ABSTRACT FROM AUTHOR]

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

Heavy metals (HMs) and polychlorobiphenyls (PCBs) enter the Arctic environment through a variety of anthropogenic sources with deleterious effects towards biota and public health. Bacteria first transfer toxic compounds to higher trophic levels and, due to the tight link existing between prokaryotic community functions and the type and concentration of contaminants, they may be useful indicator of pollution events and potential toxicity to other forms of life. The occurrence and abundance of HM-tolerant and PCB-oxidizing bacteria in the sub-Arctic Pasvik river area, heavily impacted by anthropogenic modifications, was related to HM and PCB contamination. This latter more likely derived from local inputs rather than a global contamination with higher PCB and HM amounts (and higher bacterial viable counts) that were determined in inner and middle sections of the River. Finally, a panel of bacteria with potential applications in the bioremediation of cold environments were selected and phylogenetically identified., (Copyright © 2019 Elsevier Ltd. All rights reserved.)