A snapshot of the taxonomic composition and metabolic activity of the microbial community in an Arctic harbour (Ny-Ålesund, Kongsfjorden, Svalbard)

Within the Svalbard archipelago, the Kongsfjorden is an important marine ecosystem, that is recognised as one of the main representative Arctic glacial fjords. Prokaryotic organisms are key drivers of important ecological processes like carbon fluxes, nutrient mineralization and energy transfer as well as sentinels of environmental pollution, especially in sediments, that are a repository of contaminants. In some areas of the Arctic the structure and metabolic activity of microbial community in the organic matter turnover and globally in the functioning of the benthic domain are mostly unknown yet. A snapshot of the main microbial parameters such as bacterial abundance (by microscopic and plate counts), structure (by 16S rRNA sequencing) and metabolic activity was provided in Ny-Ålesund harbour, contextually in seawater and sediment samples. Fluorogenic substrates were used to assess the microbial ability to utilize organic substrates such as proteins, polysaccharides and organic phosphates through specific enzymatic assays (leucine aminopeptidase-LAP, beta-glucosidase-GLU and alkaline phosphatase-AP, respectively). The metabolic profiles of psychrophilic heterotrophic bacterial isolates were also screened using a qualitative assay. The phylogenetic analysis of the microbial community revealed that Proteobacteria prevailed among the observed taxonomic groups. Several of the observed sequences were assigned to clones found in harbours, microbial biofilms, antifouling paints or oil-polluted facilities of cold environments, highlighting a signature of human pressure on the polar habitat of Ny-Ålesund harbour.