Structure and function of natural microbial community in a harbour of an Arctic glacial fjord (Kongsfjorden, Svalbard)

The Kongsfjorden Fjord, located in Svalbard Islands (Norway), is an important marine ecosystem widely investigated by the international scientific community. This area is considered the most representative than other open fjords in the Arctic and it is affected by the inflow of Atlantic waters as well as by glacier melt water runoff (Hop et al., 2002). Prokaryotic communities play a key role in relevant processes such as carbon fluxes, energy transfers and nutrient regeneration and can be viewed both as sentinels and amplifiers of global change. In this context, further research is needed to quantify the role of these microorganisms in the flux of organic matter in the Arctic marine food web. In this study the main principal chemical-physical parameters, bacterial abundance (DAPI, CFU and MPN count) and structure (16S rRNA clone libraries) and extracellular activity were analyzed at 3 sites in Ny-Ålesund harbour (Svalbard islands), 2 for seawater and 1 for sediment samplings. The metabolic function of the microbial community was studied through isolation of psychrophilic heterotrophic bacteria and measurements of potential enzymatic activity rates on organic polymers (leucine aminopeptidase_LAP, beta-glucosidase-GLU and alkaline phosphatase-AP) by fluorogenic substrates. Phylogenetic analysis of community structure reveals that Proteobacteria were the most abundant group. Many of analyzed sequences were affiliated to clones identified in cold areas, in ports, in biofilm covering, antifouling paint and in oil contaminated facility. These results highlight different signs of human settlement in sampling sites.