Preliminary observations on the microbial communities of an extreme hydrological system: the Bayelva River catchment (Western Svalbard, High Arctic Norway)

Glacier melting results in the mobilization-transport of microorganisms, along with organic/ inorganic compounds and solid particles, stored since a long time via meltwaters. In this context, the Bayelva catchment (79°N 12°E, Svalbard Islands, High Arctic Norway) is a crucial site for establishing the links between microbial communities and hydrology dynamics in the Svalbard glaciers. Two field campaigns were carried out in spring and summer 2022 in the Bayelva River catchment, from its glaciers (i.e., Austre and Vestre Brøggerbreen) and periglacial/proglacial systems up to the fjord, in a marine sector significantly affected by the river. Flowrates at the Bayelva River section close to the fjord varied between 2 and 9 m3/s in June. Glacier snowpack, glacial meltwater, groundwater, river and fjord water were collected. Samples were analysed for culturable heterotrophic bacteria and total prokaryotes, microbial enzymatic activities (leucin aminopeptidase, LAP, beta-glucosidase, GLU, alkaline phosphatase, AP), and total chlorophyll-a concentration. Prokaryotic abundance was quite low in snowpack (103 cells/ml of melted snow), but it increased in river and fjord water. Prokaryotes were predominantly coccus-shaped and appeared as individual cells or aggregates. Viable counts, differing among the used culture media, were in the order of 102 CFUs/ml, with lower values in snow than in the other analyzed samples. The lowest enzymatic activities were recorded in snow samples, with higher LAP than GLU and AP values. Mean chlorophyll-a concentration was higher in seawater (0.5 mg/m3) compared to the river (0.1 mg/m3), where the greatest variability was observed. This study furnished preliminary data useful to quantify the microbial biomass mobilization and its transfer from the investigated glacial system to the Kongsfjorden.