Environmental characteristics of a tundra river systemin Svalbard. Part 1: Bacterial abundance, community structure and nutrient levels

The Arctic hosts a set of unique ecosystems, characterised by extreme environmental conditions and undergoing a rapid change resulting fromthe average temperature rising. We present a study on an aquatic ecosystemof the Revelva catchment (Spitsbergen), based on samples collected from the lake, river and their tributaries, in the summer of 2016. The landscape variety of the study site and the seasonal change in the hydrological regimemodify the availability of nutrients. In general, the upper part of the catchment consists of themountain rocky slopes which are especially abundant in iron minerals, sulphides and phosphorusminerals. The lower part of the catchment is covered by plants-lichens, saxifrages and bryophytes, which are a different source of nutrients. In the analysed water samples, the maximum concentrations of nutrients such as iron, boron and phosphorus were 0.28 mu g L-1, 4.52 mu g L-1 and 1.91 mu g L-1, respectively, in June, while in September, Fe and B reached the concentrations of 1.32 mu g L-1 and 2.71 mu g L-1, respectively. The concentration of P in September was belowthe detection limit of 1.00 mu g L-1, which may be explained by the necessity of bacteria to consume it immediately on current needs. We noted also an increase in TOC concentration between the June and September samples, which could originate both from the biomass accumulation in the catchment and the permafrost melting contributing to the hydrological regime of the river. The bacterial community developed in this environment consisted mainly of Proteobacteria, Actinobacteria, Bacteroidetes and Firmicutes phylum, while the presence of Acidobacteria was less pronounced than in other tundra-related environments. The described catchment shows that despite the relatively small amount of bioavailable nutrients, the Revelva systemis biodiverse and one of the most significant biogeochemical changes occurs there in response to seasonally switching water sources. (c) 2018 Elsevier B. V. All rights reserved.