Abstract
The effects of climate change-induced ice melting on the microbial communities in different glacial-fed aquatic systems have been reported, but seasonal dynamics remain poorly investigated. In this study, the structural and functional traits of the aquatic microbial community were assessed along with the hydrological and biogeochemical variation patterns of the Arctic Pasvik River under riverine and brackish conditions at the beginning (May = Ice-melt (−)) and during the ice-melting season (July = Ice-melt (+)). The microbial abundance and morphometric analysis showed a spatial diversification between the riverine and brackish stations. Results highlighted different levels of microbial respiration and activities with different carbon and phosphorous utilization pathways, thus suggesting an active biogeochemical cycling along the river especially at the beginning of the ice-melting period. At Ice-melt (−), Gammaproteobacteria and Alphaproteobacteria were dominant in riverine and brackish stations, respectively. Conversely, at Ice-melt (+), the microbial community composition was more homogeneously distributed along the river (Gammaproteobacteria > Alphaproteobacteria > Bacteroidetes). Our findings provide evidence on how riverine microbial communities adapt and respond to seasonal ice melting in glacial-fed aquatic ecosystems.
Highlights
The inputs of glacial and snow meltwaters into Arctic and sub-Arctic rivers are increasing due to the unprecedented effects of global warming on the cryosphere, with repercussions on the river flow dynamics and ecology
Warming effects deriving from climate change processes are expected to be more and more pronounced at high latitudes, where most of the global carbon pool is stored [31,32] with worrying effects on the entire ecological system, impacting physical, biogeochemical, and ecological levels [4]
A survey on physical-chemical parameters, functional, and diversity traits of Arctic microbial communities is proposed in a perspective of more or less advanced state of ice melting, mentioned as Ice-melt (−) and Ice-melt (+) seasons
Summary
The inputs of glacial and snow meltwaters into Arctic and sub-Arctic rivers are increasing due to the unprecedented effects of global warming on the cryosphere, with repercussions on the river flow dynamics and ecology. Arctic rivers have attracted less attention than Arctic lakes, despite their central role in polar ecosystem functioning by connecting glacier meltwaters to downstream aquatic systems (e.g., estuaries, coastal systems, 4.0/). Arctic freshwater systems are considered sentinels of climate change [3], and their microbial communities could be used as indicators of changing conditions [4]. The Arctic Ocean is subject to large river inputs, which bring low-salinity waters, organic matter and nutrients, and mobilized ancient carbon, with the rising temperatures and permafrost thawing [5]. The increasing riverine inputs and the consequent pulses of organic matter affects the microbial communities, which could respond by changing their structural and functional traits [6,7]
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