English
norskBlar i forfatter "Vonnahme, Tobias"
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Early spring subglacial discharge plumes fuel under-ice primary production at a Svalbard tidewater glacier
(Journal article; Tidsskriftartikkel; Peer reviewed, 2021-04-27)Subglacial upwelling of nutrient-rich bottom water is known to sustain elevated summer primary production in tidewater-glacier-influenced fjord systems. However, the importance of subglacial upwelling during the early spring season has not been considered yet. We hypothesized that subglacial discharge under sea ice is present in early spring and that its flux is sufficient to increase phytoplankton ... -
Interannual differences in sea ice regime in the north-western Barents Sea cause major changes in summer pelagic production and export mechanisms
(Journal article; Tidsskriftartikkel; Peer reviewed, 2023-11-22)The Barents Sea is a highly dynamic and productive marine ecosystem and a hotspot of global warming. Variability in sea ice extent is a common feature in the Barents Sea with substantial movements of the sea ice edge on short-term, seasonal to interannual time scales. Historically the northern Barents Sea (north of 75◦N) has been ice-covered in winter, but recently it has become the area with most ... -
Light and freshwater discharge drive the biogeochemistry and microbial ecology in a sub-Arctic fjord over the Polar night
(Journal article; Tidsskriftartikkel; Peer reviewed, 2022-09-30)The polar night has recently received increased attention as a surprisingly active biological season. Yet, polar night microbial ecology is a vastly understudied field. To identify the physical and biogeochemical parameters driving microbial activity over the dark season, we studied a sub-Arctic fjord system in northern Norway from autumn to early spring with detailed monthly sampling. We focused ... -
Microbial diversity and ecology in the coastal Arctic seasonal ice zone
(Doctoral thesis; Doktorgradsavhandling, 2021-03-11)Marine microbes are crucial for the marine food web and carbon cycle. Algae are the main source of organic matter in the oceans with algae blooms triggering reoccurring bacterial succession patterns. Bacteria can recycle nutrients from organic matter coming from land or algae, fueling regenerated primary production. Terrestrial freshwater inputs can have substantial impacts on Arctic marine microbes ... -
Modeling silicate–nitrate–ammonium co-limitation of algal growth and the importance of bacterial remineralization based on an experimental Arctic coastal spring bloom culture study
(Journal article; Tidsskriftartikkel; Peer reviewed, 2021-03-11)Arctic coastal ecosystems are rapidly changing due to climate warming. This makes modeling their productivity crucially important to better understand future changes. System primary production in these systems is highest during the pronounced spring bloom, typically dominated by diatoms. Eventually the spring blooms terminate due to silicon or nitrogen limitation. Bacteria can play an important role ... -
Terrestrial Inputs Shape Coastal Bacterial and Archaeal Communities in a High Arctic Fjord (Isfjorden, Svalbard)
(Journal article; Tidsskriftartikkel; Peer reviewed, 2021-02-26)The Arctic is experiencing dramatic changes including increases in precipitation, glacial melt, and permafrost thaw, resulting in increasing freshwater runoff to coastal waters. During the melt season, terrestrial runoff delivers carbon- and nutrient-rich freshwater to Arctic coastal waters, with unknown consequences for the microbial communities that play a key role in determining the cycling and ...
