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• Carlsen, Eira Catharine Lødrup; Wei, Jing; Lejzerowicz, Franck; Kjær, Sigrid Trier; Westermann, Sebastian & Hessen, Dag Olav [Vis alle 8 forfattere av denne artikkelen] (2025). Redox determines greenhouse gas production kinetics and metabolic traits in water-saturated thawing permafrost peat. ISME Communications. 5(1). doi: 10.1093/ismeco/ycaf009. Fulltekst i vitenarkiv Vis sammendrag

  Redox conditions, influenced by the availability of oxygen, are expected to dictate the rate of CO2 and CH4 production and to shape the composition and metabolism of microbial communities. Here, we use thawing permafrost peat in thermokarst water under a gradient of initial O2 concentrations to experimentally cover the variability in redox conditions potentially found across thawing landscapes. The three main greenhouse gases, CO2, CH4 and N2O, responded differently to O2 absence. CO2 production along the O2 gradient could be modeled by the Michaelis Menten equation revealing a sharp decrease when oxygen dropped under 100 μM. Under anoxic conditions CO2 yield decreased by 98% and maximum net production rate by 85% when compared to oxic conditions during the 11 days after thaw. N2O production was observed under anoxic conditions, while CH4 yield and CH4 accumulation rates did not differ across the redox gradient. The latter is due to the release of stored CH4 due to thawing. Differences between oxic and anoxic conditions were reflected in the microbial genomic composition, with changes in taxonomic and functional groups, such as N2O reducers, fermenters, denitrifiers and sulfur reducers increasing under anoxic conditions. Genomic changes towards less efficient central metabolism further explained the CO2 production yields and rates limited by O2 availability as predicted by thermodynamics. Together with the Michaelis Menten models the metabolic reconstruction pinpoint to critical thresholds of CO2 release at suboxic conditions and thus need to be considered when explaining and modeling highly variable CO2 emissions across thawing landscapes.

• Schultze, Sabrina; Langva, Hilde Kleppe; Wei, Jing; Chatzigeorgiou, Marios; Rundberget, Thomas & Hessen, Dag Olav [Vis alle 9 forfattere av denne artikkelen] (2024). Do DOM quality and origin affect the uptake and accumulation of a lipid-soluble contaminant in a filter feeding ascidian species (Ciona) that can target small particle size classes? Aquatic Toxicology. ISSN 0166-445X. 273. doi: 10.1016/j.aquatox.2024.107026. Fulltekst i vitenarkiv Vis sammendrag

  The widely reported increase of terrestrial dissolved organic matter (terrDOM) in northern latitude coastal areas (“coastal darkening”) can impact contaminant dynamics in affected systems. One potential impact is based on differences in chemical adsorption processes of the molecularly larger terrDOM compared to marine DOM (marDOM) that leads to increased emulsification of lipophilic contaminants with terrDOM. Filter feeders filter large amounts of water and DOM daily and thus are directly exposed to associated contaminants through both respiration and feeding activity. Thus, increased exposure to terrDOM could potentially lead to an increase in bioaccumulation of lipid soluble contaminants in filter feeders. To assess the effect of DOM on bioaccumulation in filter feeders, we exposed the mucous based filter feeding ascidian Ciona intestinalis (formerly known as Ciona intestinalis Type B), to the lipophilic veterinary drug teflubenzuron (log KOW: 5.39) in combination with four DOM treatments: TerrDOM, marDOM, a mix of the two called mixDOM, and seawater without DOM addition. The exposure lasted for 15 days, after which the individuals in all DOM treatments showed a trend towards higher bioaccumulation of Teflubenzuron than those in the seawater control. However, there was considerable overlap in posterior distributions. Against our expectations, marDOM resulted in the highest bioaccumulation factor (BAF), followed by mixDOM, with terrDOM resulting in the lowest BAF except for seawater (kinetic BAF L/kg median, 2.5 %–97.5 % percentile marDOM 94, 74–118; mixDOM 82, 63–104; terrDOM 79; 61-99; seawater 61, 44–79). All BAFs were below the level of concern according to the EU REACH regulation (BAF < 2000 L / kg) and, therefore, likely not environmentally problematic in the examined context. However, the results show that DOM can act as a dietary vector; thus, different combinations of contaminants, DOM, and filter feeding organisms should be tested further.

• Colls, Miriam; Viza, Aida; Zufiarre, Aitziber; Camacho-Santamans, Alba; Laini, Alex & González-Ferreras, Alexia Maria [Vis alle 85 forfattere av denne artikkelen] (2024). Impacts of diffuse urban stressors on stream benthic communities and ecosystem functioning: A review. Limnetica. ISSN 0213-8409. 43(1), s. 89–108. doi: 10.23818/limn.43.07. Fulltekst i vitenarkiv Vis sammendrag

  Catchment urbanisation results in urban streams being exposed to a multitude of stressors. Notably, stressors originating from diffuse sources have received less attention than stressors originating from point sources. Here, advances related to diffuse urban stressors and their consequences for stream benthic communities are summarised by reviewing 92 articles. Based on the search criteria, the number of articles dealing with diffuse urban stressors in streams has been increasing, and most of them focused on North America, Europe, and China. Land use was the most common measure used to characterize diffuse stressor sources in urban streams (70.7 % of the articles characterised land use), and chemical stressors (inorganic nutrients, xenobiotics, metals, and water properties, including pH and conductivity) were more frequently reported than physical or biological stressors. A total of 53.3 % of the articles addressed the impact of urban stressors on macroinvertebrates, while 35.9 % focused on bacteria, 9.8 % on fungi, and 8.7 % on algae. Regarding ecosystem functions, almost half of the articles (43.5 %) addressed changes in community dynamics, 40.3 % addressed organic matter decomposition, and 33.9 % addressed nutrient cycling. When comparing urban and non-urban streams, the reviewed studies suggest that urbanisation negatively impacts the diversity of benthic organisms, leading to shifts in community composition. These changes imply functional degradation of streams. The results of the present review summarise the knowledge gained to date and identify its main gaps to help improve our understanding of urban streams.

• Wang, Qiuying; Wei, Jing; Wan, Bin; An, Qiong; Gao, Jie & Zhuang, Guoqiang (2024). The regulation effect of preventing soil nitrogen loss using microbial quorum sensing inhibitors. Environmental Research. ISSN 0013-9351. 246. doi: 10.1016/j.envres.2024.118136. Fulltekst i vitenarkiv
• Wei, Jing; Fontaine, Laurent; Parra, Nicolas Valiente; Dörsch, Peter; Hessen, Dag Olav & Eiler, Alexander (2023). Trajectories of freshwater microbial genomics and greenhouse gas saturation upon glacial retreat. Nature Communications. 14. doi: 10.1038/s41467-023-38806-w. Fulltekst i vitenarkiv Vis sammendrag

  Abstract Due to climate warming, ice sheets around the world are losing mass, contributing to changes across terrestrial landscapes on decadal time spans. However, landscape repercussions on climate are poorly constrained mostly due to limited knowledge on microbial responses to deglaciation. Here, we reveal the genomic succession from chemolithotrophy to photo- and heterotrophy and increases in methane supersaturation in freshwater lakes upon glacial retreat. Arctic lakes at Svalbard also revealed strong microbial signatures form nutrient fertilization by birds. Although methanotrophs were present and increased along lake chronosequences, methane consumption rates were low even in supersaturated systems. Nitrous oxide oversaturation and genomic information suggest active nitrogen cycling across the entire deglaciated landscape, and in the high Arctic, increasing bird populations serve as major modulators at many sites. Our findings show diverse microbial succession patterns, and trajectories in carbon and nitrogen cycle processes representing a positive feedback loop of deglaciation on climate warming.

• Parra, Nicolas Valiente; Eiler, Alexander; Allesson, Lina; Andersen, Tom; Clayer, Francois & Crapart, Camille Marie [Vis alle 13 forfattere av denne artikkelen] (2022). Catchment properties as predictors of greenhouse gas concentrations across a gradient of boreal lakes. Frontiers in Environmental Science. 10. doi: 10.3389/fenvs.2022.880619. Fulltekst i vitenarkiv Vis sammendrag

  Boreal lakes are the most abundant lakes on Earth. Changes in acid rain deposition, climate, and catchment land use have increased lateral fluxes of terrestrial dissolved organic matter (DOM), resulting in a widespread browning of boreal freshwaters. This browning affects the aqueous communities and ecosystem processes, and boost emissions of the greenhouse gases (GHG) CH 4 , CO 2 , and N 2 O. In this study, we predicted biotic saturation of GHGs in boreal lakes by using a set of chemical, hydrological, climate, and land use parameters. For this purpose, concentrations of GHGs and nutrients (organic C, -P, and -N) were determined in surface water samples from 73 lakes in south-eastern Norway covering wide ranges in DOM and nutrient concentrations, as well as catchment properties and land use. The spatial variation in saturation of each GHG is related to explanatory variables. Catchment characteristics (hydrological and climate parameters) such as lake size and summer precipitation, as well as NDVI, were key determinants when fitting GAM models for CH 4 and CO 2 saturation (explaining 71 and 54%, respectively), while summer precipitation and land use data were the best predictors for the N 2 O saturation, explaining almost 50% of deviance. Our results suggest that lake size, precipitation, and terrestrial primary production in the watershed control the saturation of GHG in boreal lakes. These predictions based on the 73-lake dataset was validated against an independent dataset from 46 lakes in the same region. Together, this provides an improved understanding of drivers and spatial variation in GHG saturation in boreal lakes across wide gradients of lake and catchment properties. The assessment highlights the need to incorporate multiple explanatory parameters in prediction models of GHGs for extrapolation across the boreal biome.

• Allesson, Lina; Andersen, Tom; Dörsch, Peter; Eiler, Alexander; Wei, Jing & Hessen, Dag Olav (2020). Phosphorus availability promotes bacterial DOC-mineralization, but not cumulative CO2-production. Frontiers in Microbiology. 11. doi: 10.3389/fmicb.2020.569879. Fulltekst i vitenarkiv Vis sammendrag

  The current trend of increasing input of terrestrially derived dissolved organic carbon (DOC) to boreal freshwater systems is causing increased levels of carbon dioxide (CO 2 ) supersaturation and degassing. Phosphorus (P) is often the most limiting nutrient for bacterial growth and would thus be expected to increase overall mineralization rates and CO 2 production. However, high carbon (C) to P ratios of terrestrially derived DOC could also cause elevated cell-specific respiration of the excess C in heterotrophic bacteria. Using data from a survey of 75 Scandinavian lakes along an ecosystem gradient of DOC, we estimated in situ CO 2 production rates. These rates showed a unimodal response with DOC-specific CO 2 production negatively related to DOC:total phosphorus (TP) ratio, and a turning point at 5 mg C L −1 , indicating higher DOC turnover rates in productive than in unproductive lakes. To further assess the dependency of bacterial respiration (BR) on DOC and P, we monitored CO 2 production in incubations of water with a gradient of DOC crossed with two levels of inorganic P. Finally, we crossed DOC and P with a temperature gradient to test the temperature dependency of respiration rates [as oxygen (O 2 ) consumption]. While total CO 2 production seemed to be unaffected by P additions, respiration rates, and growth yields, as estimated by ribosomal gene copy numbers, suggest increased bacterial growth and decreased cell-specific respiration under non-limited P conditions. Respiration rates showed a sigmoid response to increasing DOC availability reaching a plateau at about 20 mg C L −1 of initial DOC concentrations. In addition to these P and DOC level effects, respiration rates responded in a non-monotonic fashion to temperature with an increase in respiration rates by a factor of 2.6 (±0.2) from 15 to 25°C and a decrease above 30°C. The combined results from the survey and experiments highlight DOC as the major determinant of CO 2 production in boreal lakes, with P and temperature as significant modulators of respiration kinetics.

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• Carlsen, Eira Catharine Lødrup; Pismeniuk, Anfisa; Wei, Jing; Ippach, Mats Rouven; Dörsch, Peter & Westermann, Sebastian [Vis alle 9 forfattere av denne artikkelen] (2026). FROM PEAT TO PONDS: LANDSCAPE HETEROGENEITY DRIVES METABOLIC NETWORKS AND GREENHOUSE GAS RELEASE FROM THAWING PERMAFROST. Fulltekst i vitenarkiv Vis sammendrag

  As permafrost landscapes degrade, they transform into a hydrological mosaic of dry palsas, collapsing thermokarst slumps, and water-saturated ponds. This physical reorganization creates steep gradients in redox potential and organic matter quality, fundamentally altering the thermodynamic constraints on microbial metabolism. We investigated greenhouse gas (CO2, CH4, N2O) production potentials across several permafrost thaw gradients in sub-Arctic peatlands of Northern Norway, linking landscape-scale changes to genome-resolved metabolic networks. By integrating high-resolution metagenomics with organic matter and greenhouse gas production characterization, we found that thaw features act as distinct thermodynamic bioreactors. In water-saturated, anoxic peat layers, oxygen limitation selects for "slow" metabolic guilds specialized in fermentation and methanogenesis while other oxygenated features are constrained by the quality of organic matter—specifically the accumulation of polyphenols and aromatic compounds acts as a metabolic "latch". We show that the shift from oxic to anoxic conditions triggers a non-linear restructuring of the microbial network, where less efficient central metabolism drives high N2O and CH4 yields but suppressed CO2 production. These findings demonstrate that predicting the permafrost-carbon feedback requires mapping the "metabolic landscape"—where organic matter quality and redox thresholds ultimately tune the greenhouse gas release from thawing landscapes to the atmosphere.

• Carlsen, Eira Catharine Lødrup; Wei, Jing; Lejzerowicz, Franck Laurent Patrick; Ippach, Mats Rouven; Pismeniuk, Anfisa & Kjær, Sigrid Trier [Vis alle 10 forfattere av denne artikkelen] (2025). Greenhouse gas production kinetics and metabolic traits in thawing permafrost peat. Fulltekst i vitenarkiv Vis sammendrag

  While numerous drivers of greenhouse gas emission (GGE) have been suggested to drive variabilities across thawing landscapes, experimental validations are still widely lacking . Here, I will present results from several experimental studies capturing drivers of GGE across thawing permafrost landscapes like redox, organic matter and microbial source community. Our findings reveal clear responses of the greenhouse gases to redox conditions across the landscape. CO2 production showed a drastic decline when O2 dropped below 100 μM; specifically, under anoxic conditions, CO2 yield and maximum net production rates decreased by around 90 % compared to oxic conditions. CH4 levels remained consistent across O2 gradients, until at least 6 months upon thawing. Functional groups like N2O reducers, fermenters, denitrifiers, and sulfur reducers increased under anoxic conditions, and the reduced CO2 production rates and yields under anoxic conditions were reflected by genomic changes towards reduced central metabolic efficiency. Our data thus points towards critical GGE thresholds under suboxic conditions across thawing landscapes. Moreoever, gas dynamics seem to be primarily influenced by permafrost conditions rather than source community colonization. Our experiments provide increased knowledge on the variable GGE across thawing permaforst landscapes influenced by variable redox conditions and permafrost´s organic matter legacy.

• Allesson, Lina; Andersen, Tom; Dörsch, Peter; Eiler, Alexander; Wei, Jing & Hessen, Dag Olav (2020). Corrigendum: Phosphorus Availability Promotes Bacterial DOC-Mineralization, but Not Cumulative CO2-Production (Front.Microbiol, (2020), 11, (569879), 10.3389/fmicb.2020.569879). Frontiers in Microbiology. 11. doi: 10.3389/fmicb.2020.614974. Fulltekst i vitenarkiv

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