Eira Catharine Lødrup Carlsen

• Carlsen, Eira Catharine Lødrup; Wei, Jing; Lejzerowicz, Franck; Kjær, Sigrid Trier; Westermann, Sebastian & Hessen, Dag Olav [Show all 8 contributors for this article] (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. Full text in Research Archive Show summary

  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.

• Carlsen, Eira Catharine Lødrup; Hjelset, Sverre; Gomes, Tania; Igartua, Amaia; Sørensen, Lisbet & Booth, Andy [Show all 8 contributors for this article] (2024). Synthetic and natural rubber associated chemicals drive functional and structural changes as well as adaptations to antibiotics in in vitro marine microbiomes. Ecotoxicology and Environmental Safety. ISSN 0147-6513. 273. doi: 10.1016/j.ecoenv.2024.116134. Full text in Research Archive Show summary

  The leaching of additives from plastics and elastomers (rubbers) has raised concerns due to their potential negative impacts on the environment and the development of antibiotic resistance. In this study, we investigated the effects of chemicals extracted from two types of rubber on microbiomes derived from a benthic sea urchin and two pelagic fish species. Additionally, we examined whether bacterial communities preconditioned with rubber-associated chemicals displayed adaptations to antibiotics. At the highest tested concentrations of chemicals, we observed reduced maximum growth rates and yields, prolonged lag phases, and increased alpha diversity. While the effects on alpha and beta diversity were not always conclusive, several bacterial genera were significantly influenced by chemicals from the two rubber sources. Subsequent exposure of sea urchin microbiomes preconditioned with rubber chemicals to the antibiotic ciprofloxacin resulted in decreased maximum growth rates. This indicates a more sensitive microbiome to ciprofloxacin when preconditioned with rubber chemicals. Although no significant interaction effects between rubber chemicals and ciprofloxacin exposure were observed in bacterial alpha and beta diversity, we observed log-fold changes in two bacterial genera in response to ciprofloxacin exposure. These findings highlight the structural and functional alterations in microbiomes originating from various marine species when exposed to rubber-associated chemicals and underscore the potential risks posed to marine life.

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• Carlsen, Eira Catharine Lødrup; Pismeniuk, Anfisa; Wei, Jing; Ippach, Mats Rouven; Dörsch, Peter & Westermann, Sebastian [Show all 9 contributors for this article] (2026). FROM PEAT TO PONDS: LANDSCAPE HETEROGENEITY DRIVES METABOLIC NETWORKS AND GREENHOUSE GAS RELEASE FROM THAWING PERMAFROST. Full text in Research Archive Show summary

  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.

• Riis-Pedersen, Christine; Carlsen, Eira Catharine Lødrup; Lejzerowicz, Franck Laurent Patrick; Hessen, Dag Olav & Eiler, Alexander (2026). HOW OPTICS AND THERMODYNAMICS SHAPE METHANE EMISSIONS FROM LAKES. Full text in Research Archive Show summary

  The interactions of light regime and physical stratification can be argued to dictate greenhouse gas flux through determining the thermodynamics in lake systems. Using geochemical profiling and metagenomics, we reconstructed metabolic networks in a wide range of lakes including ferruginous (iron-rich) and euxinic (sulfide-rich) systems. We observed significant methane accumulation in the anoxic monimolimnion—up to 420 µM in ferruginous lakes—yet surface levels remained low, indicating a highly efficient biofilter at the chemoclines. We identified a tight thermodynamic coupling between phototrophs and methanotrophs driven by oxidant regeneration. In ferruginous lakes, anoxygenic phototrophs likely use reduced iron (Fe2+) as an electron donor. This process regenerates oxidized iron (Fe3+), while in euxinic light energy is utilized to recycle essential electron acceptors such as SO42- (e.g., Chlorobium), required for anaerobic methane oxidation. Oxygenic phototrophs (e.g., Cyanobium) detected at and above the chemocline likely provide oxygen. This supply sustains aerobic methanotrophs like Crenothrix and Methylobacter even in suboxic waters. Hence methanotrophic capacity is ultimately constrained by optical properties selecting for low-intensity light anoxygenic or high-intensity oxygenic phototrophs. Consequently, levels of chromophoric dissolved organic matter determine methane oxidation rates. We conclude that chemoclines function as dynamic, light-powered engines for methane removal, sensitive to brownification and climate-induced shifts in stratification.

• Riis-Pedersen, Christine; Carlsen, Eira Catharine Lødrup; Hessen, Dag Olav; Lejzerowicz, Franck Laurent Patrick; Andersen, Tom & Dörsch, Peter [Show all 8 contributors for this article] (2025). Microbial drivers of methane cycling in meromictic as compared to holomictic lakes. Full text in Research Archive
• Carlsen, Eira Catharine Lødrup; Wei, Jing; Lejzerowicz, Franck Laurent Patrick; Ippach, Mats Rouven; Pismeniuk, Anfisa & Kjær, Sigrid Trier [Show all 10 contributors for this article] (2025). Greenhouse gas production kinetics and metabolic traits in thawing permafrost peat. Full text in Research Archive Show summary

  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.

• Carlsen, Eira Catharine Lødrup; Hylland, Ketil; Gomes, Tania; Sørensen, Lisbet; Booth, Andrew & Eiler, Alexander (2022). Plastic leachates as drivers for bacterial community structure and functioning, including antibiotic resistance. Full text in Research Archive
• Carlsen, Eira Catharine Lødrup; Eiler, Alexander; Hylland, Ketil & Gomes, Tania (2022). Double trouble: plastic leachates as drivers for increased adaptations to antibiotics? The effects of plastic leachates and ciprofloxacin on the sea urchin microbiome. Universitetet i Oslo. Full text in Research Archive

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