Sebastian Petters

Cold seeps associated with cold-water corals have been reported worldwide. Yet, there are still knowledge gaps regarding ecological relationships due to contrasting observations. As a part of a larger multidisciplinary project on cold seeps off the Vesterålen coast (northern Norway), we analysed sediment (carbon-nitrogen systematics, foraminifera) and pore fluid (sulfate, dissolved inorganic carbon, methane) geochemistry and seafloor habitats (orthomosaics and habitat maps). Microbial mats are the dominant seep-related community, forming white patches of a few ten cm in diameter, mostly distributed along the edges of methane-derived authigenic carbonates and on sedimented spots. Mats are associated with sulfate-methane transition zones as shallow as 5 cm and high production of 13C-depleted dissolved inorganic carbon, an evidence of ongoing anaerobic oxidation of methane, also recorded in foraminiferal tests. We also report the discovery of a macroscopic white biofilm, observed while slicing a pushcore onboard. Organic matter analyses indicated that the sediment interval hosting this biofilm is associated with a sharp drop in δ13C values, as negative as −43.4 ‰. Results from 16S rRNA gene analyses on the uppermost 10 cm in the same core showed a significant shift in microbial community. Protebacteria-dominated communities near the seafloor transition to a Halobacterota-dominated composition in correspondence of the biofilm interval, with amplicon sequence variants pointing to ANME-1b anaerobic methanotrophs. The presence of a methane-charged sediment substrate leading to carbonate crust formation, the heterogeneous topography and food supply by high-energy currents appears to be a prerequisite for cold-water corals development and their spatial distribution in this area. Our results provide biogeochemical and seafloor habitat context to cold-water corals, contributing to the understanding of potential influence of methane seepage on corals. Furthermore, the produced seafloor orthomosaics and habitat maps will facilitate the monitoring of habitat changes in response to future climate-driven environmental disturbances.

Cold seeps associated with cold-water corals have been reported worldwide. Yet, there are still knowledge gaps regarding ecological relationships due to contrasting observations. Here, we report the results from a multidisciplinary study on cold seeps off the Vesterålen coast (northern Norway) hosting coral mounds. We discuss the geochemical results from sediment (carbon-nitrogen systematics, foraminifera) and pore fluids (sulfate, dissolved inorganic carbon, methane) in relation to seafloor habitats (orthomosaics and habitat maps). Microbial mats are the dominant seep-related community, forming white patches of a few ten cm in diameter, mostly distributed along the edges of methane-derived authigenic carbonates and cracks on top of them. Foraminifera tests in the sediment display negative δ¹³C values down to − 18.5 ‰, suggesting ongoing authigenic carbonate precipitation. We also report the discovery of a macroscopic white biofilm, observed while slicing a pushcore onboard. Organic matter analyses indicated that the sediment interval hosting this biofilm is associated with a sharp drop in δ¹³C values, as negative as −43.4 ‰. Results from 16S rRNA gene analyses on the uppermost 10 cm in the same core showed a significant shift in microbial community. Protebacteria-dominated communities near the seafloor transition to a Halobacterota-dominated composition mainly consisting of ANME-1b anaerobic methanotrophs in correspondence of the biofilm interval. Corals in this area are spatially associated with seafloor chemosynthetic habitats and bubbling, but not vice versa, suggesting that seafloor emissions do not influence coral distribution. Instead, the presence of a methane-charged sediment substrate leading carbonate crust formation and food supply by high-energy currents appears to be a prerequisite for cold-water corals development in this area.

Cold seeps associated with cold-water corals have been reported worldwide. Yet, there are still knowledge gaps regarding ecological relationships due to contrasting observations. Here, we report the results from a multidisciplinary study on cold seeps off the Vesterålen coast (northern Norway) hosting coral mounds. We discuss the geochemical results from sediment (carbon-nitrogen systematics, foraminifera) and pore fluids (sulfate, dissolved inorganic carbon, methane) in relation to seafloor habitats (orthomosaics and habitat maps). Microbial mats are the dominant seep-related community, forming white patches of a few ten cm in diameter, mostly distributed along the edges of methane-derived authigenic carbonates and cracks on top of them. Foraminifera tests in the sediment display negative δ¹³C values down to − 18.5 ‰, suggesting ongoing authigenic carbonate precipitation. We also report the discovery of a macroscopic white biofilm, observed while slicing a pushcore onboard. Organic matter analyses indicated that the sediment interval hosting this biofilm is associated with a sharp drop in δ¹³C values, as negative as −43.4 ‰. Results from 16S rRNA gene analyses on the uppermost 10 cm in the same core showed a significant shift in microbial community. Protebacteria-dominated communities near the seafloor transition to a Halobacterota-dominated composition mainly consisting of ANME-1b anaerobic methanotrophs in correspondence of the biofilm interval. Corals in this area are spatially associated with seafloor chemosynthetic habitats and bubbling, but not vice versa, suggesting that seafloor emissions do not influence coral distribution. Instead, the presence of a methane-charged sediment substrate leading carbonate crust formation and food supply by high-energy currents appears to be a prerequisite for cold-water corals development in this area.

Cold seeps associated with cold-water corals have been reported worldwide. Yet, there are still knowledge gaps regarding ecological relationships due to contrasting observations. Here, we report the results from a multidisciplinary study on cold seeps off the Vesterålen coast (northern Norway) hosting coral mounds. We discuss the geochemical results from sediment (carbon-nitrogen systematics, foraminifera) and pore fluids (sulfate, dissolved inorganic carbon, methane) in relation to seafloor habitats (orthomosaics and habitat maps). Microbial mats are the dominant seep-related community, forming white patches of a few ten cm in diameter, mostly distributed along the edges of methane-derived authigenic carbonates and cracks on top of them. Foraminifera tests in the sediment display negative δ¹³C values down to − 18.5 ‰, suggesting ongoing authigenic carbonate precipitation. We also report the discovery of a macroscopic white biofilm, observed while slicing a pushcore onboard. Organic matter analyses indicated that the sediment interval hosting this biofilm is associated with a sharp drop in δ¹³C values, as negative as −43.4 ‰. Results from 16S rRNA gene analyses on the uppermost 10 cm in the same core showed a significant shift in microbial community. Protebacteria-dominated communities near the seafloor transition to a Halobacterota-dominated composition mainly consisting of ANME-1b anaerobic methanotrophs in correspondence of the biofilm interval. Corals in this area are spatially associated with seafloor chemosynthetic habitats and bubbling, but not vice versa, suggesting that seafloor emissions do not influence coral distribution. Instead, the presence of a methane-charged sediment substrate leading carbonate crust formation and food supply by high-energy currents appears to be a prerequisite for cold-water corals development in this area.

Cold seeps associated with cold-water corals have been reported worldwide. Yet, there are still knowledge gaps regarding ecological relationships due to contrasting observations. Here, we report the results from a multidisciplinary study on cold seeps off the Vesterålen coast (northern Norway) hosting coral mounds. We discuss the geochemical results from sediment (carbon-nitrogen systematics, foraminifera) and pore fluids (sulfate, dissolved inorganic carbon, methane) in relation to seafloor habitats (orthomosaics and habitat maps). Microbial mats are the dominant seep-related community, forming white patches of a few ten cm in diameter, mostly distributed along the edges of methane-derived authigenic carbonates and cracks on top of them. Foraminifera tests in the sediment display negative δ¹³C values down to − 18.5 ‰, suggesting ongoing authigenic carbonate precipitation. We also report the discovery of a macroscopic white biofilm, observed while slicing a pushcore onboard. Organic matter analyses indicated that the sediment interval hosting this biofilm is associated with a sharp drop in δ¹³C values, as negative as −43.4 ‰. Results from 16S rRNA gene analyses on the uppermost 10 cm in the same core showed a significant shift in microbial community. Protebacteria-dominated communities near the seafloor transition to a Halobacterota-dominated composition mainly consisting of ANME-1b anaerobic methanotrophs in correspondence of the biofilm interval. Corals in this area are spatially associated with seafloor chemosynthetic habitats and bubbling, but not vice versa, suggesting that seafloor emissions do not influence coral distribution. Instead, the presence of a methane-charged sediment substrate leading carbonate crust formation and food supply by high-energy currents appears to be a prerequisite for cold-water corals development in this area.

Cold seeps associated with cold-water corals have been reported worldwide. Yet, there are still knowledge gaps regarding ecological relationships due to contrasting observations. Here, we report the results from a multidisciplinary study on cold seeps off the Vesterålen coast (northern Norway) hosting coral mounds. We discuss the geochemical results from sediment (carbon-nitrogen systematics, foraminifera) and pore fluids (sulfate, dissolved inorganic carbon, methane) in relation to seafloor habitats (orthomosaics and habitat maps). Microbial mats are the dominant seep-related community, forming white patches of a few ten cm in diameter, mostly distributed along the edges of methane-derived authigenic carbonates and cracks on top of them. Foraminifera tests in the sediment display negative δ¹³C values down to − 18.5 ‰, suggesting ongoing authigenic carbonate precipitation. We also report the discovery of a macroscopic white biofilm, observed while slicing a pushcore onboard. Organic matter analyses indicated that the sediment interval hosting this biofilm is associated with a sharp drop in δ¹³C values, as negative as −43.4 ‰. Results from 16S rRNA gene analyses on the uppermost 10 cm in the same core showed a significant shift in microbial community. Protebacteria-dominated communities near the seafloor transition to a Halobacterota-dominated composition mainly consisting of ANME-1b anaerobic methanotrophs in correspondence of the biofilm interval. Corals in this area are spatially associated with seafloor chemosynthetic habitats and bubbling, but not vice versa, suggesting that seafloor emissions do not influence coral distribution. Instead, the presence of a methane-charged sediment substrate leading carbonate crust formation and food supply by high-energy currents appears to be a prerequisite for cold-water corals development in this area.

Cold-water corals in the Hola area off the coast of Vesterålen (N. Norway), thrive on a substrate made of methane-derived carbonate and are closely associated with microbial mats. High resolution seafloor imagery and sediment samples collected during the EMAN7 expedition in June 2022 allowed us to reconstruct the spatial relationships between methane seepage and seafloor habitats and gain insights into subsurface biogeochemical processes directly influencing benthic ecosystems. Here, we present the fine-scale orthomosaics and habitat maps covering 1680 m2 of seafloor in proximity to the coral mounds and the geochemistry (sedimentary carbon and nitrogen, pore waters) of a pushcore and blade core collected from a microbial mat and a reference area, respectively. The push core revealed the presence of a macroscopic microbial biofilm at 9 cm depth within the sediment, which is associated with a sharp drop in downcore δ13C of sedimentary organic matter and dissolved inorganic carbon and in C/N ratios. Results from 16S rRNA gene analyses conducted on the uppermost 10 cm of sediment in the pushcore showed a drop in alpha diversity and a compositional change from high abundance of ASVs representing Protebacteria to those representing Halobacterota that we ascribe to the occurrence of methanotrophic consortia performing anaerobic oxidation of methaneAcknowledgments: this research was funded by EMAN7 project (Research Council of Norway grant No. 320100) and supported by AKMA project (Research Council of Norway grant No. 287869) and EXTREMES (UArctic UA 06/2024)

The methane-cycling microbiomes in Arctic permafrost-affected soils play crucial roles in the production and consumption of this important greenhouse gas. However, little is known about the distributions of Arctic methanogens and methanotrophs across the regional scale and along the vertical soil profile, as well as their responses to the widespread permafrost thaw. Using a unique sample set from nine different locations across the pan-Arctic, we identified methanogen and methanotroph phylotypes in 729 datasets of 16S rRNA gene amplicons.In 621 samples of intact permafrost soils across the pan-Arctic, only 22 methanogen and 26 methanotroph phylotypes were identified. Relative abundances of both functional groups varied significantly between sites and soil horizons. Only four methanogen phylotypes were detected at all locations, with the hydrogenotrophic Methanobacterium lacus dominating. Remarkably, the permafrost soil methane filter was almost exclusively comprised of a few phylotypes closely related to the obligate methanotrophic species Methylobacter tundripaludum.In degraded permafrost sites in Alaska, M. tundripaludum also dominated the methanotroph microbiome in the wet site. However, in dry, water-drained former permafrost site, Methylocapsa phylotypes, closely related with the atmospheric methane oxidizing bacteria, were exclusively found and dominant, indicating a massive restructuring of the methanotroph guild that consequently resulted in functional changes from a soil methane filter to an atmospheric methane sink. This study provides first insights into the identity and intricate spatial distribution of methanotrophs and methanogens in permafrost soils at a pan-Arctic scale and their responses to different water status after permafrost degradation. These findings point towards a few key microbes particularly relevant for future studies on Arctic CH4 dynamics in a warming climate and that under future dry conditions more atmospheric CH4 uptake in Arctic upland soils might happen.

Marine microalgae are a promising innovation platform for carbon capture and utilization (CCU) biotechnologies to mitigate industrial greenhouse gas emissions. However, industrial-scale cultivation of algal mono-cultures is challenging and often unscalable. Non-axenic microalgae in large semi-open photobioreactors lead to the co-cultivation of diverse microbial communities. There is limited knowledge about the “bioreactor ecology” involving microalgae interacting with the microbiome and its subsequent impact on process stability and productivity. In this study, we describe the semi-continuous industrial mass cultivation of the cold-adapted marine diatom, Porosira glacialis UiT201, by investigating the prokaryotic and microeukaryotic (phytoplankton and heterotrophic protist) communities. Data were collected in two consecutive time series experiments, representing the initiation and operation of an preindustrial scale CCU photobioreactor (300,000 liters). The first experiment experienced a culture “crash” of the focal strain after 39 days, while the second culture remained stable and “healthy” for 60 days. The results highlight that this mass cultivation system represents a unique industrial marine microbial ecosystem. The succession of the prokaryotic community was primarily driven by species replacement, indicating turnover due to selective bioreactor conditions and/or biological interactions. Nonetheless, the bioreactor consistently harbors a recurring and abundant core microbiome, suggesting that the closely associated bacterial community is influenced by microalgae-specific properties and can endure a dynamic and variable environment. The observed culture collapse of P. glacialis coincided with changes in the core microbiome structure and different environmental growth conditions compared to the stable and “healthy” experiment. These findings imply that cohabiting microbial taxa within industrial microalgae cultivation likely play a critical role in stabilizing the conversion of industrial CO ₂ into marine biomass, and changes in community structure serve as an indicator of process stability.