This article from Muhammed Fatih Sert reports on the connectivity between cold seeps and coral reefs through the dissolved organic carbon (DOC) cycle, revealing a potential duality: – Cold seep-derived organic carbon fuels cold-water corals, acting as a carbon and energy source. – At the same time, seep-driven inorganic carbon plays a role in water column redox, making corals more vulnerable.
Cold seeps are geological features that release methane from the seabed to the water column. In oxygenated sea water column, seeping methane is consumed by specialized microbes that convert it into carbon dioxide. Although the increase in carbon dioxide can lead to ocean acidification, cold seeps are often found in the Hola trough of Northern Norway near cold-water corals (CWCs), which are vulnerable to changes in ocean acidity. This raises questions about how these features coexist in the same marine ecosystem and how they impact each other. We investigated the carbon exchange between cold seeps and CWCs by analyzing seawater samples. Our data on nutrients, organic matter, and microbial compositions implied cooccurring carbon processes such as methane oxidation and organic matter synthesis. Notably, cold seeps might support CWCs by producing dissolved organic matter that corals feed on. However, this relationship may be valid for a moderate amount of methane release. If methane release increases, consequent acidification may influence the CWC reefs in the future.
The 1st EMAN7 publication has been published in Journal of Geophysical Research: Oceans! In the article “Contrasting Methane Seepage Dynamics in the Hola Trough Offshore Norway: Insights From Two Different Summers”, we show that increased bottom temperature and low tide conditions boost methane activity, while strong currents and intermittent seep activity explain the thinly distributed microbial mats and low methane concentrations in the Hola Trough.
1Department of Geosciences, UiT-The Arctic University of Norway, Tromsø, Norway
2Department of Earth and Environmental Sciences, University of Milano-Bicocca, Milano, Italy
Methane seepage in the Hola area off the coast of Vesterålen (N. Norway) has long been known for its peculiar association with cold-water coral mounds, but only recently it was possible to explore the distribution of seafloor ecosystems using a Remotely Operated Vehicle (ROV) and to conduct microhabitat-specific samplings for biogeochemical investigations. Here, we describe the results from sediment (carbon-nitrogen systematics) and pore fluid geochemistry (sulfate, dissolved inorganic carbon, methane) and interpret them in relation to the seafloor ecosystems. Microbial mats are the dominant seep-related community and form small white patches of a few tens of cm in diameter located at various distances from the coral mounds. Seep carbonates are widespread at this location and form extensive pavements. The seafloor distribution of methane bubbling and chemosynthetic communities seem controlled by fractures in the carbonates. Microbial mats are associated with intense sulfate-driven anaerobic oxidation of methane producing shallow sulfate-methane transitions coupled with highly 13C-depleted dissolved inorganic carbon in the pore water.
Acknowledgments: this research was supported by Eman7 project (Research Council of Norway grant No. 320100) and AKMA project (Research Council of Norway grant No. 287869).
How to cite: Argentino, C., Panieri, G., Fallati, L., Savini, A., Barrenechea Angeles, I., Akinselure, A., and Ferré, B.: Biogeochemistry of seep-impacted sediments at a cold-water coral site off the Vesterålen coast, Northern Norway, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-6944, https://doi.org/10.5194/egusphere-egu24-6944, 2024.
Modeling the fate of methane in the water column by model coupling
Knut Ola Dølven1,Håvard Espenes2,Magnus Drivdal2,Muhammed Fatih Serth1,and Bénédicte Férré1
1UiT, The Arctic University of Norway, Department of Geoscience, Tromsø, Norway (knut.o.dolven@uit.no)
Estimates of atmospheric methane emissions due to seabed methane seepage are hard to constrain. Additionally, high concentrations of methane can have an impact on local biology due to local ocean acidification. In both cases, better tools for modeling the fate of methane in the water column are needed.
We present a new approach where we include and couple a wide range of water column processes by using several already verified models in tandem, attempting to form a complete modelling framework for the fate of methane in the water column. Included processes are gas phase changes, advection, dilution, direct and diffusive atmospheric flux and microbial oxidation. The modelling framework allows for a complete estimate of atmospheric emissions, both direct and diffusive fluxes, as well as the 3-dimensional distribution of methane in the water column. The framework can be applied to specific seep sites of interest using hydroacoustic data as input. Additionally, it is also possible to simulate atmospheric fluxes in potential edge cases and future scenarios in areas where local seepage is expected to change or is unknown.
We tested the methodology using hydroacoustic field data from a seep site in the Hola trough offshore North-Western Norway in Spring 2020. We calculated both direct and diffusive atmospheric methane fluxes, distribution of methane in the water column and its potential for affecting local biology due to acidification.
How to cite: Dølven, K. O., Espenes, H., Drivdal, M., Serth, M. F., and Férré, B.: Modeling the fate of methane in the water column by model coupling, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-20009, https://doi.org/10.5194/egusphere-egu24-20009, 2024.
Carbon cycling in coexisting marine ecosystems: Cold seeps and coral reefs in Northern Norway
Muhammed Fatih Sert1,Knut Ola Dølven1,Sebastian Petters2,Timo Kekäläinen3,Janne Jänis3,Jorge Corrales-Guerrero4,and Bénédicte Ferré1
1UiT- The Arctic University of Norway, Geosciences Department, Norway (muhammed.f.sert@uit.no)
2Faculty of Biosciences, Fisheries, and Economics, UiT-The Arctic University of Norway, Tromsø, Norway
3Department of Chemistry, Faculty of Science and Forestry, University of Eastern Finland, Joensuu, Finland
4Institute of Marine Research, Bergen, Norway
Cold seeps and cold water corals (CWCs) coexist on Northern Norway’s continental shelf at the Hola trough between Lofoten and Vesterålen. Here, cold seeps release methane from the seabed, yet only a limited amount reaches the atmosphere. The remaining methane dissolves and disperses in nearby seeps. Methane is unreactive for most microorganisms in the water column, yet it is a unique energy and carbon source for methane-oxidizing bacteria (MOB). MOBs metabolize methane and release carbon dioxide as the end product of oxidation. Increasing carbon dioxide may constrain pH-sensitive CWCs in the region. We investigated the biogeochemistry of carbon, carbon isotopes, nutrients, dissolved organic matter (DOM) compositions and microbial diversity through water column profiles and water samples collected in June 2022. Preliminary results indicated that elevated methane increases dissolved inorganic carbon concentrations and modifies carbon isotopic compositions. Additionally, DOM compositions implied a positive correlation between prokaryotic diversity and protein-like DOM components at cold seeps and the entire water column near CWCs, suggesting analogous microbial modifications. Our preliminary conclusion suggests cold seeps and CWCs symbiotically coexist in Northern Norway continental shelves; however, enhanced water temperatures and consequent increase in methane release at cold seeps may mitigate the functioning of CWCs in future.
This study is supported by the Research Council of Norway, project number 320100, through the project EMAN7 (Environmental impact of Methane seepage and sub-seabed characterization at LoVe-Node 7).
How to cite: Sert, M. F., Dølven, K. O., Petters, S., Kekäläinen, T., Jänis, J., Corrales-Guerrero, J., and Ferré, B.: Carbon cycling in coexisting marine ecosystems: Cold seeps and coral reefs in Northern Norway, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-3890, https://doi.org/10.5194/egusphere-egu24-3890, 2024.
EMAN7: understanding methane seepage dynamics in the Hola Trough
Bénédicte Ferré1,Thibaut Barreyre2,3,stefan Bünz1,Claudio Argentino1,Jorge Corrales-Guerrero4,Knut Ola Dølven1,Marie Stetzler1,Luca Fallati5,Muhamed Fatih Sert1,Giuliana Panieri1,Samuel Rastrick4,Tina Kutti4,and Manuel Moser1
1Department of Geosciences, UiT the Arctic University of Norway, Tromsø, Norway (benedicte.ferre@uit.no)
2Department of Earth Science/K.G. Jebsen Centre for Deep Sea Research, University of Bergen, Bergen, Norway
3Geo-Ocean, CNRS, Univ Brest, Ifremer, UMR6538, F-29280 Plouzané, France
4Institute of Marine Research, Bergen, Norway
5Department of Earth and Environmental Sciences (DISAT), University of Milano-Bicocca, Milano, Italy
The Hola Trough, offshore Norway’s Lofoten-Vesterålen (LoVe) area, has been of interest for many years due to its rich marine life and potential oil and gas resources. There, coral mounds thrive around methane seepage. The LoVe observatory network monitors this unique environment. Using this observatory platform, associated dataset and research expeditions at sea, the project EMAN7 (Environmental impact of Methane seepage and sub-seabed characterization at LoVe-Node 7) aims to understand the environmental impact of methane seepage as well as its spatio-temporal variability.
The comparison of methane seep activity during two summers with different environmental conditions revealed 3.5 times more seeps when a combination of warmer bottom water and low tide changes the sediment pore pressure. Piezometer data, recording subseafloor pore pressure and bottom temperature, support these findings. Sub-seafloor investigations identified pathways for gas migration in methane seep areas, influenced by topography.
This study is supported by the Research Council of Norway, project number 320100, through the project EMAN7.
How to cite: Ferré, B., Barreyre, T., Bünz, S., Argentino, C., Corrales-Guerrero, J., Dølven, K. O., Stetzler, M., Fallati, L., Sert, M. F., Panieri, G., Rastrick, S., Kutti, T., and Moser, M.: EMAN7: understanding methane seepage dynamics in the Hola Trough, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-8501, https://doi.org/10.5194/egusphere-egu24-8501, 2024.
Claudio Argentino (3rd from the right) presented data from the Hola area off the coast of Vesterålen (N. Norway) at the conference GIMS15: Gas in Marine Sediments. During the conference he described imagery, sediment and pore fluid datasets collected in 2022 that his group combined to reconstruct biogeochemical processes in the sediment and their control over seafloor ecosystems. The conference was set in Cadiz (Spain), so he had the opportunity to visit the oldest city in Europe, founded by Phoenicians over three thousand years ago.
The first cruise of EMAN7 occurred from June 8th to 16th 2022 onboard RV Kronprins Haakon. Using the equipment from the ship and the ROV Ægir6000, we collected visual and physical data in order to characterize the seafloor, subseafloor and the local biology as well the water column and bubbles escaping the seafloor. We also performed corals transplant to study adaptation and installed Piezometers and temperature probes for fluid flow calculation. A blog of the cruise can be found following this link, and the cruise report can be found here.
Scientific and technical crewRV Kronsprins HaakonROV ÆGIR6000
