Articles | Volume 20, issue 5
https://doi.org/10.5194/os-20-1423-2024
© Author(s) 2024. This work is distributed under
the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
https://doi.org/10.5194/os-20-1423-2024
© Author(s) 2024. This work is distributed under
the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
Research article
| 
30 Oct 2024
Research article |
| 30 Oct 2024
| 30 Oct 2024
Alkalinity sources in the Dutch Wadden Sea
Mona Norbisrath
CORRESPONDING AUTHOR
Institute of Carbon Cycles, Helmholtz-Zentrum Hereon, 21502 Geesthacht, Germany
Institute for Chemistry and Biology of the Marine Environment (ICBM), Carl von Ossietzky University of Oldenburg, 26129 Oldenburg, Germany
now at: Department of Marine Chemistry and Geochemistry, Woods Hole Oceanographic Institution, Woods Hole, MA 02543, USA
Justus E. E. van Beusekom
Institute of Carbon Cycles, Helmholtz-Zentrum Hereon, 21502 Geesthacht, Germany
Helmuth Thomas
Institute of Carbon Cycles, Helmholtz-Zentrum Hereon, 21502 Geesthacht, Germany
Institute for Chemistry and Biology of the Marine Environment (ICBM), Carl von Ossietzky University of Oldenburg, 26129 Oldenburg, Germany
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Mona Norbisrath, Andreas Neumann, Kirstin Dähnke, Tina Sanders, Andreas Schöl, Justus E. E. van Beusekom, and Helmuth Thomas
Biogeosciences, 20, 4307–4321, https://doi.org/10.5194/bg-20-4307-2023, https://doi.org/10.5194/bg-20-4307-2023, 2023
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Total alkalinity (TA) is the oceanic capacity to store CO2. Estuaries can be a TA source. Anaerobic metabolic pathways like denitrification (reduction of NO3− to N2) generate TA and are a major nitrogen (N) sink. Another important N sink is anammox that transforms NH4+ with NO2− into N2 without TA generation. By combining TA and N2 production, we identified a TA source, denitrification, occurring in the water column and suggest anammox as the dominant N2 producer in the bottom layer of the Ems.
Mona Norbisrath, Johannes Pätsch, Kirstin Dähnke, Tina Sanders, Gesa Schulz, Justus E. E. van Beusekom, and Helmuth Thomas
Biogeosciences, 19, 5151–5165, https://doi.org/10.5194/bg-19-5151-2022, https://doi.org/10.5194/bg-19-5151-2022, 2022
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Total alkalinity (TA) regulates the oceanic storage capacity of atmospheric CO2. TA is also metabolically generated in estuaries and influences coastal carbon storage through its inflows. We used water samples and identified the Hamburg port area as the one with highest TA generation. Of the overall riverine TA load, 14 % is generated within the estuary. Using a biogeochemical model, we estimated potential effects on the coastal carbon storage under possible anthropogenic and climate changes.
Kubilay Timur Demir, Moritz Mathis, Jan Kossack, Feifei Liu, Ute Daewel, Christoph Stegert, Helmuth Thomas, and Corinna Schrum
EGUsphere, https://doi.org/10.5194/egusphere-2024-3449, https://doi.org/10.5194/egusphere-2024-3449, 2024
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This study examines how variations in the ratios of carbon, nitrogen and phosphorus in organic matter affect carbon cycling in the Northwest European shelf seas. Traditional models with fixed ratios tend to underestimate biological carbon uptake. By integrating variable ratios into a regional model, we find that carbon dioxide uptake increases by 10–33 %. These results highlight the need to include variable ratios for accurate assessments of regional and global carbon cycles.
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The study highlights the inter-seasonal variability of the carbonate dynamics of the East Frisian Wadden Sea, the world's largest intertidal area. During spring, increased biological activity leads to lower CO2 and nitrate levels, while total alkalinity (TA) rises slightly. In summer, TA increases, enhancing the ocean's ability to absorb CO2. Our research emphasizes the vital role of these intertidal regions in regulating carbon, contributing to a better understanding of carbon storage.
Louise C. V. Rewrie, Burkard Baschek, Justus E. E. van Beusekom, Arne Körtzinger, Gregor Ollesch, and Yoana G. Voynova
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After heavy pollution in the 1980s, a long-term inorganic carbon increase in the Elbe Estuary (1997–2020) was fueled by phytoplankton and organic carbon production in the upper estuary, associated with improved water quality. A recent drought (2014–2020) modulated the trend, extending the water residence time and the dry summer season into May. The drought enhanced production of inorganic carbon in the estuary but significantly decreased the annual inorganic carbon export to coastal waters.
Mona Norbisrath, Andreas Neumann, Kirstin Dähnke, Tina Sanders, Andreas Schöl, Justus E. E. van Beusekom, and Helmuth Thomas
Biogeosciences, 20, 4307–4321, https://doi.org/10.5194/bg-20-4307-2023, https://doi.org/10.5194/bg-20-4307-2023, 2023
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Total alkalinity (TA) is the oceanic capacity to store CO2. Estuaries can be a TA source. Anaerobic metabolic pathways like denitrification (reduction of NO3− to N2) generate TA and are a major nitrogen (N) sink. Another important N sink is anammox that transforms NH4+ with NO2− into N2 without TA generation. By combining TA and N2 production, we identified a TA source, denitrification, occurring in the water column and suggest anammox as the dominant N2 producer in the bottom layer of the Ems.
Nele Lehmann, Hugues Lantuit, Michael Ernst Böttcher, Jens Hartmann, Antje Eulenburg, and Helmuth Thomas
Biogeosciences, 20, 3459–3479, https://doi.org/10.5194/bg-20-3459-2023, https://doi.org/10.5194/bg-20-3459-2023, 2023
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Riverine alkalinity in the silicate-dominated headwater catchment at subarctic Iskorasfjellet, northern Norway, was almost entirely derived from weathering of minor carbonate occurrences in the riparian zone. The uphill catchment appeared limited by insufficient contact time of weathering agents and weatherable material. Further, alkalinity increased with decreasing permafrost extent. Thus, with climate change, alkalinity generation is expected to increase in this permafrost-degrading landscape.
Johannes J. Rick, Mirco Scharfe, Tatyana Romanova, Justus E. E. van Beusekom, Ragnhild Asmus, Harald Asmus, Finn Mielck, Anja Kamp, Rainer Sieger, and Karen H. Wiltshire
Earth Syst. Sci. Data, 15, 1037–1057, https://doi.org/10.5194/essd-15-1037-2023, https://doi.org/10.5194/essd-15-1037-2023, 2023
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The Sylt Roads (Wadden Sea) time series is illustrated. Since 1984, the water temperature has risen by 1.1 °C, while pH and salinity decreased by 0.2 and 0.3 units. Nutrients (P, N) displayed a period of high eutrophication until 1998 and have decreased since 1999, while Si showed a parallel increase. Chlorophyll did not mirror these changes, probably due to a switch in nutrient limitation. Until 1998, algae were primarily limited by Si, and since 1999, P limitation has become more important.
Mona Norbisrath, Johannes Pätsch, Kirstin Dähnke, Tina Sanders, Gesa Schulz, Justus E. E. van Beusekom, and Helmuth Thomas
Biogeosciences, 19, 5151–5165, https://doi.org/10.5194/bg-19-5151-2022, https://doi.org/10.5194/bg-19-5151-2022, 2022
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Total alkalinity (TA) regulates the oceanic storage capacity of atmospheric CO2. TA is also metabolically generated in estuaries and influences coastal carbon storage through its inflows. We used water samples and identified the Hamburg port area as the one with highest TA generation. Of the overall riverine TA load, 14 % is generated within the estuary. Using a biogeochemical model, we estimated potential effects on the coastal carbon storage under possible anthropogenic and climate changes.
Bryce Van Dam, Nele Lehmann, Mary A. Zeller, Andreas Neumann, Daniel Pröfrock, Marko Lipka, Helmuth Thomas, and Michael Ernst Böttcher
Biogeosciences, 19, 3775–3789, https://doi.org/10.5194/bg-19-3775-2022, https://doi.org/10.5194/bg-19-3775-2022, 2022
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We quantified sediment–water exchange at shallow sites in the North and Baltic seas. We found that porewater irrigation rates in the former were approximately twice as high as previously estimated, likely driven by relatively high bioirrigative activity. In contrast, we found small net fluxes of alkalinity, ranging from −35 µmol m−2 h−1 (uptake) to 53 µmol m−2 h−1 (release). We attribute this to low net denitrification, carbonate mineral (re-)precipitation, and sulfide (re-)oxidation.
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Biogeosciences, 19, 2007–2024, https://doi.org/10.5194/bg-19-2007-2022, https://doi.org/10.5194/bg-19-2007-2022, 2022
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Estuaries can significantly alter nutrient loads before reaching coastal waters. Our study of the heavily managed Ems estuary (Northern Germany) reveals three zones of nitrogen turnover along the estuary with water-column denitrification in the most upstream hyper-turbid part, nitrate production in the middle reaches and mixing/nitrate uptake in the North Sea. Suspended particulate matter was the overarching control on nitrogen cycling in the hyper-turbid estuary.
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Ocean acidification has a range of potentially harmful consequences for marine organisms. It is related to total alkalinity (TA) mainly produced in oxygen-poor situations like sediments in tidal flats. TA reduces the sensitivity of a water body to acidification. The decomposition of organic material and subsequent TA release in the tidal areas of the North Sea (Wadden Sea) is responsible for reduced acidification in the southern North Sea. This is shown with the results of an ecosystem model.
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Ocean acidification is the process by which the oceans are changing due to carbon dioxide emissions from human activities. Studying this process in the Arctic Ocean is essential as this ocean and its ecosystems are more vulnerable to the effects of acidification. Water chemistry measurements made in recent years show that waters in and around the Canadian Arctic Archipelago are considerably affected by this process and show dynamic conditions that might have an impact on local marine organisms.
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Biogeosciences, 17, 2839–2851, https://doi.org/10.5194/bg-17-2839-2020, https://doi.org/10.5194/bg-17-2839-2020, 2020
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Biogeosciences Discuss., https://doi.org/10.5194/bg-2019-265, https://doi.org/10.5194/bg-2019-265, 2019
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Jacoba Mol, Helmuth Thomas, Paul G. Myers, Xianmin Hu, and Alfonso Mucci
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In the fall of 2014, the upwelling of water from the deep Canada Basin brought water onto the shallower Mackenzie Shelf in the Beaufort Sea. This increased the concentration of CO2 in water on the shelf, which alters pH and changes the transfer of CO2 between the ocean and atmosphere. These findings were a combined result of water sampling for CO2 parameters and the use of a computer model that simulates water movement in the ocean.
Tom J. S. Cox, Justus E. E. van Beusekom, and Karline Soetaert
Biogeosciences, 14, 5271–5280, https://doi.org/10.5194/bg-14-5271-2017, https://doi.org/10.5194/bg-14-5271-2017, 2017
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Photosynthesis by phytoplankton is a key source of oxygen (O2) in aquatic systems. We have developed a mathematical technique to calculate the rate of photosynthesis from time series of O2. Additionally, the approach leads to a better understanding of the influence on O2 measurements of the tides in coasts and estuaries. The results are important for correctly interpreting the data that are gathered by a growing set of continuous O2 sensors that are deployed around the world.
Rachel Hussherr, Maurice Levasseur, Martine Lizotte, Jean-Éric Tremblay, Jacoba Mol, Helmuth Thomas, Michel Gosselin, Michel Starr, Lisa A. Miller, Tereza Jarniková, Nina Schuback, and Alfonso Mucci
Biogeosciences, 14, 2407–2427, https://doi.org/10.5194/bg-14-2407-2017, https://doi.org/10.5194/bg-14-2407-2017, 2017
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This study assesses the impact of ocean acidification on phytoplankton and its synthesis of the climate-active gas dimethyl sulfide (DMS), as well as its modulation, by two contrasting light regimes in the Arctic. The light regimes tested had no significant impact on either the phytoplankton or DMS concentration, whereas both variables decreased linearly with the decrease in pH. Thus, a rapid decrease in surface water pH could alter the algal biomass and inhibit DMS production in the Arctic.
William J. Burt, Helmuth Thomas, Lisa A. Miller, Mats A. Granskog, Tim N. Papakyriakou, and Leah Pengelly
Biogeosciences, 13, 4659–4671, https://doi.org/10.5194/bg-13-4659-2016, https://doi.org/10.5194/bg-13-4659-2016, 2016
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This study assesses the state of the carbon cycle in Hudson Bay, an ecologically important region of the Canadian Arctic. Results show that river input, sea-ice melt, biological activity, and general circulation patterns all have significant, and regionally dependent, impacts on the carbon cycle. The study also highlights the importance of detailed sampling procedures in highly stratified waters, and reveals that the deep Hudson Bay is primarily filled with waters of Pacific origin.
Fabian Große, Naomi Greenwood, Markus Kreus, Hermann-Josef Lenhart, Detlev Machoczek, Johannes Pätsch, Lesley Salt, and Helmuth Thomas
Biogeosciences, 13, 2511–2535, https://doi.org/10.5194/bg-13-2511-2016, https://doi.org/10.5194/bg-13-2511-2016, 2016
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We used the ECOHAM5 model to provide a consistent picture of the physical and biological drivers of oxygen deficiency in the North Sea. Regions susceptible to oxygen deficiency are characterised by low tidal mixing and moderate water depth (~ 40 m). Variations in upper layer productivity drive the year-to-year variability of bottom oxygen conditions. The model-based analysis reveals that benthic and pelagic remineralisation account for 90 % of bottom oxygen consumption observed at North Dogger.
N. Jiao, C. Robinson, F. Azam, H. Thomas, F. Baltar, H. Dang, N. J. Hardman-Mountford, M. Johnson, D. L. Kirchman, B. P. Koch, L. Legendre, C. Li, J. Liu, T. Luo, Y.-W. Luo, A. Mitra, A. Romanou, K. Tang, X. Wang, C. Zhang, and R. Zhang
Biogeosciences, 11, 5285–5306, https://doi.org/10.5194/bg-11-5285-2014, https://doi.org/10.5194/bg-11-5285-2014, 2014
A. Canion, J. E. Kostka, T. M. Gihring, M. Huettel, J. E. E. van Beusekom, H. Gao, G. Lavik, and M. M. M. Kuypers
Biogeosciences, 11, 309–320, https://doi.org/10.5194/bg-11-309-2014, https://doi.org/10.5194/bg-11-309-2014, 2014
S. E. Craig, H. Thomas, C. T. Jones, W. K. W. Li, B. J. W. Greenan, E. H. Shadwick, and W. J. Burt
Biogeosciences Discuss., https://doi.org/10.5194/bgd-10-11255-2013, https://doi.org/10.5194/bgd-10-11255-2013, 2013
Revised manuscript not accepted
W. J. Burt, H. Thomas, K. Fennel, and E. Horne
Biogeosciences, 10, 53–66, https://doi.org/10.5194/bg-10-53-2013, https://doi.org/10.5194/bg-10-53-2013, 2013
Related subject area
Approach: In situ Observations | Properties and processes: Biogeochemistry and nutrient cycles
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Nicolas Metzl, Claire Lo Monaco, Coraline Leseurre, Céline Ridame, Gilles Reverdin, Thi Tuyet Trang Chau, Frédéric Chevallier, and Marion Gehlen
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Short summary
We present an observational study investigating total alkalinity (TA) in the Dutch Wadden Sea. Discrete water samples were used to identify the TA spatial distribution patterns and locate and shed light on TA sources. By observing a tidal cycle, the sediments and pore water exchange were identified as local TA sources. We assumed metabolically driven CaCO3 dissolution as the TA source in the upper, oxic sediments and anaerobic metabolic processes as TA sources in the deeper, anoxic ones.
We present an observational study investigating total alkalinity (TA) in the Dutch Wadden Sea....
