Articles | Volume 22, issue 13
https://doi.org/10.5194/bg-22-3375-2025
© Author(s) 2025. This work is distributed under
the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
https://doi.org/10.5194/bg-22-3375-2025
© Author(s) 2025. This work is distributed under
the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
Research article
| 
11 Jul 2025
Research article |
| 11 Jul 2025
| 11 Jul 2025
Spring–neap tidal cycles modulate the strength of the carbon source at the estuary–coast interface
Department of Coastal Productivity, Institute of Carbon Cycles, Helmholtz-Zentrum Hereon, Max-Planck-Str. 1, 21502 Geesthacht, Germany
Louise C. V. Rewrie
Department of Coastal Productivity, Institute of Carbon Cycles, Helmholtz-Zentrum Hereon, Max-Planck-Str. 1, 21502 Geesthacht, Germany
Rüdiger Röttgers
Department of Optical Oceanography, Institute of Carbon Cycles, Helmholtz-Zentrum Hereon, Max-Planck-Str. 1, 21502 Geesthacht, Germany
Yoana G. Voynova
Department of Coastal Productivity, Institute of Carbon Cycles, Helmholtz-Zentrum Hereon, Max-Planck-Str. 1, 21502 Geesthacht, Germany
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Salem Ibrahim Salem, Andre Valente, Shubha Sathyendranath, Andrei Chuprin, Théo Renard, Jaime Pitarch, Ruth Airs, Moreno Ana, Maria-Manuel Angelico, David Antoine, Robert Arnone, Florinda Artuso, Paulo O. Oliveira, William Balch, Kathryn Barker, Ray Barlow, Simon Bélanger, Marco Bellacicco, Jean-François Berthon, Şükrü Beşiktepe, Francesco Bignami, Yngve Borsheim, Astrid Bracher, Federica Braga, Vittorio Brando, Robert J. W. Brewin, Vanda Brotas, Elisabetta Canuti, Francisco P. Chavez, Andrés Cianca, Hervé Claustre, Lesley Clementson, Simone Colella, Raul Costa, Cristina Nunes, Richard Crout, Emmanuel Devred, Annalisa Di Cicco, Federico Falcini, Ivan Farace, Afonso Ferreira, Scott Freeman, Robert Frouin, Carlos García-Soto, Isabella Giardina, Stuart W. Gibb, Arthur Gleason, Ralf Goericke, Richard Gould, Michael Grant, Nathalie Guillocheau, Hiroto Higa, Stanford B. Hooker, Chuamin Hu, Joji Ishizaka, Thomas Jackson, Mati Kahru, Milton Kampel, Bokyung Kim, Holger Klein, Piotr Kowalczuk, Susanne Kratzer, Raphael Kudela, Antonia Lai, Rosario Lavezza, Jesus Ledesma, Huiwon Lee, Steven Lohrenz, Hubert Loisel, Vivian Lutz, Antonio Mannino, Francesca Margiotta, Victor Martinez-Vicente, Salvatore Marullo, Luca Massi, Patricia Matrai, Atsushi Matsuoka, David McKee, Chiara Melillo, Carlos B. Mendes, Brian G. Mitchell, Tiffany Moisan, Enrique Montes, Frank Muller-Karger, Aimee Neeley, Michael Novak, Leonie O'Dowd, Michael Ondrusek, Emanuele Organelli, Heeyoon Park, Trevor Platt, Francesca Polonelli, Alex Poulton, Mariella Ragni, Michel Repecaud, Maurizio Ribera d’Alcalà, Tamara Rodriguez-Ramos, Rüdiger Röttgers, Manuel Ruiz-Villarreal, Michela Sammartino, Rosalia Santoleri, Gian Marco Scarpa, Thomas Schroeder, Valeria Segura, Timothy Smyth, Denise Smythe-Wright, Heidi M. Sosik, Joanna Stoń-Egiert, Malcolm Taberner, Jing Tan, Rob Thomas, Crystal Thomas, Gavin Tilstone, Andreia Tracana, Michael Twardowski, Vincenzo Vellucci, Gianluca Volpe, Kenneth Voss, Jeremy Werdell, Marcel Wernand, Bozena Wojtasiewicz, Simon Wright, Sunmi Yang, Giuseppe Zibordi, Maria Laura Zoffoli, and Steve Groom
Earth Syst. Sci. Data Discuss., https://doi.org/10.5194/essd-2026-539, https://doi.org/10.5194/essd-2026-539, 2026
Preprint under review for ESSD
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This paper presents the fourth version of the ESA Ocean Colour Climate Change Initiative global in situ bio-optical database. The updated compilation combines observations from many international data sources collected between 1996 and 2025 and includes major expansions in coverage and variables. The dataset provides a consistent reference for validating satellite ocean-colour products and supports algorithm development and long-term climate studies.
Morgan Reed Raven, Nitai Amiel, Dror L. Angel, James P. Barry, Thomas M. Blattmann, Laura Boicenco, Antoine Crémière, Natalya Evans, Nora Gallarotti, Sebastian Haas, Jan-Hendrik Hehemann, Peter Krost, Pranay Lal, David Lordkipanidze, Tiia Luostarinen, Aaron M. Martinez, Allison J. Matzelle, Selma Menabit, Mihaela Muresan, Andreas Neumann, Jean-Daniel Paris, Christopher R. Pearce, Nick Reynard, Daniel L. Sanchez, Florence Schubotz, Violeta Slabakova, Adrian Stanica, Elena Stoica, Andrew K. Sweetman, Tina Treude, Yoana G. Voynova, and Nikolaos D. Zarokanellos
Biogeosciences, 23, 3755–3776, https://doi.org/10.5194/bg-23-3755-2026, https://doi.org/10.5194/bg-23-3755-2026, 2026
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In addition to reducing emissions, vast quantities of CO2 will need to be removed from the atmosphere to meet climate goals. One strategy known as Marine Anoxic Carbon Storage (MACS) would bury plant carbon for thousands of years in parts in the ocean that lack oxygen, where carbon preservation can be highly efficient. We evaluate the environmental and other impacts of hypothetical large-scale MACS deployment from an interdisciplinary, international perspective and present a research roadmap.
Claudia Thölen, Jochen Wollschläger, Michael G. Novak, Rüdiger Röttgers, and Oliver Zielinski
Biogeosciences, 23, 3697–3721, https://doi.org/10.5194/bg-23-3697-2026, https://doi.org/10.5194/bg-23-3697-2026, 2026
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In a mesocosm study, the investigation of colored and fluorescent dissolved organic matter provided information on its transformation, enrichment, and exchange processes within the sea-surface microlayer and the underlying water. Photodegradation was suggested as the main sink, exceeding microbial alteration, and indicating that light and biological processes, such as the induced phytoplankton bloom, jointly shaped organic matter composition under strong vertical mixing.
Annabeth McCall, Martin Hieronymi, P. Paul Overduin, Lisa Bröder, Julie Lattaud, Rüdiger Röttgers, Irina Overeem, Anne Morgenstern, Guido Grosse, and Bennet Juhls
EGUsphere, https://doi.org/10.5194/egusphere-2026-997, https://doi.org/10.5194/egusphere-2026-997, 2026
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This study examines how organic carbon and sediments move from the Mackenzie River through its delta to the Beaufort Sea. Using data from 2009–2024, we show that dissolved and particulate carbon decline offshore, with major changes in low-salinity mixing zones. As water optical properties also shift, satellite carbon estimates require tailored methods. These findings improve understanding of Arctic carbon fluxes and their influence on CO₂ exchange and the greater Arctic Ocean carbon budget.
Martin Hieronymi, Daniel Behr, Shun Bi, and Rüdiger Röttgers
Earth Syst. Sci. Data, 18, 1307–1329, https://doi.org/10.5194/essd-18-1307-2026, https://doi.org/10.5194/essd-18-1307-2026, 2026
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We present a scientific description of a satellite-based dataset and its novel processing chain. The dataset provides water quality parameters for lakes, rivers, coastal waters, as well as the entire North Sea and Baltic Sea. It further includes a novel estimate of organic carbon across diverse water bodies and the results of an optical water type classification. The dataset and its underlying algorithm provide a valuable foundation for future oceanographic and limnological analyses.
Riaz Bibi, Mariana Ribas-Ribas, Leonie Jaeger, Carola Lehners, Lisa Gassen, Edgar Fernando Cortés-Espinoza, Jochen Wollschläger, Claudia Thölen, Hannelore Waska, Jasper Zöbelein, Thorsten Brinkhoff, Isha Athale, Rüdiger Röttgers, Michael Novak, Anja Engel, Theresa Barthelmeß, Josefine Karnatz, Thomas Reinthaler, Dmytro Spriahailo, Gernot Friedrichs, Falko Asmussen Schäfer, and Oliver Wurl
Biogeosciences, 22, 7563–7589, https://doi.org/10.5194/bg-22-7563-2025, https://doi.org/10.5194/bg-22-7563-2025, 2025
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A multidisciplinary mesocosm study was conducted to investigate biogeochemical processes and their relationships in the sea-surface microlayer and underlying water during an induced phytoplankton bloom. Phytoplankton-derived organic matter, fuelled microbial activity and biofilm formation, supporting high bacterial abundance. Distinct temporal patterns in biogeochemical parameters and greater variability in the sea-surface microlayer highlight its influence on air–sea interactions.
Julia Meyer, Yoana G. Voynova, Bryce Van Dam, Lara Luitjens, Dagmar Daehne, and Helmuth Thomas
Biogeosciences, 22, 6255–6273, https://doi.org/10.5194/bg-22-6255-2025, https://doi.org/10.5194/bg-22-6255-2025, 2025
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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
Biogeosciences, 20, 4931–4947, https://doi.org/10.5194/bg-20-4931-2023, https://doi.org/10.5194/bg-20-4931-2023, 2023
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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.
Gesa Schulz, Tina Sanders, Yoana G. Voynova, Hermann W. Bange, and Kirstin Dähnke
Biogeosciences, 20, 3229–3247, https://doi.org/10.5194/bg-20-3229-2023, https://doi.org/10.5194/bg-20-3229-2023, 2023
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Nitrous oxide (N2O) is an important greenhouse gas. However, N2O emissions from estuaries underlie significant uncertainties due to limited data availability and high spatiotemporal variability. We found the Elbe Estuary (Germany) to be a year-round source of N2O, with the highest emissions in winter along with high nitrogen loads. However, in spring and summer, N2O emissions did not decrease alongside lower nitrogen loads because organic matter fueled in situ N2O production along the estuary.
André Valente, Shubha Sathyendranath, Vanda Brotas, Steve Groom, Michael Grant, Thomas Jackson, Andrei Chuprin, Malcolm Taberner, Ruth Airs, David Antoine, Robert Arnone, William M. Balch, Kathryn Barker, Ray Barlow, Simon Bélanger, Jean-François Berthon, Şükrü Beşiktepe, Yngve Borsheim, Astrid Bracher, Vittorio Brando, Robert J. W. Brewin, Elisabetta Canuti, Francisco P. Chavez, Andrés Cianca, Hervé Claustre, Lesley Clementson, Richard Crout, Afonso Ferreira, Scott Freeman, Robert Frouin, Carlos García-Soto, Stuart W. Gibb, Ralf Goericke, Richard Gould, Nathalie Guillocheau, Stanford B. Hooker, Chuamin Hu, Mati Kahru, Milton Kampel, Holger Klein, Susanne Kratzer, Raphael Kudela, Jesus Ledesma, Steven Lohrenz, Hubert Loisel, Antonio Mannino, Victor Martinez-Vicente, Patricia Matrai, David McKee, Brian G. Mitchell, Tiffany Moisan, Enrique Montes, Frank Muller-Karger, Aimee Neeley, Michael Novak, Leonie O'Dowd, Michael Ondrusek, Trevor Platt, Alex J. Poulton, Michel Repecaud, Rüdiger Röttgers, Thomas Schroeder, Timothy Smyth, Denise Smythe-Wright, Heidi M. Sosik, Crystal Thomas, Rob Thomas, Gavin Tilstone, Andreia Tracana, Michael Twardowski, Vincenzo Vellucci, Kenneth Voss, Jeremy Werdell, Marcel Wernand, Bozena Wojtasiewicz, Simon Wright, and Giuseppe Zibordi
Earth Syst. Sci. Data, 14, 5737–5770, https://doi.org/10.5194/essd-14-5737-2022, https://doi.org/10.5194/essd-14-5737-2022, 2022
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A compiled set of in situ data is vital to evaluate the quality of ocean-colour satellite data records. Here we describe the global compilation of bio-optical in situ data (spanning from 1997 to 2021) used for the validation of the ocean-colour products from the ESA Ocean Colour Climate Change Initiative (OC-CCI). The compilation merges and harmonizes several in situ data sources into a simple format that could be used directly for the evaluation of satellite-derived ocean-colour data.
Kirstin Dähnke, Tina Sanders, Yoana Voynova, and Scott D. Wankel
Biogeosciences, 19, 5879–5891, https://doi.org/10.5194/bg-19-5879-2022, https://doi.org/10.5194/bg-19-5879-2022, 2022
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Nitrogen is an important macronutrient that fuels algal production in rivers and coastal regions. We investigated the production and removal of nitrogen-bearing compounds in the freshwater section of the tidal Elbe Estuary and found that particles in the water column are key for the production and removal of water column nitrate. Using a stable isotope approach, we pinpointed regions where additional removal of nitrate or input from sediments plays an important role in estuarine biogeochemistry.
Gesa Schulz, Tina Sanders, Justus E. E. van Beusekom, Yoana G. Voynova, Andreas Schöl, and Kirstin Dähnke
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.
Tristan Petit, Børge Hamre, Håkon Sandven, Rüdiger Röttgers, Piotr Kowalczuk, Monika Zablocka, and Mats A. Granskog
Ocean Sci., 18, 455–468, https://doi.org/10.5194/os-18-455-2022, https://doi.org/10.5194/os-18-455-2022, 2022
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We provide the first insights on bio-optical processes in Storfjorden (Svalbard). Information on factors controlling light propagation in the water column in this arctic fjord becomes crucial in times of rapid sea ice decline. We find a significant contribution of dissolved matter to light absorption and a subsurface absorption maximum linked to phytoplankton production. Dense bottom waters from sea ice formation carry elevated levels of dissolved and particulate matter.
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Short summary
We found that biogeochemical variability at the land–sea interface (LSI) in two major temperate estuaries is modulated by the 14 d spring–neap tidal cycle, with large effects on dissolved inorganic and organic carbon concentrations and distribution. As this effect increases the strength of the carbon source to the atmosphere by up to 74 % during spring tide, it should be accounted for in regional models, which aim to resolve biogeochemical processing at the LSI.
We found that biogeochemical variability at the land–sea interface (LSI) in two major temperate...
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