Articles | Volume 21, issue 6
https://doi.org/10.5194/os-21-3471-2025
© Author(s) 2025. This work is distributed under
the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
Special issue:
https://doi.org/10.5194/os-21-3471-2025
© 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 Dec 2025
Research article |
| 11 Dec 2025
| 11 Dec 2025
Diel variability affects the inorganic carbon system in the sea-surface microlayer and influences air-sea CO2 flux estimates
Ander López-Puertas
CORRESPONDING AUTHOR
Center for Marine Sensors (ZfMarS), Institute for Chemistry and Biology of the Marine Environment (ICBM), School of Mathematics and Science, Carl von Ossietzky Universität Oldenburg, Ammerländer Heerstraße 114–118, 26129 Oldenburg, Germany
Instituto Universitario de Investigación Marina (INMAR), Universidad de Cádiz, 11510, Puerto Real, Cádiz, Spain
Oliver Wurl
Center for Marine Sensors (ZfMarS), Institute for Chemistry and Biology of the Marine Environment (ICBM), School of Mathematics and Science, Carl von Ossietzky Universität Oldenburg, Ammerländer Heerstraße 114–118, 26129 Oldenburg, Germany
Sanja Frka
Laboratory for Marine and Atmospheric Biogeochemistry, Division for Marine and Environmental Research, Ruđer Bošković Institute, Bijenicka c. 54, 10000 Zagreb, Croatia
Mariana Ribas-Ribas
Center for Marine Sensors (ZfMarS), Institute for Chemistry and Biology of the Marine Environment (ICBM), School of Mathematics and Science, Carl von Ossietzky Universität Oldenburg, Ammerländer Heerstraße 114–118, 26129 Oldenburg, Germany
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Amavi Silva, Surandokht Nikzad, Theresa Barthelmeß, Anja Engel, Hartmut Herrmann, Manuela van Pinxteren, Kai Wirtz, Oliver Wurl, and Markus Schartau
Biogeosciences, 23, 1697–1718, https://doi.org/10.5194/bg-23-1697-2026, https://doi.org/10.5194/bg-23-1697-2026, 2026
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We conducted the first meta-analysis combining marine and freshwater studies to understand organic matter enrichment in the surface microlayer. Nitrogen-rich, particulate compounds are often enriched, with patterns varying by multiple factors. We recommend tracking both absolute concentrations and normalized enrichment patterns to better assess ecological conditions. Our study also introduces improved statistical methods for analyzing and comparing surface microlayer data.
Carsten Rauch, Lisa Deyle, Leonie Jaeger, Edgar Fernando Cortés-Espinoza, Mariana Ribas-Ribas, Josefine Karnatz, Anja Engel, and Oliver Wurl
Ocean Sci., 22, 403–426, https://doi.org/10.5194/os-22-403-2026, https://doi.org/10.5194/os-22-403-2026, 2026
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Microsensors measuring oxygen and temperature were used to gain high-resolution profiles across the surface of a water basin, in which an algal bloom was induced. These novel data show that the oxygen at the sea surface is highly influenced by algal blooms, while the temperature is only indirectly affected by them. Since algal blooms occur globally, this has considerable implications for calculating global air-sea exchanges of gases or heat, especially under low-wind conditions.
Lina A. Holthusen, Hermann W. Bange, Thomas H. Badewien, Julia C. Muchowski, Tina Santl-Temkiv, Jennie Spicker Schmidt, Oliver Wurl, and Damian L. Arévalo-Martínez
The Cryosphere, 20, 535–550, https://doi.org/10.5194/tc-20-535-2026, https://doi.org/10.5194/tc-20-535-2026, 2026
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In spring 2023, in the Fram Strait, we investigated the near-surface distribution of the greenhouse gases methane and nitrous oxide in open leads and under sea ice to address the lack of observations in the Arctic Ocean. The study area acted as a source for both gases, and the onset of sea ice melt affected their concentrations and emissions. Surface-active substances accumulated in the sea-surface microlayer of open leads during an algal bloom, potentially attenuating greenhouse gas emissions.
Falko Asmussen-Schäfer, Mariana Ribas-Ribas, Oliver Wurl, and Gernot Friedrichs
EGUsphere, https://doi.org/10.5194/egusphere-2025-5276, https://doi.org/10.5194/egusphere-2025-5276, 2026
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We developed a way to quantify how molecules accumulate at the ocean surface on a nanometer scale. Using laser spectroscopy and electrochemical methods, we measured how densely these molecular films cover the water surface. Such single-molecule-thick layers can greatly influence gas exchange between the ocean and the atmosphere. By comparing our results with existing data sets, we produced a first global estimate of potential film coverage.
Jasper Zöbelein, Shubham Sawle, Gernot Friedrichs, Mariana Ribas-Ribas, Carola Lehners, Katharina Paetz, Maximilian Pflaum, and Hannelore Waska
EGUsphere, https://doi.org/10.5194/egusphere-2025-6563, https://doi.org/10.5194/egusphere-2025-6563, 2026
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The ocean is glazed with a one-millimetre biofilm that controls the flow of gases and energy from the atmosphere. To investigate how this film forms, we cultivated microscopic algae in a tank under controlled, windless conditions. Our results show that carbohydrates released by these algae rise to the surface, forming "carbo-slicks" that create this gel-like layer. This demonstrates that biological production is a key driver of the sea surface, which is crucial for understanding carbon exchange.
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.
Edgar Fernando Cortés-Espinoza, Alisa Wüst, Ander Lopéz-Puertas, Oliver Wurl, José Martín Hernández-Ayón, Hannelore Waska, and Mariana Ribas-Ribas
EGUsphere, https://doi.org/10.5194/egusphere-2025-5265, https://doi.org/10.5194/egusphere-2025-5265, 2025
This preprint is open for discussion and under review for Biogeosciences (BG).
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In a mesocosm experiment, we measured carbon system variables to examine how organic matter accumulation increases organic alkalinity and alters seawater pH in the sea-surface microlayer and underlying water during an induced phytoplankton bloom. Organic alkalinity was consistently higher in the sea-surface microlayer, and during bloom peak its pH effect extended into the underlying water, reducing and sometimes reversing surface–subsurface pH differences.
Lisa Gassen, Samuel M. Ayim, Leonie Jaeger, Jens Meyerjürgens, Mariana Ribas-Ribas, and Oliver Wurl
Ocean Sci., 21, 2787–2804, https://doi.org/10.5194/os-21-2787-2025, https://doi.org/10.5194/os-21-2787-2025, 2025
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This study investigates how abrupt weather changes, such as shifts in air temperature, wind speed and precipitation, impact temperature and salinity in the ocean’s skin layer (upper first millimetre). Two events in the harbour of Bremerhaven and one event in the North Sea revealed that the skin layer reacts instantly, with greater temperature changes than those at a depth of 100 cm, underscoring its key role in air-sea interactions and climate dynamics.
Michelle Albinus, Thomas H. Badewien, Lisa Gassen, Oliver Wurl, and Jens Meyerjürgens
EGUsphere, https://doi.org/10.5194/egusphere-2025-4953, https://doi.org/10.5194/egusphere-2025-4953, 2025
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This study reveals how short-lived and narrow freshwater-driven ocean "light" filaments form and evolve within tidal fronts. Using multi-platform in situ observations, it is shown that these submesoscale features can rapidly form and reshape in near-surface waters, influencing how energy and heat alter just below the ocean-atmosphere interface.
Lisa Deyle, Thomas H. Badewien, Oliver Wurl, and Jens Meyerjürgens
Earth Syst. Sci. Data, 16, 2099–2112, https://doi.org/10.5194/essd-16-2099-2024, https://doi.org/10.5194/essd-16-2099-2024, 2024
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A dataset from the North Sea of 85 surface drifters from 2017–2021 is presented. Surface drifters enable the analysis of ocean currents by determining the velocities of surface currents and tidal effects. The entire North Sea has not been studied using drifters before, but the analysis of ocean currents is essential, e.g., to understand the pathways of plastic. The results show that there are strong tidal effects in the shallow North Sea area and strong surface currents in the deep areas.
Manuela van Pinxteren, Sebastian Zeppenfeld, Khanneh Wadinga Fomba, Nadja Triesch, Sanja Frka, and Hartmut Herrmann
Atmos. Chem. Phys., 23, 6571–6590, https://doi.org/10.5194/acp-23-6571-2023, https://doi.org/10.5194/acp-23-6571-2023, 2023
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Important marine organic carbon compounds were identified in the Atlantic Ocean and marine aerosol particles. These compounds were strongly enriched in the atmosphere. Their enrichment was, however, not solely explained via sea-to-air transfer but also via atmospheric in situ formation. The identified compounds constituted about 50 % of the organic carbon on the aerosol particles, and a pronounced coupling between ocean and atmosphere for this oligotrophic region could be concluded.
Manuela van Pinxteren, Tiera-Brandy Robinson, Sebastian Zeppenfeld, Xianda Gong, Enno Bahlmann, Khanneh Wadinga Fomba, Nadja Triesch, Frank Stratmann, Oliver Wurl, Anja Engel, Heike Wex, and Hartmut Herrmann
Atmos. Chem. Phys., 22, 5725–5742, https://doi.org/10.5194/acp-22-5725-2022, https://doi.org/10.5194/acp-22-5725-2022, 2022
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A class of marine particles (transparent exopolymer particles, TEPs) that is ubiquitously found in the world oceans was measured for the first time in ambient marine aerosol particles and marine cloud waters in the tropical Atlantic Ocean. TEPs are likely to have good properties for influencing clouds. We show that TEPs are transferred from the ocean to the marine atmosphere via sea-spray formation and our results suggest that they can also form directly in aerosol particles and in cloud water.
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Short summary
We studied how daily cycles affect inorganic carbon variables in the ocean's surface microlayer. Using data from three full days and nights off the Croatian coast, we found that thermohaline properties and key indicators like pH and pCO₂ change significantly from day to night. Ignoring nighttime conditions may lead to global carbon budget errors and highlights the need for continuous ocean observations.
We studied how daily cycles affect inorganic carbon variables in the ocean's surface microlayer....
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