Articles | Volume 22, issue 23
https://doi.org/10.5194/bg-22-7865-2025
© 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-22-7865-2025
© Author(s) 2025. This work is distributed under
the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
Research article
| 
09 Dec 2025
Research article |
| 09 Dec 2025
| 09 Dec 2025
Wet and dry seasons modulate coastal coccolithophore dynamics off South-western Nigeria (Gulf of Guinea)
Falilu O. Adekunbi
Department of Marine Sciences, Faculty of Science, University of Lagos (UNILAG), Lagos, Nigeria
Nigerian Institute for Oceanography and Marine Research, (NIOMR) Lagos, Nigeria
Institut de Ciència i Tecnologia Ambientals (ICTA-UAB), Universitat Autònoma de Barcelona, Barcelona, Spain
Institut de Ciència i Tecnologia Ambientals (ICTA-UAB), Universitat Autònoma de Barcelona, Barcelona, Spain
Gerald Langer
Institut de Ciència i Tecnologia Ambientals (ICTA-UAB), Universitat Autònoma de Barcelona, Barcelona, Spain
Marine Biogeosciences, Alfred-Wegener-Institut, Helmholtz-Zentrum für Polar- und Meeresforschung, Bremerhaven, Germany
Lucian O. Chukwu
Department of Marine Sciences, Faculty of Science, University of Lagos (UNILAG), Lagos, Nigeria
Marta Alvarez
Instituto Español de Oceanografía (IEO-CSIC), A Coruña, Spain
Shakirudeen Odunuga
Department of Geography, Faculty of Social Sciences, University of Lagos (UNILAG), Lagos, Nigeria
Kai G. Schulz
Centre for Coastal Biogeochemistry, School of Environment Science and Engineering, Southern Cross University, Lismore, NSW 2480, Australia
Patrizia Ziveri
Institut de Ciència i Tecnologia Ambientals (ICTA-UAB), Universitat Autònoma de Barcelona, Barcelona, Spain
Catalan Institution for Research and Advanced Studies (ICREA), Barcelona, Spain
Departamento de Biología Animal, Biología Vegetal y Ecología, Universitat Autònoma de Barcelona, Barcelona, (ICTA-UAB), Spain
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Marta Álvarez, Maribel I. García-Ibáñez, Nico Lange, Alex Kozyr, Antón Velo, Toste Tanhua, Giuseppe Civitarese, Carolina Cantoni, Malek Belgacem, Katrin Schroeder, Rubén Acerbi, Laurent Coppola, Thibaut Wagener, Noelia M. Fajar, Susana Flecha, Michele Giani, Louisa Giannoudi, Elisa F. Guallart, Abed El Rahman Hassoun, Emma I. Huertas, Valeria Ibello, Mehdia A. Keraghel, Férial Louanchi, Anna Luchetta, Fiz F. Pérez, Carsten Schirnick, Ekaterini Souvermezoglou, Lidia Urbini, Montserrat Vidal, and Patrizia Ziveri
Earth Syst. Sci. Data, 18, 4915–4941, https://doi.org/10.5194/essd-18-4915-2026, https://doi.org/10.5194/essd-18-4915-2026, 2026
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CARIMED (CARbon, tracers, and ancillary data In the MEDiterranean Sea) is a high-quality, FAIR (Findability, Accessibility, Interoperability, and Reusability) dataset integrating hydrographic, biogeochemical, and transient tracer data from 46 research cruises (1976–2018) across the Mediterranean Sea. The data underwent rigorous, basin-adapted quality control to remove systematic biases, unifying four decades of fragmented data, delivering two complementary products: the aggregated original cruise data product and the bias-adjusted data synthesis product.
Philipp Suessle, Kai Georg Schulz, Joana Barcelos e Ramos, Nico Manuel Sievers, Julieta Schneider, Juliane Katharina Tammen, Leila Kittu, Laura Marín-Samper, Maarten Boersma, and Ulf Riebesell
Biogeosciences, 23, 4691–4710, https://doi.org/10.5194/bg-23-4691-2026, https://doi.org/10.5194/bg-23-4691-2026, 2026
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Ocean alkalinity enhancement (OAE) is a negative emission technology that may alter marine diatom communities and particle export. We show that unequilibrated OAE did not change bloom magnitude or particle fluxes, but reduced silica ballasting. The losses intensified during sinking, consistent with pH-enhanced silica dissolution. Our results show that OAE can modify biological-pump efficiency through export-phase alteration of BSi:POC, even when community biomass production remains unchanged.
Athina Kekelou, Gerald Langer, and Patrizia Ziveri
Biogeosciences, 23, 2831–2845, https://doi.org/10.5194/bg-23-2831-2026, https://doi.org/10.5194/bg-23-2831-2026, 2026
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Fish otolith formation is key for understanding the incorporation of elements into biominerals. It is often assumed that the final step of biomineralization consists of inorganic precipitation as the fluid where biominerals form can hardly be sampled. Thanks to fish ear anatomy, this can be overcome with otoliths. By comparing otolith formation and inorganic precipitation, we proved that this assumption is not always true. Our findings could refine models and shed light on biomineralization.
Gerald Langer, Ian Probert, Jeremy R. Young, and Patrizia Ziveri
Biogeosciences, 23, 1795–1808, https://doi.org/10.5194/bg-23-1795-2026, https://doi.org/10.5194/bg-23-1795-2026, 2026
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Coccolithophores are important marine CaCO3 producers and their biominerals, the coccoliths, partly dissolve in the upper water column where dissolution is unexpected. Studying coccolith dissolution in field samples is hampered by a paucity of experimental studies describing dissolution morphologies. Here we fill this gap by experimentally dissolving different coccolithophores and applying our results to field samples.
Fiz F. Pérez, Marta López-Mozos, Marcos Fontela, Maribel I. García-Ibáñez, Noelia Fajar, Xosé Antonio Padín, Mónica Castaño-Carrera, Mercedes de la Paz, Lidia I. Carracedo, Marta Álvarez, Herlé Mercier, Pascale Lherminier, and Antón Velo
Earth Syst. Sci. Data, 18, 801–821, https://doi.org/10.5194/essd-18-801-2026, https://doi.org/10.5194/essd-18-801-2026, 2026
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Ocean acidification threatens marine ecosystems and the climate and is commonly assessed through ocean pH measurements. This study provides a new twenty-year dataset of pH measurements from the North Atlantic, derived from the correction and reevaluation of both historical and recent pH measurements affected by methodological bias. This revised dataset enables a more accurate reassessment of pH trends and carbon variables under novel and updated methodological standards.
Julieta Schneider, Ulf Riebesell, Charly André Moras, Laura Marín-Samper, Leila Richards Kittu, Joaquín Ortíz-Cortes, and Kai Georg Schulz
Biogeosciences, 23, 137–153, https://doi.org/10.5194/bg-23-137-2026, https://doi.org/10.5194/bg-23-137-2026, 2026
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Ocean Alkalinity Enhancement (OAE) is an approach to sequester atmospheric CO2 in the ocean and may alleviate ocean acidification. A large-scale mesocosm experiment in Norway tested calcium- and silicate-based OAE, increasing total alkalinity (TA) by 0–600 µmol kg-1 and measuring CO2 gas exchange. While TA remained stable, we found mineral-type and/or pCO2/pH effects on coccolithophorid calcification, net community production and zooplankton respiration, providing insights for future OAE trials.
Malek Belgacem, Katrin Schroeder, Marta Álvarez, Siv K. Lauvset, Jacopo Chiggiato, Mireno Borghini, Carolina Cantoni, Tiziana Ciuffardi, and Stefania Sparnocchia
Earth Syst. Sci. Data, 17, 5315–5336, https://doi.org/10.5194/essd-17-5315-2025, https://doi.org/10.5194/essd-17-5315-2025, 2025
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The Mediterranean Sea is changing rapidly, underscoring the urgent need for high-quality datasets to quantify trends and assess impacts on biogeochemical cycles. O2 is a key indicator of marine ecosystem health and plays a central role in CO2 and nutrient cycling. We compiled a regional-scale dataset of O2 in the western Mediterranean to provide a robust observational foundation for assessing O2 variability, associated with climate change, and anomalies related to deoxygenation processes.
Stefania Bianco, Manuela Bordiga, Gerald Langer, Patrizia Ziveri, Federica Cerino, Andrea Di Giulio, and Claudia Lupi
Biogeosciences, 22, 1821–1837, https://doi.org/10.5194/bg-22-1821-2025, https://doi.org/10.5194/bg-22-1821-2025, 2025
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This work focuses on the response in culture experiments to increasing CO2 of the coccolithophore species Helicosphaera carteri, a unicellular marine calcifying microalgae. The absence of significant changes in coccolith malformations, along with stable size, shape, and calcification-to-photosynthesis ratio, is indicative of H. carteri low sensitivity to CO2 rise, together with its ability to maintain a stable contribution to the marine rain ratio under future climate changes.
Lennart Thomas Bach, Aaron James Ferderer, Julie LaRoche, and Kai Georg Schulz
Biogeosciences, 21, 3665–3676, https://doi.org/10.5194/bg-21-3665-2024, https://doi.org/10.5194/bg-21-3665-2024, 2024
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Ocean alkalinity enhancement (OAE) is an emerging marine CO2 removal method, but its environmental effects are insufficiently understood. The OAE Pelagic Impact Intercomparison Project (OAEPIIP) provides funding for a standardized and globally replicated microcosm experiment to study the effects of OAE on plankton communities. Here, we provide a detailed manual for the OAEPIIP experiment. We expect OAEPIIP to help build scientific consensus on the effects of OAE on plankton.
Charly A. Moras, Tyler Cyronak, Lennart T. Bach, Renaud Joannes-Boyau, and Kai G. Schulz
Biogeosciences, 21, 3463–3475, https://doi.org/10.5194/bg-21-3463-2024, https://doi.org/10.5194/bg-21-3463-2024, 2024
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We investigate the effects of mineral grain size and seawater salinity on magnesium hydroxide dissolution and calcium carbonate precipitation kinetics for ocean alkalinity enhancement. Salinity did not affect the dissolution, but calcium carbonate formed earlier at lower salinities due to the lower magnesium and dissolved organic carbon concentrations. Smaller grain sizes dissolved faster but calcium carbonate precipitated earlier, suggesting that medium grain sizes are optimal for kinetics.
Aaron Ferderer, Kai G. Schulz, Ulf Riebesell, Kirralee G. Baker, Zanna Chase, and Lennart T. Bach
Biogeosciences, 21, 2777–2794, https://doi.org/10.5194/bg-21-2777-2024, https://doi.org/10.5194/bg-21-2777-2024, 2024
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Ocean alkalinity enhancement (OAE) is a promising method of atmospheric carbon removal; however, its ecological impacts remain largely unknown. We assessed the effects of simulated silicate- and calcium-based mineral OAE on diatom silicification. We found that increased silicate concentrations from silicate-based OAE increased diatom silicification. In contrast, the enhancement of alkalinity had no effect on community silicification and minimal effects on the silicification of different genera.
Siv K. Lauvset, Nico Lange, Toste Tanhua, Henry C. Bittig, Are Olsen, Alex Kozyr, Marta Álvarez, Kumiko Azetsu-Scott, Peter J. Brown, Brendan R. Carter, Leticia Cotrim da Cunha, Mario Hoppema, Matthew P. Humphreys, Masao Ishii, Emil Jeansson, Akihiko Murata, Jens Daniel Müller, Fiz F. Pérez, Carsten Schirnick, Reiner Steinfeldt, Toru Suzuki, Adam Ulfsbo, Anton Velo, Ryan J. Woosley, and Robert M. Key
Earth Syst. Sci. Data, 16, 2047–2072, https://doi.org/10.5194/essd-16-2047-2024, https://doi.org/10.5194/essd-16-2047-2024, 2024
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GLODAP is a data product for ocean inorganic carbon and related biogeochemical variables measured by the chemical analysis of water bottle samples from scientific cruises. GLODAPv2.2023 is the fifth update of GLODAPv2 from 2016. The data that are included have been subjected to extensive quality controlling, including systematic evaluation of measurement biases. This version contains data from 1108 hydrographic cruises covering the world's oceans from 1972 to 2021.
Nico Lange, Björn Fiedler, Marta Álvarez, Alice Benoit-Cattin, Heather Benway, Pier Luigi Buttigieg, Laurent Coppola, Kim Currie, Susana Flecha, Dana S. Gerlach, Makio Honda, I. Emma Huertas, Siv K. Lauvset, Frank Muller-Karger, Arne Körtzinger, Kevin M. O'Brien, Sólveig R. Ólafsdóttir, Fernando C. Pacheco, Digna Rueda-Roa, Ingunn Skjelvan, Masahide Wakita, Angelicque White, and Toste Tanhua
Earth Syst. Sci. Data, 16, 1901–1931, https://doi.org/10.5194/essd-16-1901-2024, https://doi.org/10.5194/essd-16-1901-2024, 2024
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The Synthesis Product for Ocean Time Series (SPOTS) is a novel achievement expanding and complementing the biogeochemical data landscape by providing consistent and high-quality biogeochemical time-series data from 12 ship-based fixed time-series programs. SPOTS covers multiple unique marine environments and time-series ranges, including data from 1983 to 2021. All in all, it facilitates a variety of applications that benefit from the collective value of biogeochemical time-series observations.
Kai G. Schulz, Lennart T. Bach, and Andrew G. Dickson
State Planet, 2-oae2023, 2, https://doi.org/10.5194/sp-2-oae2023-2-2023, https://doi.org/10.5194/sp-2-oae2023-2-2023, 2023
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Ocean alkalinity enhancement is a promising approach for long-term anthropogenic carbon dioxide sequestration, required to avoid catastrophic climate change. In this chapter we describe its impacts on seawater carbonate chemistry speciation and highlight pitfalls that need to be avoided during sampling, storage, measurements, and calculations.
Siv K. Lauvset, Nico Lange, Toste Tanhua, Henry C. Bittig, Are Olsen, Alex Kozyr, Simone Alin, Marta Álvarez, Kumiko Azetsu-Scott, Leticia Barbero, Susan Becker, Peter J. Brown, Brendan R. Carter, Leticia Cotrim da Cunha, Richard A. Feely, Mario Hoppema, Matthew P. Humphreys, Masao Ishii, Emil Jeansson, Li-Qing Jiang, Steve D. Jones, Claire Lo Monaco, Akihiko Murata, Jens Daniel Müller, Fiz F. Pérez, Benjamin Pfeil, Carsten Schirnick, Reiner Steinfeldt, Toru Suzuki, Bronte Tilbrook, Adam Ulfsbo, Anton Velo, Ryan J. Woosley, and Robert M. Key
Earth Syst. Sci. Data, 14, 5543–5572, https://doi.org/10.5194/essd-14-5543-2022, https://doi.org/10.5194/essd-14-5543-2022, 2022
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GLODAP is a data product for ocean inorganic carbon and related biogeochemical variables measured by the chemical analysis of water bottle samples from scientific cruises. GLODAPv2.2022 is the fourth update of GLODAPv2 from 2016. The data that are included have been subjected to extensive quality controlling, including systematic evaluation of measurement biases. This version contains data from 1085 hydrographic cruises covering the world's oceans from 1972 to 2021.
Aaron Ferderer, Zanna Chase, Fraser Kennedy, Kai G. Schulz, and Lennart T. Bach
Biogeosciences, 19, 5375–5399, https://doi.org/10.5194/bg-19-5375-2022, https://doi.org/10.5194/bg-19-5375-2022, 2022
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Ocean alkalinity enhancement has the capacity to remove vast quantities of carbon from the atmosphere, but its effect on marine ecosystems is largely unknown. We assessed the effect of increased alkalinity on a coastal phytoplankton community when seawater was equilibrated and not equilibrated with atmospheric CO2. We found that the phytoplankton community was moderately affected by increased alkalinity and equilibration with atmospheric CO2 had little influence on this effect.
Charly A. Moras, Lennart T. Bach, Tyler Cyronak, Renaud Joannes-Boyau, and Kai G. Schulz
Biogeosciences, 19, 3537–3557, https://doi.org/10.5194/bg-19-3537-2022, https://doi.org/10.5194/bg-19-3537-2022, 2022
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This research presents the first laboratory results of quick and hydrated lime dissolution in natural seawater. These two minerals are of great interest for ocean alkalinity enhancement, a strategy aiming to decrease atmospheric CO2 concentrations. Following the dissolution of these minerals, we identified several hurdles and presented ways to avoid them or completely negate them. Finally, we proceeded to various simulations in today’s oceans to implement the strategy at its highest potential.
Shao-Min Chen, Ulf Riebesell, Kai G. Schulz, Elisabeth von der Esch, Eric P. Achterberg, and Lennart T. Bach
Biogeosciences, 19, 295–312, https://doi.org/10.5194/bg-19-295-2022, https://doi.org/10.5194/bg-19-295-2022, 2022
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Oxygen minimum zones in the ocean are characterized by enhanced carbon dioxide (CO2) levels and are being further acidified by increasing anthropogenic atmospheric CO2. Here we report CO2 system measurements in a mesocosm study offshore Peru during a rare coastal El Niño event to investigate how CO2 dynamics may respond to ongoing ocean deoxygenation. Our observations show that nitrogen limitation, productivity, and plankton community shift play an important role in driving the CO2 dynamics.
Siv K. Lauvset, Nico Lange, Toste Tanhua, Henry C. Bittig, Are Olsen, Alex Kozyr, Marta Álvarez, Susan Becker, Peter J. Brown, Brendan R. Carter, Leticia Cotrim da Cunha, Richard A. Feely, Steven van Heuven, Mario Hoppema, Masao Ishii, Emil Jeansson, Sara Jutterström, Steve D. Jones, Maren K. Karlsen, Claire Lo Monaco, Patrick Michaelis, Akihiko Murata, Fiz F. Pérez, Benjamin Pfeil, Carsten Schirnick, Reiner Steinfeldt, Toru Suzuki, Bronte Tilbrook, Anton Velo, Rik Wanninkhof, Ryan J. Woosley, and Robert M. Key
Earth Syst. Sci. Data, 13, 5565–5589, https://doi.org/10.5194/essd-13-5565-2021, https://doi.org/10.5194/essd-13-5565-2021, 2021
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GLODAP is a data product for ocean inorganic carbon and related biogeochemical variables measured by the chemical analysis of water bottle samples from scientific cruises. GLODAPv2.2021 is the third update of GLODAPv2 from 2016. The data that are included have been subjected to extensive quality control, including systematic evaluation of measurement biases. This version contains data from 989 hydrographic cruises covering the world's oceans from 1972 to 2020.
Kai G. Schulz, Eric P. Achterberg, Javier Arístegui, Lennart T. Bach, Isabel Baños, Tim Boxhammer, Dirk Erler, Maricarmen Igarza, Verena Kalter, Andrea Ludwig, Carolin Löscher, Jana Meyer, Judith Meyer, Fabrizio Minutolo, Elisabeth von der Esch, Bess B. Ward, and Ulf Riebesell
Biogeosciences, 18, 4305–4320, https://doi.org/10.5194/bg-18-4305-2021, https://doi.org/10.5194/bg-18-4305-2021, 2021
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Upwelling of nutrient-rich deep waters to the surface make eastern boundary upwelling systems hot spots of marine productivity. This leads to subsurface oxygen depletion and the transformation of bioavailable nitrogen into inert N2. Here we quantify nitrogen loss processes following a simulated deep water upwelling. Denitrification was the dominant process, and budget calculations suggest that a significant portion of nitrogen that could be exported to depth is already lost in the surface ocean.
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Short summary
This study is the first to explore seasonal changes in coccolithophores, microscopic algae important for ocean life and the carbon cycle, off the coast of Nigeria. Their abundance and diversity increased during the rainy season, driven by shifts in the Intertropical Convergence Zone. Despite regional differences, these coastal communities show patterns similar to other parts of the world, revealing possible shared environmental pressures.
This study is the first to explore seasonal changes in coccolithophores, microscopic algae...
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