Summary:
Calcifying plankton, some of the ocean’s smallest organisms, play an outsized role in regulating Earth’s carbon cycle – but they are largely missing from current climate models. A new Review published this week in Science by researchers at the Institute of Environmental Science and Technology at the Universitat Autònoma de Barcelona (ICTA-UAB) highlights how the oversimplification of coccolithophores, foraminifers, and pteropods in climate simulations may distort projections of ocean–atmosphere carbon exchange.
These microscopic organisms produce calcium carbonate (CaCO₃), forming shells that influence seawater chemistry and help transfer carbon from the atmosphere to the deep ocean. Yet much of this material dissolves in the upper ocean through processes such as predation, aggregation, and microbial respiration – a phenomenon called “shallow dissolution” – which is largely absent from key Earth System Models, including CMIP6.
The review emphasizes that each plankton group has unique functional traits that determine its ecological role, geographic distribution, and vulnerability to climate change. Coccolithophores are highly sensitive to acidification, while foraminifers and pteropods face threats from warming and oxygen loss. Ignoring this diversity risks oversimplifying the ocean’s carbon cycle and limiting the accuracy of climate predictions.
The study calls for integrating these dynamics into models to refine projections of carbon sequestration and future climate change.
— Press Release —
Tiny ocean organisms missing from climate models may hold the key to Earth’s carbon future
The ocean’s smallest engineers, calcifying plankton, quietly regulate the Earth’s thermostat by capturing and cycling carbon. However, a new review in Science by an international team led by the Institute of Environmental Science and Technology at the Universitat Autònoma de Barcelona (ICTA-UAB) finds that these organisms, coccolithophores, foraminifers, and pteropods, are oversimplified in the climate models used to predict our planet’s future.
By omitting these plankton, current models may underestimate key processes in the global carbon cycle and the ocean’s capacity to respond to climate change. Calcifying plankton build minute shells of calcium carbonate (CaCO₃), a critical component of the ocean’s carbon cycle. These organisms influence seawater chemistry and facilitate the transfer of carbon from the atmosphere to the deep ocean. This “carbon pump” helps regulate Earth’s climate and influences everything from ocean chemistry to the fossil record.
“Plankton shells are tiny, but together they shape the chemistry of our oceans and the climate of our planet,” said Patrizia Ziveri, ICREA research professor at ICTA-UAB and lead author of the study. “By leaving them out of climate models, we risk overlooking fundamental processes that determine how the Earth system responds to climate change.”
But as the authors show, much of this calcium carbonate never reaches the seabed. Instead, a large fraction dissolves in the upper ocean – a process known as “shallow dissolution.” Driven by biological interactions like predation, particle aggregation, and microbial respiration, shallow dissolution profoundly alters the ocean’s chemistry, but remains largely absent from key Earth System Models (e.g. CMIP6) that inform global climate assessments.
The study highlights the unique traits of different calcifying plankton groups, which determine their geographic distribution, ecological role, and vulnerabilities. Coccolithophores, the main producers of CaCO₃, are especially sensitive to acidification, as they lack specialized pumps to remove acidity from their cells. Foraminifers and pteropods do, but they face different pressures, from oxygen loss to warming waters. Together, these groups shape the fate of carbon in the ocean. Ignoring their diversity risks oversimplifying how the ocean responds to climate stressors.
Read also: Plankton science: Balancing old and new technologies
The paper calls for urgent efforts to better quantify group-specific production, dissolution, and export of calcium carbonate, and to incorporate these dynamics into climate models. Doing so would allow for more accurate projections of ocean–atmosphere feedbacks, carbon sequestration, and even the interpretation of sediment records used to reconstruct past climates.
“If we ignore the ocean’s smallest organisms, we might miss important climate dynamics,” says Dr. Ziveri. “Integrating calcifying plankton into climate models could offer sharper predictions and deeper insights into how ecosystems and societies may be affected.”
The researchers conclude that addressing these knowledge gaps is critical to developing a new generation of climate models that better capture the biological complexity of the oceans.
Journal Reference:
Patrizia Ziveri, Gerald Langer, Sonia Chaabane, Joost de Vries, William Robert Gray, Nina Keul, Ian A. Hatton, Clara Manno, Richard Norris, Sven Pallacks, Jeremy R. Young, Ralf Schiebel, Stergios Zarkogiannis, Griselda Anglada-Ortiz, Stefania Bianco, Thibault de Garidel-Thoron, Michaël Grelaud, Arturo Lucas, Ian Probert, and P. Graham Mortyn, ‘Calcifying plankton: From biomineralization to global change’, Science 390, 6771, eadq8520 (2025). DOI: 10.1126/science.adq8520
Article Source:
Press Release/Material by Universitat Autonoma de Barcelona (UAB)
Featured image: The pteropod Limacina helicina collected in West Greenland waters. Credit: Alena Sakovich and Clara Manno
