Tiny ocean organisms missing from climate models may hold the key to Earth’s carbon future

The ocean’s smallest engineers, planktonic calcifying organisms, quietly regulate the Earth’s thermostat by capturing and cycling carbon. At the base of the food web (as primary producers and primary consumers), these organisms have impacted carbon dynamics since the Mesozoic. Usually these groups are studied individually, but in 2025 we published a holistic review and found that these groups of organisms called 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.But much of this CaCO₃ 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 largely dominate the CaCO₃ producers, but 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.