In the grand narrative of Earth’s climate system, diminutive marine organisms often slip under the radar, their microscopic scales belying their monumental impact on our planet’s biological and chemical equilibrium. Among these key players are calcifying plankton—an eclectic group encompassing coccolithophores, foraminifers, and pteropods. These organisms have long fascinated oceanographers and climatologists alike, not only for their extraordinary biomineralization processes but also for their pivotal role in mediating the global carbon cycle. A recently published critical review in Science, spearheaded by international researchers at the Institute of Environmental Science and Technology, Universitat Autònoma de Barcelona (ICTA-UAB), reveals a striking oversight embedded within current climate models, one that may be stalling our full understanding of oceanic carbon dynamics.
Calcifying plankton construct elaborate shells from calcium carbonate (CaCO₃), a biochemical feat that seamlessly integrates into the marine carbon pump. This pump is responsible for transferring carbon atoms captured from atmospheric CO₂ into ocean depths, thereby regulating not only the chemistry of seawater but the climatic trajectory of the Earth itself. These microscopic architects produce and recycle carbon in quantities so vast that their cumulative influence rivals some of the largest biological pumps on the planet. Yet, as the new review elucidates, the diverse physiology and ecological roles of these groups are commonly homogenized or excluded entirely from Earth System Models (ESMs) that project future global climate scenarios.
One of the study’s groundbreaking insights pertains to the concept of “shallow dissolution.” Contrary to assumptions that once formed calcium carbonate shells sink unabated to the ocean floor, a significant fraction of this mineralized carbon dissolves within the upper ocean strata. This process is intricately mediated by biological factors such as predation dynamics, particle aggregation phenomena, and the metabolic activity of microbial communities. The dissolution of calcium carbonate in these shallow waters alters the ocean’s carbonate chemistry, impacting pH buffering capacity and thus modulating the ocean-atmosphere exchange of CO₂—a feedback loop currently underrepresented in major climate models like CMIP6.
Diving deeper into the intricacies of the individual plankton groups, the review highlights their unique biochemical adaptations and respective vulnerabilities amid accelerating ocean acidification and warming. Coccolithophores, responsible for the lion’s share of CaCO₃ production, exhibit a marked sensitivity to increased acidity due to their lack of specialized cellular mechanisms to expel excess H⁺ ions. This physiological constraint may limit their calcification rates and consequently their capacity to sequester carbon. Conversely, foraminifers and pteropods possess more robust ion regulation pathways, potentially conferring resilience to acidification, but these taxa face additional stressors, including hypoxia and escalating sea temperatures, which may disrupt their development and ecological functions.
The ecological ramifications of neglecting these taxonomically and functionally distinct plankton in climate simulations are profound. Oversimplification risks obscuring critical feedback mechanisms that govern carbon export efficiency and ocean chemistry dynamics. Since calcifying plankton contribute both to immediate biogeochemical cycles and the sedimentary records used for paleoclimate reconstruction, their accurate representation is indispensable both for forecasting future events and understanding the Earth’s climatic past. The omission of shallow dissolution processes, alongside the diverse responses of plankton groups to environmental change, may result in systemic bias or gaps in predictive models.
Furthermore, the review underscores that ocean biogeochemistry is an ecosystem tightly interwoven with planktonic calcification processes. Variability in carbonate shell composition, size, and dissolution rates directly influences not only carbon sequestration but also the marine carbonate chemistry that many organisms depend upon. Consequently, the genomic and physiological diversity present within these assemblages shapes ocean chemistry at scales far beyond individual organisms. Accounting for these biochemical and ecological nuances promises to unlock more accurate climate predictions and a finer understanding of ocean-atmosphere interactions.
Technological advances, particularly in imaging analysis and molecular biology, fuel optimism that these knowledge gaps can be bridged. Enhanced imaging methodologies enable unprecedented observation of calcification patterns and dissolution dynamics at microscale resolutions. Coupling these insights with oceanographic and ecological data allows for the refinement of parameterizations within ESMs, setting the stage for more biologically realistic climate forecasting frameworks. Such integrative approaches may reveal hitherto hidden feedback loops inherent in marine ecosystems vulnerable to climate perturbations.
The authors champion a recalibration of climate modeling architecture to integrate group-specific biomineralization and dissolution pathways. This integration is poised to revise contemporary perspectives on carbon fluxes and oceanic responses to global warming. Understanding how calcifying plankton respond to multifaceted stressors—ocean acidification, hypoxia, temperature shifts—will offer a clearer narrative of potential ecosystem trajectories and their implications for climate regulation. The review posits that this biologically nuanced approach is not merely an additive improvement but a transformative recalibration for predictive science.
From a broader lens, this research compels a reconsideration of how small-scale biological phenomena aggregate to effect large-scale planetary processes. The minute CaCO₃ shells produced by plankton collectively orchestrate shifts in seawater alkalinity and carbon burial efficiency. These changes propagate through marine food webs and sedimentary layers, eventually influencing atmospheric CO₂ concentrations and global temperature regulatory mechanisms. As such, these tiny organisms serve both as indicators of ocean health and active agents mediating climate feedbacks.
Ignoring the complexity and heterogeneity of calcifying plankton in climate models is akin to overlooking the subtle yet decisive mechanics within a finely tuned machinery. The study’s lead author, Professor Patrizia Ziveri, emphasizes the urgency in integrating these plankton groups’ biomineralization cycles into climate predictions to avoid blind spots that could undermine the accuracy of global change projections. By embedding this biological dimension, climate models will evolve toward capturing essential ecological feedbacks and thereby support informed policymaking and environmental stewardship.
Ultimately, as climate challenges deepen, the fusion of marine biology, geochemistry, and climate science emerges as a frontier of critical importance. The review’s call to action stresses interdisciplinary collaboration and technological innovation to transcend current model limitations. This concerted effort promises not only to safeguard a comprehensive understanding of oceanic carbon cycling but also to illuminate the pathways through which our planet’s smallest organisms orchestrate its largest evolutionary shifts under anthropogenic pressure.
In conclusion, calcifying plankton are far more than marine curiosities; they are indispensable modulators of Earth’s climate engine. Their roles in calcium carbonate production, shallow dissolution, and carbon transfer underscore the urgent need to rethink climate model structures. Future research must prioritize deciphering the nuanced biomineralization pathways and responses of these groups to ocean stressors. Only then can scientific forecasts embody the biological realities that shape our oceans and the global climate system with precision and foresight.
Subject of Research: Not applicable
Article Title: Calcifying plankton: From biomineralization to global change
News Publication Date: 23-Oct-2025
Web References: http://dx.doi.org/10.1126/science.adq8520
Image Credits: Alena Sakovich and Clara Manno
Keywords: Ocean acidification, Ocean pH, Ocean chemistry, Carbon cycle, Biogeochemical cycles, Biogeochemistry, Climate change
