Sixth international symposium on the ocean in a high-CO₂ world

Published 11 November 2026 Events , Science , Web sites and blogs Leave a Comment

From 13 to 16 October 2026, nearly 350 researchers gathered in Wellington, New Zealand, for the 6th International Symposium on the Ocean in a High-CO₂ World. Supported by the Prince Albert II of Monaco Foundation through its OACIS initiative, the event brought together the international scientific community to advance research and cooperation on ocean acidification. HSH Prince Albert II of Monaco addressed participants in a video message, recalling Monaco’s longstanding engagement on this issue.

Held every four years, the Symposium is the world’s largest scientific gathering dedicated to ocean acidification. Under the theme “Moving from Understanding to Action using Multiple Knowledge Systems”, this sixth edition focused on translating scientific knowledge into concrete responses to ocean acidification and related pressures, including ocean warming, deoxygenation and pollution.

A longstanding commitment to ocean acidification research

In his video address, HSH Prince Albert II of Monaco recalled the second edition of the Symposium, hosted in Monaco in 2008. That meeting led to the Monaco Declaration, signed by 155 scientists from 26 countries, which helped raise awareness among policymakers of the threats posed by ocean acidification.

Nearly two decades later, the Sovereign Prince highlighted the progress achieved in understanding how acidification interacts with other marine pressures, exploring innovative ocean-based solutions such as ocean alkalinity enhancement, and recognising the contribution of local and Indigenous knowledge to scientific research.

“This progress on three frontiers – increased understanding, innovation and inclusivity – provides a blueprint for how to ensure science has real influence on public policy and its findings are translated into action.”

HSH Prince Albert II of Monaco also reaffirmed the importance of addressing ocean acidification as a long-term threat to marine ecosystems and the future of humanity.

Watch HSH Prince Albert II of Monaco’s video message

Advancing international cooperation through OACIS

The Foundation supported the Symposium through its Ocean Acidification and other ocean Changes – Impacts and Solutions (OACIS) initiative, in cooperation with the International Atomic Energy Agency’s Marine Environment Laboratories in Monaco and their Ocean Acidification International Coordination Centre (OA-ICC).

As members of the international organising committee, OACIS and the OA-ICC co-led several workshops addressing scientific and policy priorities in the Asia-Pacific region, international capacity-building efforts, and the future of the Global Ocean Acidification Observing Network (GOA-ON).

Discussions also introduced a new framework to assess options for addressing marine biodiversity loss linked to ocean acidification, in support of the Kunming-Montreal Global Biodiversity Framework.

Supporting the next generation of ocean scientists

The Symposium also offered an opportunity to strengthen the participation of early-career researchers in international scientific discussions.

Eight early-career scientists from Argentina, Brazil, India, Indonesia, Mauritius, Mexico and Portugal received support to present their research and exchange knowledge with experts from around the world.

The plenary sessions were livestreamed, making the discussions accessible to a wider international audience.

Watch the Symposium’s plenary sessions

The Foundation acknowledges the contributions of the host, the Victoria University of Wellington, as well as the Symposium’s many partners, including IOC-UNESCO, the University of Washington, NOAA Ocean Acidification Program, the University of Gothenburg, the Laboratoire d’Océanographie de Villefranche (LOV), the Ocean Acidification Alliance, Ocean Acidification Research for Sustainability (OARS), the Global Ocean Acidification Observing Network (GOA-ON), and the Embassy of France in New Zealand.

Through OACIS and its longstanding scientific partnerships, the Prince Albert II of Monaco Foundation continues to support research, international cooperation and the development of science-informed responses to the changes affecting our ocean.

Photos: ©Tākina Events and ©Lina Hansson

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Analysis of the effects of seawater acidification on the biochemical composition and digestive enzyme activities of Oratosquilla oratoria (in Chinese)

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Objective

This study aimed to investigate the effects of CO2-induced seawater acidification on the biochemical composition and digestive enzyme activities of mantis shrimp (Oratosquilla oratoria).

Method

A 49-day aquaculture experiment was conducted. Three acidified treatment groups (pH 7.90, pH 7.70, pH 7.50) were established by introducing CO2 gas into seawater, using natural seawater (pH 8.10) serving as the control.

Result

(1) Under acidified conditions, the muscle moisture content of O. oratoria increased with decreasing pH levels. From day 21 onward, the moisture content in the pH 7.70 and pH 7.50 groups exhibited significantly higher than that in the control group (P < 0.05). Conversely, the contents of ash, crude protein, and crude lipid contents decreased with pH reduction. All acidified groups displayed significantly lower ash content than the control from day 7 onward (P < 0.05). The crude protein levels in respective acidified groups became significantly lower than those in the control starting on days 28 (pH 7.90 group), 14 (pH 7.70 group), and 7 (pH 7.50 group), respectively (P < 0.05). All acidified groups showed significantly reduced crude lipid content compared to the control from day 7 onward (P < 0.05). (2) Pepsin and trypsin activities showed an initial increase followed by a decrease, while lipase activity exhibited a gradual increasing trend. Although acidified groups exhibited marginally higher pepsin and trypsin activities than the control at day 7, these enzymes showed declining trends subsequently, with significant inhibition observed in pepsin by day 21 and trypsin by day 35, respectively (P < 0.05). Lipase activities in the acidified groups became significantly elevated compared to the control starting on day 28 (pH 7.90 group), day 7 (pH 7.70 group), and day 7 (pH 7.50 group), respectively (P < 0.05).

Conclusion

When seawater acidification reached pH levels of 7.50–7.30, it induced a stress response in the mantis shrimp (Oratosquilla oratoria). After 7–14 days of exposure, energy reserves such as crude fat and crude protein were mobilized to cope with the acidic conditions. Although the activities of digestive enzymes including pepsin, trypsin, and lipase were temporarily enhanced, this response failed to alleviate the stress caused by seawater acidification.

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Warming, thresholds and extinctions: lessons from past hyperthermals on land and at sea

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The current biodiversity crisis is driven primarily by human activities, including global warming resulting from human greenhouse-gas emissions, which act as multifaceted environmental stressors. Rising temperatures compromise organismal performance through thermal stress, creating demographic erosion and triggering ecological cascades that propagate across populations and ecosystems. The fossil record offers a unique archive for evaluating these dynamics, documenting biological responses to a wide spectrum of past climate regimes, including warming events far exceeding those experienced in human history and the conditions projected to take place during the coming century. Drawing on events across the Phanerozoic, we emphasize mechanisms that link climate change to extinction in both marine and terrestrial realms. Extreme ancient warming episodes reveal a recurring “deadly trio” of global warming, ocean acidification and deoxygenation, processes that mirror the emerging drivers of the contemporary crisis. Focusing on the Cenozoic and the Pleistocene Ice Ages, we review mammalian responses to rapid climatic fluctuations and highlight the synergistic contribution of Homo to Late Quaternary megafaunal collapse. Our synthesis shows that past crises provide key insights into extinction thresholds, rates of environmental change, and the vulnerability of ecological functions under warming. Critically, comparison with ancient analogs suggests that future extinction risk on land may exceed anything observed during past warming episodes, due to the unprecedented velocity of modern warming combined with direct anthropogenic pressures such as habitat loss and fragmentation. In the oceans, projected warming and deoxygenation point toward extinction intensities comparable to those of the most extreme hyperthermal events. Collectively, the evidence indicates that Earth is approaching temperature conditions historically associated with major extinction episodes.

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Exploring biomineralization in echinoderms: a review of gene regulatory networks through bibliometrics and comparative genomics

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Simple Summary

Echinoderms, including sea urchins, sea cucumbers, starfish, brittle stars, and crinoids, produce mineralized skeletons that vary greatly in form among different groups and developmental stages. Understanding how these skeletons form is important for revealing the biological mechanisms underlying skeletal development and diversity. This review summarizes the development and major research themes of echinoderm biomineralization studies and examines the genes involved in skeletal formation across different echinoderm groups. We show that many genes controlling skeletal development are broadly shared among echinoderms, whereas some genes directly involved in mineral formation vary considerably among groups. By integrating previous biological studies with literature-based and genomic comparisons, this review provides a broader understanding of the molecular basis of echinoderm biomineralization and highlights important questions for future research beyond the extensively studied sea urchins.

Abstract

Biomineralization is a defining feature of echinoderms and underlies the formation of their calcitic endoskeletons. Considerable progress has been made in understanding the molecular basis of echinoderm biomineralization, particularly in sea urchins. However, studies of other echinoderm classes remain limited, and a comprehensive comparison of biomineralization genes and gene regulatory networks across the phylum is still lacking. Here, we combine bibliometric analysis with comparative genomic evidence to summarize current advances in echinoderm biomineralization research. Bibliometric analyses reveal the development of the field, major research themes, and emerging directions, whereas comparative genomic analyses provide an overview of biomineralization genes and gene regulatory networks across different echinoderm classes. Comparative evidence indicates that many transcription factors associated with skeletogenesis are widely distributed across echinoderms. In contrast, biomineralization genes exhibit substantial variation among echinoderm classes. These similarities and differences suggest that broadly shared developmental regulators have been integrated with lineage-specific biomineralization genes to generate the diversity of echinoderm skeletal structures. This review provides a comprehensive overview of biomineralization genes and gene regulatory networks in echinoderms and establishes a comparative framework for future studies of skeletal development, gene regulation, and the evolution of biomineralization across the phylum.

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Expansion of low-chlorophyll regions in the tropical Indian Ocean: spatial patterns and physical–biogeochemical associations

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Context

The Indian Ocean has been warming at a faster rate than the global average; hence, evaluating decadal (2015–24) shifts in key oceanographic parameters across the Tropical Indian Ocean is crucial to understand how this warming may be contributing to the expansion of low-productivity regions and the onset of ocean desertification.

Aims

To evaluate trends in satellite-derived chlorophyll-a (Chl-a), sea-surface temperature and sea-surface salinity, alongside complementary ocean reanalysis data for nutrients, dissolved oxygen, partial pressure of carbon dioxide and pH to evaluate the physical and biogeochemical drivers of expanding low-productivity zones.

Methods

Using satellite observations and ocean reanalysis products from the Copernicus Marine Environment Monitoring Service (CMEMS), we analysed monthly and seasonal climatologies. Trends were evaluated using autocorrelation-corrected Mann–Kendall tests, Theil–Sen slopes and climate event departure analysis (El Niño–Southern Oscillation, ENSO, and Indian Ocean Dipole, IOD).

Key results

Oligotrophic waters (Chl-a < 0.1 mg m−3) expanded northward (15°S to 15°N), strongly driven by surface warming (r = −0.72). Reanalysis showed a diagnostic nutrient decoupling (stable pools, reduced biological uptake), persistent oxygen depletion and widespread ocean acidification (pH declining ~0.002 year−1). Inter-annual climate modes (ENSO and IOD) heavily modulated these decadal trends.

Conclusions

Surface warming drives oligotrophic expansion across the Tropical Indian Ocean, suppressing biological productivity despite available nutrient pools and accelerating basin-wide acidification.

Implications

Expanding low-productivity waters and concurrent acidification threaten marine food webs, underscoring the urgent need for integrated basin-wide observational networks.

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Pathways to calcification in coccolithophores

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Calcification by coccolithophores represents a major biogeochemical process in the oceans. Calcification involves the formation of calcite coccoliths within a Golgi-derived compartment inside the cell. These are secreted to the cell surface where they form the coccosphere. Coccolithophore calcification is underpinned by membrane transport processes that deliver the inorganic carbon and calcium substrates from the external seawater to the site of calcification and by the removal of products, namely protons produced in the calcification reactions. Understanding these critical aspects of calcification will provide clearer insights into the responses of coccolithophores to chemical and physical conditions, both in terms of short-term acclimation and long-term adaptation to a changing ocean. In this review we consider these processes, their localization and the specific transporters likely to be involved. We also consider how transport processes are linked to structural aspects of the cell, providing specialized pathways for the substantial ion fluxes involved.

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The role of international courts and tribunals in shaping expertise – the ITLOS advisory opinion on climate change in an Arctic expertise context

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Despite a considerable focus in the literature on how expertise comes to be defined, there has so far been little interest in how expertise is shaped in the wording of treaties and the subsequent application by courts. This presents a gap in the literature, as international treaties and courts have significant impact on the definition of expertise. Set in an Arctic context, where Western science and Indigenous Knowledge are increasingly considered to be complementary bodies of knowledge, this paper uses a decolonial approach to demonstrate how international law and the courts that apply it can impact processes of expertise-building. The paper concludes that there is two-way relationship between international law and expertise (international courts are influenced by, and influence, how expertise is perceived). This becomes relevant when the underlying processes on which the courts base their definition of expertise are shaped by colonial dynamics, as there is a danger of maintaining existing colonial legacies, which can negatively impact the ongoing process of re-defining expertise in a decolonial manner.

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Coastal jellyfish blooms: causes, consequences, and policy frameworks for sustainable management

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Highlights

  • Jellyfish blooms creates significant challenges for sustainable coastal management.
  • Blooms are caused by combined influence of environmental and anthropogenic factors.
  • Management approaches can significantly reduce the coastal pollution.
  • Multidisciplinary approach is necessary for long−term success in mitigating jellyfish blooms.

Abstract

The growing occurrence of coastal jellyfish blooms worldwide creates significant challenges for sustainable coastal management. In recent years, occurrence of the jellyfish bloom has also been reported in the coastal area of Cox’s Bazar, Bangladesh, which tend to disrupt the ecosystem balance as well as decreases the appeal of the beach. These blooms are shaped by combined influence of environmental and anthropogenic factors including ocean warming, nutrient enrichment, overfishing, destruction of lobster, sea turtle, and other natural predators, and habitat modification, particularly the expansion of coastal infrastructure that facilitate polyp persistence. Therefore, this review synthesizes worldwide patterns of coastal jellyfish blooms, identifies the key drivers of bloom development and recurrence, and analyzes their ecological and socio−economic impacts. Special attention is given to the consequences for fisheries, aquaculture operations, and tourism, as well as to the role of human mediated environments in reinforcing bloom formation. Moreover, management strategies applied across regions are critically reviewed, revealing uneven implementation and limited long−term effectiveness. By bridging scientific evidence with management needs, this review underscores the need for integrated adaptive frameworks to manage jellyfish blooms under ongoing environmental change.

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Acidification states and controlling factors in subsurface and bottom water of the Beibu Gulf, China

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Previous studies in the Beibu Gulf have documented the distributions and controlling factors of carbonate system parameters in surface waters; however, their dynamics in subsurface and bottom waters remain poorly constrained. Here, we present the first observations of pH and the aragonite saturation state (Ωarag) in subsurface and bottom waters of the Beibu Gulf during spring and fall 2024. In spring, pH and Ωarag in subsurface and bottom waters off Ledong were predominantly governed by physical mixing. In contrast, their variability off Dongfang was driven jointly by biological respiration occurring outside the Dongfang oil/gas field and by respiration within the field itself. Quantitative analysis revealed that respiration outside the field increased dissolved inorganic carbon (DIC) concentrations by ~18 ± 3 µmol kg−1, a magnitude comparable to that attributable to in-field respiration (~18 ± 7 µmol kg−1). Collectively, these two respiration sources induced only slightly declines in pH (0.03 ± 0.01 and 0.04 ± 0.01) but statistically significant reductions in Ωarag (0.18 ± 0.03 and 0.21 ± 0.08, respectively). During fall, carbonate system dynamics in subsurface and bottom waters off both Dongfang and Ledong were dominated by physical mixing. The differential influence of North Pacific Tropical Water (NPTW) resulted in a decline in Ωarag from 2.99 ± 0.10 off Dongfang to 2.75 ± 0.32 off Ledong. All observed Ωarag values remained well above the thermodynamic saturation threshold (Ωarag = 1), indicating no immediate risk of ocean acidification to calcifying organisms in the study area under current conditions. This study helps bridge a critical observational gap in the regional inorganic carbonate system. However, due to sampling constraints, carbonate system parameters are reported here for spring and fall only. Observations for summer and winter, as well as multi-year time-series measurements, are planned for the near future.

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Amazon river plume control on carbonate chemistry in the western tropical Atlantic

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The Amazon River Plume (ARP) modulates the carbonate system of the western Tropical Atlantic (WTA) through physical and biological processes, including freshwater dilution, biological carbon uptake, and circulation-driven transport; however, its basin-scale impact has not been quantitatively assessed. Here we combine climatological spatial anomalies of sea surface salinity (SSS), carbonate system variables, and biogeochemical indicators to determine the percentage contribution of offshore ARP waters to regulate carbonate chemistry during wet and dry seasons. We show that ARP-derived freshwater and nutrients drive ∼8%–10% reductions in sea surface fugacity (fCO2), total alkalinity, dissolved inorganic carbon and carbonate ion concentrations across the WTA during the wet season, closely matching a ∼9% decrease in SSS. These reductions represent a substantial perturbation to carbonate chemistry across the offshore plume-influenced WTA, strengthening the role of the ARP in modulating carbon cycling and atmospheric CO2 uptake. These findings identify physical dilution, enhanced photosynthesis and nitrogen cycle transformations, as strong first-order controls on carbonate system drawdown, supporting CO2 uptake in low-SSS waters. ARP-driven reductions in fCO2 extend far beyond the plume through offshore export by the North Brazil Current and North Equatorial Countercurrent, decreasing fCO2 by up to 20 μatm near 10°N and modulating carbonate chemistry across the equatorial Atlantic. Together, these results demonstrate that the ARP is a major regulator of sea surface carbonate chemistry in the WTA, enhancing atmospheric CO2 uptake through coupled physical–biological processes. The spatial anomaly approach provides a robust framework for quantifying river-plume impacts on basin-scale carbon cycling.

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Ocean acidification and mass extinctions: reconstructing CO2 from fluid inclusions

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The composition of Earth’s atmosphere and oceans have varied over the Phanerozoic and is tightly coupled with the planet’s climate and the extinction and evolution of life. Central to Earth’s climate and habitability is the concentration of CO2 in the atmosphere-ocean system, where rapid perturbations of CO2 correspond with hyperthermal and mass extinction events. These intervals of environmental catastrophes coincide with several periods of large-scale volcanic eruptions (million km3 of lava) called Large Igneous Provinces (LIPs), capable of releasing massive quantities of CO2. Among these events, the end-Triassic extinction (ETE; 201.564 Ma) represents one of the most severe biotic crises of the Phanerozoic and is temporally associated with the emplacement of the Central Atlantic Magmatic Province (CAMP). As one of the most voluminous large igneous provinces, CAMP is characterized by repeated disruptions to the global carbon cycle and intense ocean acidification events. However, understanding the relationship between the massive release of CO2, ocean chemistry, and extinction dynamics requires robust constraints on ancient CO2 concentrations. For time intervals prior to the ice core record, CO2 reconstructions rely on geochemical proxies derived from fossils and minerals. While these proxies often reproduce similar long-term trends, they commonly diverge in absolute CO2 estimates, limiting confidence in quantitative reconstructions of ancient atmospheric and oceanic carbon reservoirs. Direct constraints on CO2 in deep time can overcome this limitation, which can be achieved by using fluid inclusions hosted in minerals that precipitated in equilibrium with the environment. These fluid inclusions trap and preserve aliquots of ancient air and brine at the time of mineral formation in which the bulk gas compositions can be directly quantified using mass spectrometry and Raman spectroscopy. Fluid inclusions have increasingly been recognized to be excellent archives of past environmental conditions, including temperature, salinity, and atmospheric composition, though uncertainties remain about carbon speciation, the fidelity of preserved gas and brine compositions, and the broader applicability of using fluid inclusions to reconstruct major carbon cycle perturbations. This dissertation applies direct and quantitative methods to extract CO2 concentrations from fluid inclusions trapped in sedimentary minerals. Confocal Raman spectroscopy is used to quantify carbonate system parameters using fluid inclusions hosted in calcite, enabling reconstruction of pH and pCO2 conditions during mineral formation. Subsequently, fluid inclusions in halite are assessed for their reliability to trap gases during mineral precipitation and validate their use for ancient CO2 reconstructions. Fluid inclusion analyses were applied to deep ocean bedded cherts, showing repeated pulses of elevated CO2 and associated decreases in ocean pH and aragonite saturation state across the ETE and the Triassic-Jurassic transition. Integration of these records with carbon cycle modeling constrains the magnitude and pacing of the carbon release associated with CAMP volcanism and shows that large, repeated CO2 injections are sufficient to reproduce observed perturbations in ocean chemistry. By combining fluid inclusion analyses with carbon cycle modeling and independent geological and paleontological constraints, link large igneous province volcanism, repeated disruptions to the global carbon cycle, mass extinctions, and widespread ocean acidification during the end-Triassic.

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Quantifying coastal ocean anthropogenic carbon changes and their uncertainties

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Despite recent progress in quantifying anthropogenic carbon (Canth) in global oceans, coastal regions remain understudied due to methodological and observational challenges. Here, we develop and generalize a Regional rEgression–based Coastal Anthropogenic carbon estimation algorithm (RECA) designed specifically for coastal environments. Regional rEgression–based Coastal Anthropogenic carbon estimation algorithm builds upon the extended multiple linear regression framework, incorporating adaptations such as improved regression construction strategies, optimized data selection, and reduced subjectivity in decision-making, creating a unified approach across diverse coastal settings. Using synthetic datasets with known ∆Canth from global ocean biogeochemical model simulations across multiple North American coastal regions, we estimate that the uncertainty of RECA is about 3.25 μmol kg−1. We also compare RECA with two other regression-based algorithms, originally developed for the open ocean, to evaluate their performance in coastal environments after some adaptations. All three approaches have similar biases but different strengths, underscoring the importance of using a consistent method. An ensemble approach combining these three algorithms modestly improves reconstruction fidelity, but at the cost of increased complexity. We also evaluate the contributions of non-steady-state variations of both natural and Canth components because uncertainty about these components has long challenged the interpretation of regression-based ∆Canth results. We find that the algorithms indeed remove most, but not all, of the natural variations and appear to capture some, but not all, of the non-steady-state Canth. This methodological framework provides a robust, broadly applicable, and easy-to-implement tool for estimating coastal ∆Canth with uncertainty quantification, allowing us to more confidently track Canth accumulation in a changing dynamic coastal ocean.

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Ocean acidification pushes Mediterranean marine calcifiers toward a tipping point

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The increasing emission of carbon dioxide (CO2) is altering seawater chemistry, lowering ocean pH and threatening marine biodiversity. Predicting how marine biota will be adversely affected by ocean acidification (OA) remains a key challenge. Here, we document that functional morphological traits offer a more robust metric of calcifier sensitivity to OA than taxonomic diversity alone. Using benthic foraminifera from a Mediterranean CO2 vent system, we identify an empirically derived pH threshold beyond which community structure and function shift markedly. Applying this threshold to end-of-century projections under Shared Socioeconomic Pathway SSP5-8.5 reveals that most western Mediterranean coastal zones will exceed critical acidification levels by 2090–2100. These results highlight the susceptibility of the Mediterranean coastal ecosystems to OA under high-emission scenarios, underscoring the risk of widespread biodiversity loss and impaired ecosystem functioning. Our approach provides a trait-based framework for forecasting ecosystem responses to OA and informing adaptation strategies in climate-sensitive marine regions.

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Southern Ocean productivity and carbonate chemistry imprinted on coccolith morphology across the last Glacial-Holocene transition

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Highlights

  • Glacial C. pelagicus coccoliths were larger, with broader distal shields.
  • Coccolith size variability tracked glacial-Holocene STF productivity changes.
  • Dust-driven Fe fertilisation enhanced glacial nutrient utilisation along the STF.
  • Coccolith distal shield thinning linked to deglacial Southern Ocean CO₂ outgassing.
  • C. pelagicus morphometry records Southern Ocean carbonate chemistry variability.

Abstract

The Southern Ocean plays a key role in regulating atmospheric CO₂ through changes in overturning circulation and is projected to undergo major warming and ocean acidification under future climate scenarios. Coccolithophores, a dominant calcifying phytoplankton group in the northern Southern Ocean, are expected to be particularly sensitive to such changes. Here, we evaluate glacial–Holocene coccolith size variability using morphometric analyses of Coccolithus pelagicus from sediment core ABP S4 located at the Subtropical Front (STF) in the western Indian sector of the Southern Ocean. Mean coccolith size was calculated from statistically robust populations to minimise intra-coccosphere variability. Glacial intervals are characterized by larger coccoliths with broader distal shields (coccolith rim), whereas deglacial and Holocene intervals exhibit smaller coccoliths with thinner distal shield. Coccolith size variability closely corresponds with regional paleoproductivity records, indicating enhanced glacial carbonate production along the STF, while previous studies report increased opal production at the Subantarctic Front (SAF). Together, these findings suggest elevated glacial productivity across the Subantarctic Zone (SAZ) driven by more efficient nutrient utilisation under dust-induced Fe fertilisation. While overall coccolith size reflects changes in productivity and nutrient availability, the distal shield area appears more sensitive to deglacial carbonate chemistry changes. Deglacial reductions in the distal shield area paralleled enhanced Southern Ocean CO₂ outgassing and reinvigorated overturning circulation, indicating strong carbonate chemistry control on coccolith calcification. These findings highlight the potential of coccolith morphometry for tracking Southern Ocean productivity, carbon cycling, and the sensitivity of calcifying phytoplankton to future environmental change.

Graphical abstract

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Global change reshapes marine microbial communities, functions and One Health outcomes

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Marine microorganisms underpin primary production, biogeochemical cycling and host-associated symbioses, supporting climate regulation, coastal protection, fisheries and other ecosystem services. Rapid global change, including ocean warming and marine heatwaves, acidification, deoxygenation, eutrophication, pollution and overuse reshape microbial communities and their functions across marine habitats. These changes can alter carbon, nitrogen and sulfur cycles, promote microbialization and harmful algal blooms, disrupt host–microbiome associations and modify pathogen and antimicrobial resistance dynamics, collectively amplifying the ecological and societal impacts of global change. This Review frames marine microbiomes as cross-scale mediators that translate external pressures, including climate change, pollution, eutrophication and habitat degradation, into altered microbial metabolism, biogeochemical fluxes, host-associated health outcomes, ecosystem service consequences and broader One Health risks. We synthesize shared mechanisms and cross-habitat patterns, highlight cases in which microbiome interventions and stewardship could mitigate impacts and/or accelerate recovery, and outline management options ranging from the reduction of local stressors to emerging microbiome stewardship approaches in ecosystem restoration. Building upon this, we outline pathways for embedding marine microbiome science into globally coordinated One Health strategies, operational management protocols and financing frameworks that align economic incentives with long-term ecosystem and public health outcomes.

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Ocean Seminar – Facing the unknown: modern planktonic foraminifera migration is not enough, by Sonia Chaabane

Published 10 November 2026 Events , Science Leave a Comment

The Ocean’s Challenge groups are organizing a new seminar by Sonia Chaabane, from the IRD CEREGE, Aix-en-Provence, France.

Seminar: “Facing the unknown: modern planktonic foraminifera migration is not enough”

Speaker: Sonia Chaabane, IRD CEREGE, Aix-en-Provence, France

Rising atmospheric CO₂ concentrations are driving ocean warming and acidification, reshaping marine habitats and threatening calcifying organisms such as planktonic foraminifera. These microorganisms play an important role in marine biogeochemical cycles, while their fossil record provides valuable archives of past environmental and climatic changes. However, their responses to ongoing climate change, particularly their capacity to adapt through geographical and vertical migration, remain poorly understood at the global scale.

To address this knowledge gap, the FORCIS (Foraminifera in a Changing Ocean) project has compiled the most comprehensive database to date of living planktonic foraminifera distributions, encompassing over 180,000 samples collected since 1910 across different ocean basins, depths, and sampling techniques. This extensive dataset provides a unique opportunity to investigate long-term changes in species abundance, diversity, and ecological niches in response to changing ocean conditions.

Our century-scale analyses reveal substantial poleward shifts in planktonic foraminifera distributions, accompanied by increasing diversity at mid- and high latitudes. Several species have also shifted their vertical habitats towards deeper, cooler waters, potentially as a response to warming surface conditions. Despite these movements, global planktonic foraminifera abundance has declined by 24.2 ± 0.1% over the last eight decades.

Looking ahead, projections for 2050 and 2100 suggest that tropical species will increasingly experience environmental conditions beyond their currently observed ecological niches, particularly in terms of temperature and carbonate chemistry. Ecological niche models further predict habitat contractions, continued poleward redistribution, and potential biodiversity losses in tropical oceans.

Together, these findings suggest that although geographical and vertical migration represent important responses to climate change, they may not be sufficient to compensate for the accelerating pace of ocean warming and acidification. These changes also have important implications for marine biodiversity, ocean carbon cycling, and the reliability of planktonic foraminifera as paleoceanographic proxies.

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Ocean acidification reshapes phytoplankton phosphorus metabolism under phosphate-limited conditions

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Phosphorus (P) availability constrains marine productivity, yet how ocean acidification interacts with intensifying phosphate limitation remains unresolved. Here we present multi-omics analyses of >1,000 generations of experimental diatom evolution to disentangle evolutionary and acclimation-driven responses to ocean acidification under different phosphate regimes. Long-term selection under elevated CO2 produced heritable increases in growth and carbon fixation that persisted irrespective of phosphate availability. In contrast, ocean acidification-driven reductions in particulate organic phosphorus were reversed after reciprocal transfers between selection treatments under phosphate limitation, indicating acclimation and environment-dependent P allocation. Multi-omics analyses indicate that the particulate organic phosphorus decline could be attributed to depletion of cellular P reserves and enrichment of non-P cell membrane lipids under combined ocean acidification and phosphate stress. Coastal mesocosm experiments revealed similarly reduced particulate organic phosphorus in natural phytoplankton at low-phosphate stations under ocean acidification. Global meta-transcriptomes further indicate widespread upregulation of gene expression in non-P cell membrane lipid pathways in high-pCO2 and low-phosphate regions. Earth system models predict a 211% to 2,185% decline in particulate organic phosphorus by 2100 under the under the Shared Socioeconomic Pathway (SSP)2–4.5 or SSP5–8.5 scenarios, respectively. These results show that ocean acidification could intensify nutrient imbalance and reshape global phosphorus cycling in marine ecosystems.

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Ocean acidification impairs the chiton shadow defensive response via degradation of aragonitic lenses

Published 9 November 2026 Science Leave a Comment
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Ocean acidification (OA) has the potential to disrupt the behavior of marine organisms by altering the function of γ-aminobutyric acid type A (GABAA) receptors. In addition, OA can impair sensory performance by reducing the calcification of mineralized sensory structures. Some species of polyplacophoran mollusks (chitons) possess calcified visual organs (aragonitic lenses) that contribute to shadow defense responses triggered by sudden decreases in overhead illumination. Therefore, we hypothesized that OA affects this response by impairing GABAA-mediated signaling or lens calcification. To test this hypothesis, we exposed chitons to “control” or acidified seawater and examined their shadow defensive behavior with and without gabazine, a GABAA antagonist known to restore OA-induced GABAergic dysfunction. Although gabazine did not eliminate behavioral differences between the control and acidified groups, acidification reduced the response strength, suggesting that factors other than GABAA-mediated signaling may contribute to the observed behavioral impairment. Microscopic observations revealed clouding of aragonitic lenses under acidic conditions, suggesting reduced optical performance. Overall, our results indicate that OA-induced degradation of calcified lens structures is associated with impaired shadow defense responses and may contribute to behavioral dysfunction. To the best of our knowledge, this study provides the first evidence that acidification-induced physical and optical changes in the visual anatomy can alter behavioral performance in animals.

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Transient disturbance and community convergence of coral-associated microbial communities under acidification, benzo[a]pyrene pollution, and combined stress in coral Acropora millepora

Published 9 November 2026 Science Leave a Comment
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Ocean acidification (OA), driven by global climate change together with pollution from organic contaminants, is increasing the ecological risk faced by coral reef ecosystems. The coral holobiont comprises diverse microbial communities that collectively support the coral host in coping with and adapting to environmental stress. However, the response of the coral holobiont to the combined stress of acidification and benzo[a]pyrene (BaP) remains poorly understood. In this study, Acropora millepora was selected as a model species to investigate the responses of coral-associated microbiomes to acidification (pH 7.8), BaP exposure (10 µg·L−1) and their combined effects. We found that while the cell density of coral-associated Symbiodiniaceae increased significantly with prolonged exposure time in all treatment groups, and there were no temporal differences in chlorophyll-a contents. The Symbiodiniaceae community was stable within all treatments, with Cladocopium as the dominant genus, and subtype C3u had the highest relative abundance (>70%). A rapid and significant increase in rare bacteria taxa was observed in the single-stress treatments (acidification, BaP), whereas prolonged exposure led to an increasing number of unique bacteria taxa in the combined-stress group in two weeks. Surprisingly, the main community structure of core coral-associated bacteria in the combined treatment group was close to that of the control group. Across all treatments, core coral-associated bacteria (including Sphingomonadaceae and Burkholderiaceae) consistently dominated the microbial community, while core coral-associated archaea exhibited more stochastic variations. Collectively, these results highlight the critical role of coral-associated microbiomes in rapidly and flexibly responding to environmental stressors, thereby contributing to the maintenance of holobiont stability under multiple stress conditions.

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Spectroscopic transduction in miniaturized lab-on-a-chip devices: functional nanomaterials and edge AI integration for real-time in situ environmental monitoring of heavy metals, pesticides, and marine pollutants

Published 9 November 2026 Science Leave a Comment
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The rising demand for real-time, in situ monitoring of heavy metals, pesticides, marine pollutants, and ocean acidification proxies has exposed the limitations of conventional laboratory-based spectroscopic methods, which suffer from slow turnaround, high costs, and poor adaptability to remote environments. This critical review surveys advances from 2023–2026 in microfluidic lab-on-a-chip (LOC) platforms that integrate functional nanomaterials with spectroscopic transduction (primarily fluorescence, absorbance, surface-enhanced Raman scattering (SERS), surface plasmon resonance (SPR), and quantum dot-based optical detection) and edge-deployable AI. Emphasis is placed on how nanomaterials enhance spectroscopic signals within microfluidic channels while addressing laminar flow control, passive mixing, antifouling, and stability in high-salinity and high-pressure marine matrices. The convergence with lightweight, hardware-aware AI/ML for on-chip denoising, drift compensation, multiplexing, and anomaly detection is examined under strict power and memory constraints. Ocean acidification monitoring requiring high-precision spectrophotometric pH and total alkalinity (TA) measurements serves as a rigorous benchmark for Arctic, open-ocean, and buoy deployments. Performance metrics, matrix interferences, autonomy limitations, and scalability barriers of these spectroscopic LOC systems are critically evaluated, with a forward-looking roadmap toward autonomous, IoT-enabled, and biodegradable spectroscopic microfluidic platforms for sustainable environmental monitoring.

Continue reading ‘Spectroscopic transduction in miniaturized lab-on-a-chip devices: functional nanomaterials and edge AI integration for real-time in situ environmental monitoring of heavy metals, pesticides, and marine pollutants’

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