Ocean acidification impairs embryonic development and disrupts ink sac gene expression in the pharaoh cuttlefish (Sepia pharaonis)

Published 12 November 2026 Science Leave a Comment
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Background: Ocean acidification (OA) represents a growing threat to marine biodiversity, particularly affecting the sensitive early life stages of invertebrates. While the physiological impacts of OA are widely recognized, its specific effects on organogenesis and the molecular regulation of defensive traits in cephalopods remain poorly understood. This study investigated the influence of acidified seawater on the embryonic development and ink sac formation in the Pharaoh cuttlefish (Sepia pharaonis).

Methods: Embryos were reared under four pH conditions (8.0, 7.7, 7.3, and 6.5). Embryonic growth, survival, hatching success, and ink sac morphogenesis were monitored throughout development. The expression of melanin synthesis–related genes, including tyr, per, and spNOS, was quantified using qRT-PCR.

Results: Ocean acidification impaired embryonic development in a pH-dependent manner. Severe acidification (pH 6.5) resulted in complete mortality and no surviving embryos by Day 9, while moderate acidification (pH 7.3) led to delayed development and failure to hatch by Day 11, compared to the hatching observed in the control group. Ink sac development was markedly inhibited under acidified conditions, resulting in reduced size and pigmentation. Consistent with these morphological abnormalities, the expression of melanin synthesis markers, including tyrosinase (tyr) and peroxidase (per), exhibited a biphasic response, with early transient induction followed by consistent downregulation across all acidified treatments, while, the expression of the regulatory gene Sepia pharaonis nitric oxide synthase (spNOS) was significantly suppressed under severe acidification.

Conclusions: These findings provide evidence that OA is associated with disrupted embryogenesis and impaired ink sac formation in S. pharaonis, accompanied by altered expression of melanin synthesis-related genes. The resulting reduction in defensive capacity may increase the vulnerability of hatchlings and potentially affect population recruitment under future ocean acidification scenarios.

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3DSeaVizKit: an interactive spatiotemporal visualization toolkit for ocean data

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Highlights

  • Web-based toolkit for interactive 3D visualization of ocean data.
  • Efficient pipeline for multivariate and multiresolution ocean products.
  • Unified framework for scalar, vector, Lagrangian, and uncertainty fields.
  • Reveals circulation, coherent structures, transport pathways, and 3D dynamics.
  • Demonstrated in coastal, regional, biogeochemical, and uncertainty applications.

Abstract

Scientific understanding, prediction, and communication to stakeholders are common objectives of ocean simulations and observing campaigns. Achieving these objectives can be greatly facilitated by advanced tools for exploring dynamic three-dimensional ocean data. Many scientific visualizations of spatiotemporal simulations rely on static two-dimensional representations that omit one or more spatial dimensions, potentially obscuring important features and relationships. A toolkit capable of creating coherent three-dimensional visualizations of ocean processes should move beyond isolated two-dimensional views and support the exploration of increasingly high-resolution simulations and large multidisciplinary observational data sets. In this work, we present 3DSeaVizKit, a visualization toolkit that processes multidisciplinary oceanographic data in a modular and computationally efficient manner to create portable, web-based, interactive 3D visualizations. Built upon the Plotly JavaScript library, the toolkit enables exploratory analysis of complex ocean fields directly within a web browser. We provide a software pipeline tailored to the computational demands of multivariate 3D ocean visualization and demonstrate its utility for revealing transport pathways, coherent structures, circulation features, biogeochemical-acidification interactions, subduction dynamics, and forecast uncertainties in high-resolution ocean simulations. The toolkit supports scalar fields such as temperature, salinity, and biogeochemical tracers; vector fields such as velocity and vorticity; and Lagrangian products including trajectories, flow maps, and coherent structures. Applications include the visualization of the Loop Current system and eddy interactions in the Gulf of Mexico, subduction processes and forecast uncertainties in the Alboran Sea, coupled biogeochemical and ocean-acidification dynamics in Massachusetts Bay, and transport pathways and coherent structures around Nantucket and Martha’s Vineyard.

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Potential governing mechanisms of iodine radioisotopes behavior in marine and freshwater fish: transfer, accumulation, biotransformation, and uncertainties under climate change

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Highlights

  • Waterborne iodine isotopes uptake shifts from the gills to the GIT in seawater.
  • Exposure pathway and chemical form shape biodistribution and kinetics.
  • Accumulation in the gills and liver is determined more by species-specific factors.
  • Climate stressors nonlinearly alter iodine isotopes metabolism.

Abstract

The anthropogenic, long-lived radioisotope 129I is a growing long-term concern for aquatic ecosystems due to its predominantly chronic release from nuclear industry facilities, high environmental mobility, and strong biological affinity. Unlike well-studied radionuclides, the mechanisms governing the transfer, accumulation, and biotransformation of iodine radioisotopes in marine and freshwater biota remain insufficiently understood, particularly in fish, which represent a critical link in human exposure pathways. This knowledge gap limits the accuracy of radiological risk assessments and the development of effective mitigation strategies for a contaminant that persists on geological time scales. These uncertainties are further amplified under climate change, as rising temperatures, acidification, and increased co-occurring pollutant loads alter fish physiology and affect iodine metabolism. In aquatic systems, 129I occurs mainly as iodide and iodate, both biologically relevant and involved in enzymatically mediated pathways leading to the synthesis of iodine-containing compounds, including thyroid hormones. Despite the ecological and physiological importance of these processes, existing reviews largely address iodine in fish in a general or thyroid-centered context. This review synthesizes and critically evaluates current knowledge on the mechanisms of iodine radioisotope transfer, accumulation, and biotransformation in marine and freshwater fish, with particular emphasis on membrane transport systems, tissue-specific metabolism, and climate change effects.

Graphical Abstract

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Physio–biochemical and transcriptomic responses of the marine green microalga Chlorella sp. to elevated pH and total alkalinity

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The effects of elevated pH and total alkalinity (TA ≈ HCO3– + 2CO32–) on marine primary productivity–the cornerstone of marine food webs and trophic dynamics–remains poorly understood. In this study, we investigated the physiological, biochemical and transcriptomic responses of the green microalga Chlorella sp. to elevated pH (pH = 8.30, TA = 2353 μmol kg–1) and elevated TA under high pH conditions (pH = 8.30, TA = 3854 μmol kg–1). Elevated pH reduced the growth rate and cellular carbohydrate contents, and down–regulated transcripts encoding key enzymes involved in photosynthetic carbon fixation (including ribulose–1,5–bisphosphate carboxylase/oxygenase (Rubisco) and carbonic anhydrase), as well as ion transport components (V–type H+ ATPase and Na+ (K+, urea)–H+ transporter). Conversely, elevated TA significantly enhanced the growth rate and increased cellular particulate organic carbon and carbohydrate contents. Furthermore, elevated TA mitigated the inhibitory effect of high pH by up–regulating or stabilizing gene expressions involved in carbon fixation, fatty acid biosynthesis and degradation pathways, V–type H+ ATPase and H+ exporter. Overall, these findings demonstrate that elevated TA effectively relieves high–pH stress and stimulates photosynthetic carbon uptake in Chlorella sp., providing valuable scientific insights in phytoplankton–mediated carbon dioxide removal (CDR) strategies.

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Seawater pH measurement: a critical metrological assessment of operational scales and the unified pH scale

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Ocean acidification, driven by rising anthropogenic CO2, causes a measurable decrease in seawater pH with consequences for marine ecosystems. Accurate, traceable pH measurement is essential for ocean monitoring sensors. This critical review examines five pH scales: the IUPAC activity scale (pH), the free proton scale (pHF), the total proton scale (pHT), the seawater scale (pHSWS), and the unified scale (pHabs). For each scale, the analytical methods, metrological assumptions, traceability chain to the SI, and measurement uncertainties are analyzed. The review updates the foundational 2016 work with subsequent developments and focuses particularly on the application of pHabs to saline solutions. In its current differential-potentiometric realization, pHabs yields an expanded uncertainty U(pH) ≈ 0.2 in seawater. GOA-ON expresses its goals as standard uncertainties (k = 1): 0.003 (climate) and 0.02 (weather), equivalent to U ≤ 0.006 and U ≤ 0.04 for k = 2. The reported U(pH) ≈ 0.2 is therefore approximately 33 times the climate-quality target and approximately 5 times the weather-quality target, compared at the same coverage. The dominant contribution is the residual liquid-junction potential; the standard uncertainty of 6.3 mV (k = 1) reported in dilute solutions corresponds, at 25 °C, to u(pH) ≈ 0.1 and U(pH) ≈ 0.2 for k = 2, consistent with the reported U(pH) ≈ 0.2. However, this dilute-solution estimate is not a validated uncertainty for seawater and should not be extrapolated to seawater without experimental validation. Liquid-junction effects are therefore a priority for potentiometric sensors and for the current pHabs realization. Spectrophotometric pHT sensors avoid a liquid junction but have distinct uncertainty contributions related to indicator characterization, optical measurement, temperature, salinity, and sample perturbation.

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Tissue-specific expression responses of antioxidant, immune, and metabolic genes in juvenile yellowfin tuna (Thunnus albacares) under acute low-pH stress

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Acute reductions in seawater pH may disrupt acid–base regulation and physiological homeostasis in marine fish, but tissue-specific molecular responses in juvenile yellowfin tuna remain poorly understood. Juveniles of yellowfin tuna were exposed for 48 h to four seawater pH levels (8.1, 7.6, 7.1, and 6.6), with three replicate tanks per treatment. The expression of selected antioxidant-, immune-, inflammatory-, and metabolism-related genes in the liver and gill was quantified using qRT-PCR. In the gill, most examined genes were upregulated under low-pH exposure, although the magnitude and pH dependence of the responses varied among genes. In the liver, antioxidant genes and most immune-related genes were downregulated, whereas tnf-α was upregulated at pH 7.1. Hepatic metabolic genes also exhibited treatment-dependent responses: mdh2 was significantly downregulated across all low-pH treatments, whereas pck2 was significantly upregulated only at pH 7.1 and 6.6. In contrast, dgat1b was significantly downregulated exclusively at pH 7.1 and 6.6. These contrasting expression patterns demonstrate marked tissue specificity in the acute low-pH response of juvenile yellowfin tuna, with broader transcriptional activation in the gill and selective suppression and metabolic adjustment in the liver. The findings provide an initial molecular basis for further evaluating the physiological consequences of acute and chronic low-pH exposure in this high-metabolic-rate pelagic species.

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Microhabitat-driven variation in predator–prey interactions between the crab Acanthocyclus hassleri and the mussel Perumytilus purpuratus

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Highlights

  • Microhabitat variability modulates predator–prey interactions in rocky intertidal systems.
  • Tide pool mussels experience recurrent hyposalinity and low pH conditions.
  • Reduced shell resistance increases predation vulnerability in tide pool mussels.
  • Fine-scale coastal heterogeneity drives trait-mediated trophic interactions.

Abstract

This study evaluates how the microhabitat of origin of the mussel Perumytilus purpuratus is associated with its vulnerability to predation by the crab Acanthocyclus hassleri. A comparison was made of individuals of P. purpuratus from three intertidal microhabitats: higher limit, lower limit, and tide pool (HL, LL, TP, respectively). The latter receives freshwater inputs associated with an adjacent stream and rainfall. Three environmental variables (salinity, temperature, and pH) and prey shell-breaking strength were measured, and predation experiments using single-prey and mixed-prey diets were also conducted. These experiments evaluated attack rate, handling time, attack zone, size of prey consumed, and crushing claw force. The results indicate that TP experience more extreme conditions, with lower salinity and pH during low tide compared with the other microhabitats (HL and LL). These conditions were associated with lower shell-breaking strength, which may reduce prey resistance to predator attacks. While attack rate remained similar across different diets, under a mixed diet, the predator A. hassleri showed greater consumption of mussels from TP. Tide pool prey also tended to require less handling time than prey from the other microhabitats. The anterior region of the prey shell (umbo area) was the most frequently attacked, regardless of the microhabitat. Smaller individuals from LL were more frequently consumed, whereas larger prey sizes were targeted in HL and TP. A. hassleri possesses the strength necessary to attack prey from all three microhabitats. Overall, these findings suggest that microhabitat-associated differences in shell characteristics may influence prey vulnerability to predation and shape prey selection by A. hassleri.

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Cross-network synergies fundamental to sustained global ocean carbon observing

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Abstract

The ocean’s critical role in absorbing anthropogenic carbon dioxide (CO2) and the resulting changes in the ocean carbon cycle are monitored by global-scale observing networks, including the Global Ocean Ship-based Investigations Program (GO-SHIP), Surface Ocean CO2 Observing Network (SOCONET), and Biogeochemical-Argo (BGC-Argo). Given the scale of the challenge to characterize the evolving ocean carbon cycle, no single network is sufficient; a coordinated, collaborative, cross-network approach is essential. This manuscript describes the overarching research questions driving these three networks and details their inherent synergies and dependencies, such as GO-SHIP and SOCONET delivering reference-quality measurements for validation of other in situ and satellite-based data, GO-SHIP providing opportunities for float deployment, and BGC-Argo filling gaps with high-frequency autonomous data. We provide recommendations for optimizing these relationships and an intra-network strategy moving forward. As representatives of the science committees for these networks, we are committed to sustaining and enhancing the collaborative structure necessary to fill critical knowledge gaps in ocean carbon cycle research, improve climate prediction, and enable future ocean ecosystem forecasting.

Plain Language Summary

The ocean plays a vital role in absorbing human-caused emissions of carbon dioxide, but this process is changing the ocean’s carbon cycle. Monitoring these vast global ocean changes requires a coordinated approach involving three major ocean observing networks: GO-SHIP, SOCONET, and BGC-Argo. This paper details how to maximize synergies across these networks to close critical knowledge gaps, improve climate prediction, and enable ocean ecosystem forecasts.

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Red list of ecosystems assessment of Pacific coral reefs

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Coral reefs of the Pacific region extend across approximately 30°N to 30°S, covering roughly 35 500 km2. They range from tropical waters of Papua New Guinea in the West to subtropical latitudes, such as Southeastern Pitcairn or Northern Hawaii borders. This encompasses 21 coral reef ecoregions as defined by the Marine Ecoregions Of the World (MEOW) and Marine and Coastal Biodiversity Management in Pacific Island Countries (MACBIO) classifications. The region hosts exceptionally diverse coral and reef fish communities, the latter featuring high levels of endemism in various locations, and is characterised by extensive tropical archipelagos and atolls spanning wide gradients in ocean productivity, human influence, remoteness, geomorphology and climatic conditions. These ecosystems face increasing pressure from ocean warming and marine heatwaves, acidification, extreme weather events, invasive and harmful species outbreaks, overfishing, coastal development and pollution. The IUCN Red List of Ecosystems assessment, based on the benthic and fish datasets from the Global Coral Reef Monitoring Network (1993-2024) and the NOAA Degree Heating Weeks (DHW) dataset (1985-2025), found that coral reefs within all 21 Pacific ecoregions were at a high risk of collapse (i.e. featuring declining attributes to levels where the ecosystem transforms into a different type or is completely lost). This result was, however, largely driven by future climate change projections. Indeed, several criteria assessed in this work are still showing optimistic trends at the regional scale, especially when looking at the actual distribution of Pacific coral reefs or when comparing past and recent estimates of coral cover decline. Under Criterion A (decline in hard coral cover distribution), about 72% of the Pacific reef surface area (14 ecoregions) was classified as Least Concern, while 14% (3 ecoregions) was Vulnerable and 13% (4 ecoregions) was Endangered. Under Criterion B (restricted distribution), about 95% of the Pacific reef area (17 ecoregions) was Least Concern, while 3% (encompassing 3 ecoregions) was Vulnerable. Under Criterion C1 (observed thermal stress), the trend is reversed, with 49% of the reef area (9 ecoregions) classified as Vulnerable, 19% (6 ecoregions) as Endangered and the remaining 32% as either Near Threatened (5 ecoregions) or Least Concern (New Caledonia only). Criterion C2 (projected thermal stress) drives the entire Pacific reef area and all 21 ecoregions to Critically Endangered. Under Criterion D (alteration of biotic interactions), about 52% of the reef area (7 ecoregions) was either Least Concern or Near Threatened, 16% (7 ecoregions) was Vulnerable and 32% (7 ecoregions) was either Endangered or Critically Endangered. These results highlight the need to consolidate reef resilience towards future climate change and to reinforce the conservation of coral reef habitats through strengthened area-based management, sustainable fisheries operation, climate adaptation measures and accelerated global efforts to reduce greenhouse gas emissions.

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Acidified seawater stalls cuttlefish embryo growth and ink sac gene activity in lab study

Published 12 November 2026 Press releases Leave a Comment

Laboratory-reared embryos of the Pharaoh cuttlefish (Sepia pharaonis) developed poorly, formed smaller and paler ink sacs, and showed sharply altered expression of melanin-synthesis genes when their seawater was acidified, according to a new study published in Frontiers in Physiology. The research, conducted at Lingnan Normal University in Zhanjiang, China, exposed cuttlefish eggs to four pH levels — 8.0 as a control, plus 7.7, 7.3 and 6.5 — and tracked their growth, survival, organ formation and gene activity day by day. The results point to the embryonic stage as a particularly sensitive window in the life of a cephalopod, an animal whose adults are known to buffer external pH changes reasonably well.

The experimental design was straightforward but demanding. Live egg masses were collected from coastal waters off Zhanjiang in April 2021 and pre-cultured for three days at 28 degrees Celsius and a salinity of 23 parts per thousand to synchronize developmental stages. Eggs from 15 different females were mixed and evenly distributed across four treatment systems, each with three replicate tanks, so that every group contained offspring from all parental sources. Acidified seawater was produced by equilibrating filtered water with a high-purity carbon dioxide and air mixture, with pH adjusted solely by regulating gas flow rather than adding chemical acids. Water chemistry was monitored daily, and the carbonate system parameters were calculated with CO2SYS software. The treatments spanned a wide chemical range: mean pCO2 rose from about 415 microatmospheres in the control to roughly 1,350 at pH 7.7, 3,150 at pH 7.3 and 17,500 at pH 6.5, while the aragonite saturation state fell from 3.75 to 0.15 across the same gradient.

The developmental consequences followed the severity of acidification. On day one, embryos in all treatments looked alike, corresponding roughly to stage 17 of cuttlefish development, with a large transparent yolk sac and a well-defined mantle. By day four, divergence appeared: control embryos and those at pH 7.7 and 7.3 progressed normally, showing mantle expression, yolk absorption and the appearance of chromatophores, while embryos at pH 6.5 showed clear retardation, no visible chromatophores and a persistently large yolk sac. By day seven the gap had widened further, and by day nine the pH 6.5 group had suffered complete mortality, with yolk sac degeneration and tissue deterioration. Control embryos hatched by day 11. Embryos at pH 7.3 remained alive until that point but were markedly developmentally delayed and suffered increased mortality, while the pH 7.7 group showed pronounced developmental delay and failed to hatch, with data collection ending on day nine.

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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

Published 11 November 2026 Science Leave a Comment
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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

Published 11 November 2026 Science Leave a Comment
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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

Published 11 November 2026 Science Leave a Comment
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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

Published 10 November 2026 Science Leave a Comment
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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

Published 10 November 2026 Science Leave a Comment
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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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