Posts Tagged 'methods'

Method for correcting the temperature dependence of field-type glass electrode pH sensors

Published 14 August 2026 Science Leave a Comment
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Seawater pH measurement is essential for monitoring ocean acidification and its biogeochemical impacts. Glass electrode pH sensors are widely used for in situ applications due to their ease of operation, low power consumption, and no reagent requirements. However, their accuracy can be affected by temperature-dependent effects, particularly those associated with the internal reference solution. Conventional calibration methods based on the Nernst response do not explicitly account for temperature-induced variations in the internal solution, which may lead to systematic bias under conditions with large temperature gradients. In this study, a correction method is proposed to address temperature-dependent errors by modeling the internal pH (pHin). The model incorporates two primary temperature-dependent contributions: the intrinsic temperature dependence of the phosphate buffer and potential shifts caused by activity changes in saturated KCl. These effects are combined through the electrode response factor (fR), defined as the ratio of the observed electrode slope to the theoretical Nernst slope, to estimate pHin as a function of temperature and correct measured pH values to a reference temperature of 25 °C. Application of the method to vertical seawater profiles demonstrated a reduction in deviation from colorimetric reference measurements. The corrected results showed reduced temperature-dependent bias across depth. This approach provides a practical framework for improving the reliability of in situ glass electrode pH measurements under varying thermal conditions. The proposed method addresses equilibrium temperature-dependent effects of the internal solution but does not explicitly account for transient hysteresis, pressure effects, or long-term sensor drift.

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pH–salinity-driven regulation in carbon utilization kinetics of the intertidal seagrass Zostera japonica along China’s coastline

Published 27 July 2026 Science Closed
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Highlights

  • We innovatively define two biophysical parameters (pH change rate and acceleration) of Zostera japonica photosynthesis.
  • pH change acceleration is sensitive to the regulation of carbon utilization pathways during Z. japonica photosynthesis.
  • A progressive pH–salinity-driven regulation mode of carbon utilization pathways in Z. japonica photosynthesis is summarized.
  • The impact of ocean acidification and alkalization on seagrass is characterized from a new biophysical standpoint.

Abstract

Seagrass carbon concentration mechanisms are modulated by seawater pH and salinity, yet their progressive regulation in photosynthetic inorganic carbon utilization pathways remain poorly characterized. This study novelly mathematically characterized first-order (pH change rate) and second-order (pH change acceleration) derivatives from pH-drift experiments in the intertidal seagrass Zostera japonica along China’s coastline. The pH change-based method effectively highlights the dissolved inorganic carbon (DIC) utilization and biomass accumulation of seagrass, while pH change acceleration is sensitive to the progressive switch of DIC utilization pathways during Z. japonica photosynthesis. As pH increases, six significant regulations emerge that have ecophysiological significance: a. primary regulation via reaching the CO2 compensation point; b. extracellular carbonic anhydrase (exCA) activity dropping to negligible levels; c. diminished efficiency of proton pump-mediated extracellular acidification in supplying CO2; d. regulation via reaching the bicarbonate saturation point; e. regulation via reaching the bicarbonate compensation point; and f. regulation via enhanced respiratory CO2 into seawater temporarily stimulating photosynthesis as a feedback. We summarize a progressive and universal pH–salinity-driven regulation mode reflecting different combinations of DIC utilization pathways and their respective intensities. Specifically, seawater pH modulates the mode’s fluctuating thresholds, while salinity governs the amplitude. Unexpectedly, elevated salinity serves as an effective stimulant for Z. japonica to maintain strong DIC utilization intensity in high pH (> 9.1) environments. Ocean acidification could increase pH change acceleration by 166%, enhancing carbon fixation, whereas artificial ocean alkalinity enhancement (Ca(OH)2 supplementation and olivine-seawater weathering) could reduce it by 165% and 105%, respectively, risking mortality of Z. japonica. Additionally, the salinity-dependent braking point (where acceleration drops to zero) serves as a critical threshold for seagrass photosynthesis and a new factor for transplantation-based restoration.

Continue reading ‘pH–salinity-driven regulation in carbon utilization kinetics of the intertidal seagrass Zostera japonica along China’s coastline’

Entering the era of directly supporting society with observation-based ocean acidification data

Published 2 July 2026 Science Closed
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Ocean acidification is a growing concern for many nations around the world. However, our capacity to monitor changes in carbonate chemistry with sufficient spatial and temporal resolution, has until now, been limited, which has impeded effective action and decision-making at international, national, and regional levels. Recent advancements in machine learning have enabled the integration of Earth observation data with in situ measurements, enhancing data coverage and improving our ability to monitor ocean acidification globally. Here, we highlight how space agencies, particularly the European Space Agency, have supported the development of such products and explore their utility for a broad spectrum of end users, ranging from scientists to resource managers to policy makers and the general public. Spatial and temporal resolution of these products is now on the order of 0.25 × 0.25° and 8-daily, respectively; with similar or slightly enhanced accuracy compared to other methods (e.g., fCO2 in open and coastal ocean are 13 and 25 μatm, respectively). We provide five use cases that demonstrate how the data can be used to: (a) communicate ocean acidification; (b) aid marine planning activities; (c) set up national monitoring and understand baseline conditions; (d) assess impacts of aquaculture; and (e) assess impacts to coral habitats. While these developments represent significant progress, further efforts will enhance the efficacy of observational-data in coastal waters, and could develop complementary biological or water quality indicators. These activities will be accelerated by further building global capacity to ensure equitable access and application of these tools.

Plain Language Summary

Ocean acidification, a change in ocean chemistry caused by the long-term increase in atmospheric carbon dioxide, is a growing global concern. However, it is hard to track these changes accurately across the entire ocean, making it difficult for governments and communities to understand the threat and respond effectively. New advances in machine learning now make it possible to combine satellite data with ocean measurements which have improved our ability to monitor ocean acidification. Here, we highlight how projects funded by the European Space Agency have helped to develop tools that make this information accessible and useful for multiple groups, including scientists, resource managers, policy makers, and the general public. We present five examples for using the data: raising awareness about ocean acidification, supporting marine planning, creating national monitoring systems, understanding the effects on aquaculture like shellfish farming, and evaluating risks to coral reefs. This progress has been long needed, and efforts are beginning to focus on further improving our abilities to observe coastal areas, where conditions can change quickly. Future efforts can now focus on exploring new ways to track changes, and making sure people around the world have the tools and training needed to use these new resources effectively.

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High-precision performance of a full-ocean-depth pH sensor: calibration and assessment under simulated hadal pressure conditions

Published 23 June 2026 Science Closed
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Real-time in situ pH monitoring in the hadal zone is essential for resolving deep-sea carbon dynamics but is severely challenged by extreme hydrostatic pressures and complex biochemical environments. Current sensors often lack the necessary robustness and calibration protocols for full-ocean-depth applications. To address these challenges, we developed a solid-state electrochemical pH sensor system comprising a fouling-resistant sulfonated poly(ether ether ketone)/ionic liquid composite IrOx (SP/IL-IrOx) working electrode and a pressure-tolerant silica-stabilized ionic liquid (Si-StabIL) reference electrode. Using Tris-artificial seawater (Tris-AS) buffers, we established a standardized high-pressure calibration protocol and systematically evaluated sensor performance over the full-ocean-depth pressure range (0.1−120 MPa) under simulated hadal pressure conditions. The sensor exhibited near-Nernstian sensitivity with high reversibility and repeatability, with potential deviations of no more than 1.6 mV, corresponding to less than 0.03 pH units across the investigated pressure range. Long-term reliability was demonstrated by a minimal drift of only 0.01 pH units during continuous operation in the Tris-AS buffer at 120 MPa for 65 h. Crucially, the sensor captured the nonlinear, pressure-driven acidification of simulated hadal-zone seawater during a 7 day pressurization experiment while maintaining stable response in calibration buffers. These results demonstrate the robustness of the sensor system and provide an experimental basis for calibration and pH assessment under simulated full-ocean-depth pressure conditions.

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Marine radionuclides in climate change studies: Pacific Ocean and marginal seas

Published 22 June 2026 Science Closed
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Highlights

  • Marine radionuclides with well-constrained input histories have proven to be sensitive tracers.
  • Radionuclides in oceanic compartments enable to study transport and biogeochemical processes.
  • A decline in vertical mixing of upper waters in the North Pacific over recent decades was identified.
  • Radionuclides were used in climate change studies in marginal seas of the NW Pacific.

Abstract

Observed global warming has profoundly affected the world’s oceans, which are experiencing increasingly frequent marine heatwaves and a slowdown of the Global Meridional Overturning Circulation. These changes disrupt ocean circulation patterns, alter biogeochemical cycles, enhance surface ocean acidification, and drive poleward migration of marine organisms. Marine radionuclides (e.g., 3H, 14C, 90Sr, 129I, 134Cs, 137Cs, and Pu isotopes), released from nuclear activities since the 1940s, provide time-resolved tracers of oceanic processes owing to their well-documented input functions and distinct chemical behaviors. Their distributions in seawater, bottom sediments, and marine biota have recorded climate-driven modifications in ocean circulation and stratification. The Pacific Ocean, the largest ocean basin on Earth, has undergone changes in recent decades under ongoing climate forcing. Long-term radionuclide observations indicate a decline in vertical mixing in the upper North Pacific Ocean, likely associated with enhanced stratification. Variability linked to Asian monsoon systems and El Niño–Southern Oscillation (ENSO) events is also clearly reflected in radionuclide records from the marginal seas of the Northwest Pacific. Radionuclide datasets provide essential reference benchmarks for calibrating and validating Ocean General Circulation Models and Earth System Models under future climate scenarios. To strengthen predictive capability, coordinated international, high-resolution sampling programs covering the entire world ocean are required, together with measurement campaigns employing newly developed ultra-sensitive analytical techniques. Particular attention should be given to the Southern, Arctic, and Subarctic Oceans because of their critical role in the global climate system and the current scarcity of comprehensive radionuclide data.

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Real-time acidification monitoring through Sofar buoy and SAMI-pH integration

Published 23 April 2026 Science Closed
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Ocean acidification (OA) impairs the ability of corals to build and maintain reef structures by reducing calcium carbonate deposition and accelerating the dissolution of existing frameworks. OA conditions can result from both natural pH fluctuations, driven by diel and seasonal variability in biological activity and water quality, and long-term increases in atmospheric CO2 absorption. Accurate characterization of OA requires precise, high-frequency time-series data, particularly in nearshore ecosystems where benthic community metabolism can cause rapid, localized shifts in carbonate chemistry. However, continuous, high-resolution pH monitoring remains challenging, and most existing technologies lack real-time feedback capabilities. Here, we present a real-time acidification monitoring system that integrates a Sofar Spotter buoy with a Sunburst SAMI-pH sensor. The system delivers continuous environmental data (benthic pH and temperature, surface temperature, wind, wave height, and barometric pressure) and sensor health diagnostics (battery levels and cellular connectivity status) to a public-facing dashboard. This system enables real-time access to high-frequency pH data and provides a modular and cost-effective alternative to larger, more complex platforms such as MAPCO2 buoys. Increased accessibility supports broader and more scalable monitoring efforts, supporting scientists, resource managers, and policymakers in tracking diel, seasonal, and long-term OA dynamics.

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Individual foraminiferal analysis: a promising tool for high-resolution temperature and pH reconstruction

Published 27 March 2026 Science Closed
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Compared with traditional bulk foraminiferal analysis methods, in situ analysis of individual foraminiferal tests (individual foraminiferal analysis or IFA) offers several advantages over traditional bulk methods, including enhanced temporal resolution where fossiliferous sample material is limited as well as potentially resolving seasonal-scale climate variability in deep time. Despite these advantages, applications of element-to‑calcium (El/Ca) ratios and δ11B in benthic foraminifera using IFA remain limited, and the biogeochemical drivers of intra-test and inter-test geochemical variability are poorly constrained. In this study, we systematically evaluate El/Ca ratios and δ11B in individual benthic foraminifera. By analysing Holocene epifaunal benthic foraminiferal species Cibicidoides wuellerstorfi from a deep ocean core site (ODP Site 999), we conclude that intra- and inter-test variabilities are regulated by ontogenetic effects resulting in inter-test variabilities of ±0.14 mmol/mol Mg/Ca, ± 14 μmol/mol B/Ca, and ± 0.18 ‰ δ11B. Application of the IFA method to epifaunal benthic foraminifera species Cibicides lobatulus from a box core in the English Channel, UK reveals ~0.1 pH units acidification and ~ 1 °C warming since the mid-19th century. By demonstrating that individual-level variability in reconstructed temperature and pH tracks seasonal trends in the available contemporaneous water-column instrumental measurements at the same site, we provide a ground-truthing to our multi-proxy IFA methodology, and also demonstrate the potential for benthic IFA to provide seasonal-scale reconstructions of ocean climate over hundreds to millions of years.

Continue reading ‘Individual foraminiferal analysis: a promising tool for high-resolution temperature and pH reconstruction’

Experimental exposure to climate change scenarios imposed alterations on the morphological traits of sessile and low-motility marine invertebrates

Published 24 March 2026 Science Closed
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Background

Over the past 50 years, the oceans have absorbed over 90% of global warming heat, leading to warming, acidification and declining oxygen levels that are disrupting marine ecosystems and altering species distributions and productivity. The vulnerability of marine organisms to these changes depends on their biological traits, habitat conditions and adaptive capacity, influencing their growth, behaviour and overall population health. Micro-computed tomography (micro-CT) has been previously used for studying the morphological traits of marine invertebrates, which provide important insights into species functionality and responses to climate change and ocean acidification. Micro-CT enables non-destructive, high-resolution 3D analysis of internal and external structures, allowing precise measurement of traits such as density, porosity and morphology that are valuable for climate change research.

New information

The present manuscript describes micro-CT imaging datasets generated to investigate the effects of climate change on the morphological structure of two benthic marine invertebrates: the low-motility gastropod Hexaplex trunculus (Linnaeus, 1758) and the sessile sponge Chondrilla nucula Schmidt, 1862. Both species are considered particularly vulnerable to environmental stressors. To date, no study has investigated the effects of ocean warming and acidification on sponges using micro-CT technology. Using a common garden experimental design, individuals from geographically distinct populations exposed to different natural environmental regimes were subjected to combined warming and acidification scenarios to assess their morphological responses and adaptive capacity.

Continue reading ‘Experimental exposure to climate change scenarios imposed alterations on the morphological traits of sessile and low-motility marine invertebrates’

Coulometric readout of ion-selective electrodes for an aquatic pH probe

Published 17 March 2026 Science Closed
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Ion-selective electrodes are widely used for the detection of ions in aqueous solutions such as natural waters. Their origin traces back to 1909 with the invention of the pH glass electrode. Nowadays, routine pH measurements are still performed by potentiometric measurements with glass electrodes. The phase-boundary potential difference at the glass membrane-sample interface, measured against a reference electrode, relates to solution pH following the Nernst equation. While being user-friendly, they suffer from multiple drawbacks. Firstly, their sensitivity is intrinsically dictated by the Nernst equation and is limited to 59.2 mV/pH at 25 °C. This might not be sufficient for applications where high precision pH sensing is required, such as ocean acidification monitoring. Secondly, a Nernstian response can only be obtained if all the other potential differences in the overall electrochemical cell are constant over the whole experimental procedure. This is not the case when, for example, the temperature or the ionic strength of the sample change during the measurement routine. The former influences the glass electrode itself, while the latter rather affects the reference electrode via liquid junction potential variations.

This thesis presents enhancements to the potentiometric experimental setup for pH sensing with glass or polymeric membrane pH electrodes, achieved through the integration of electronic components, chemical symmetry and open liquid junctions. A dynamic electrochemical readout called constant potential coulometry is explored for in situ pH sensing in coastal waters by implementation in a submersible probe deployed in the Krka River estuary in April 2025.

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Ocean acidification at the crossroads I: harmonizing unpurified and purified meta-cresol purple spectrophotometric pHT measurements based on absorbance data

Published 11 March 2026 Science Closed
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Consistent monitoring of seawater spectrophotometric pH on the total hydrogen ion scale (pHT) has been questioned by an evolving method, with changes in parameterization and the purity of the meta-cresol purple (mCP). Using real seawater samples, we demonstrate that spectrophotometric pHT measurements obtained with unpurified (UNPUR) and purified (PUR) mCP can be harmonized to within 0.003 pH units, the climate-goal threshold. This agreement is only achieved when mCP impurities at 434 nm are quantified for both the UNPUR and PUR mCP, assuming no impurities affect 545 nm absorbances, and impurity-corrected absorbance data at 434 nm are used in the same parameterization to calculate pHT. We applied this approach to a ship-based pHT time series transitioning from UNPUR to PUR mCP measurements. Our results show that previous claims suggesting that UNPUR mCP underestimates pHT in the upper pH range are misleading, as they were based on the inappropriate use of absorbances obtained with UNPUR mCP with a parameterization developed for PUR mCP. In fact, our data reveal better agreement between UNPUR and PUR pHT in the upper pH range of seawater, while UNPUR mCP tends to overestimate pHT in the lower pH range. These findings highlight the urgent need for the global chemical oceanography community to establish a spectrophotometric pHT method with full traceability to the International System of Units (SI), along with affordable and distributed certified reference materials and characterized purified mCP. This work supports the need for harmonization efforts to ensure the reliability of pHT data in global synthesis products.

Continue reading ‘Ocean acidification at the crossroads I: harmonizing unpurified and purified meta-cresol purple spectrophotometric pHT measurements based on absorbance data’

High vertical resolution measurements of pH, pCO2, total alkalinity, and dissolved inorganic carbon using a new approach: the carbonate profiler

Published 4 March 2026 Science Closed
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The equilibrium between the different parameters of the marine carbonate system–dissolved inorganic carbon (DIC), total alkalinity (TA), partial pressure of CO2, and pH–is the core of ocean acidification studies, evaluation of inorganic carbon inventory, and air-sea CO2 fluxes. To date, it has been challenging to simultaneously measure all those components in the water column due to different sampling methodologies, and especially in stratified waters, where sharp vertical biogeochemical gradients may occur. In this study, we designed a low-cost and easy-to-assemble pumping system, which, combined with a CTD profiler, makes a PUMP-CTD system that can efficiently serve as a precise water column sampler, allowing for simultaneous measurements and sampling of dissolved inorganic carbon, total alkalinity, partial pressure of CO2, and pH with high vertical resolution. Importantly, this water sampler (denoted as the carbonate profiler) can be easily integrated with equilibrator-based continuous pCO2 measurement systems, which are routinely used for underway data acquisition, making them suitable for water column sampling as well. We tested the carbonate profiler in the open ocean water column, where we obtained excellent consistency between measured pCO2 and calculated values based on pH and DIC. Afterwards, we tested the operability of the system by measuring the vertical variability of all the components of the marine carbonate system in the Vistula River estuarine waters (southern Baltic Sea) and within the Arctic fjords affected by continental freshwater runoff. Overall, this system performed outstandingly, with a vertical resolution of half a meter, proving its utility in accurately measuring steep biogeochemical changes in the water column regardless of the analytical method used.

Continue reading ‘High vertical resolution measurements of pH, pCO2, total alkalinity, and dissolved inorganic carbon using a new approach: the carbonate profiler’

Neglecting organic alkalinity introduces greater error than assuming boron to salinity ratios in Arctic sea ice brine carbonate system calculations

Published 3 March 2026 Science Closed
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While total alkalinity (AT) is traditionally attributed to dissolved inorganic constituents, dissolved organic matter (DOM) can significantly contribute to AT as organic alkalinity (OrgAlk), introducing errors in calculated carbonate parameters, such as the CaCO3 saturation state (Ω) and partial pressure of CO2 (pCO2). This study presents measurements of OrgAlk in the Arctic Ocean sea ice system and assesses its influence on carbonate speciation, with OrgAlk contributing 0.1–1.0% to AT. Sea ice brine exhibited elevated DOM and OrgAlk, with an OrgAlk/DOC ratio of 0.13 ± 0.06 µmol kg− 1 µM− 1, consistent with global ocean values. Correcting AT for OrgAlk increased computed pCO2 up to 84 µatm and decreased Ω ≤ 0.2 for aragonite and ≤ 0.3 for calcite compared to un-adjusted values. Elevated brine pCO2 suggests that conventional estimates of Arctic sea ice CO2 uptake may be overestimated when AT is used as an input parameter, particularly in spring as OrgAlk is released. The omission of OrgAlk contributed greater errors to calculated carbonate parameters than the differences in boron from using direct measurements versus salinity based ratios, highlighting the necessity of accounting for even minor OrgAlk to refine predictions of surface pCO2, net air-sea CO2 flux, and the fate of CaCO3 minerals.

Continue reading ‘Neglecting organic alkalinity introduces greater error than assuming boron to salinity ratios in Arctic sea ice brine carbonate system calculations’

A standardised experimental setup for simulating ocean warming and acidification in benthic marine invertebrates

Published 26 February 2026 Science Closed
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Recent studies identify ocean warming and acidification as major drivers of ecological change in the Eastern Mediterranean, posing serious threats to marine biodiversity, particularly for sessile or low-mobility organisms that cannot escape unfavourable conditions. At the same time, the need for standardised experimental approaches capable of generating high-quality data on organismal responses to multiple climate stressors has become increasingly evident. This manuscript presents a fully detailed and replicable experimental framework for simulating ocean warming and acidification in benthic marine invertebrates under controlled laboratory conditions. Detailed protocols include the technical set-up, experimental design, selection of climate scenarios, monitoring procedures and criteria for species selection and demonstrating its application through a validation case study from the MACCIMO project.

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Metrological assessment of pHT in TRIS buffers within artificial seawater: implications for high-salinity reference materials

Published 19 February 2026 Science Closed
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Anthropogenic CO2 emissions drive ocean acidification through changes in the carbonate system, lowering seawater pH. In contrast, salinity variations arise from physical processes such as freshwater fluxes and circulation. This study reports the preparation and Harned cell characterization of three equimolal TRIS buffer solutions (0.01 mol·kg−1, 0.025 mol·kg−1, and 0.04 mol·kg−1) in artificial seawater (ASW) matrices with practical salinities of 35 and 50 and temperatures of 20 °C, 25 °C, and 30 °C. Determined pHT values achieved expanded uncertainties (𝑈pHT ≤ 0.006), meeting Global Ocean Acidification Observing Network (GOA-ON) “climate” quality standards. Absolute salinity (SA) was concurrently measured via density (TEOS-10), revealing systematic deviations from practical salinity due to TRIS content. A nonlinear regression model was developed to predict pHT as a function of salinity, temperature, and TRIS molality, with r2 = 0.99998. These results provide a robust dataset for developing Certified Reference Materials (CRMs) for pHT calibration under climate-relevant high-salinity environments at different temperature conditions, offering a practical tool for high-accuracy calibration in variable marine conditions.

Continue reading ‘Metrological assessment of pHT in TRIS buffers within artificial seawater: implications for high-salinity reference materials’

Experimental exposure to climate change scenarios imposed alterations on the morphological traits of sessile and low-motility marine invertebrates

Published 6 February 2026 Science Closed
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Over the past 50 years, the oceans have absorbed over 90% of global warming heat, leading to warming, acidification, and declining oxygen levels that are disrupting marine ecosystems and altering species distributions and productivity. The vulnerability of marine organisms to these changes depends on their biological traits, habitat conditions, and adaptive capacity, influencing their growth, behavior, and overall population health. Micro-computed tomography (micro-CT) has been previously used for studying the morphological traits of marine invertebrates, which provide important insights into species functionality and responses to climate change and ocean acidification. Micro-CT enables non-destructive, high-resolution 3D analysis of internal and external structures, allowing precise measurement of traits such as density, porosity, and morphology that are valuable for climate change research.

The present manuscript describes micro-CT imaging datasets generated to investigate the effects of climate change on the morphological structure of two low-motility benthic marine invertebrates: the gastropod Hexaplex trunculus and the sponge Chondrilla nucula. Both species are considered particularly vulnerable to environmental stressors. To date, no study has investigated the effects of ocean warming and acidification on sponges using micro-CT technology. Using a common garden experimental design, individuals from geographically distinct populations exposed to different natural environmental regimes were subjected to combined warming and acidification scenarios to assess their morphological responses and adaptive capacity.

Continue reading ‘Experimental exposure to climate change scenarios imposed alterations on the morphological traits of sessile and low-motility marine invertebrates’

Untargeted mass spectrometry to investigate ocean acidification in Cancer borealis using optimized metabolite extraction methods

Published 5 February 2026 Science Closed
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Ocean acidification (OA) refers to the ongoing decline in ocean pH caused by the cascading effects of increased atmospheric CO2, which has significant negative impacts on various marine organisms, particularly crustaceans with calcified shells. However, research on the metabolic responses of crustaceans remains limited. In this study, we performed untargeted metabolomics on hemolymph samples from Cancer borealis (Jonah crab), a crustacean species well known for its tolerance to temperature and pH changes, to investigate its metabolic responses to OA. Two extraction methods—isopropanol (IPA) and acidified methanol (AcMeOH)—were employed to capture a broad range of metabolites and small peptides. Both methods enabled comprehensive detection; however, IPA yielded more consistent and extensive metabolite coverage, identifying 43 lipids compared to only 15 with AcMeOH. We identified 15 metabolites that responded significantly to OA. Several metabolites, including the potential neuropeptide cycloprolylglycine and the exogenous compound curcumin, exhibited concentration changes under OA exposure, suggesting their potential relevance in stress response pathways triggered by environmental stress. Overall, we highlight IPA as a more effective extraction method for untargeted metabolomics in crustacean hemolymph. Our study elucidates metabolic dynamics that enhance our understanding of the physiological adaptability of marine crustaceans under environmental stress and provides a comprehensive dataset that for future OA research.

Continue reading ‘Untargeted mass spectrometry to investigate ocean acidification in Cancer borealis using optimized metabolite extraction methods’

New ocean sensors could transform how scientists track the marine carbon cycle

Published 3 February 2026 Web sites and blogs Closed
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The world’s oceans do far more than support vital marine ecosystems and provide food and recreation. They help regulate the Earth’s climate, absorbing vast amounts of heat and CO2, acting as one of the planet’s most important buffers against climate change.

Yet despite this vital role, scientists still struggle to track exactly how and where the ocean absorbs and stores CO2 – and how that process is changing.

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Rintala is leading an international team that aims to extend ocean observing capacity by developing sensors for platforms that can operate beyond normal shipping routes and deep below the surface – far from ships and human intervention

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At the heart of the effort is the development of the world’s first autonomous sensor capable of accurately measuring total alkalinity in the ocean – from the sea floor to the surface.

Total alkalinity is a key chemical indicator that scientists use to understand the ocean carbon system and estimate how much CO2 seawater can absorb and store.

It is also critical for tracking ocean acidification – a process driven by rising CO2 levels that lowers seawater pH and threatens marine ecosystems, particularly shell-building plankton and molluscs.

“Ocean acidification is very harmful for many marine organisms,” said Rintala. “It can cause cascading effects that ripple up the food web.”

Until now, total alkalinity has usually been measured by collecting fixed seawater samples from ships and analysing them later in onshore laboratories. That approach provides valuable data, but only at isolated points in time and space.

“If we are interested in the carbon content of the ocean as a whole, we need to measure deeper,” said ocean scientist Socratis Loucaides, based at the UK’s National Oceanography Centre (NOC).

Loucaides and his colleagues at NOC are leading the development of a radically different approach: a compact lab-on-a-chip sensor that performs a miniature chemistry experiment inside the instrument itself.

Inside the device, a small seawater sample is mixed with an acid of known strength and a dye that changes colour depending on acidity. A light-based sensor then reads those colour changes to calculate the alkalinity of the surrounding seawater.

By doing this directly in the deep ocean, the sensor can build up a far more detailed picture of how carbon is stored and transported over time – and potentially reveal early warning signs of change.

Continue reading ‘New ocean sensors could transform how scientists track the marine carbon cycle’

Y/Ho ratios in marine sediments unveil Neoproterozoic ocean acidification

Published 28 January 2026 Science Closed
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Understanding Precambrian seawater pH is critical for unraveling Earth’s early marine environments and biospheric evolution. Yet, quantitative constraints remain elusive due to the lack of robust proxies. Here, we demonstrate that yttrium/holmium (Y/Ho) fractionation during adsorption onto marine sediments serves as a novel and reliable pH proxy. Experimental results reveal that Y/Ho fractionation in ferruginous sediments follows a pH-dependent power-law relationship, while in argillaceous sediments, it is jointly controlled by pH and salinity at low salinities (< 29‰) but stabilizes (KdY/Ho ≈ 0.4) at higher salinities (≥ 29‰). Temperature exerts a negligible influence, ensuring broad applicability across geological timescales. Leveraging these relationships, we develop a quantitative method to reconstruct paleo-seawater pH using Y/Ho ratios from coexisting ferruginous and argillaceous sediments. Validation against modern and Phanerozoic records confirms the proxy’s accuracy (e.g., pH 8.21 ± 0.22 for modern Pacific sediments). Application to Neoproterozoic meta-pelites and iron formations reveals prolonged oceanic acidification (pH 5.9–6.4), deviating from previous model-based neutral-to-alkaline estimates. This acidic state, likely sustained by CO2 outgassing from carbonatite-alkaline volcanism during Rodinia’s breakup, challenges conventional views of Precambrian ocean chemistry. Our findings provide a transformative tool for probing early Earth’s environmental dynamics and highlight the interplay between tectonics, magmatism, and marine pH evolution.

Continue reading ‘Y/Ho ratios in marine sediments unveil Neoproterozoic ocean acidification’

An experimental approach to study climate change stress in benthic marine invertebrates

Published 26 January 2026 Science Closed
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Climate change is altering ocean temperature and chemistry, with ocean warming and acidification posing serious threats to marine biodiversity, particularly for sessile or low-mobility organisms that cannot escape unfavorable conditions. The MACCIMO project investigated the effects of these stressors on the sponge Chondrilla nucula and the gastropod Hexaplex trunculus using an integrative approach that examined molecular, physiological, morphological, and symbiotic responses. By applying a common garden experiment to populations from different Mediterranean regions, the study aimed to distinguish genetic and environmental influences on stress tolerance and assess intraspecific variability. Three experimental scenarios were simulated, including a control treatment and two climate change treatments based on the “high GHG emissions” RCP 8.5 scenario. A semi-enclosed experimental system with precise control of temperature and pH was designed which can be easily replicated to support laboratory studies on the effects of climate change and ocean acidification on small marine invertebrates across multiple biological levels.

Continue reading ‘An experimental approach to study climate change stress in benthic marine invertebrates’

Detecting the acidity of the ocean with sound, the role of lead in human evolution, and how the universe ends (podcast)

Published 22 January 2026 Media coverage Closed
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First up on the podcast, increased carbon dioxide emissions sink more acidity into the ocean, but checking pH all over the world, up and down the water column, is incredibly challenging. Staff Writer Paul Voosen joins host Sarah Crespi to discuss a technique that takes advantage of how sound moves through the water to detect ocean acidification.

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This week’s episode was produced with help from Podigy.

Continue reading ‘Detecting the acidity of the ocean with sound, the role of lead in human evolution, and how the universe ends (podcast)’

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