Having evolved in the chronically cold and thermally stable waters of the Southern Ocean (SO) for millions of years, Antarctic fish possess a suite of physiological specializations that enable them to survive at temperatures near the freezing point of seawater. Adaptations include the evolution of antifreeze proteins, modifications of membrane composition, altered metabolic processes, unique mechanisms of oxygen transport and utilization, and distinctive cellular stress responses. This review synthesizes current knowledge of the physiological adaptations of Antarctic fish, focusing on the mechanisms that support survival in extreme cold environments. We examine adaptations related to cold tolerance, osmoregulation, metabolism, reproduction, sensory biology and oxygen transport and discuss the evolutionary processes that have shaped these traits. We further evaluate how ongoing climate-driven changes, including ocean warming, acidification and biological invasions, may affect Antarctic fish populations and ecosystems. Understanding the physiological foundations underlying Antarctic fish adaptation provides important insights into evolutionary responses to environmental extremes and provides a framework for predicting potential vulnerabilities of polar marine organisms in a rapidly changing world.
Continue reading ‘Adaptation to extreme environments: a review of Antarctic fish physiology’Posts Tagged 'Antarctic'
Adaptation to extreme environments: a review of Antarctic fish physiology
Published 2 November 2026 Science Leave a CommentTags: Antarctic, biological response, fish, performance, physiology, reproduction, review
Closer to danger: southern Ocean pteropods build their shells deeper in the water column during winter-spring
Published 29 October 2026 Science Leave a CommentTags: Antarctic, biological response, chemistry, mollusks, morphology, zooplankton
Shelled pteropods are at risk from ocean acidification, with known effects on their shell durability and calcification. Pteropods typically form their aragonitic shells over specific depth ranges known as the “calcification depth,” which varies depending on species and habitats. Some Southern Ocean waters are already undersaturated with respect to aragonite and this could negatively affect shelled pteropods. However, the calcification depths of pteropods have not been determined nor used to infer consequences of changing seawater carbonate chemistry in the Southern Ocean. In this study, we analyzed the stable oxygen isotopic composition of Limacina rangii shells, collected by sediment traps in the sub-Antarctic zone, to estimate their calcification depth. Shallow calcification depths (13–126 m) were detected in summer–autumn, while L. rangii calcified their shells deeper in the water column during winter–spring (302–525 m). Recent shoaling of the aragonite saturation horizon is likely to negatively affect pteropods that calcify their shells in deep water. Such shoaling could affect pteropod calcification, shell integrity and threaten population viability.
Continue reading ‘Closer to danger: southern Ocean pteropods build their shells deeper in the water column during winter-spring’Functional saturation of Earth’s habitable domains: constraints on land systems and potential in marine environments
Published 16 October 2026 Science ClosedTags: algae, Antarctic, North Atlantic, phanerogams, review, socio-economy
In this context, functional saturation is defined as the state in which a system’s capacity to sustain additional productive or regulatory functions becomes constrained due to cumulative anthropogenic pressures, even if some physical space remains available. This review examines whether the progressive contraction of terrestrial plant communities under intensifying anthropogenic pressure can be functionally compensated by the expansion of marine macroalgal systems in a high-CO2 world. Integrating perspectives from Earth system ecology, biogeochemistry, and spatial analysis, the study evaluates three interdependent dimensions: the saturation of habitable terrestrial space, the relative openness yet ecological constraint of marine environments, and the dynamic coupling between atmospheric CO2 and ocean chemistry. The synthesis reveals a fundamental asymmetry between land and ocean systems. Terrestrial ecosystems are undergoing direct structural transformation through land-use change, resulting in a measurable contraction of ecologically functional space and increasing transgression of planetary boundaries. In contrast, marine systems retain substantial geometric space but are subject to diffuse, cumulative stressors, particularly in productive coastal zones where macroalgal communities are most viable. Elevated CO2 exerts dual effects on marine primary producers, simultaneously enhancing photosynthetic potential while intensifying ocean acidification, with temporally lagged responses mediated by air–sea exchange dynamics. Although macroalgae may exhibit localized increases in productivity, their capacity to provide long-term carbon sequestration and ecosystem stability remains inherently limited due to rapid biomass turnover, susceptibility to regime shifts, and the interaction of multiple stressors. The available evidence suggests that marine macroalgal expansion is unlikely to fully compensate for terrestrial vegetation loss at global ecological and biogeochemical scales. Instead, the Earth system is undergoing a net reduction in biospheric resilience, characterized by declining terrestrial complexity and increasingly unstable marine productivity. These findings challenge assumptions of compensatory redistribution of primary production and underscore the necessity of preserving terrestrial ecosystems alongside mitigating pressures on marine environments.
Continue reading ‘Functional saturation of Earth’s habitable domains: constraints on land systems and potential in marine environments’Surficial acidic and CO2 plumes in marine shallow hydrothermal vents of Deception Island active volcano, Antarctica
Published 17 September 2026 Science ClosedTags: Antarctic, chemistry, field, vents
We characterize surficial seawater physico-chemical conditions and dissolved CO2 dynamics at the active volcanic system of Deception Island (Antarctica), with emphasis on identifying hydrochemical plumes associated with shallow sea hydrothermal vents (SHV). During the austral summers of 2024 and 2025, spatial surveys of pH, temperature, salinity, and total alkalinity were conducted along the inner coast of Port Foster. Acidification plumes (down to pH ~ 6.1), carbonate undersaturation, and elevated total alkalinity (2,400–7,000 μmol kg⁻1) were identified in areas affected by volcanic–hydrothermal emissions. Dissolved CO2 reached up to 90,000 μatm, with extreme values approaching 160,000 μatm, far exceeding atmospheric equilibrium. The results reveal a strong tidal control on CO2 dynamics in Port Foster, with low tide conditions enhancing nearshore accumulation and potential outgassing. Fluid compositions suggest mixed contributions from hydrothermal inputs, seawater, and meteoric components. These findings highlight the value of carbonate system parameters for detecting and monitoring SHV activity, and position Deception Island as a natural laboratory to investigate volcanic impacts on coastal ocean acidification under polar conditions.
Continue reading ‘Surficial acidic and CO2 plumes in marine shallow hydrothermal vents of Deception Island active volcano, Antarctica’The molecular footprint of global change in Antarctic coral
Published 21 July 2026 Science ClosedTags: Antarctic, biological response, BRcommunity, corals, laboratory, molecular biology, multiple factors, physiology, temperature
Anthropogenic CO2 emissions are altering marine ecosystems through two interconnected processes: climate change and ocean acidification, both of which are particularly affecting the Southern Ocean. However, the molecular responses of cold-water corals to these stressors remain poorly understood. In this study, we investigated the transcriptomic response of the Antarctic coral Malacobelemnon daytoni exposed to ocean acidification (pH ~7.7; LpH) and elevated temperatures (+2°C and +4°C above ambient; T1 and T2, respectively) under controlled laboratory conditions. Using high-throughput RNA sequencing (RNA-Seq), we compared gene expression profiles across six treatments, including a control (pH ~8.1, CpH; 0–1°C; CT), acidification, warming, and their combinations. Principal component analysis revealed treatment-specific clustering and greater transcriptomic dispersion under LpH conditions. Differential expression analysis identified between 475 and 767 differentially expressed genes (DEGs), with the strongest transcriptional responses observed under combined stress conditions (LpH + T1 and LpH + T2). Combined exposure to ocean acidification and warming elicited the largest gene expression response, suggesting enhanced, potentially non-additive effects of multiple stressors. Functional enrichment analyses revealed differential regulation of genes associated with protein folding, signal transduction, energy metabolism, oxidative stress, and regulation of cell death. Our findings demonstrate that Malacobelemnon daytoni exhibits complex, treatment-dependent gene expression responses to environmental stressors. These results highlight the capacity of this Antarctic octocoral to mount molecular responses to projected future ocean conditions while also emphasizing its potential vulnerability to the interacting effects of ocean warming and acidification.
Continue reading ‘The molecular footprint of global change in Antarctic coral’A systematic bias in float pH leads to overestimation of derived pCO2 and underestimation of carbon uptake by the Southern Ocean
Published 17 June 2026 Science ClosedTags: Antarctic, chemistry
The carbon flux estimated from biogeochemical Argo float data indicates a lower annual carbon uptake by the Southern Ocean compared to fluxes derived from other observations (e.g., ship and aircraft measurements). The root cause of this discrepancy remains controversial, with growing evidence suggesting that potential biases in float-derived pCO2 may be a plausible explanation. Here, we perform a multi-variable comparison of vertical profiles between float- and ship based-data and reveal consistent discrepancies in pH, pCO2 and dissolved inorganic carbon, which are not found in other variables such as dissolved oxygen, nitrate and total alkalinity. Our findings are consistent with a previously unrecognized negative bias in float pH driving a positive offset in float-derived pCO2. The float-derived surface pCO2 is, on average, biased high by 15 ± 3 µatm compared to ship data, representing a larger magnitude of bias than previously recognized. Biases exist in both surface and deep waters, including old deep waters containing minimal anthropogenic carbon. A more sophisticated adjustment for float pH, involving multiple cross-reference depths, may be required for accurate estimation of air-sea CO2 exchange in the Southern Ocean.
Continue reading ‘A systematic bias in float pH leads to overestimation of derived pCO2 and underestimation of carbon uptake by the Southern Ocean’Assessing recent anthropogenic carbon dioxide and acidification in the Ross Sea, Antarctica
Published 5 June 2026 Science ClosedTags: Antarctic, chemistry, field
Over the past decade, the East Ross Sea has experienced a significant decline in sea ice, enabling direct observational studies of regional carbon dynamics. The accumulation rate of anthropogenic CO2 in the East Ross Sea is up to six times higher than the long-term Industrial Era mean due to the inflow of seawater from the Amundsen Sea by accelerated glacial melting. In contrast, the West Ross Sea exhibited comparatively smaller changes. Measurements of dissolved inorganic carbon and stable carbon isotope indicate that, over the period 2011–2020, changes in δ13C (Suess effect) and anthropogenic CO2 were 0.20 ± 0.06‰ and −5 ± 2 μmol kg−1 in the West Ross Sea, and −0.15 ± 0.01‰ and 9 ± 1 μmol kg−1 in the East Ross Sea. These findings suggest rapid acidification in the East Ross Sea, with aragonite undersaturation likely to occur by the mid-2030s, accompanied by an expected pH decrease of ∼0.2 units by the end of the century.
Continue reading ‘Assessing recent anthropogenic carbon dioxide and acidification in the Ross Sea, Antarctica’Acidification in coastal waters of Adélie Land, Antarctica (1985–2025)
Published 29 April 2026 Science ClosedTags: Antarctic, chemistry, field, modeling, regionalmodeling, sensor
Ocean acidification is expected to be particularly severe in Antarctic continental shelves due to enhanced anthropogenic carbon uptake in cold waters in response to rising atmospheric CO2, sea-ice retreat, freshening and climate-change feedbacks. Models suggest that undersaturated conditions with respect to aragonite (Ωar), a major form of calcium carbonate formed by marine species, could be reached as soon as 2052 for austral winter. Here we present new ocean carbonate system observations from cruises conducted since 2010 in the Adélie Land coastal region in East Antarctica, along with data from a BCG-Argo float and results from a neural network model for the period 1985–2025. The region is a permanent CO2 sink and was most pronounced since 2006. The CO2 sink leads to a positive increase of surface water total CO2 concentrations (CT) (+0.44 ± 0.01 µmol.kg-1.yr-1) and to a progressive decrease of pH (-0.013 per decade) and Ωar (-0.035 per decade) for the winter season. The lowest surface Ωar of 1.2 was observed in winter 2024 from the float data, a critical limit for some marine species such as pteropod. A projection of the CT concentrations in the future, based on observed anthropogenic CO2 concentrations and emissions scenarios, suggests that aragonite saturation state (Ωar = 1) will occur in surface waters as soon as 2055 in the Adélie Land region, which is part of a larger area of East Antarctica proposed as a Marine Protected Area by the Commission for the Conservation of Antarctic Marine Living Resources since the early 2010s.
Continue reading ‘Acidification in coastal waters of Adélie Land, Antarctica (1985–2025)’Short-term tolerance to ocean acidification of the sub-antarctic sea-urchin arbacia dufresnii
Published 29 January 2026 Science ClosedTags: Antarctic, biological response, echinoderms, laboratory, molecular biology, morphology, physiology
The accumulation of anthropogenic CO2 in the ocean is impacting the carbonate system chemistry in seawater, particularly in polar regions. Acidified seawater can impair the echinoderms internal regulation of pH due to an increase in hydrogen ions concentration, potentially affecting growth, and calcification, among other physiological activities. The goal of this work was to assess the effects of Ocean Acidification (OA) on Arbacia dufresnii, a sub-Antarctic sea urchin species. Adult specimens were exposed to three pH treatments: 7.4, 7.7, and 8.0 (control), for 21 up to 23 days. We assessed spine regeneration, a proxy of calcification, by cutting spines at the base of the shaft and evaluating the magnesium content, height, and weight of the regenerated part. The coelomic fluid was sampled for pH assessment and magnesium and calcium content analysis. The RNA/DNA ratio, a proxy of metabolic activity, was assessed in the gonads and body walls. The spine regenerated weight was significantly correlated to regenerated height but not to treatments. The coelomic fluid pH (6.77 ± 0.34) did not differ between treatments (pANOVA = 0.15). No significant differences were observed between treatments regarding RNA/DNA ratio in both body wall (pANOVA = 0.65) and gonads (pKruskal-Wallis = 0.34), the spine regenerated height (pANOVA = 0.35) and Mg regenerate content (pANOVA = 0.58). Our results suggest that A. dufresnii owns physiological mechanisms to cope with OA conditions during short-term exposure.
Continue reading ‘Short-term tolerance to ocean acidification of the sub-antarctic sea-urchin arbacia dufresnii’Nonlinear interactions of timing and amplitude biases in modeled Southern Ocean pCO2: the roles of dissolved inorganic carbon, total alkalinity, and sea surface temperature
Published 21 January 2026 Science ClosedTags: Antarctic, chemistry, modeling, regionalmodeling
The Southern Ocean is a major sink for atmospheric carbon dioxide and critical to the current and future carbon cycle. This net annual CO2 flux reflects the balance between strong seasonal variability characterized by opposing periods of winter outgassing and summer uptake. Using a simple framework, we evaluate how model biases in both the amplitude and timing of dissolved inorganic carbon (DIC) and total alkalinity (TA) and in the amplitude of sea surface temperature (SST) impact simulated pCO2. We examine seasonal CO2 fluxes and pCO2 south of the Subantarctic Front in 42 Earth System Model and three state estimate simulations. Only 11 of the 45 simulations have a seasonal pCO2 cycle with a correlation of ≥0.7 to observed pCO2, while 26 have a correlation of <0. Four of the well-correlated models accurately represent the seasonality of SST, DIC, and TA, while TA biases compensate for DIC or SST biases in the other seven. DIC and SST amplitude biases are related to mixed layer (MLD) biases, with shallow MLDs, especially in the summer, correlated with larger amplitude DIC and SST cycles than observed. The amplitude of seasonal Net Primary Production is correlated to DIC and TA timing. We provide input on the main adjustments needed to correct the simulated pCO2 seasonality in each of the evaluated models. These findings highlight the difficulty and importance of capturing the seasonal processes influencing the carbonate system to correctly model and predict the Southern Ocean carbon sink and its response to a changing climate.
Continue reading ‘Nonlinear interactions of timing and amplitude biases in modeled Southern Ocean pCO2: the roles of dissolved inorganic carbon, total alkalinity, and sea surface temperature’Distinct biochemical profiles in Antarctic seaweeds reflect acclimation to polar and hydrothermal environments with implications for biomass nutritional value
Published 1 December 2025 Science ClosedTags: algae, Antarctic, biological response, chemistry, field, physiology, vents
Highlights
- Chlorophyll a content in some seaweed species increased with latitude along the Antarctic Peninsula.
- Seaweeds from fumarole vent sites revealed variations in fatty acids and pigments.
- Lower nutritional value in Antarctic seaweeds from fumarole sites suggests potential responses to ocean warming and acidification.
- Species-specific biochemical shifts in Antarctic seaweeds are anticipated under global change scenarios.
Abstract
Global change is driving ocean warming (OW) and acidification (OA), impacting marine ecosystems worldwide, including polar regions. Seaweeds, as key primary producers in coastal ecosystems, synthesize a wide range of biochemical compounds that support higher trophic levels. Their biochemical composition is conditioned by local environmental factors, including seawater temperature, pH, and nutrient availability. However, how polar seaweeds respond to ongoing global change remains poorly understood. In this study, we examined the influence of local environmental changes on the biochemical composition – including fatty acids (FA), pigments, carbon, and nitrogen – of nine Antarctic brown and red seaweed species. Specifically, we considered a latitudinal gradient from the South Shetland Islands (⁓62°S) to Yalour Island (⁓65°S), and the presence of active fumarole vents at Deception Island. Our results reveal species-specific and location-dependent biochemical shifts in most species. While chlorophyll a concentrations tended to increase with latitude, specimens collected from fumarole vents exhibited a reduction in total FA content, PUFA:SFA (polyunsaturated to saturated fatty acid) ratios, PUFA omega-3, and pigment concentrations. These shifts under hydrothermal influence are likely driven by elevated seawater temperatures and acidic conditions, suggesting a potential decline in nutritional value under future global change scenarios. Additionally, higher magnesium content was found in the skeletons of crustose coralline algae from shallow waters than in those at 22 m depth. Our results highlight the species-specific nature of biochemical responses to environmental stressors, underlining the complexity of predicting the impacts of global change on seaweed physiology and the potential cascading effects on Antarctic food webs.
Continue reading ‘Distinct biochemical profiles in Antarctic seaweeds reflect acclimation to polar and hydrothermal environments with implications for biomass nutritional value’Compound marine heatwaves and acidity extremes in the Southern Ocean
Published 21 November 2025 Science ClosedTags: Antarctic, chemistry, modeling, regionalmodeling
Abstract
Compound extremes of temperature and acidity that extend over substantial fractions of the water column can be particularly damaging to marine organisms, as they experience not only additional stress by the potentially synergistic effects of these two stressors, but also a reduction in habitable vertical space. Here, we detect and analyze such column-compound extremes (CCX) in the Southern Ocean between 1980 and 2019, and characterize their duration, intensity, and spatial extent. To this end, we use daily output from a hindcast simulation of the Regional Ocean Modeling System (ROMS), coupled with the Biological Elemental Cycling (BEC) model. We first detect extremes in temperature and acidity ([]) within the top 300 m using a relative threshold of 95% and then identify CCX where conditions are extreme for both stressors for at least 50 m of the water column. When analyzed on a fixed baseline, positive trends in ocean warming and acidification caused CCX to last longer, intensify, and expand throughout the Southern Ocean. In the Antarctic zone, CCX expanded between 1980 and 2019 more than ten times in volume, lasted up to 120 days longer, and doubled in anomaly. Some of the largest and longest events occurred in Antarctic Marine Protected Areas (MPAs), covering more than 200,000 km2 and persisting for over 500 days. CCX in the Subantarctic and Northern zones quadrupled in volume and increased by more than 30% in anomaly. Across the Southern Ocean, the increasing occurrence of CCX exacerbates the risks to marine ecosystems from warming and acidification.
Plain Language Summary
Extreme heat events in the ocean, known as Marine HeatWaves (MHW), are becoming more common due to climate change. These events can be even more harmful when they occur at the same time as Ocean Acidity eXtreme (OAX) events, synergistically causing stress for marine life. In this study, we looked at how often these combined events in the upper ocean, called Column-Compound eXtremes (CCX), occurred in the Southern Ocean between 1980 and 2019. We used a numerical model simulation to investigate changes in CCX during the study period. Compared to conditions in 1980, we find that CCX in the Antarctic zone have expanded more than 10 times in volume and lasted up to 120 days longer. In addition, expansive and intense CCX are found in Antarctic Marine Protected Areas (MPAs), posing a threat to vulnerable ecosystems. These events covered more than 200,000 km2 and lasted more than 500 days. The increasing occurrence of CCX across the Southern Ocean exacerbates the risks to marine ecosystems arising from ocean warming and acidification.
Key Points
- In the Antarctic zone, Column-Compound eXtremes (CCX) occupied in 2019 relative to 1980 ten times more volume and doubled in anomaly
- Marine Protected Areas in the Ross Sea and Antarctic Peninsula are disproportionately affected by the largest, longest, most intense CCX
- More than 70% of surface marine heatwaves contain CCX in 2019, although up to 60% of CCX occur without any surface expression
Anthropogenic forcing and upwelling accelerate aragonite undersaturation in the Prydz Bay, East Antarctica
Published 18 November 2025 Science ClosedTags: Antarctic, chemistry, field
Abstract
The Southern Ocean is one of the rapidly acidifying regions globally, yet direct observational constraints on its carbonate chemistry remain scarce. Here, we combine shipboard measurements of pH and aragonite saturation state (Ωarag) from the summer 2015 Chinese National Antarctic Research Expedition with reconstructed wintertime conditions to characterize acidification in Prydz Bay. We report the first observation-based occurrence of surface aragonite undersaturation (Ωarag < 1.0) in the northern basin—emerging nearly two decades earlier than model projections. Surface Ωarag undersaturation is primarily driven by accelerated uptake of anthropogenic CO2 and shoaling of the aragonite saturation horizon, fueled by persistent upwelling of CO2-rich Circumpolar Deep Water. In the ocean interior, organic matter remineralization, CaCO3 dissolution, and continued anthropogenic CO2 intrusion further lower pH and Ωarag. Our results demonstrate that Prydz Bay is at the forefront of Southern Ocean acidification, highlighting the urgent need to incorporate both anthropogenic and natural biogeochemical feedbacks into high-resolution models to better predict future ecological impacts.
Plain Language Summary
The Southern Ocean is acidifying faster than most of the oceans on Earth, but most of what we know comes from computer models rather than direct observations. In Prydz Bay, East Antarctica, we combine shipboard data collected in summer 2015 with reconstructed winter conditions to track changes in seawater acidity (pH) and aragonite saturation (Ωarag), a key factor for shell-building marine life. We discover that seasonal expansion of low pH and nearly undersaturated aragonite led to the unforeseen early emergence of surface aragonite undersaturation in the northern basin. Strikingly, conditions that models predicted would not occur until around year 2038 have appeared nearly 20 years earlier. This rapid shift is driven by increased uptake of atmospheric CO2 and the rising influence of deep CO2-rich waters. In deeper layers, ongoing CO2 intrusion and the breakdown of organic material make the water even more acidic. These findings reveal that Prydz Bay is on the front lines of ocean acidification, underscoring the urgent need to reduce CO2 emissions and to better understand natural feedbacks in order to protect Antarctic marine ecosystems.
Key Points
- Surface near-undersaturated Ωarag emerged in Prydz Bay during summer, nearly two decades ahead of model predictions
- Enhanced atmospheric CO2 uptake and rapid shoaling of the aragonite saturation horizon dominate surface Ωarag undersaturation
- Persistent upwelling of CO2-rich deep water combined with anthropogenic CO2 penetration shoal the Ωarag saturation horizon
Effects of ocean acidification on fatty acid composition in the Antarctic snail Neobuccinum eatoni
Published 31 October 2025 Science ClosedTags: adaptation, Antarctic, biological response, laboratory, mollusks, otherprocess, physiology
Introduction: Ocean acidification (OA), resulting from the absorption of increasing atmospheric CO2 by the oceans, represents a major threat to marine organisms. Despite growing concern, the biochemical responses of Antarctic species to OA remain poorly understood.
Methods: This study investigated the impact of OA (pH 7.70 ± 0.09) on the fatty acid (FA) composition of the Antarctic snail Neobuccinum eatoni over a two-month experimental period (December 2015–March 2016). Fatty acid profiles were analyzed in multiple tissues to assess potential alterations induced by low-pH (LpH) conditions.
Results: Significant tissue-specific changes in FA composition were detected, particularly in the mantle and gill. Under LpH exposure, notable modifications occurred in long-chain polyunsaturated fatty acids (LC-PUFAs) such as 22:5n-3, 22:6n-3, and 24:5n-6. Elevated LC-PUFA levels in the mantle suggested a compensatory response to oxidative stress, while shifts in the n-3/n-6 ratios in the gill pointed to potential alterations in immune and anti-inflammatory functions.
Discussion: Indicators of homeoviscous adaptation (HVA), including PUFA/SFA ratios and mean chain length (MCL), revealed biochemical strategies used by N. eatoni to maintain membrane fluidity under acidified conditions. This study provides the first evidence of FA-based responses to elevated pCO₂ in an Antarctic gastropod, highlighting the potential of fatty acids as sensitive biomarkers of physiological adaptation to environmental stressors.
Continue reading ‘Effects of ocean acidification on fatty acid composition in the Antarctic snail Neobuccinum eatoni’What recreating Scott’s Antarctic expedition reveals about our seas today
Published 14 August 2025 Media coverage ClosedTags: Antarctic
The research trip retraced the routes of Borchgrevik’s Southern Cross, Shackleton’s Discovery and Scott’s Terra Nova expedition in January. Photograph: Courtesy of Dr Hugh Carter
Three glass specimen jars full of satsuma-sized sea urchins sit on Dr Hugh Carter’s desk in the Natural History Museum. Each one, collected from the depths of the Southern Ocean by polar teams led by Sir Ernest Shackleton, Capt Robert Falcon Scott and the Norwegian Carsten Borchgrevink, tells a tale of heroic exploration and scientific endeavour.
Now, more than a century later, Carter, the Natural History Museum’s (NHM) curator of marine invertebrates, hopes the preserved Antarctic urchins, 50 in all, will help tell a different, increasingly urgent story of modern times: how changes in the world’s southernmost waters may be affecting marine life.
In January, the biologist undertook a six-week long research trip to visit the exact sites sampled by Borchgrevink’s Southern Cross, Shackleton’s Discovery and Scott’s ill-fated Terra Nova expedition between 1898 and 1913.
His voyage, part of a multidisciplinary expedition run by the National Institute of Water and Atmosphere (Niwa), supported by the Antarctic Science Platform in New Zealand, partly retraced the route made by Scott. Scott and four other explorers, including the chief scientist, Edward Wilson, perished in the ice around a month after the samples sitting on Carter’s desk were collected.
…
Carter’s theory is that comparing the “tests” or shell of the urchins (a type of invertebrate known as echinoderms, which include starfish and sea cucumbers) in the NHM’s collection with modern samples will help reveal more about the impact of ocean acidification, often called the “evil twin” of the climate crisis. Acidification is caused when carbon dioxide is rapidly absorbed into the ocean, where it then reacts with water molecules leading to a fall in the pH of the seawater.
Preliminary findings on Carter’s ship, the deep water research vessel the RV Tangaroa, appeared to confirm his worst fears.
Continue reading ‘What recreating Scott’s Antarctic expedition reveals about our seas today’Antarctic fishes in a changing climate: a comparative approach to predicting species-specific futures
Published 12 August 2025 Science ClosedTags: adaptation, Antarctic, biological response, fish, multiple factors, otherprocess, performance, temperature
The polar regions are experiencing climate change at the fastest rates on Earth and serve as bellwethers for the profound threats facing species, ecosystems, and physical processes worldwide due to uncurbed anthropogenic greenhouse gas emissions. My dissertation research focuses on early life stages of Antarctic fishes, which are thought to be particularly vulnerable to climate change due to their unique evolutionary history and specialization to their stenothermal habitat. I used a comparative framework, examining four closely related species in the Nototheniidae family – Trematomus bernacchii, Trematomus pennellii, Trematomus nicolai, and Pagothenia borchgrevinki – to understand how subtle interspecific variation in traits may impact species-specific performance under projected future ocean conditions. I first measured basal characteristics across the four species, as very little is known about Antarctic fishes at young life stages, focusing on metabolic traits and the exploration-avoidance axis of behavior, two key dimensions of species fitness and drivers of niche differentiation. While basal metabolic demands appeared relatively conserved across species at the juvenile life stage, I found divergent behavioral strategies that could be a critical driver of niche differentiation in Antarctic fish assemblages. T. bernacchii and T. pennellii showed risk-prone behavior, T. nicolai showed avoidant behavior, and P. borchgrevinki showed cautious exploratory behavior. I also observed a potentially conserved freezing strategy in response to novelty, which, when paired with in situ observations, indicates that freezing may be an important predator avoidance strategy in these fishes. I then focused on the two ‘risky’ species – Trematomus bernacchii and Trematomus pennellii – to explore how acclimation to projected future ocean warming and ocean acidification conditions may impact their risk-prone behavior. While acclimation to warming and elevated pCO₂ affected behavior in both species, the effect sizes of pCO₂ were small, and warming was the driving force behind behavioral modifications. In both species, fishes acclimated to ocean warming conditions demonstrated reduced exploratory activity and showed indications of neophilia. These responses amplified over time, and T. pennellii demonstrated a stronger response (i.e., effect sizes) in both behaviors. Consistent with previous physiological and behavioral studies, while limited, our results support the inference that T. pennellii have a particularly risk-prone strategy when faced with novelty that is amplified when acclimated to warming. My final chapter proposes a novel ‘ice reef’ framework and emphasizes how three-dimensional ice habitat formed by platelet, anchor, and brinicle ice may function as critical nursery and refugia habitats for young polar fishes. Drawing on in situ observations and the literature, I discuss the recurring behavioral, physiological, and morphological features across a diversity of polar fishes, suggesting ice-associated and ice-obligate life history strategies may be much more widespread than previously acknowledged. As climate change rapidly alters ice phenology and stability, the loss of ice reefs could jeopardize fish recruitment, community resilience, and key ecosystem services. This perspective underscores the urgent need to study ice reefs before they disappear altogether.
Continue reading ‘Antarctic fishes in a changing climate: a comparative approach to predicting species-specific futures’Responses of the natural phytoplankton assemblage to Patagonian dust input and anthropogenic changes in the Southern Ocean
Published 10 July 2025 Science ClosedTags: Antarctic, biological response, community composition, growth, laboratory, morphology, multiple factors, nutrients, otherprocess, physiology, phytoplankton, temperature
Abstract
The cumulative effects of multi‐faceted changes on the phytoplankton community of the Southern Ocean (SO) are not yet known, which is a major limitation to predicting the future direction of the biological carbon pump. Thus, our study aimed to estimate the effects of intensified Patagonian dust inputs, warming and acidification on the growth, composition and production of phytoplankton assemblages in the Polar Frontal Zone (PFZ) and the High‐Nutrient Low‐Chlorophyll (HNLC) region of the Indian sector of the SO during the austral summer 2022. Natural phytoplankton communities were incubated for 5‐day under 4 scenarios (present and future conditions, and 2 intermediate scenarios). In the PFZ, +3°C and acidification stimulated the growth of phytoplankton, mainly cyanobacteria, while intensified dust inputs alone did not have notable impact. Conversely, in HNLC waters, the addition of Fe‐dust alone increased the total chlorophyll a of diatoms (mainly F. kerguelensis), whereas the negative effect of acidification and +3°C counteracted the positive impact of dust input on the diatoms. In these waters, future conditions benefited smaller species (haptophytes and cyanobacteria). The net particulate organic carbon production (POC) was also unaltered by future conditions, suggesting that primary production may not change in the future SO. However the increase in the length and number of long‐chain diatoms under future HNLC conditions may indicate that POC export could intensify in the future.
Plain Language Summary
Phytoplankton in the Southern Ocean (SO) play a critical role in absorbing atmospheric carbon dioxide and supporting marine ecosystems, however their response to future environmental changes remains unclear. This study examined how increased dust inputs, warming, and acidification affect the phytoplankton community in two contrasted biogeochemical domains of the SO, the Polar Frontal Zone (PFZ) and the High‐Nutrient Low‐Chlorophyll (HNLC) region. In the PFZ, warming and acidification favored the smaller phytoplankton species, while in the HNLC region, iron‐rich dust stimulated diatom species, though this effect was attenuated by warming and acidification. While overall the production of organic carbon by phytoplankton remained unchanged, diatoms may enhance carbon export to deeper waters under future conditions due to increased number and length of chain‐forming species. These findings highlighted the complexity of phytoplankton responses, which vary across regions and are influenced by interactive environmental factors. Understanding the impact of these environmental factors on phytoplankton is critical to predicting how future changes will shape the role of the SO in the global carbon cycle.
Continue reading ‘Responses of the natural phytoplankton assemblage to Patagonian dust input and anthropogenic changes in the Southern Ocean’Ocean acidification decreases molting but not survival of Antarctic amphipods Djerboa furcipes, Gondogeneia antarctica, and Prostebbingia gracilis
Published 10 July 2025 Science ClosedTags: Antarctic, biological response, crustaceans, laboratory, morphology, mortality, physiology, zooplankton
Ocean acidification refers to a decrease in the pH of the world’s oceans from the oceanic uptake of human-derived atmospheric CO2. Low pH is known to decrease the calcification and survival of many calcifying invertebrates. Shallow, hard bottom communities along the Western Antarctic Peninsula often have incredibly large numbers of invertebrate mesograzers that shelter on and are mutualists with the dominant brown macroalgae. The common amphipod species Djerboa furcipes, Gondogeneia antarctica, and Prostebbingia gracilis were collected from the immediate vicinity of Palmer Station, Antarctica (64°46′S, 64°03′W) in January–February 2023 and maintained under three different pH treatments simulating ambient conditions (approximately pH 8.0), near-future conditions for 2100 (pH 7.7), and distant future conditions (pH 7.3) for 8 weeks. Molt number and mortality were monitored throughout the course of the experiment. After the 8 week exposure, amphipods were analyzed for their biochemical compositions including the Mg/Ca ratio of their exoskeletons. There was no significant difference in biochemical composition or survival among the pH treatments for any of the amphipod species. All three species, however, had significantly fewer total numbers of molts in the pH 7.3 treatment than in the ambient treatment. These results suggest that amphipods may be able to maintain their survival in decreased pH by reallocating energy into compensatory behaviors, such as acid–base regulation, and away from energy expensive processes like molting.
Continue reading ‘Ocean acidification decreases molting but not survival of Antarctic amphipods Djerboa furcipes, Gondogeneia antarctica, and Prostebbingia gracilis’Spatial variability of marine carbonate system along the Drake Passage and northern Antarctic Peninsula during the austral summer
Published 27 June 2025 Science ClosedTags: Antarctic, chemistry, field
Highlights
- Sea surface pCO2, O2 and hydrographic parameters were measured, whereas Alk was estimated through different approaches.
- In Drake Passage, photosynthesis drives carbonate variability north of the Polar Front and upwelling dominates to the south.
- Photosynthesis reduces pCO2 and increases pH and carbonate concentration at enclosed coastal Antarctic areas.
- Lowest pH in the northern Antarctic Peninsula likely results from mixing of waters rich in natural and anthropogenic carbon.
- Calcite and aragonite are mostly supersaturated though aragonite undersaturation occurs under Dense Shelf Water influence.
Abstract
The influence of physical and biogeochemical processes on the variability of the carbonate system in the Southern Ocean remains poorly constrained. Understanding this influence is crucial to distinguish natural variations from anthropogenic impacts and accurately interpret observed trends. Here, we investigate how physical and biogeochemical processes influence the spatial distribution of summer carbonate system variables along the Drake Passage and northern Antarctic Peninsula. Continuous, high-frequency surface partial pressure of CO2 (pCO2), dissolved oxygen (O2) and essential hydrographic variables were collected during the austral summer of 2019, whereas other carbonate system variables were estimated after the reconstruction and evaluation of total alkalinity. Our findings show that in the Drake Passage, Circumpolar Deep Water upwelling increases the pCO2 (> 400 μatm) and dissolved inorganic carbon (> 2175 μmol kg−1), leading to reduced pH (< 7.99) south of the Polar Front. North of the Polar Front, photosynthesis lowers pCO2 (< 390 μatm), while increasing pH (> 8.00) and carbonate ions (> 110 μmol kg−1), with enrichment occurring in the Subantarctic coccolithophore growth region. Along the northern Antarctic Peninsula, including Gerlache Strait, Antarctic Sound, and Admiralty Bay, photosynthesis and sea ice/glacial melt are the main drivers of pCO2 reductions to levels below 350 μatm. The mixing of Circumpolar Deep Water with Weddell Sea Dense Shelf Water can naturally and anthropogenically raise pCO2 and decrease pH in northern Antarctic Peninsula waters, where pH is generally lower (as low as 7.90) compared to adjacent areas. Nevertheless, most environments remain supersaturated with respect to carbonate minerals calcite and aragonite, although signs of aragonite undersaturation have occur in surface waters influenced by Dense Shelf Water. These findings offer new insights into carbonate system processes across a large Southern Ocean region, improving understanding of spatial variability in marine carbon dynamics.
Continue reading ‘Spatial variability of marine carbonate system along the Drake Passage and northern Antarctic Peninsula during the austral summer’Antarctic macroalgal-associated amphipod assemblages exhibit long-term resistance to ocean acidification
Published 19 June 2025 Science ClosedTags: abundance, algae, Antarctic, biological response, BRcommunity, community composition, crustaceans, laboratory, mortality, otherprocess
The pH of the world’s oceans has decreased since the Industrial Revolution due to the oceanic uptake of increased atmospheric CO2 in a process called ocean acidification. Low pH has been linked to negative impacts on the calcification, growth, and survival of calcifying invertebrates. Along the Western Antarctic Peninsula, dominant brown macroalgae often shelter large numbers of diverse invertebrate mesograzers, many of which are calcified. Mesograzer assemblages in this region are often composed of large numbers of amphipods which have key roles in Antarctic macroalgal communities. Understanding the impacts of acidification on amphipods is vital for understanding how these communities will be impacted by climate change. To assess how long-term acidification may influence the survival of different members in these assemblages, mesograzers, particularly amphipods, associated with the brown alga Desmarestia menziesii were collected from the immediate vicinity of Palmer Station, Antarctica (S64°46′, W64°03′) in January 2020 and maintained under three different pH treatments simulating ambient conditions (approximately pH 8.1), near-future conditions for 2100 (pH 7.7), and distant future conditions (pH 7.3) for 52 days then enumerated. Total assemblage number and the relative proportion of each species in the assemblage were found to be similar across the pH treatments. These results suggest that amphipod assemblages associated with D. menziesii may be resistant to long-term exposure to decreased pH.
