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Round-the-world ocean races such as The Ocean Race and the Vendée Globe expose sailors to some of the planet's most remote and extreme marine environments, creating a unique opportunity to study both environmental conditions and human responses to them. In this comment we highlight how these events can function as mobile climate laboratories, enabling the simultaneous collection of oceanographic and atmospheric data alongside human biometric information, including physiological, psychological, and cognitive indicators. Integrating disciplines such as climatology, oceanography, ecology, and human health sciences enables investigation of how humans adapt to environmental stressors while also improving environmental monitoring. Establishing coordinated interdisciplinary research programs could strengthen climate resilience research, enhance ocean and human health monitoring, and support more sustainable engagement with marine environments.

The Atlantic Meridional Overturning Circulation (AMOC), a major ocean current system, could transition to a weak state. Despite severe associated climate impacts, assessing the AMOC's response under global warming and its proximity to possible critical thresholds remains difficult. To understand future Earth system stability, a global dynamical view is needed beyond the local stability analysis associated with classical early-warning methods. Using an intermediate-complexity climate model, we explore the stability landscape of the AMOC for different atmospheric CO2 concentrations. We explicitly compute the edge state (or Melancholia state), a chaotic saddle on the basin boundary separating the strong and weak AMOC attractors found in the model. Despite being unstable, the edge state can govern the transient climate for centuries, supporting centennial AMOC oscillations driven by atmosphere-ice-ocean interactions in the North Atlantic. At increased CO2 levels projected for the near future, we reveal a boundary crisis where the current AMOC attractor disappears by colliding with the edge state. Under crisis overshoot, long chaotic transients owing to a 'ghost state' lead to ensemble splitting under time-varying forcing. Rooted in dynamical systems theory, our results offer an explanation of large ensemble variance and apparent 'stochastic bifurcations' observed in earth system models under intermediate forcing scenarios. This article is part of the theme issue 'Critical transitions and intelligent control in complex systems'.

Seamounts are hotspots of seafloor biodiversity in the open sea, and microorganisms are the base of seamount food webs. However, the mechanism shaping the vertical distribution patterns of microbial community composition in seamount sediment cores remains elusive. Here, we analyzed the microbial communities in seven sediment cores collected from a seamount in the Western Philippine Ocean and its adjacent valley. We investigated the assembly of bacterial and archaeal communities in three sediment cores that contained complete profiles of microbial communities and deciphered how changes in community assembly processes altered β-diversity. In addition, we explored the microbial co-occurrence patterns in the three cores and their correlation with environmental variables. The results revealed that bacterial community assembly was dominated by drift, dispersal limitation, homogenizing dispersal, and homogeneous selection, whereas archaeal community assembly was dominated by drift. Besides, the variability of microbial co-occurrence patterns among the three sediment cores was driven mainly by trace elements. This study supported that dispersal limitation led to a higher β-diversity, whereas homogeneous selection, homogenizing dispersal, and drift resulted in a relatively lower β-diversity. Overall, this study offers key insights into the microbial occurrence patterns and community assembly in seamount sediment cores, and illustrates how different community assembly processes affect β-diversity.IMPORTANCEβ-Diversity (site-to-site variation in species composition) is important for understanding the mechanisms that generate and maintain biodiversity, but the origin of β-diversity is still largely unknown. Variations in β-diversity can be related to changes in assembly processes, but there is still a lack of a quantitative evaluation for the effects of different assembly processes on β-diversity. Here, we investigated the microbial community assembly in three sediment cores collected from a seamount in the Western Philippine Ocean and its adjacent valley. We compared the differences in β-diversity among bacterial communities that were driven by different assembly processes and found that β-diversity was enhanced by dispersal limitation but decreased by homogeneous selection, homogenizing dispersal, and drift. Our findings underscore the differential impacts of assembly processes on β-diversity, which advances the understanding of the origin of β-diversity.

Sea level rise (SLR) threatens coastal ecosystems, critical for sequestering carbon (C), providing habitat, and reducing storm surge. Mangrove forests are particularly efficient in C sequestration and are host to a variety of dependent species. Using United States (U.S.) National Oceanic Atmospheric Administration data, we estimated future mangrove inundation from SLR at 0.3, 0.61, and 3.0 m in the U.S. By 3.0 m of SLR (around the middle of next century), we estimate mangrove area loss to be almost half of current areas, or 47.4% of the approximately 266.7 thousand ha currently present. To estimate C sequestration and ecosystem service loss, we compared scenarios where inundated mangrove areas convert to salt marsh vs open ocean. We estimate sequestration loss to be approximately 30-199 thousand metric tons C y-1 from 3.0 m of SLR. Combined with decreases in other ecosystem services, this represents an annual loss of $5.8 billion (in USD and Int$) per meter of SLR. Migration poleward, although unlikely in areas with coastal development, may reduce some impacts in select locations. Overall, we conclude mangrove areas and their accompanying ecosystem services are likely to be greatly reduced by SLR in the future.

Kelp, brown macroalgae in the order Laminariales, provide ecosystem services vital to ocean biodiversity. However, kelp forests worldwide are declining due to abiotic stressors such as ocean warming. In this study, we present results from high-resolution confocal microscopy and in vivo imaging system imaging using protocols developed to visualize kelp gametophyte cells exposed to heat-stress treatments. Imaging revealed chloroplast mislocalization, fragmentation, and subsequent loss of chloroplasts in heat-stressed gametophyte cells. Additionally, nuclei exhibited fragmentation and a progressive loss of fluorescent signal, and the associated microbiome proliferated under various heat-stress treatments. Notably, because brown algae possess a continuous outer membrane that connects the nuclear envelope and the chloroplast envelope, these observations suggest a cellular vulnerability underlying thermal sensitivity in brown macroalgae. Finally, by comparing heat-stress tolerant and heat-stress sensitive genotypes, we found that genotypes with higher heat tolerance exhibited substantially fewer abnormalities compared to sensitive ones.

Protected areas are a critical component of efforts to reverse biodiversity loss by 2050. In the ocean, free-drifting fish aggregating devices (dFADs) are released in large numbers by industrial purse seine fishing companies to help catch tuna. These devices can enter marine protected areas (MPAs) undetected, potentially leading to wildlife entanglement, plastic pollution, and habitat degradation. Here we investigate processes by which dFADs may compromise MPA objectives and assess the burden they put on existing MPAs. By analyzing drift, strandings, and expert interview data, we show that dFADs have likely interacted with 53% of the global MPA network by area and stranded in 174 protected areas, which are home to at least 490 at-risk species. While recent improvements to dFAD design should reduce harm to wildlife, our findings suggest that improved regulation, transparency, and industry accountability are required to mitigate additional effects on MPAs, especially around documented hotspots in the central Pacific, western Indian Ocean, and Caribbean.

Karst aquifers are a crucial source of water, supplying approximately 10% of the global population and often serving as the sole water resource in certain regions. These aquifers are characterized by highly heterogeneous flow dynamics and exhibit significant temporal variability in both hydrodynamic and physico-chemical conditions. Continuous monitoring of these parameters is essential for advancing our understanding of karst aquifer functioning; however, comprehensive, high-frequency datasets remain limited. We present a comprehensive dataset covering 13 karst springs monitored across nine observatories of the French Karst National Observatory Service (SNO KARST), spanning various hydroclimatic regions (oceanic, mountainous, Mediterranean). The SNO KARST aims to strengthen knowledge-sharing and to promote cross-disciplinary research on karst systems at the national scale. The dataset includes: (1) hydrodynamic data (water level, discharge), and (2) physico-chemical data (water temperature, electric conductivity, pH, dissolved oxygen, turbidity, Total Organic Carbon (TOC), Dissolved Organic Carbon (DOC), nitrate, and organic matter fluorescence). Spanning over a decade of continuous monitoring, such a dataset is required for the analysis of the hydrological and physico-chemical dynamics of karst aquifers, the assessment of their vulnerability to pollution and climate change, and the modeling of hydrodynamic and hydrochemical variables, ultimately aiming to improve the management and preservation of these critical water resources in contrasted contexts.

Rivers are major pathways for plastic pollution to oceans, with high emissions in tropical regions. Research in the Saigon River showed that invasive water hyacinths (WHs) can trap macroplastics and serve as proxies for detecting river plastic using remote sensing. We explore this phenomenon and its detection methods transferability to the Chao Phraya River. Along a 62.1 km river course, WHs trapped an average of 32% of floating plastics, reaching local maxima of 78%, comparable to 54%-82% in the Saigon. Plastic concentration in WHs was 59 times higher than in open water, increasing downstream. Object detection models transferred well for WHs and entangled plastics (Chao Phraya: mAP50 = 68% and 54%; Saigon River: mAP50 = 70% and 52%) but poorly for free-floating plastics (23% vs. 48%). Physical sampling found 14 times more plastics within WHs than imagery, highlighting WHs' role in trapping plastics and their potential for monitoring and targeted clean-up efforts.

Polar marine invertebrate giants are proposed to have emerged from the greater availability of environmental oxygen, overcoming the viscosity of cold water and avoiding oxygen poisoning. However, molecular evidence on their metabolic adaptations is lacking to date. Consequently, we characterised the metabolome profiles of a number of marine Antarctic giants and their regular-size relatives exposed acutely in the laboratory either under mean seasonal conditions or elevated temperature. Giants from very distinct taxa share the differential utilisation of metabolic pathways involved in energy production, suggesting an adaptive convergence of metabolic reprogramming to meet the challenge of possessing larger bodies and facing harsh polar conditions. Further, we show that giants are not just larger regular-size species, as indicated by a breakpoint in the allometric relationship for metabolomics scores. Finally, giants do not appear to be more sensitive to ocean warming when compared to their regular-size relatives, all species tested showing no short-term metabolomics reprogramming under elevated temperatures.

Oil pollution is one of the most persistent and harmful anthropogenic pressures on global marine and coastal ecosystems. Accidental discharges, chronic leaks, operational spills from shipping, offshore drilling, and industrial activities release millions of tons of hydrocarbons annually, threatening marine biodiversity, fisheries, and coastal livelihoods. Remote sensing has become the primary technology for oil spill detection, mapping, and monitoring, offering synoptic, repeatable, and objective coverage of extensive marine areas. This paper presents a systematic review of remote sensing for oil spill detection, mapping, and monitoring, grounded in a bibliometric analysis of 2856 verified documents authored by 6473 researchers, retrieved from five major academic databases (OpenAlex, CrossRef, EuropePMC, SemanticScholar, and CORE), spanning the period 2000 to 2026. Annual publication output grew from 16 documents in 2000 to a peak of 244 in 2025, reflecting a 15-fold growth driven by the Deepwater Horizon disaster (2010), the launch of Sentinel-1 (2014-2016), and the proliferation of deep learning frameworks. The review examines the physical principles of oil detection across the electromagnetic spectrum; compares radar, optical, hyperspectral, and thermal sensor platforms; and evaluates developments in artificial intelligence (AI) and data fusion methods for automated detection. Validation protocols, regional case studies from the Gulf of Mexico, North Sea, Mediterranean, Arctic, and Caspian Sea, and the integration of Earth observation with decision-support frameworks are also assessed. Key findings confirm that no single sensor is universally superior: synthetic aperture radar (SAR) provides all-weather, day-night capability, while optical and hyperspectral sensors deliver spectral and compositional insight. Deep learning models, particularly U-Net and transformer-based architectures, have achieved exceptional detection accuracy but face persistent challenges of data scarcity, look-alike discrimination, and limited cross-regional transferability. Emerging innovations in multi-sensor constellations, physics-informed deep learning, and cloud-native processing are identified as pathways toward real-time environmental intelligence and improved ocean governance.

The climate system's nonlinear dynamics is influenced by various external forcings and internal feedbacks, which can give rise to regional and even global tipping points that may lead to significant, potentially irreversible changes. Palaeoclimatic records reveal that Earth's climate has shifted between distinct equilibria, including a 'hothouse Earth' state with temperatures about 10 K higher than at present. However, a specific mechanism for a sudden tipping to an alternate stable state, several degrees warmer than the present climate, has yet to be presented. We introduce a temperature-carbon-vegetation (TCV) model comprising an energy balance model (EBM) of global temperature, coupled with global terrestrial and ocean CO2 dynamics, and with vegetation ecosystem change. Our model exhibits a new tipping mechanism that leads to a hothouse Earth under a high-emission scenario. Its simulations align with both observations and Intergovernmental Panel on Climate Change (IPCC)-class global climate models (GCMs) prior to tipping. The two processes that produce global tipping are: (i) temperature-albedo feedback owing to darkening of the terrestrial cryosphere by glacial microalgae and (ii) limits to vegetation adaptation that lead to reduced carbon absorption. This article is part of the theme issue 'Critical transitions and intelligent control in complex systems'.

Underwater target recognition is essential for ocean monitoring, with ship radiated noise analysis being a fundamental technique. This paper proposes a detection method based on block sparse enhancement. A harmonic dictionary is constructed and block sparse reconstruction is applied to enhance line spectrum components in the Detection of Envelope Modulation on Noise spectrum. A detection strategy that integrates harmonic structure and fundamental frequency continuity is designed. Simulations and SWellEx-96 data demonstrate that the proposed method achieves better clarity, higher signal-to-noise ratio (SNR) gain, and improved stability under low SNR conditions compared to traditional approaches.

Subterranean estuaries play a key role in the land-ocean interface by modulating groundwater-borne and recycled solutes discharged to the coast. Despite their importance for coastal ecosystems, the sensitivity of these systems to human activities is still unknown. To address this gap, dissolved organic matter (DOM) and dissolved inorganic nutrients of a pristine site were compared with those from two nearby, semiurban sites characterized by contrasting oxygen conditions. The local aquifers surrounding the semiurban subterranean estuaries contained more nitrogen, silicate, and DOM of higher molecular weight than the aquifers surrounding the pristine site. Despite the different chemical composition of the arriving fresh groundwater, N/P ratios and the quantity of humic-like DOM compounds at the pristine site were intermediate between those of the two semiurban sites. This pattern reflected the intermediate permeability and oxygenation of the pristine beach, highlighting the role of the sediment matrix in modulating the exported solutes. Enhanced oxygenation at one semiurban site resulted from a human-derived gravel layer that increased sediment permeability and reduced internal residence times. The anthropogenic alteration of the sediment permeability had a greater influence on the nutrients and DOM found in subterranean estuaries than did the chemical composition of the inland aquifers.

The long-lived fission product technetium-99 (99Tc, t 1/2 = (2.111 ± 0.012) × 105 years) was successfully detected in small-volume (10 L, and 1 g, respectively) environmental samples such as Pacific Ocean and river water, Antarctic snow, and peat. Its presence in the environment is almost exclusively of anthropogenic origin and the determined levels are attributed to nuclear weapons testing in the 1950s and 60s as no local contamination source is known to be present at these sampling sites. A unique capability for Accelerator Mass Spectrometry (AMS) measurements of environmental 99Tc at unprecedented sensitivity was established, first using the Gas-filled Analysing Magnet System (GAMS, Germany) and after its shutdown, at the Heavy Ion Accelerator Facility (HIAF, Australia). New chemical extraction and measurement techniques, including improved non-isotopic normalisation, enabled detection limits as low as 0.6 femtograms (fg) per sample for Antarctic snow, and enhancement of precision from 30% (GAMS) to 16% (HIAF). The rather high concentrations of about 280 fg (99Tc) per g (dry mass) measured in peat indicate Tc accumulation in this archive, which opens the possibility of studying its migration behaviour even under reducing conditions. Furthermore, it allowed deduction of an improved estimate of the global 99Tc inventory to (120-190) TBq. The first direct detection of 99Tc at 8 fg L-1 in river water highlights the need for further studies in urban areas to evaluate potential contributions from nuclear medicine. The achieved sensitivity allows monitoring of on-going releases, improving the risk assessment of releases from nuclear waste repositories and tracer applications in environmental sciences.

Marine phages are, through the infection of their bacterial hosts, key regulators of microbiome and carbon fluxes in the ocean. Despite their important role, the specific molecular mechanisms that underlie infection are so far understudied. Previously, the podovirus Cobetia marina virus 1 (Carin-1), which infects the marine γ-proteobacterium C. marina, was shown to display exopolysaccharide depolymerase activity. This activity is likely to mediate degradation of the host capsule to facilitate access to the bacterial membrane receptor, but no corresponding gene could be annotated in the genome of Carin-1 by comparative genomics. Biochemical characterization enabled assignment of this activity to Dpo31, a protein sharing less than 10% sequence identity with any characterized protein. Here, we report the structural domain organization and biochemical characterization of Dpo31, revealing an overall structure that is analogous to podovirus tail-spike proteins, allowing us to locate the depolymerase activity to the D3 domain and to identify original structural features that explain the absence of detectable similarity at the primary-sequence level.

The poor prognosis of hemodialysis (HD) patients following transcatheter aortic valve replacement (TAVR) has been established; however, data on the outcomes in the latest generation of devices remain inconsistent. The authors aimed to compare the 1-year clinical outcomes post-TAVR using the latest generation of devices in HD and non-HD patients. From the multicenter registry, 760 HD and 3,928 non-HD patients were identified from the OCEAN-TAVI (Optimized transCathEter vAlvular iNtervention-Transcatheter Aortic Valve Implantation; UMINID:000020423) registry. To minimize differences in baseline characteristics, 1:1 propensity score matching (PSM) was performed (490 patients each). The primary clinical endpoint was all-cause mortality at 1 year. Secondary endpoints included cardiovascular death, stroke, and heart failure rehospitalization. In the overall cohort, during 208 (41-373) days of follow-up, HD patients had higher 1-year mortality than non-HD patients (105 of 760 [13.8%] vs 189 of 3,928 [4.8%], HR: 2.62; 95% CI: 2.13-3.23; P < 0.001); this difference was attenuated (59 of 490 [12.0%] vs 65 of 490 [13.3%], HR: 1.03; 95% CI: 0.75-1.42; P = 0.858) following well-balanced PSM. There were no significant differences in any secondary endpoints between the 2 groups after PSM; however, HD remained an independent predictor of 1-year mortality in a multivariate analysis of the cohort before PSM. The poor prognostic value of HD was attenuated after adjusting for baseline risk factors. These findings suggest that the poor outcomes of HD patients result from the burden of multiple comorbidities in addition to the HD risk itself. Considering TAVR as a treatment option for exceptionally high-risk populations will aid in the careful patient selection and realistic prognostic assessments.

Marine fungi were assumed to have a minor role in carbon cycling, unable to compete with bacteria. A new PLOS Biology study challenges this dogma, showing fungi can dominate labile dissolved organic matter assimilation, reshaping our understanding of ocean carbon retention and storage.