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Probing invisible neutrino decay with the first six detection units of KM3NeT/ORCA
No full textn the era of precision measurements of neutrino oscillation parameters, it is necessary for experiments to disentangle discrepancies that may indicate physics beyond the Standard Model in the neutrino sector. KM3NeT/ORCA is a water Cherenkov neutrino detector under construction and anchored at the bottom of the Mediterranean Sea. The detector is designed to study the oscillations of atmospheric neutrinos and determine the neutrino mass ordering. This paper focuses on the initial configuration of ORCA, referred to as ORCA6, which comprises six out of the foreseen 115 detection units of photosensors. A high-purity neutrino sample was extracted during 2020 and 2021, corresponding to an exposure of 433 kton-years. This sample is analysed following a binned log-likelihood approach to search for invisible neutrino decay, in a three-flavour neutrino oscillation scenario, where the third neutrino mass state �\u273 decays into an invisible state, e.g. a sterile neutrino. The resulting best fit of the invisible neutrino decay parameter is eV2, corresponding to a scenario with θ23 in the second octant and normal neutrino mass ordering. The results are consistent with the Standard Model, within a 2.1 σ interval.</span
Wetland topography drives salinity resilience in freshwater tidal ecosystems
No full textThe restoration and creation of tidal freshwater wetlands is increasingly becoming important, yet the success of these efforts is limited by salt intrusion, a growing concern due to climate change and human activities. Key topographical features, such as (re)constructed channel network, might help mitigate salt intrusion in these areas. Using a hydrodynamic model and idealized topographies based on real-world data from natural marshes and various constructed wetlands, we analysed how topographies respond to saltwater intrusion events. Our findings reveal that, although wetland topographies based on natural marshes experience faster salinity increases at the onset of an event, they also achieve quicker salinity reductions at its conclusion, resulting in shorter overall periods of salinization compared to artificial wetland designs (e.g. up to 8.10 % in the drought simulations and 48.72 % in the storm surge simulations). The rapid reduction in salinity is driven by the distinct topography of natural marshes, particularly the creek system, which amplifies salt fluxes. Compared to the reference topography, the natural marsh topography exhibited 6.50 % higher salt fluxes in drought (S + W) simulations and up to 41.02 % higher in storm surge (S + W) simulations. These findings emphasize the importance of incorporating natural marsh characteristics, such as slope and channel network design, into tidal freshwater wetland restoration and creation projects to improve resilience against salt intrusion and ensure their long-term sustainability in the face of climate change
Separation timescales of vertically migrating zooplankton and other (a)biotic materials in the Benguela system
No full textPlankton, plastics, nutrients, and other materials in the ocean can exhibit different dispersion patterns depending on their individual transport properties. These dispersion patterns can provide information on the effective timescales of interaction between different types of materials in a highly dynamic ocean environment, such as the Benguela system in the southeast Atlantic Ocean. In this study, we compare the timescales and spatial distribution of separation for zooplankton performing Diel Vertical Migration (DVM) while drifting with currents to those of other materials: (a) positively buoyant plastics or planktonic organisms passively floating near the ocean\u27s surface; (b) nutrients or pollutants passively advecting in the three-dimensional flow; and (c) sinking biogenic particulate matter. We apply the drift properties of each material type in Lagrangian flow modeling to simulate the movement of virtual particles across the Benguela system. Our results indicate faster separation between zooplankton performing DVM and the other particle types during the upwelling season in the austral spring and summer. We also observe a decrease in the separation timescales between zooplankton performing DVM and other particle types as the zooplankton migration depth increases. Despite the differences in separation timescales across seasons, different particle types can become trapped in coherent features such as eddies, fronts, and filaments, indicating prolonged exposure of zooplankton to prey and pollutants in these coherent ocean features.</span
Polysaccharide-degrading archaea dominate acidic hot springs: genomic and cultivation insights into a novel <i>Thermoproteota</i> lineage
No full textThe expansion of sequencing technologies and bioinformatics has greatly advanced our understanding of microbial “dark matter,” yet the isolation of pure cultures, especially among Archaea, remains rare and challenging. Cultivation is still essential for the reliable characterization of microbial metabolism, which cannot be fully replaced by metagenomics and other omics-based approaches. Here, we report the first cultivated representatives of a deep-branching archaeal lineage previously known as Candidatus Marsarchaeota. Our phylogenomic analyses place these isolates within the phylum Thermoproteota as a novel order, Tardisphaerales. Members of Tardisphaerales dominate the prokaryotic communities in acidic hot springs below 70°C, comprising up to 40% of the total microbial population, underscoring their ecological significance. Functional genomics and culture experiments reveal a thermoacidophilic, anaerobic lifestyle, with energy metabolism based on carbohydrate fermentation, particularly of polysaccharides. This metabolic capability is supported by numerous glycosidase-encoding genes and by unprecedented metabolic versatility among thermoacidophiles. The isolates possess complete glycolysis, Entner-Doudoroff, and pentose-phosphate pathways, allowing them to utilize different sugars. Specialization in polysaccharide hydrolysis presumably provides an adaptive advantage for these slow-growing archaea, as most other heterotrophic thermoacidophiles prefer peptides or simple sugars. Furthermore, robust defense mechanisms against reactive oxygen species and persistence in acidic conditions enable Tardisphaerales to outcompete other heterotrophs and maintain dominance in these extreme habitats. The discovery and cultivation of this new order expand prokaryotic taxonomy and reveal the key players in carbon cycling in acidic geothermal ecosystems.</span
Cryptic infection of a giant virus in a unicellular green alga
No full textSpecies of the green alga Chlamydomonas have long been used as a model organism for eukaryote biology and photosynthesis. Only recently has this alga been discovered to be host to a giant, 617,000–base pair DNA virus that is integrated into the algal genome. Using long-read sequencing, Erazo-Garcia et al. found that this giant endogenous viral element can produce active virus particles from apparently healthy algal cultures and in wild populations. The widespread presence of virus relicts hints that virus integration is common in this alga and that selection is acting to deactivate them. This giant virus contains several RNA-guided nucleases that are encoded by mobile sequences and, along with other proteins, these nucleases are packaged into its particle
Evaluating the environmental impact of cleaning the North Pacific Garbage Patch
No full textCleanup of existing plastic pollution is crucial to mitigate its impact on marine ecosystems, but such efforts must ensure benefits outweigh potential environmental damage caused by the cleanup. Here, we present an impact assessment framework and apply it to evaluate whether cleaning the North Pacific Garbage Patch (NPGP) benefits marine life and carbon cycling, using The Ocean Cleanup as a case study. Our findings indicate that marine life is more vulnerable to plastic pollution than to macroplastic cleanup, with average vulnerability scores (1 = low, 3 = high) of 2.3 for macroplastics, 1.9 for microplastics, and 1.8 for cleanup, suggesting a net positive impact. An 80% cleanup could reduce macroplastic concentrations to within reported safe levels for marine mammals and sea turtles. Estimated cleanup-related carbon emissions [0.4–2.9 million metric tons (Mt) in total] are significantly lower than potential long-term microplastics impacts on ocean carbon sequestration (15–30 Mt C per year). However, uncertainties remain regarding effects on air-sea carbon exchange. Our framework serves as a critical tool for assessing trade-offs between plastic pollution and remediation impacts. It demonstrates the environmental net benefits of the proposed NPGP cleanup and can be adapted to similarly evaluate other remediation plans
The impact of offshore wind turbine foundations on local hydrodynamics and stratification in the Southern North Sea
No full textThe development of offshore wind farms (OWFs) in the North Sea is a crucial component for the transition to renewable energy. However, local hydrodynamics in the vicinity of OWF turbine foundations may be affected due to their interaction with tidal currents. This study investigates the impact of offshore wind turbine foundations on local hydrodynamics and stratification in the southern North Sea. We conducted a series of measurements around a single monopile in the Belgian part of the North Sea, focusing on hydrodynamics, salinity and temperature both near the surface and over the water column, and turbulent kinetic energy (TKE). Our results indicate that the foundation-induced wake significantly affects local hydrodynamics, leading to a well-defined band of colder, more saline water at the surface and warmer, less saline water near the seabed. This is quantified through the Potential Energy Anomaly (PEA), which shows a marked decrease in the wake-affected area. The wake is spatially confined, with a width of approximately 70 meters and a length of less than 400 meters downstream of the monopile. Additionally, our measurements reveal an increase in TKE within the wake, indicating enhanced turbulent mixing. This mixing reduces vertical gradients in salinity and temperature, leading to a more homogeneous water column. The findings highlight the importance of considering monopile-induced mixing in large-scale hydrodynamic and ecosystem models, as these effects can influence nutrient transport, primary production, and overall ecosystem dynamics. Furthermore, our research provides valuable data for validating and improving the models used to predict the ecological impact of OWFs
Reviews and syntheses: Review of proxies for low-oxygen paleoceanographic reconstructions
No full textA growing body of observations has revealed rapid changes in both the total inventory and the distribution of marine oxygen over the latter half of the 20th century, leading to increased interest in extending oxygenation records into the past. The use of paleo-oxygen proxies has the potential to extend the spatial and temporal range of current records, constrain pre-anthropogenic baselines, provide datasets necessary to test climate models under different boundary conditions, and ultimately understand how ocean oxygenation responds beyond decadal-scale changes. This review seeks to summarize the current state of knowledge about proxies for reconstructing Cenozoic marine oxygen: sedimentary features, sedimentary redox-sensitive trace elements and isotopes, biomarkers, nitrogen isotopes, foraminiferal trace elements, foraminiferal assemblages, foraminiferal morphometrics, and benthic foraminiferal carbon isotope gradients. Taking stock of each proxy reveals some common limitations as the majority of proxies functions best at low-oxygen concentrations, and many reflect multiple environmental drivers. We also highlight recent breakthroughs in geochemistry and proxy approaches to constraining pelagic (in addition to benthic) oxygenation that are rapidly advancing the field. In light of both the emergence of new proxies and the persistent multiple driver problem, the need for multi-proxy approaches and data storage and sharing that adhere to the principles of findability, accessibility, interoperability, and reusability (FAIR) is emphasized. Continued refinements of proxy approaches and both proxy–proxy and proxy–model comparisons are likely to support the growing needs of both oceanographers and paleoceanographers interested in paleo-oxygenation records.</span
Three subspecies of Black-tailed Godwit share non-breeding sites in the world\u27s largest river delta
No full textDuring the non-breeding season (September–April), Black-tailed Godwits (Limosa limosa) are commonly seen in coastal and inland wetlands of the Ganges-Brahmaputra-Meghna Delta in Bangladesh. We hypothesize that the Ganges-Brahmaputra-Meghna Delta, at the overlap between the Central Asian and East Asian–Australasian flyways, may host three subspecies that breed in disjunct areas of temperate and northern Asia: L. l. limosa, L. l. melanuroides, and L. l. bohaii. We used mitochondrial DNA (mtDNA) haplotype network and biometric analysis to determine subspecies in captured individuals, and deployed GPS–GSM transmitters to verify breeding areas of individuals with subspecies assignments. To test for differential habitat preferences, we sampled birds at two ecologically distinct habitats known to host the largest concentrations of non-breeding Black-tailed Godwits in Bangladesh: Nijhum Dweep National Park, a tidal coastal habitat with brackish water on the south-central coast, and Tanguar Haor (‘backmarsh’), a seasonal freshwater floodplain in the north. During the non-breeding seasons of 2021–2022 and 2022–2023, we sampled and measured 93 Black-tailed Godwits, 54 of which were equipped with GPS–GSM transmitters. Our mtDNA haplotype network analysis confirmed the presence of limosa, melanuroides, and bohaii subspecies at the study sites. Thus, indeed, Black-tailed Godwits subspecies, despite having distinct breeding ranges, exhibit (partially) overlapping non-breeding ranges in Asia. The subspecies composition differed significantly between sites, with limosa and bohaii dominating in Tanguar Haor and melanuroides in Nijhum Dweep. Of the 21 individuals that were tracked to their breeding grounds, 18 migrated to the expected breeding range of their respective subspecies. However, one bird with a limosa haplotype migrated to a known breeding area of bohaii, whereas two birds with melanuroides haplotypes migrated to the supposed breeding range of limosa. Therefore, while ecological factors at both ends of the flyways may shape the morphological and behavioural differences between Black-tailed Godwit subspecies, their delineations and possible gene flow require further studies.</span
An integrated approach to environmental health assessment of a coral reef ecosystem based upon Foraminifera
No full textThe reef system is the main feature of the Recife de Fora Marine Park (RFMP) on the East Brazilian coast. High hydrodynamics introduce nutrients, sediment, and contaminants from rivers while promoting reef flat erosion. To identify threats to reef ecosystems, we employed a foraminifera-based assessment using the FoRAM Index and the FORAM Stress Index, combined with analyses of environmental variables. Results revealed instability/stress in part of the western backreef stations, near the Buranhém river output, and a general estuarine influence. Reef flat and backreef surroundings data are marked by health decline and instability/stress, while forereef data indicated equilibrium/stability. Active offshore processes partially compensated for coastal negative influences, helping the system to remain healthy by the active “cleansing” of waves and tides. The results established a baseline of ecosystem quality for low-cost biodiversity queries, representing an advance in assessment using foraminifera important in long-term monitoring programs