Extreme Mediterranean rainfall impact on sedimentary routing systems: what can we learn from Storm Alex using in situ detrital 10Be?

Understanding how extreme meteorological events influence sediment transport is critical for predicting landscape evolution under a changing climate. Detrital cosmogenic 10Be can provide insights into sediment dynamics following extreme rainfall, but high-resolution datasets tracking 10Be variations before and after a storm, alongside long-term records, remain rare. The Var catchment (French Southern Alps) presents a unique case study, as its 10Be signal was well-documented before the October 2020 Storm Alex (>500 mm of rainfall/24 h), which triggered flash floods, mobilized large sediment volumes, and formed a 10 km-long sediment plume in the Mediterranean Sea. We compare 10Be concentrations in river sediments collected pre-storm (2016–2018), and at +7 days, +21 days, +4 months, and +7 months post-storm. We also use a historical offshore sample and contextualize these results with a 75 ka-long 10Be record from deep-sea sediment cores. At the Var outlet, 10Be concentrations initially increased by ~25 % at +7 and +21 days, attributed to the mobilization of 10Be-rich sediments from the upstream Var and Tinée sub-catchments. Concentrations returned to pre-storm levels within four months, primarily due to dilution with 10Be-poor sediments from the Vésubie sub-catchment fluvioglacial terraces. While short-term 10Be fluctuations at the Var outlet reflect complex sediment sourcing, our comparison with the 0–75 ka record confirms that major glaciation events and potential anthropic influences remain distinguishable, demonstrating that 10Be is a robust proxy of denudation changes, even when extreme events are involved

Le congrès One Ocean Science, un éclairage scientifique pour la 3e conférence des Nations unies sur l'Océan

A defining feature of the 3rd United Nations Ocean Conference was its precursor: an international scientific congress designed to base political commitments on the best available knowledge. The analysis carried out in this article of the link between scientific recommendations and the commitments made highlights the value of such an approach, with the launch of several actions aimed at improving the protection and preservation of the ocean. This is the case, for example, with the establishment of a coalition of countries seeking to place the ocean at the heart of national climate plans, echoing the recommendation to use oceanbased approaches to achieve the objectives of the Paris Agreement. It is also the case with the significant increase in the surface area of marine protected areas, in response to the recommendation to protect marine ecosystems while honoring international commitments. The analysis also points to shortcomings, such as the failure of negotiations on the international plastics treaty. It further shows that certain issues raised by scientists, such as ocean-based food, have not been discussed during the conference. Overall, the efficacy of this science-policy interface argues strongly for its continuation at the 4th edition in 2028.La 3e conférence des Nations-Unies sur l’océan s’est distinguée des précédentes éditions par l’organisation en amont d’un congrès scientifique international. Celui-ci avait pour objectif de fournir des recommandations afin que les engagements pris par les Etats et gouvernements soient basés sur les meilleures connaissances scientifiques disponibles. Cet article analyse le lien entre les recommandations scientifiques et les engagements pris et montre l’intérêt d’une telle démarche avec le lancement de plusieurs actions visant à améliorer la protection et la préservation de l’océan. Elle pointe également des lacunes : certains sujets portés par les scientifiques n’ont pas trouvé écho dans l’agenda international dédié à l’océan. Le succès de la charnière colloque scientifique – conférence onusienne plaide pour sa reconduction lors de la 4e édition prévue en 202

How contrasted environments in the Humboldt Current System, Pacific Warm Pool and South Pacific Gyre, shape contrasted ecosystems. A modeling approach using APECOSM

Pelagic ecosystems exhibit a strong regional heterogeneity, driven by physical and biogeochemical characteristics. Using the global 3D marine ecosystem model APECOSM, we simulate six high-trophic-level communities, capturing their size structure, spatial distribution, and trophic interactions up to 1,000 meters depth. We examine how different environments shape their contrasting organisation and interactions in three Pacific Ocean regions: the productive Humboldt Current System, the oligotrophic South Pacific Gyre, and the thermally stratified Pacific Warm Pool. Simulations reveal strong regional contrasts in ecosystem responses. In the Humboldt, high primary production supports important biomass of small coastal pelagic fish. Seasonal warming enables tuna to forage in these productive waters, while low-oxygen conditions restrict the vertical range and abundance of mesopelagic organisms and concentrate epipelagic organisms close to the surface. In the Warm Pool, apex predators remain abundant despite low primary production, thanks to efficient trophic transfer and biomass import from neighbouring regions. Seamounts concentrate mesopelagic organisms into shallow layers, making them accessible to epipelagic predators. In contrast, the South Pacific Gyre supports sparse, imported high-trophic-levels with limited trophic coupling and strong intra-community predation. We quantify regional differences in trophic transfer efficiency and network complexity, identifying thresholds below which high-trophic-levels collapse. These findings illustrate the emergent plasticity of pelagic ecosystems and the importance of bottom-up control of high-trophic-level biomass. They emphasise the importance of temperature, transport, light and oxygen in modulating horizontal and vertical distributions, controlling the co-occurrence of predators and prey, and influencing the formation of schools, ultimately impacting trophic interactions and community assemblages

Differences in telomere length and telomerase gene expression with age and among tissues in the Pacific oyster

Marine organisms are continuously exposed to chemical stressors, highlighting the need for operational biomarkers that can be reliably implemented in biomonitoring programmes. Telomere length (TL) has emerged as a promising biomarker of cumulative stress, but its application in ecotoxicology remains limited due to two main challenges: (i) methodological difficulties in obtaining reliable TL measurements from preserved samples, and (ii) incomplete understanding of telomere dynamics across tissues and life stages in sentinel marine species. In this study, we addressed both limitations in the Pacific oyster Crassostrea gigas. First, we compared different DNA extraction methods and selected a protocol suitable for isolating high-molecular-weight DNA from frozen oyster tissues. The qPCR assay was then optimized to minimise technical biases and ensure accurate TL quantification. Using this optimized method, we assessed TL variation across tissues and age classes. Significant tissue-specific differences were observed, with the digestive gland exhibiting the shortest telomeres. In addition, a clear age-related decrease in TL was detected across all tissues. Finally, RT-qPCR analyses revealed lower expression of the telomerase gene in adult tissues compared to early developmental stages, in line with the absence of detectable telomerase activity in adults. Together, these findings provide a methodological and biological framework for future investigations into the effects of chemical stress on telomere dynamics in oysters

Optimised use of passive samplers enabled early detection of SARS-CoV-2 variants BA.4 and BA.5 in sewage water

Wastewater-based epidemiology emerged as a valuable method to monitor the COVID-19 epidemic and the dynamic of SARS-CoV-2 variants. Because of its ease of deployment and low cost, membrane-based passive sampling is a prime alternative for deploying a monitoring network in wastewater, especially when automatic samplers cannot be used. However, the performance of these strategies for the identification of low-abundance viruses needs to be evaluated. Passive sampling using nylon membranes and grab sampling were carried out in parallel in the sewers of two French cities in April and May 2022, for the detection of norovirus GII (NoV GII) and SARS-CoV-2. SARS-CoV-2 sequencing was performed to compare the performance of passive samplers and their paired grab sampler in identifying Omicron sub-lineages. Direct lysis and elution methods from nylon membranes were equally effective for virus recovery and SARS-CoV-2 sequencing. For all sites, the virus concentrations in passive and grab samples were very similar. A near-complete genome coverage at a depth of 30 was obtained for most samples, using ARTIC multiplex PCR (V4.1) and Illumina MiSeq. There was a high proportion of low-frequency mutations for both methods and rare mutations in the S gene were detected, which could reflect the presence of cryptic lineages. Even though a large proportion of BA.2 lineage was detected in sewage, most importantly this study provides the first evidence that the use of passive sampling enables early detection of SARS-CoV-2 variants BA.4 and BA.5, that is, before they are identified in the population

A 1000-year-long record of diatom production and climate variability from the Gulf of Tehuantepec (Eastern Tropical North Pacific)

We examined the productivity variability in diatom assemblages during two contrasting climatological periods: the Medieval Warm Period (MWP) and the Little Ice Age (LIA), in the Gulf of Tehuantepec (GT), Eastern Tropical North Pacific. The GT is an important fisheries region in Southern Mexico, largely dependent on ocean productivity. Climatologically, the GT is seasonally affected by a strong north-wind regime and the Intertropical Convergence Zone interactions. These winds promote intense mixing and upwelling in winter to spring months and stratification conditions during the rest of the year; therefore, this climatic variability is expected to have been affected by the MWP and LIA conditions. The MWP (~784 to ~1426 CE) was characterized by the predominance of a warm-water and low-productivity assemblage formed by Neodelphineis pelagica, Thalassionema nitzschioides var. parvum, Thalassiosira eccentrica, Thalassiosira oestrupii, Cyclotella litoralis, Thalassiosira lineata, Fragilariopsis doliolus, Nitzschia interruptestriata and other minor taxa. Early LIA (~1436 to ~1620 CE) was characterized by the predominance of a cold-water and high-productivity diatom assemblage constituted by Chaetoceros spores, Thalassionema nitzschioides, Thalassionema bacillare, Lioloma pacificum, and Thalassiosira nanolineata. Comparing the MWP diatom assemblage to that from the Current Warm Period (1850 CE to present, as reported in a previously published study in the GT) showed that the last 150 years have been the warmest in the integrated ~1400-year GT record

Seeing yew for the forest: a call to action for improving conservation and restoration of the European yew (Taxus baccata L.)

The European yew (Taxus baccata L.) is a long-lived conifer of ecological, cultural, and historical importance across Eurasia. Despite its remarkable resilience, wide distribution, and symbolic importance, the species has experienced a long-term decline due to a complex interplay of climatic fluctuations, megafaunal extinctions, human exploitation, and insufficient regeneration. Recent studies in palaeoecology, archaeology, dendroecology, and conservation have revealed a species with greater ecological plasticity and a broader historical distribution than previously assumed. However, many fundamental questions remain unresolved, particularly regarding its biogeographical history, population dynamics, recruitment processes, and the drivers of its decline. This review stems from prior investigations of yew in the French Pyrenees and, more broadly, across Europe. These efforts led to a transdisciplinary seminar and opened a collaboration uniting more than 30 researchers across Eurasia. By synthesizing a wide array of data and perspectives, the article highlights key knowledge gaps and outlines emerging research priorities. These are organized thematically—past, present, and future—and include 25 questions on the species' ecological niche, life-history strategies, human interactions, genetic resilience, and conservation under global change. The article advocates for a shift towards integrative and long-term conservation strategies that embrace the historical legacies of yew populations, the general ecology of the species along with local ecological context dependence, and the urgency of future threats. By identifying pressing research needs, this review seeks to lay the foundation for new collaborative initiatives and to support evidence-based conservation of this emblematic yet understudied species

Assessing the Effects of Three Harmful Microalgal Species on Spermatozoa and Embryos of the King Scallop Pecten Maximus

The reproductive process plays a crucial role in the renewal of populations of marine bivalves and represents an economic issue for exploited species like the king scallop Pecten maximus. However, environmental phenomena, such as harmful microalgal blooms (HAB), can affect key reproductive life stages, such as gametes and embryos. This study examines the effects of exposure to three harmful microalgal species (Alexandrium minutum, Lingulodinium polyedra, and Pseudo-nitzschia australis) on spermatozoa and embryos of king scallops P. maximus. The physiological responses of spermatozoa were evaluated after exposure to low (LC) and high concentrations (HC) of each microalgal species. While none of the tested microalgal strains showed direct toxicity, oxidative stress was associated to HC of A. minutum, and morphological changes were observed after exposure to L. polyedra and P. australis. Embryos of P. maximus were also exposed to HC of the same three microalgae species and examined under a microscope after 4h, 24h, and 48h of exposure. Exposure to A. minutum hindered cell division of embryos within the first four hours of development, leading to complete embryo lethality at 24 hours. No significant changes in early development were noted during the initial 48 hours of exposure to L. polyedra and P. australis. These findings underscore the diverse effects of harmful microalgal species, emphasizing the need for targeted fishery and shellfishery management, both spatially and temporally, especially when bivalves and harmful algal bloom species potentially coincide during bivalve reproduction and recruitment

Benthic ecological changes in response to fish farming waste deposition in tropical environment: combining field and modelling approaches

While substantial progress has been made in evaluating the ecological carrying capacity (ECC) for fish farming in temperate regions, studies in tropical environment remain scarce, and benthic ecological thresholds are still lacking. This study combines spatial measurements of waste deposition (quantified with sediment traps and depositional modelling approaches), with measurements of sediment physical and biogeochemical properties and macrobenthic community structure at a shallow, non-dispersive site in Martinique. Despite minimal changes in sediment physical and biogeochemical properties, pronounced effects were observed on macrobenthic communities structure. At farm sites, benthic communities were highly perturbed (extremely low diversity and abundance of individuals) and dominated by few individuals of second-order opportunistic species. At sites located between 25 and 150 m from the farm, benthic communities were similar and characterised by higher diversity and abundance, with the presence of sensitive species to OM enrichment. The benthic response was strongly driven by organic waste deposition, which was elevated directly beneath and adjacent to the fish cages. The benthic response to depositional fluxes was best described by M-AMBI index. Notably, the transition from ‘Moderate’ to ‘Poor’ ecological status occurred within a depositional range of 1.2–3.0 kg m−2 year−1 for POM and 0.6–1.1 kg m−2 year−1 for TOC, with model predictions suggesting that these effects may extend up to 30 m from the farm. This study represents a step forward in defining benthic ecological thresholds for tropical fish farming and will help decision makers in fostering the sustainable development of aquaculture in these regions

Global ocean indicators: Marking pathways at the science-policy nexus

Ocean knowledge is crucial for shaping policies that enable sustainable development, adaptation, and well-being at all levels, as everyone—either directly or indirectly—depends on the ocean, which today faces escalating threats from climate change, pollution, and biodiversity loss, pushing us beyond critical planetary boundaries. Ocean indicators are crucial for translating ocean science and data into practical metrics, guidance, and tools informing on the state and health of the ocean that can be directly applied by policymakers, practitioners, and the public. Despite their critical importance, ocean indicators trail behind those for continental areas, limiting effective monitoring and policy integration. Developing reliable, comparable, and regularly updated ocean indicators, backed by a unified international framework, is essential for delivering coherent, actionable insights that can guide global goals and protect the ocean's future. This paper establishes a scientific foundation for ocean indicators through international and multidisciplinary collaboration, presenting defined criteria and a set of pilot indicators for the ocean’s physical, biogeochemical, biodiversity, and ecosystem aspects. The proposed framework offers a solid foundation for generating indicators that not only track the ocean state but also provide outputs for application in informing policy and decision-making