Shifts in Greenland interannual climate variability lead Dansgaard-Oeschger abrupt warming by hundreds of years

During the Last Glacial Period (LGP), Greenland experienced approximately thirty abrupt warming phases, known as Dansgaard-Oeschger (D-O) Events, followed by cooling back to baseline glacial conditions. Studies of mean climate change across warming transitions reveal indistinguishable phase-offsets between shifts in temperature, dust, sea salt, accumulation and moisture source, thus preventing a comprehensive understanding of the “anatomy” of D-O cycles (Capron et al,. 2021). One aspect of abrupt change that has not been systematically assessed is how high-frequency, interannual-scale climatic variability surrounding mean temperature changes across D-O transitions. Here, we utilize the EGRIP ice core high-resolution water isotope record, a proxy for temperature and atmospheric circulation, to quantify the amplitude of 7–15 year isotopic variability for D-O events 2–13, the Younger Dryas and the Bølling-Allerød. On average, cold stadial periods consistently exhibit greater variability than warm interstadial periods. Most notably, we often find that reductions in the amplitude of the 7–15 year band led abrupt D-O warmings by hundreds of years. Such a large phase offset between two climate parameters in a Greenland ice core has never been documented for D-O cycles. However, similar centennial lead times have been found in proxies of Norwegian Sea ice cover relative to abrupt Greenland warming (Sadatzki et al., 2020). Using HadCM3, a fully coupled general circulation model, we assess the effects of sea ice on 7–15 year temperature variability at EGRIP. For a range of stadial and interstadial conditions, we find a strong relationship in line with our observations between colder simulated mean temperature and enhanced temperature variability at the EGRIP location. We also find a robust correlation between year-to-year North Atlantic sea-ice fluctuations and the strength of interannual-scale temperature variability at EGRIP. Thus, both paleoclimate proxy evidence and model simulations suggest that sea ice plays a substantial role in high-frequency climate variability prior to D-O warming. This provides a clue about the anatomy of D-O Events and should be the target of future sea-ice model studies

A new continental hydrogen play in Damara Belt (Namibia)

Serpentinization is commonly presented as the main source of natural hydrogen (H2) in the continental domains. However, recent works in Australia and Brazil showed that Archean–Paleoproterozoic banded iron formations could be another natural source of H2 gas. Although the reaction that produces hydrogen is similar (Fe2+ oxidation—H2O reduction process), the iron content may be higher in banded iron formations than in mafic igneous lithologies, potentially generating H2 more efficiently. Here, we present structural evidence that reported H2 emissions from Waterberg Basin, Namibia are associated with underlying Neoproterozoic banded iron formations—the Chuos Formation. Magnetite, a known H2-generating mineral, is ubiquitous and accompanied by other suspected H2-generating minerals (biotite and siderite) in Chuos Formation. Magnetite occurs either as pervasive cm to dm continuous metamorphic laminations in foliation and fractures planes and/or diffusely disseminated in metachert and metacarbonate levels. From this, we infer that metamorphism does not negatively affect the Fe2+ content that is required to generate hydrogen. H2 seepages in Waterberg Basin suggest that an active H2-generating system may exist at depth and that the presence of potential traps and reservoirs is likely based on field observations

DELMOGES. Description des activités de pêches, cartographie et typologie des stratégies opérant dans le golfe de Gascogne

Depuis les années 1990, la France connaît régulièrement des épisodes de mortalités importantes de dauphins, qui entraînent des pics d’échouages sur le littoral Atlantique en hiver. Depuis 2016, les échouages de petits cétacés dans le golfe de Gascogne présentant des traces de capture, atteignent des niveaux inédits. Si les données scientifiques actuelles permettent d’évaluer globalement le risque induit par ces captures accidentelles pour la conservation de la population de dauphins communs, elles sont toutefois trop lacunaires pour comprendre les déterminants écosystémiques et halieutiques à l’origine de ces captures. En concertation avec l’Office français de la biodiversité, les professionnels de la pêche et l’Etat, La Rochelle Université-CNRS et l’Institut français de recherche pour l’exploitation de la mer (Ifremer) ont construit le projet Delmoges (Delphinus Mouvements Gestion). Il vise, dans un premier temps, à combler ces lacunes en allant chercher des nouvelles données sur les habitats des dauphins, sur leurs interactions trophiques dans l’écosystème et leurs interactions techniques avec les engins de pêche. Ensuite, le projet propose d’intégrer les connaissances sur l’ensemble du socioécosystème pour envisager une diversité de scénarios de diminution des captures accidentelles incluant des solutions technologiques et, enfin, d’en évaluer les conséquences biologiques et socioéconomiques. Le livrable L311 est produit dans le contexte du « WP3 – Interactions spatio-temporelles et techniques dans les engins de pêche ». Il vise à proposer une description des activités de pêche et une typologie des flottilles opérant dans le golfe de Gascogne. La première partie présente un ensemble de chiffres et indicateurs clés de l’activité de pêche professionnelle observée dans le golfe de Gascogne en 2022 ainsi que les tendances observées sur la période 2012-2022. Ces éléments contextualisent l’analyse typologique présentée par la suite qui caractérise les stratégies (à l ‘échelle annuelle) et les tactiques (à l’échelle des marées) de pêches utilisés dans le Golfe de Gascogne entre 2000 et 2022. Ces ensembles correspondent à des groupements de navires/marées présentant des comportements de pêche (activités spatiales, temporelles, composition des prises, caractéristiques des engins et navires de pêches, volumes d’activités) homogènes. Ces stratégies/tactiques sont ensuite mises en relations avec les captures accidentelles, afin d’identifier les groupements les plus à risques au vu des données actuelles

Evaluation de la qualité des zones de production conchylicole. Département d'Ille-et-Vilaine. Période 2021-2023

Après un rappel des objectifs, du fonctionnement et de la méthode d’interprétation des résultats du réseau de surveillance microbiologique des zones de production conchylicoles (REMI) et du réseau d’observation de la contamination chimique (ROCCH), ce rapport inclut un bilan national et décrit le programme annuel du département de l’Ille-et-Vilaine (35). Il présente l’ensemble des résultats obtenus, en particulier l’estimation de la qualité microbiologique et chimique des zones de production de coquillages classées. L’année 2023 présente des résultats très similaires à l’année dernière. Ils font suite à plusieurs années de stabilisation des bruits de fond des contaminations. Aujourd’hui, l’essentiel des points ne montre plus de tendance significative à l’augmentation ou à la diminution des niveaux de contamination (95% des points de suivi – annexe 4). Le bilan de la qualité sanitaire des zones conchylicoles dans le département d’Ille-et-Vilaine est donc assez stable Les estimations de la qualité sanitaire 2023 montrent une amélioration (B vers A) pour la zone 35.04 « Sud Cézembre » (groupe 2) et une dégradation (A vers B) pour la zone 35.08 « Stockage Cancale » (groupe 3), mais cette dernière est due à un pic de contamination relevé en 2021. En baie du Mont-Saint-Michel, l’ensemble des points continue de présenter un faible bruit de fond des contaminations, malgré sept résultats qui restent déclassants. En baie de Saint-Malo et en Rance, l’état sanitaire s’était considérablement dégradé au début des années 2010. Mais depuis 2015, l’essentiel des zones suivies connaît un regain de qualité et permet un classement généralisé en qualité moyenne. Cette qualité sanitaire se maintient en 2023 avec quelques éléments : positifs (passage en bonne qualité de « Sud Cézembre », zone « Pointe de Saint-Suliac » toujours très proche du A) et négatifs (retour des alertes en Rance, toujours des alertes sanitaires parfois importantes au niveau de Dinard en lien avec son assainissement). La stratégie du suivi REMI a évolué en 2023 avec le sous-découpage de zones au centre de la baie du Mont-Saint-Michel (zones 35.06.02, 35.06.03, 35.16 et 35.17) afin de circonscrire les secteurs les plus touchés. Ces résultats sont issus d’une étude sanitaire toujours en cours sur le groupe 3 pour la partie plus au large (zones 35.11 et 35.13). De nouveaux contaminants chimiques ont été pris en compte dans l’estimation de la qualité sanitaire des zones. Il s’agit des PFAS (composés perfluoroalkylés), sans qu’aucun résultat ROCCH n’ait présenté de dépassement de seuil sur le département

Silicon isotopes in juvenile and mature Cyperus papyrus from the Okavango Delta, Botswana

The three most abundant stable isotopes of Silicon (Si), 28Si, 29Si, and 30Si, all occur in plants. Isotope studies are a potential tool to explore uptake and function of plant Si, and it is a developing field. However, there is a lack of studies from natural environments, and species from the African continent, and all plant parts including reproductive structures. In this study, naturally grown papyrus plants were sampled from the Okavango Delta and divided into five organs, i.e. umbel, culm, scales, rhizome, and roots. Samples were analysed for TN, TOC, BSi, TP concentrations, and for Si isotopes. Each organ of papyrus is represented by two samples, one from juvenile tissue and one mature (apart from the roots where age is difficult to determine). The study confirms that papyrus is a high Si-accumulating species, with BSi ranging from 0.88 % in rhizomes to 6.61 % in roots. High Si precipitation in the roots leads to an enrichment in heavy Si isotopes in the residual mobile Si pool, as light Si isotopes precipitate in phytoliths in the roots, even though in this study phytoliths were identified for all organs except for roots. In papyrus, shoot organs gradually become enriched in heavy Si isotopes along the transpiration stream, with an increase in heavy isotopes from rhizomes to scales, culm, and umbel, same pattern that has been observed for other plants in literature

Benchmark workshop on selected flatfish stocks (WKBFLATFISH).

The objective of this benchmark process was to propose and evaluate assessment methods and the data upon which they depend for the four stocks: Anglerfish (anf.27.3a46), and sole in Subarea 4 (sol.27.4), Division 7.a (sol.27.7.a) and Divisions 8.a-b (sol.27.8ab). Anglerfish was previously assessed using data limited methods (category 3), sole in subarea 4 using a statistical catch at age model (AAP) and sole in 7a and 8.a-b both assessed using extended survivor analysis (XSA). Landings, discards, survey data and commercial catch and effort data for all stocks were extensively reviewed and collated during the data workshop. For all stocks, revisions were made to the data preparations and methodology behind the derivation of the stock biomass indices, stock and catch weights, maturity data and natural mortality. All the terms of reference were covered during the data workshop and an agreement was reached on the data for to use for an assessment, projections and reference points of each stock reviewed. This was the first benchmark workshop in thirteen years for sole in 7a and eleven years for sole in 8ab. Considerable changes were made to the input data, assessment model, and consequently reference points for both stocks. For these two stocks, SAM was proposed as assessment method while Stock Synthesis (SS3) was proposed as the assessment method for sole in subarea 4 and anglerfish in subareas 4 and 6, and subdivision 3a. For sole in subarea 4, the model addressed and fixed the retrospective issue that was present in the previous assessment. For all models, the diagnostics, model fit, and retrospective model runs revealed no substantial patterns. Sensitivity runs were conducted to investigate the sensitivity to key model assumptions and the workshop reviewed and agreed on the final model configuration. The workshop further reviewed and agreed on the methods used to calculate reference points and forecasts and on the proposed reference points. For sole in 7a, the workshop encountered some issues when determining the stock recruitment relationships based on the ICES guidelines. Therefore, different scenarios were explored considering MSY reference points and their robustness tested using a MSE framework

When does a parasite become a disease? eDNA unravels complex host-pathogen dynamics across environmental stress gradients in wild salmonid populations

Infectious diseases stem from disrupted interactions among hosts, parasites, and the environment. Both abiotic and biotic factors can influence infection outcomes by shaping the abundance of a parasite's infective stages, as well as the host's ability to fight infection. However, disentangling these mechanisms within natural ecosystems remains challenging. Here, combining environmental DNA analysis and niche modelling at a regional scale, we uncovered the biotic and abiotic drivers of an infectious disease of salmonid fish, triggered by the parasite Tetracapsuloides bryosalmonae. We found that the occurrence and abundance of the parasite in the water—i.e., the propagule pressure— were mainly correlated to the abundances of its two primary hosts, the bryozoan Fredericella sultana and the fish Salmo trutta, but poorly to local abiotic environmental stressors. In contrast, the occurrence and abundance of parasites within fish hosts—i.e., proxies for disease emergence—were closely linked to environmental stressors (water temperature, agricultural activities, dams), and to a lesser extent to parasite propagule pressure. These results suggest that pathogen distribution alone cannot predict the risk of disease in wildlife, and that local anthropogenic stressors may play a pivotal role in disease emergence among wild host populations, likely by modulating the hosts' immune response. Our study sheds light on the intricate interplay between biotic and abiotic factors in shaping pathogen distribution and raises concerns about the effects of global change on pathogen emergence

Mapping the habitat refugia of Isidella elongata under climate change and trawling impacts to preserve Vulnerable Marine Ecosystems in the Mediterranean

The bamboo-coral Isidella elongata is a key habitat-forming species in the deep Mediterranean Sea. This alcyonacean is listed as an indicator of Vulnerable Marine Ecosystems (VMEs) and as Critically Endangered due to bottom trawling impacts. In this work, a modeling approach was used to predict and map the habitat suitability of I. elongata in the Mediterranean Sea under current environmental conditions. Occurrence data were modeled as a function of environmental parameters. Using climate change scenarios and fishing effort data, the risk of climate change and fisheries impacts on habitat suitability were estimated, and climate refugia were identified. A drastic loss of habitat is predicted, and climate change scenarios suggest a loss of 60% of suitable habitats by 2100. In the central Mediterranean, climate refugia overlapped with active fishing grounds. This study represents the first attempt to identify hot spots for the protection of soft bottom Vulnerable Marine Ecosystems for the entire Mediterranean Sea, and highlights areas most at risk from trawling. This work is relevant to the objectives of the EU Marine Strategy Framework and Maritime Spatial Planning Directives, the Biodiversity Strategy for 2030 regarding priority areas for conservation

Mitogenomic phylogeny of Nassariidae (Neogastropoda: Buccinoidea)

Mud snails (family Nassariidae) represent a highly diversified lineage within the superfamily Buccinoidea. Recent molecular phylogenies contradicted in some instances the traditional nassariid classification and revealed important levels of homoplasy in phenotypic characters. In order to clarify the boundaries of the family Nassariidae, as well as to inquire on the diversification of the cosmopolitan Nassariinae, a robust phylogenetic framework is needed. Here, the near-complete mitogenomes of 31 species representing almost all lineages of Nassariidae plus several buccinoid outgroups were sequenced. All mitogenomes of buccinoids shared the same gene order, which is identical to the consensus reported for caenogastropods. The monophyly of Nassariidae as previously defined was not confirmed. The reconstructed phylogeny revealed distant relationships between the genera Cyllene, Anentome, Tomlinia, Engoniophos, Phos and Antillophos and the majority of nassariids, represented by Nassariinae + Bullia. Within Nassariinae, a robust phylogeny, which recognized a total of seven regional groups, was reconstructed. The West Atlantic/Mediterranean genus Tritia was divided into three clades. The biogeographical analysis together with the inferred chronogram suggested that Nassariinae might have originated during the late Paleocene in the Indo-Pacific region. Subsequent climate change and continental drift events triggered diversification within the subfamily, leading to the worldwide distribution of current genera

Assessing the Calibration of Benthic Foraminifera Elemental Ratios from the Northeastern Atlantic

On six different species of benthic foraminifera covering various microhabitats and recovered from the Northern Atlantic Ocean, we tested the potential of the Mg/Ca and Sr/Ca ratios as proxies for paleoceanography. We performed analysis using two instruments (ICP-OES and ICP-MS) and compared results obtained from living and dead specimens. Our results are in good agreement with previous published calibrations for Hoeglundina elegans, Uvigerina mediterranea, U. peregrina, Melonis barleeanum, and Globobulimina spp. However, we observed a strong variability between living and dead specimens, and between both instrumental approaches. We discuss the impact of the cleaning procedure, as well as the natural variability between samples recovered at different depths inside the sediment. No specific trend can be deciphered from our dataset, but we observed that species from the Uvigerina genus presented the lowest external reproducibility and the best agreement between living and dead specimens. We highlight that both species should not be mixed for analysis, since U. mediterranea presents lower values and a reduced range of variability compared to U. peregrina. We explored the temperature and the Δ[CO32−] as potential controls on the variability of both ratios from U. peregrina and showed that neither of these two parameters can be discarded