French Research Institute for Exploitation of the Sea
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Ocean Circulation Modulating the Nutricline at Regional and Fine scales: A Case Study in The Northwestern Mediterranean Sea
No full textIn oligotrophic regions like the Mediterranean Sea, vertical nutrient distribution plays a key role in controlling primary production via upward fluxes. In spring 2023, the BioSWOT-Med campaign explored how fine-scale ocean dynamics modulate nutrient availability in the North Balearic Front. Combining SWOT satellite observations with targeted Lagrangian sampling, the study focused on a 50 km domain encompassing contrasting water masses at and across the front, and a fine-scale anticyclonic eddy embedded within southern waters. High-resolution nutrient profiles revealed a clear two-level structure: at the regional scale, northern waters showed shallower nutriclines and steeper vertical nutrient gradients; at finer scale, the anticyclonic eddy exhibited even deeper clines and weaker gradients compared to its surroundings. A local relation between SWOT sea surface height and the nutricline highlighted the coupling between physical fine-scale structures and nutrient dynamics, with further implications for un- derstanding nutrient supply and biogeochemical functioning in oligotrophic marine systems
Seasonal changes in the diet of the bloody cockle ( Senilia senilis ) along the Sine Saloum inverse estuary
No full textThis study investigates the food sources of Senilia senilis along the Sine Saloum estuary during the monsoon and dry seasons by combining isotopic and lipid analysis. We analyzed the fatty acids (FA) and sterol composition of digestive glands, and the carbon and nitrogen isotopic composition of muscles from 180 individuals sampled at four stations distributed along the estuary and during both seasons. Our findings reveal a spatiotemporal structure of the diet of S. senilis . In the upper estuary, S. senilis relies probably more on bacteria and zooplankton (higher proportions of 17:0, anteiso 17:0 and 15:0, 20:1 and 22:1) than downstream, where it locally finds the most homogeneous habitat (lowest isotopic diversity). The sources of nitrogen and carbon supporting planktonic communities appear to be more heterogeneous upstream, as indicated by the greater isotopic diversity at station 2. During the dry season, S. senilis relies more on dinoflagellates (higher proportions of 22:6n-3 and 18:4n-3) than during monsoon. However, during the monsoon, it has a greater diversity of FA, and therefore probably of food taxa, and relies more on diatoms (higher proportions of 16:1n-7 and 20:5n-3), likely from benthic origin. Together, these results highlight the trophic plasticity of S. senilis in response to the Sine Saloum estuary's inverse dynamics. Such changes in the environment may also modify physiological need, as revealed by non-methylated interrupted (NMI) FAs present in the individuals sampled in the part of the estuary undergoing the most brutal environmental changes
Working Group on Spatial Fisheries Data (WGSFD)
No full textThe Working Group on Spatial Fisheries Data (WGSFD) collates and analyses spatial fisheries data to evaluate fishing effort, intensity, and frequency in European waters. In 2025, the group began a new three-year cycle addressing data quality, workflow development, high-resolution data processing, and improved utility of outputs for the ICES community. The group reviewed the 2025 Vessel Monitoring System (VMS) and logbooks data call, endorsed data products subject to swept area calculation revisions for seine gears, and identified critical data gaps from non-submitting countries. The group examined methods for handling high-res-olution tracking data, particularly for small-scale fisheries, and explored machine learning ap-proaches for classifying fishing activity and gear types. Work continued on standardising spatial frameworks, with particular focus on the c-squares indexing system and resolving issues with harbour position filtering. Key findings include significant challenges with data absence from non-submitting countries (Portugal, Norway, Faroes, Greenland), which compromises data product quality in areas where fleets of these countries operate. The group identified methodological improvements needed for Scottish and Danish seine fisheries, where current swept area calculations inappropriately apply trawling methodology to fundamentally different fishing operations. High-resolution data anal-ysis demonstrated that tracking frequencies of 30 seconds or less significantly improve fishing effort estimation accuracy, particularly for small-scale and passive gear fisheries. Machine learn-ing classification models showed promising results for identifying gear types and fishing oper-ations, though data availability and computational demands present ongoing challenges. The group made four formal recommendations: publishing annual surface area ratio values at métier level 4 resolution; highlighting implications of missing VMS data in advisory processes; formally adopting c-squares as the basis of and official ICES spatial grid framework; and estab-lishing dedicated compilation of spatially explicit data on Marine Protected Areas and offshore wind farm zones. Future priorities include developing a unified spatial fisheries data tools pack-age, establishing quality control subgroups, preparing for mandatory high-resolution tracking implementation by 2029, and organising a hackathon to address workflow processing chal-lenges
Protracted melting in the Archean crust: Evidence from the Northern Kaapvaal craton
No full textOn the northern edge of the Archaean Kaapvaal craton of South Africa, granulite-facies rocks are exposed. They contain abundant melt features in the form of leucosomes, in-source granites and small granite intrusions, as well as overprint not associated with clear petrological features and evidence of remelting of previously emplaced granites. At amphibolite facies conditions further South, large granite batholiths emplace during the same period. U-Pb zircon (and occasionally monazite) dating of 36 samples (and compilation of data on 65 previously published ones) allows to build a comprehensive database of the age of melting in the Kaapvaal crust. The database reveals continuous melting from ca. 2950 Ma to ca. 2650 Ma (culminating in the formation of spectacular anatectic metapelites at ca. 2710 Ma). This peculiar pattern casts light on the evolution of the Archaean continental crust. The long duration of the melting period rules out one single cycle of heating and cooling, but the lack of clear peaks that may be related to distinct tectonic phases contrasts with modern orogenic systems. The general image that emerges is that of an accretionary complex at the edge of a stable continent. Alternating phases of extension and compression allowed the formation of closure of sedimentary basins, and the burial and melting of all the lithologies in the region. In the generally hotter Archaean Earth, the system was both hotter, and cooled down more slowly, developing a long-lived “hot orogen” at the edge of the craton
High-Latitude Eddy Statistics from SWOT assessed by in situ observations
No full textMesoscale eddies play a key role in the transport of heat, salt, and momentum, yet their statistical characterization at high latitudes has remained elusive due to the coarse resolution of conventional satellite altimetry. Here we present the first statistical description of mesoscale eddies in the Labrador Sea using observations from the Surface Water and Ocean Topography (SWOT) mission. We apply an eddy-detection algorithm directly to the native 2-km SWOT swaths, without gridding or assimilation, and validate the detections against in situ measurements from shipboard current profiler data from one cruise in 2024, as well as against a statistically derived shipboard current-profiler–based eddy census. The comparison demonstrates excellent agreement in eddy size and intensity, confirming SWOT’s ability to resolve high-latitude mesoscale structures previously undetectable in gridded altimetry. The SWOT-derived eddy census based on a full-calendar year reveals a predominance of energetic anticyclones (Irminger Rings) in the basin interior and smaller cyclones along the continental slopes, with clear seasonal variability linked to boundary current instability. These findings provide the first observational benchmark for mesoscale activity in the Labrador Sea and illustrate SWOT’s potential to extend eddy statistics to high-latitude and ice-influenced regions, opening the way for a global assessment of mesoscale variability
Investigating the predictability of Marine Heatwaves at subseasonal to seasonal timescales in New Caledonia, South Pacific
No full textMarine Heatwaves (MHWs) have emerged as one of the most important threat for marine ecosystems, with impacts such as coral bleaching, massive fish mortality and displacement of mobile fauna. In the context of climate change, it is urgent to develop strategies such as subseasonal to seasonal forecasting to help human societies adapt and react to the increasing frequency, duration and intensity of these events. Here we evaluate the predictability of MHWs at the scale of a South Pacific island country, New Caledonia, using ensemble forecasts from a dynamical coupled ocean-atmosphere model. We show that implementing a probabilistic approach where we extract information from the dispersion in the ensemble results in a higher skill than a deterministic approach where we simply compute the ensemble average. We find that longer, more intense, and wider MHWs, are more predictable than weaker, less intense, and shorter MHWs. We also find that the longest and widest MHWs occur in the cold season (June–October) during strong La Niña episodes, and that they can successfully be predicted up to 7 months in advance. In contrast, MHWs occurring during the warm season have poor or no predictability of more than a few weeks in advance. We discuss how this information can be efficiently transferred to marine stakeholders in terms of the usefulness and useability of the forecast. We recommend that future research should focus on identifying the drivers of different types of MHWs in order to understand their sources of predictability
The genomic footprints of wild Saccharum species trace domestication, diversification, and modern breeding of sugarcane
No full textSugarcane is a major crop of unclear origins due to its complex polyploid interspecific genome. We analyzed genome ancestries using whole-genome sequence data from 390 representative accessions based on repeated k-mers and chloroplast phylogeny. The results provided evidence that Saccharum officinarum was domesticated in the New Guinea region from the S. robustum wild species and revealed that its genome is a mosaic involving different S. robustum subgroups. We discovered a wild Saccharum contributor to most modern cultivars, likely originating from East Melanesia. We highlighted two early centers of sugarcane diversification associated with human transport, one in continental Asia through hybridization with different S. spontaneum subgroups and one in the Melanesian and Polynesian islands via hybridization with the discovered ancestor and Miscanthus. Finally, we revealed the genome ancestry of modern cultivars, highlighting untapped wild Saccharum diversity as a source of alleles for breeding programs
Etude de la pertinence d'un suivi DCE phytoplancton dans la masse d'eau "La Vilaine" (FRGT27)
No full textLa baie de Vilaine est un des sites les plus sensibles de la côte Atlantique à l’eutrophisation liée au développement de phytoplancton. A la mise en place de la DCE, la masse d’eau FRGT 27 « La Vilaine » avait été considérée comme turbide à dire d’expert. Lorsqu’une masse d’eau (ME) est déclarée comme « turbide », l’indicateur phytoplancton est considéré comme non pertinent, et donc les mesures de chlorophylle a et les dénombrements de phytoplancton ne sont pas réalisés. Cette étude visait à étudier la pertinence de suivre l’indicateur phytoplancton dans cette masse d’eau FRGT 27 afin d’améliorer l’évaluation de cet indicateur sur le continuum « estuaire de la Vilaine – baie de Vilaine » avec une meilleure prise en compte de l’eutrophisation. Les résultats montrent qu’au moins un bloom a été observé chaque année dans l’estuaire de Vilaine depuis 1995. Ces blooms s’échelonnent de mars à novembre avec un nombre maximal de bloom en juin et juillet. Le suivi de la biomasse et du phytoplancton réalisé au lieu « Petit Sécé » de 2022 à 2024 confirme des successions d’efflorescences chaque année dans des conditions hydroclimatiques contrastées. Malgré des turbidités plus élevées dans l’estuaire de Vilaine, la dynamique de la biomasse phytoplanctonique est comparable à celle de la masse d’eau FRGC44 située en aval, qui est suivie pour l’indicateur phytoplancton. Le calcul des indicateurs réalisé à titre indicatif sur la période d’étude de trois ans et non sur six années normalement requises pour ce calcul, classe la masse d’eau en moyen pour l’indicateur phytoplancton. Cette étude montre que l’indicateur phytoplancton est pertinent pour le suivi de la masse d’eau FRGT27. Nous recommandons de suivre les éléments de qualité « phytoplancton » en plus des éléments de qualité « hydrologie » à la station « Petit Sécé » pour la masse d’eau FRGT27 dans le cadre du réseau de contrôle de surveillance de la DCE
Optimization of cycloidal propeller performance over multiple operating points using a multi-fidelity CFD-Experimental approach
No full textCycloidal propulsion, also known as the transverse-axis system, holds significant promise for the next generation of ships. Its capability to deliver excellent maneuverability at low speeds, similar to the Voith-Schneider Propeller, and high efficiency at elevated speeds, as seen in systems like ADVPropulse and ABB-Dynafin, makes it a versatile and efficient propulsion solution for a broad range of operational scenarios. Advancements in mechatronics and blade motion control are paving the way for the development of fully electric blade-command cycloidal propellers. This innovation eliminates the constraints imposed by traditional mechanical kinematics, enabling dynamic blade pitch adjustments and significantly broadening the propeller’s operational range and performance. Building on the previously established effective pitch law optimization, the present work employs a multi-fidelity approach to reduce computational costs and better capture the complex physics, which remains challenging to fully optimize using CFD models alone. At the highest level of fidelity, experimental performance evaluations are complemented by CFD simulations, which serve as a lower-fidelity model, balancing computational efficiency and physical accuracy. This multi-fidelity optimization framework is applied across various operating conditions for both cycloidal and trochoidal modes. The resulting series of optimized pitch laws demonstrate the necessity of transitioning from cycloidal mode at low ship speeds to trochoidal mode at high ship speeds to achieve and maintain peak performance
Département Ille-et-Vilaine. 2024. Activité des navires de pêche.
No full textCe document est réalisé dans le cadre du projet « Système d’Informations Halieutiques » (SIH) de l’Ifremer, qui constitue le réseau d’observation des ressources halieutiques et des usages associés. Ce projet s’inscrit dans la mission de service d’intérêt public de l’Ifremer consistant à « connaître, évaluer et mettre en valeur les ressources des océans et permettre leur exploitation durable ». Outre la collecte des données pertinentes permettant l’analyse du secteur des pêches, le SIH a en charge l’élaboration d’indicateurs sur les flottilles de pêche et leur restitution sous forme de synthèses aux différents acteurs de la filière pêche et du grand public