French Research Institute for Exploitation of the Sea
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Preliminar Species distribution models for silky shark (Carcharhinus falciformis) in the eastern tropical Atlantic Ocean
No full textUnderstanding the spatiotemporal distributions of shark and ray species is essential for their effective conservation and management. However, modeling the distribution of these wide-ranging, highly mobile and often data-limited species presents significant challenges. This study compares three Species Distribution Modeling (SDM) approaches - Generalized Additive Mixed Models (GAMMs), Boosted Regression Trees (BRTs) and Bayesian Additive Regression Trees (BARTs) - to investigate the main drivers influencing the occurrence of silky shark (Carcharhinus falciformis) and predict its spatiotemporal distribution in the eastern tropical Atlantic Ocean. The SDMs were built using European Union tropical tuna purse seine fishery observer data for the period 2010-2023. The three modeling approaches showed good predictive performance (AUC > 0.8) and consistently identified high-probability areas for silky shark occurrence in the coastal waters off Guinea, Gabon, and Angola, and the offshore region of the southern and central tropical Atlantic Ocean. While these model predictions offer valuable insight to inform spatially-explicit ecological risk assessments and management strategies, their integration into operational risk assessment tools will require further validation of habitat predictions.Il est essentiel de comprendre la distribution spatio-temporelle des espèces de requins et de raies pour assurer une conservation et une gestion efficaces. Cependant, la modélisation de la distribution de ces espèces à large distribution, très mobiles et dont les données sont souvent limitées, présente des défis importants. Cette étude compare trois approches de modélisation de la distribution des espèces (SDM) (modèles mixtes additifs généralisés (GAMM), arbres de régression renforcée (BRT) et arbres de régression additifs bayésiens (BART)) pour étudier les principaux facteurs influençant l'occurrence du requin soyeux (Carcharhinus falciformis) et prédire sa distribution spatio-temporelle dans l'Est de l'océan Atlantique tropical. Les SDM ont été élaborés à partir des données des observateurs de la pêche ciblant les thonidés tropicaux des senneurs de l'Union européenne pour la période 2010-2023. Les trois approches de modélisation ont montré une bonne performance prédictive (AUC > 0,8) et ont identifié de manière cohérente des zones de haute probabilité concernant l'occurrence du requin soyeux dans les eaux côtières au large de la Guinée, du Gabon et de l'Angola, et dans la région au large du Sud et du centre de l'océan Atlantique tropical. Bien que les prévisions de ces modèles offrent des informations précieuses pour les évaluations des risques écologiques et les stratégies de gestion spatialement explicites, leur intégration dans les outils opérationnels d'évaluation des risques nécessitera une validation plus poussée des prévisions relatives à l'habitat.Comprender la distribución espaciotemporal de las especies de tiburones y rayas es esencial para su conservación y ordenación eficaces. Sin embargo, la modelación de la distribución de estas especies de amplia distribución, gran movilidad y, a menudo, datos limitados plantea importantes retos. Este estudio compara tres enfoques de modelación de la distribución de especies (SDM) -modelos mixtos aditivos generalizados (GAMM), Árboles de regresión potenciada (BRT) y árboles de regresión aditiva bayesiana (BART)- para investigar los principales factores que influyen en la presencia del tiburón jaquetón (Carcharhinus falciformis) y predecir su distribución espaciotemporal en el océano Atlántico oriental tropical. Los SDM se construyeron utilizando datos de observadores de la pesquería de cerco de túnidos tropicales de la Unión Europea para el periodo 2010-2023. Los tres enfoques de modelación mostraron un buen desempeño predictivo (AUC > 0,8) e identificaron sistemáticamente zonas de alta probabilidad de presencia de tiburón jaquetón en las aguas costeras de Guinea, Gabón y Angola, y en la región de alta mar del océano Atlántico tropical meridional y central. Aunque las predicciones de estos modelos ofrecen información valiosa para las evaluaciones de riesgo ecológico y las estrategias de ordenación espacialmente explícitas, su integración en herramientas operativas de evaluación de riesgos requerirá una mayor validación de las predicciones sobre hábitats
Ocean Literacy as a Strategic Asset for Regional Marine Policy: Insights From an Implementation Case Study
No full textOcean literacy (OL) has increasingly been recognised as a key enabler of participatory marine governance, with potential synergies with maritime spatial planning (MSP). These links are particularly evident in stakeholder engagement processes, which are mandated by the European MSP Directive and supported by international institutional guidelines. OL can facilitate these processes by fostering informed participation, enhancing public awareness, and supporting educational and cultural goals aligned with Sustainable Development Goal 14 “life below water.” Within the framework of the EU‐funded Regions to Boost National Maritime Spatial Planning‐MSP project, a methodology was developed to support the design of a Regional Ocean Literacy Strategy aimed at strengthening MSP implementation at the sub‐national (NUTS‐2) level. This article outlines the development of a structured toolbox to support regional OL strategies and presents the results of its empirical testing in the Sardinia region. The findings indicate that regional actors acknowledge the relevance of OL for marine management and that existing assets—such as environmental education networks and cultural initiatives—can be effectively mobilised through a strategic framework. The study demonstrates the feasibility and replicability of the approach, offering a model that can be adapted and transferred to other regional contexts across Europe
Morphogenesis of the Holocene coastal landforms on Sumba Island, Indonesia
No full textCoastal terraces, whether erosional, depositional, or bio-constructed, have been widely used to quantify Late Cenozoic vertical deformation and relative sea-level changes. Here, we review and investigate the Holocene coastal terraces of Sumba Island, Indonesia. We describe fifteen coastal sites, evenly distributed between the South and North coasts. The terraces are Holocene age, based on 14C and U/Th ages. We show that the preservation of coastal terraces in Sumba is favoured on the leeward coast (North). Holocene and older Pleistocene coastal terraces are almost absent on the windward coast (South), although modern coral reefs almost ubiquitously thrive. The morphology and the nature of the bedrock varies between the two sides of the island: while sequences of earlier Pleistocene coral reef limestones dominate in the North, Miocene/Pliocene tuffs and pelagic carbonates outcrop on the southern coast. The elevations of the Holocene inner edges range from 2.4 ± 0.7 to 6.9 ± 0.7 m above the present mean sea level. Despite disparate uplift rates, the three preserved windward terraces (out of the seven sites investigated) generally have a higher inner edge than leeward terraces. We conclude that neither glacio-eustatic oscillations, vertical deformation rates nor hydrodynamics by themselves can explain the variability in inner edge elevations on Sumba, but only a complex combination of these processes. Finally, our study serves as a solid basis for future investigation of the Holocene landforms of the island of Sumba and other similar tropical coastal zones
Driving mechanisms of the dissolved oxygen budget in the Levantine Sea: a coupled physical-biogeochemical modelling approach
No full textThe Levantine Basin is an ultra-oligotrophic region and the formation site of the Levantine Intermediate Waters. For the first time, a high-resolution 3D coupled hydrodynamic-biogeochemical model, SYMPHONIE-Eco3MS, was used to investigate the seasonal and interannual variability of dissolved oxygen (O2) in the Levantine Basin and estimate its basin-wide budget for the period 2013–2020. Our results show that the simulated O2 concentrations align well with in situ data from research cruises and Argo floats. During winter, the surface layer is undersaturated in oxygen by up to 2 % across the entire basin, leading to atmospheric oxygen absorption. The model shows that on an annual scale, the basin acts as a net sink for atmospheric oxygen, with the Rhodes Gyre exhibiting uptake rates twice as high as the rest of the Levantine Basin. The surface layer also serves as a source of dissolved oxygen for intermediate depths, with 4.2 ± 1.1 mol m-2 year-1 of dissolved oxygen vertically transported. Oxygen is transported laterally into the basin from the Ionian Sea and exported towards the Aegean Sea, with winter heat loss intensity enhancing this lateral export at both surface and intermediate layers. The Levantine Basin alternates between autotrophic and heterotrophic states, depending on the intensity of winter surface heat loss. Spatially, the Rhodes Gyre emerges as a significant oxygen pump, contributing 41 % of the total oxygen production in the surface layer in the Levantine basin. This study highlights the need for further modeling studies on pluri-annual and multi-decadal scales to explore the interannual variability and evolution of the annual oxygen budget across the entire Eastern Basin, particularly in the context of climate change
The Guiana current: a fast-lane to the Caribbean for holopelagic Sargassum contaminated in arsenic and cadmium
No full textTo date, little key information about inorganic arsenic (iAs) and cadmium (Cd) has been promulgated to help manage the massive influxes of pelagic Sargassum that have inundated the Caribbean coasts since 2011 and are causing significant environmental, health and economic impacts. In particular, the levels of iAs and Cd, which often exceed regulatory levels and limit the seaweed valorization, have not been linked to an origin or route. By analyzing a large number of samples collected at different times in Guadeloupe and Martinique, we have highlighted for the first time a route that rapidly traces back through the Guiana, North-Brazil and equatorial currents, bringing Sargassum to the Lesser Antilles in less than 3 months from the equator. All the Sargassum morphotypes from this problematic fast track displayed high levels of iAs and Cd, very often exceeding 40 ppm and 1 ppm, respectively. The other routes, which bring Sargassum more slowly, either from the Cape Verde basin or from the North Brazil Retroflection area, have low or intermediate levels of iAs and Cd. Following an in-depth examination of the cadmium-phosphorus relationship in the tropical Atlantic Ocean, we provide here for the first time an overview of the spatial disparities in the Cd and P composition of Sargassum
Wide diversity and complex evolution of M42 aminopeptidases with contrasted functional properties in Archaea
No full textM42 peptidases (TET) are ubiquitous, giant self-compartmentalized aminopeptidases forming unique tetrahedral structures. TETs may participate in protein homeostasis and amino acid recycling by processing peptides downstream of the proteasome and other related proteolytic complexes. Currently, only five TETs have been extensively studied in Archaea from the Thermococcales order, with a predominant focus on structural characterization. Therefore, a clear view of the diversity and biological activities of this large enzymatic family is lacking.
In this study, we establish robust criteria for high-throughput identification of TET peptidases from sequence data and reveal their wide taxonomic distribution in Archaea. We functionally characterize six additional TETs, including four from Asgardarcheota. Our results identify two main functional classes, with generalist TETs displaying broad-spectrum activities, and specialized TETs with more selective activities. We also report the first description of methionyl- and isoleucyl-aminopeptidases in the TET family. In addition to their diverse substrate specificities, the characterized TETs exhibit distinct activation profiles, varying in optimal temperature, pH, and metal cofactor requirements. Combining functional and phylogenetic analyses, we propose a classification of TET peptidases into 11 groups. Notably, we identify generalist group 11 as the ancestral TET in Archaea, from which specialized TETs arose following gene duplication or horizontal transfer. Finally, we highlight the presence of multiple TETs with selective activities in heterotrophic and mixotrophic organisms, suggesting a metabolic role for these enzymes in the degradation of environmental peptides.
Overall, our work illuminates an underexplored diversity of TET enzymes, uncovering a complex evolutionary history that shaped their functional diversificatio
Seasonal dynamics of dissolved organic matter along an intertidal gradient in semi-arid mangrove soils (New Caledonia)
No full textMangrove ecosystems play a key role in the global carbon cycle, notably through the production, transformation, and export of dissolved organic matter (DOM). If DOM export to adjacent ecosystems is well studied, its dynamics in mangrove soils remain poorly understood. In this study, DOM quantity and quality were investigated in semi-arid mangroves with no external organic matter input, developing along an intertidal gradient: a salt-flat, an Avicennia marina stand, and a Rhizophora stylosa stand. Soil and porewater samples were collected during both wet and dry seasons, and analysed for physicochemical parameters, total and dissolved organic carbon (TOC, DOC), chromophoric and fluorescent dissolved organic matter (CDOM, FDOM), and mineralogical composition. Our results show distinct DOM quantity and quality between habitats. The Rhizophora stylosa stand, characterized by daily tidal immersion and the lowest salinity, presented high and stable DOC concentrations throughout the year. The dominance of one humic-like fluorescent component suggests that soil DOM is primarily mangrove-derived. In this stand, tidal fluctuations are a major cause for continuous Fe reduction-oxidation cycles, which can influence DOM dynamics. In the salt-flat and the Avicennia marina stand, which suffer from water stress due to their position, significant seasonal variations were measured with higher DOC concentrations during the wet and warm season as a result of enhanced microbial activity. In these stands, due to a more open canopy cover, DOM also originates from biological activity, as evidenced by enhanced microbially-derived fluorescent component. In addition, photodegradation can occur. These findings provide new insights into DOM cycling in mangrove soils and highlight the combined effects of zonation and seasons
Framework for adding new sensors and new mission parameters in Argo
No full textIn 2018, UNESCO's Intergovernmental Oceanographic Commission approved six biogeochemical parameters for Argo floats and established a framework for future parameter additions. Since then, new sensors and CTDs have been evaluated for their readiness and cost-effectiveness in the global Argo program. The development process follows three phases: experimental, pilot, and global implementation. As Argo expands, clearer definitions of these phases and transition criteria have become necessary, along with a framework that encourages experimentation while preventing it from overwhelming Argo's core missions. This document describes the pathway for admitting new sensors and mission parameters into Argo through these three phases. While following IOC-UNESCO guidelines for new parameters, it extends to include new sensors with additional considerations for the Argo data system to prevent unnecessary burden. The framework acknowledges that not all experimental work will advance to pilot or global phases, providing transparency about required procedures and practical guidance for each development stage
High-resolution acoustic recordings of wild free-ranging short-beaked common dolphins for etho-acoustical and repertoire studies
No full textDolphins are highly vocal cetaceans with a complex acoustic repertoire. These marine mammals rely heavily on sound for critical activities: echolocation clicks for navigation and prey detection, whistles for social communication, and pulsed sounds for less well-documented purposes. Understanding their acoustic behaviour is essential for insights into their ecology, social structure, and responses to anthropogenic noise. However, to date, there has been a lack of open-access datasets of acoustic recordings of wild free-ranging short-beaked common dolphins (Delphinus delphis) coupled with observational data. Here, we present a new dataset (10.5281/zenodo.14637674, ) of high-resolution acoustic recordings of (D. delphis) observed in various behavioural states, including foraging, travelling, socializing, milling, and attraction to the boat. The dataset was collected in the northern Bay of Biscay, France, in the summers of 2020 to 2022 during surveys conducted as part of the DOLPHINFREE project. Audio recordings were made during opportunistic encounters using two devices: a single high-quality hydrophone (sampling rate 512 kHz and bit depth 32 bits) and a compact array of four hydrophones (256 to 512 kHz and 16 to 24 bits) for localization purposes. The dataset comprises over 400 min of unedited audio recordings of D. delphis accompanied by visual observations. In total, we identified about 68 000 echolocation clicks, 4600 whistle contours, and more than 350 pulsed sounds. This comprehensive resource is invaluable for detailed studies of the acoustic repertoire of (D. delphis), coupled with behavioural studies or analyses of the directionality of their acoustic emissions
Les carottes sédimentaires du golfe de Gascogne, références pour l'évaluation de la qualité chimique marine. Campagne ROCCHSED 2022
No full textConcentrations profiles of metals and organic compounds were studied in three sedimentary cores collected in the Bay of Biscay during the ROCCHSED22 cruise aboard The Thalia research vessel. These marine sedimentary archives are used to determine the pre-industrial levels of chemical contamination on a regional scale.
The three sites were selected based on morphological and sedimentary hydrodynamic considerations. They were at the head of the Capbreton canyon (core 22-04), in the south of Grande Vasière (core 22-20) and in the Vilaine bay (core 22-025). The cores were between 30 to 50 centimetres long and chronostratigraphic estimates on cores were derived from the natural radionuclide 210Pb in excess. The contaminants studied include trace metals, natural and historical organic compounds (PAHs and PCBs) and emerging contaminant such as OPEs and PFAS.
Pre-industrial concentration levels were determined from the lower horizons of the cores and enrichment factors were calculated for the upper horizons. Concentration profiles provide information on the trend for all contaminants studied. We have also studied the sources of the contaminants and how they have evolved using lead isotopes ratios (206Pb/207Pb, 206Pb/208Pb, 206Pb/204Pb), mercury profiles and the isomeric ratios of PAHs in the cores.Le présent rapport a pour objet l’étude des contaminants chimiques métalliques et organiques (classiques et émergents) dans des carottes sédimentaires prélevées dans le golfe de Gascogne lors de la campagne océanographique ROCCHSED 2022, réalisée à bord du navire de recherche N/O Thalia. Pour retracer et comprendre l’histoire de la contamination chimique dans le golfe, l’étude se concentre sur l’examen des profils des concentrations en éléments métalliques et en contaminants organiques associés à la datation des horizons des carottes sédimentaires. Ces archives sédimentaires marines sont utilisées pour définir des niveaux préindustriels permettant d’évaluer l’amplitude de l’anthropisation et obtenir des tendances historiques représentatives. Trois sites d’étude, définis d’après la morphologie et la dynamique sédimentaire dans le golfe de Gascogne, entre la zone du gouf de Capbreton au sud et la baie de Vilaine au nord ont été retenus en tête du canyon de Capbreton (carotte 22-04), à la marge sud de la grande vasière (carotte 22-20) et dans la baie de Vilaine (carotte 22-25). Les horizons des carottes de plusieurs dizaines de centimètres de longueur ont été datés à partir d’un modèle de datation mixte basé sur les mesures de 210Pb. Les caractéristiques physico-chimiques (granulométrie, porosité, densité, teneur en carbone organique) de ces colonnes sédimentaires ont été déterminées afin d’évaluer la qualité des dépôts et les processus affectant ces derniers après le dépôt. Les familles des contaminants chimiques étudiées comprennent des éléments traces métalliques et des composés organiques d’origine naturelle et anthropique. Nous avons également étudié des familles de composés organiques synthétiques seulement d’origine anthropique. Ainsi, l’étude s’intéresse à des contaminants historiques (HAP et PCB) et des contaminants émergents (OPE et PFAS). Nous avons déterminé les niveaux de concentrations préindustriels à partir des horizons inférieurs et estimé les facteurs d’enrichissement pour le golfe de Gascogne à partir des horizons supérieurs des carottes. Les résultats obtenus ont été comparés aux valeurs de référence de la convention OSPAR Les profils des concentrations associées à la datation permettent également de fournir des tendances temporelles pour tous les contaminants étudiés. Nous nous sommes également intéressés à l’identification des sources des divers contaminants et à leur évolution temporelle à partir des ratios isotopiques du plomb (206Pb/207Pb, 206Pb/208Pb, 206Pb/204Pb), des profils du mercure, ainsi que la composition et les ratios isomériques des HAP dans les carottes étudiées