Juveniles at risk: behaviour and colour changes in sole juveniles (Solea solea) after exposure to estuarine ragworms (Hediste diversicolor) contaminated with microplastics
Due to strong anthropogenic pressures and their location at the interface between continental and oceanic environments, estuarine areas are affected by significant diverse pollution and species that live in these areas are particularly exposed. Microplastic (MPs) pollution is a worldwide issue and causes substantiated trouble in estuaries where sometimes the number of MPs equal or exceed the number of fish larvae which suggest a high risk of contamination of biota especially in benthic organisms and demersal fish. There are growing evidence that, beyond intrinsic toxicity, MPs can transfer chemicals (additives or pollutants). In order to get closer to environmental situations, in this study we tackled an issue that is rarely dealt with, namely the trophic transfer of MPs and chemicals through the food chain between a sediment- and a benthic-feeder. To take into account these specificities, we used an emblematic and common species of the European coastlines, the common sole (Solea solea) and its annelid prey. Sole juveniles were fed with estuarine ragworms (Hediste diversicolor) previously exposed to MPs via enriched MPs sediment. The MPs used were either a mixture of micronized plastics collected from the Seine Estuary (eMPs, two environmental concentrations at 1 or 100 mg/kg of sediment, median size range 52-77 μm) or model MPs of PVC particles (at 1 g/kg of sediment, size range 125-250 μm), either uncontaminated or contaminated with Benzo(a)Pyrene (BaP, 11.5 μg/g MPs) or benzophenone-3 (BP3, 66 ng/g MPs). Several indicators of health status such as survival, growth, behaviour, energy metabolism, and histopathology were studied. Sole individuals fed ragworms exposed to eMPs or PVC MPs displayed a change in behaviour (place preference between black/white background). Seine Estuary eMPs lead to an increase in body colour chroma for the highest concentration and behaviour was modified with an increase in time spent on white bottom and transition number for the highest concentration when distance moved increased only at the lowest concentration. Sole exposed to BaP-PVC-MPs displayed the lowest time spent on white background compared to control and BP3-PVC-MPs group. Soles exposed to BP3-PVC MPs displayed a significant skin colour increase in chroma and a wider combination of value/chroma reflecting more diverse skin colours. Finally, lipid content in muscle and DNA damage were significantly higher in BP3-MPs. Although the exact mechanisms underpinning such changes are largely unknown, these observations are indicative of physiological stress which may have a significant impact on survival by increasing predation risks for fish juveniles, hence the ecosystem health and calls for further trophic transfer experimental research.
(Marine Environmental Research. vol. 209, n° 0141-1136, pp. 107197, 01/05/2025)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, UMR MARBEC, IRD, IFREMER, CNRS, UM, BTSB, INUC, Comue de Toulouse, OFB - DR NAQ, OFB, UB, BIOSSE, UCO, PAnTher, ONIRIS, INRAE, APEX, PAnTher, ONIRIS, INRAE, IPREM, UPPA, INC-CNRS, CNRS, GERS-LEE, UMR MARBEC PALAVAS, UMR MARBEC, IRD, IFREMER, CNRS, UM
Characterization of the daily and circadian valve behavior of the European flat oyster Ostrea edulis
Marine organisms exhibit a multitude of biological rhythms synchronized with the interactions of the sun-, earth-, and moon cycles. However, the biological rhythms in bivalves remain poorly studied. This study focuses on the native European flat oyster (Ostrea edulis), an endangered species of coastal ecosystems and a key organism in restoring of biogenic reef habitats. We aim to determine whether a molecular endogenous circadian rhythm exists in O. edulis and to characterize its daily expression. To address these questions, the oysters' valve behavior, as an output of the circadian clock expression, was recorded under different light conditions and free-running regimes using non-invasive valvometry. This work demonstrates the existence of a circadian clock mechanism that generates a labile behavioral circadian oscillation under free-running conditions. In light: dark conditions, a diel rhythm appears nocturnal, synchronizable to a shift of light phase, and remains unmodified whether the oysters are fed or not. This rhythm anticipates light: dark changes, indicating its endogenous origin. Finally, when exposed to artificial light at night the daily behavior is disrupted. This study characterizes the circadian behavioral rhythm of O. edulis's as plastic and labile. This plasticity would be advantageous in terms of ecological adaptability but increases sensitivity to anthropogenic pressures such as light pollution.
(Scientific Reports. vol. 15, n° 2045-2322, pp. 14952, 29/04/2025)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, HIFMB, OFFIS, GEODE, UT2J, Comue de Toulouse, CNRS, AWI, AWI
Confined aquifers: a need for an adaptation of sustainability concepts
Confined aquifers, distinguished by their large storage and long-term flow dynamics, are often overlooked in groundwater sustainability assessments and rely on frameworks developed for unconfined systems. Unlike unconfined aquifers, confined systems release water through the compressibility of the porous medium, without pore drainage. These properties lead to lower storativity and higher hydraulic diffusivity, resulting in different responses to hydraulic perturbations, such as pumping or recharge temporal variations. Addressing these differences is essential to develop tailored approaches for the sustainable management of confined aquifers, particularly in the context of balancing water supply for different competing demands with the environmental and socioeconomic impacts of abstraction. We develop a framework for the sustainable management of confined aquifers based on numerical models over synthetic cross sections of multi-layer flow systems. We explore the fundamental differences between confined and unconfined aquifers, particularly in terms of their hydraulic behaviour, response time to hydraulic perturbations, and the interactions with surrounding hydrogeological units. This modelling study also illustrates how confined aquifers indirectly interact with unconfined systems and surface water systems, through their connection via confining layers. A critical aspect of this work involves understanding the transient response of aquifers, which is governed by their hydraulic diffusivity and described by the concept of response time. Diffusivity governs the rate at which hydraulic disturbances propagate, and the response time describes the time required for the aquifer to reach a new equilibrium. Existing analytical formulations highlight the distinct behaviour of confined aquifers, particularly their faster response times compared to unconfined systems. However, for large-scale confined or mixed systems, response time scales may approach or even exceed those of unconfined aquifers with similar hydraulic properties and, generally, smaller extension. This underscores the importance of a proper delimitation of aquifer boundaries in the assessment of their response times. In practice, water sustainability policies are inherently scoped within site-specific areas and timeframes. Today, these policies must address increasing pressures from population growth, climate change, surface water quality issues, and other contributing factors. Groundwater models, which support management decisions, should include these factors through accurate conceptualizations of hydrogeological systems, evaluations of their response times, and scenario analyses. Through the adaptation of sustainability concepts for confined and mixed aquifer systems, this study contributes to the development of a framework that will support groundwater management strategies for confined aquifers and highlights their role as a valuable resource for long-term adaptation, emphasizing the need to protect and optimize their use in response to environmental and societal challenges.
(27/04/2025)
Bordeaux INP, UB, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, CEREGE, IRD, AMU, CdF (institution), INSU - CNRS, CNRS, INRAE
Past trajectory of a socio-ecosystem at the land-sea interface: the case of the northern watersheds of the Bay of Brest over the last 150 years
(pp. EGU25-17787, 27/04/2025)
GEO-OCEAN, UBS, IFREMER, INSU - CNRS, UBO EPE, CNRS, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, BEEP, IFREMER, UBO EPE, CNRS, GEOARCHI, UBS, UBO EPE, IBSHS, UBO EPE, GR, UR, INSU - CNRS, CNRS, LEMAR, IRD, IFREMER, UBO EPE, CNRS, GEO-OCEAN, UBS, IFREMER, INSU - CNRS, UBO EPE, CNRS, LMBA, UBS, UBO EPE, CNRS, DYNECO, IFREMER
Enigmatic deep-water seafloor depressions east of Tortue Island, Northern Haiti margin
A widespread area of seafloor depressions—ranging from circular and arcuate to elongated in shape—has been identified along the northern coast of Haiti, at water depths of 600–2000 m. These features are characterized by wavelengths spanning several hundred meters and heights of tens of meters and are associated with a series of narrow ridges exhibiting varied morphologies. Our integrated analysis, utilizing multichannel seismic reflection, high-resolution bathymetry, and sedimentological and geochemical evaluations of surface sediment cores, indicates that along-slope bottom currents significantly influence sedimentary processes in the region. Sediment cores reveal deposits comprising hemipelagites, silty and sandy contourites, fine-grained turbidites, and reworked sand layers, indicative of sedimentation within a contourite drift system. This interpretation is further supported by seismic reflection data, which display wavy reflectors and aggradational stacking patterns typical of contourite drifts.The seafloor depressions are likely erosional features that formed on the surface of a contourite drift, shaped by the interaction of bottom currents with irregular seafloor topography. Initial disturbance of the equilibrium seafloor appears to have been triggered by mass-wasting events. Subsequently, the quasi-steady flow of along-slope bottom currents influenced sediment distribution and played a critical role in the development and reshaping of the seafloor depressions through erosion along their flanks. The resulting rugged seafloor morphology likely facilitated the destabilization of bottom currents, leading to the formation of erosive eddies that further shaped the current configuration of the depressions. This study emphasizes the dynamic interplay between sedimentary processes and hydrodynamic activity, demonstrating how their combined effects govern slope sedimentation and seafloor geomorphology, producing distinctive erosional features.
(. vol. 26, pp. e2024GC012089, 27/04/2025)
iSTeP, INSU - CNRS, SU, CNRS, CY, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, CEFREM, UPVD, INSU - CNRS, CNRS, IFPEN, UCM, UEH
Using Pleiades Satellite Imagery to Monitor Multi-Annual Coastal Dune Morphological Changes
In the context of sea levels rising, monitoring spatial and temporal topographic changes along coastal dunes is crucial to understand their dynamics since they represent natural barriers against coastal flooding and large sources of sediment that can mitigate coastal erosion. Different technologies are currently used to monitor coastal dune topographic changes (GNSS, UAV, airborne LiDAR, etc.). Satellites recently emerged as a new source of topographic data by providing high-resolution images with a rather short revisit time at the global scale. Stereoscopic or tri-stereoscopic acquisition of some of these images enables the creation of 3D models using stereophotogrammetry methods. Here, the Ames Stereo Pipeline was used to produce digital elevation models (DEMs) from tri-stereo panchromatic and high-resolution Pleiades images along three 19 km long stretches of coastal dunes in SW France. The vertical errors of the Pleiades-derived DEMs were assessed by comparing them with DEMs produced from airborne LiDAR data collected a few months apart from the Pleiades images in 2017 and 2021 at the same three study sites. Results showed that the Pleiades-derived DEMs could reproduce the overall dune topography well, with averaged root mean square errors that ranged from 0.5 to 1.1 m for the six sets of tri-stereo images. The differences between DEMs also showed that Pleiades images can be used to monitor multi-annual coastal dune morphological changes. Strong erosion and accretion patterns over spatial scales ranging from hundreds of meters (e.g., blowouts) to tens of kilometers (e.g., dune retreat) were captured well, and allowed to quantify changes with reasonable errors (30%). Furthermore, relatively small averaged root mean square errors (0.63 m) can be obtained with a limited number of field-collected elevation points (five ground control points) to perform a simple vertical correction on the generated Pleiades DEMs. Among different potential sources of errors, shadow areas due to the steepness of the dune stoss slope and crest, along with planimetric errors that can also occur due to the steepness of the terrain, remain the major causes of errors still limiting accurate enough volumetric change assessment. However, ongoing improvements on the stereo matching algorithms and spatial resolution of the satellite sensors (e.g., Pleiades Neo) highlight the growing potential of Pleiades images as a cost-effective alternative to other mapping techniques of coastal dune topography.
(Remote Sensing. vol. 17, n° 2072-4292, pp. 1522, 25/04/2025)
UB, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, BRGM, UPVD
Aquatic food webs in restored marshes: a stable‐isotope approach in the Gironde estuary ( SW France)
Intertidal marshes are important habitats for nekton. However, historical draining and dyking hampered European coastal wetlands. Marsh restoration is therefore critical not only to improve their capacity to protect coastal lines but also to rehabilitate their ecological functionalities. The benefits of intertidal marsh restoration for nekton community composition and feeding ecology are examined in a case study within the largest macrotidal estuary in Western Europe (Gironde). The structure and functioning of nekton food webs are addressed using stable isotopes of carbon (δ 13 C) and nitrogen (δ 15 N). δ 13 C values of suspended particulate matter illustrated the influence of the tidal connectivity with the adjacent estuary in restored habitats. δ 15 N values of nekton and its resources evidenced little difference in food‐web complexity, but spatial or seasonal variations for some resources and consumers, related to a combination of temporal and tidal effects. The European eel ( Anguilla anguilla ) and the introduced freshwater topmouth gudgeon ( Pseudorasbora parva ) dominated food webs in the fully and partially connected marsh habitats, respectively. The isotopic niche and diet composition of A. anguilla also varied between habitats, as did the diet of other nekton species ( Chelon ramada and Palaemon longirostris ). This study informs the rehabilitation process of important functionalities of restored aquatic habitats for nekton.
(Restoration Ecology, n° 1061-2971, 21/04/2025)
UR EABX, INRAE, LIENSs, INSU - CNRS, ULR, CNRS, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS
MAGEST: Rapport scientifique sur les données 2024
Le rapport scientifique sur les données acquises en 2024 par le réseau MAGEST présente l’ensemble de ces données, avec la production de nombreuses figures permettant d’illustrer la variabilité spatio-temporelle des paramètres suivis (température, salinité, turbidité/charges en matières en suspension, oxygène dissous). Le bilan de la disposition oxygène du SAGE Estuaire de la Gironde est également détaillé et comparé à ceux des années précédentes. L’année 2024 se classe au 4ème rang des années les plus chaudes depuis le début du XXème siècle et au 7ème rang des années les plus pluvieuses depuis 1959. Le mois de septembre 2024, marqué par d’importantes précipitation et frais a mis fin à un étiage peu sévère. Ces conditions climatiques ont permis d'améliorer nettement la qualité physico-chimique des eaux des estuaires nord-aquitains par rapport aux deux années précédentes (très chaudes et marquées par de forts déficits hydrologiques). Les faits marquants du réseau MAGEST de l’année 2024 sont : - des températures moyennes journalières comprises entre 6,4 et 28,3 °C, avec un été plus tempéré d’au moins 1 °C qu’en 2023 ; - une intrusion saline, définie par une salinité (moyenne journalière) supérieure à 0.5, d’intensité et de durée très réduites (29 jours à Tonnay-Charente, 11 jours à Bordeaux) ; - une arrivée tardive (juillet) et un départ précoce (fin octobre) du bouchon vaseux à l’aval de la Charente, de la Dordogne et de la Garonne ; - des désoxygénations estivales modérées à Tonnay-Charente et à Bordeaux ; aucun site n’a enregistré des moyennes journalières < 4 mg L-1 en 2024. Les objectifs de la disposition oxygène du SAGE Estuaire de la Gironde (seuil de moyenne journalière) n’ont pas été atteints à Bordeaux, avec un total de 20 jours sous le seuil de 5 mg L-1, dont 15 jours successifs du 23 août au 6 septembre. À Libourne, les objectifs ont été atteints de justesse avec 4 jours sous le seuil objectif de 5 mg L-1. À Tonnay-Charente, il y a eu 11 jours compris entre 4 et 5 mg L-1, un bilan bien meilleur qu’en 2023 où 39 jours avaient été enregistrés des concentrations inférieures à 3 mg L-1. Enfin, deux articles d'intérêt général parus récemment sont présentés.
(19/04/2025)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS
Physiological responses to light regime of a Mediterranean lagoon strain of Chaetoceros tenuissimus and a collection strain of Chaetoceros calcitrans
Abstract Diatoms play a fundamental ecological role as primary producers in aquatic food webs. Among these, a little number of solitary species of the genus Chaetoceros are of great interest as live food for aquaculture, including major taxa like Chaetoceros calcitrans which have been well studied in terms of growth and essential lipid content. In contrast, the globally distributed species Chaetoceros tenuissimus has not been investigated as a potential live prey for aquaculture. For a preliminary analysis of the effect of culture conditions on growth and biomass content of a new strain of C. tenuissimus (CT16ED, hereafter CTEN) isolated from a Mediterranean lagoon, we first considered the light regime, comparing cultivation under a light–dark (L:D) cycle (12:12 h L:D photoperiod) and under continuous light, which conditions were also applied to a C. calcitrans strain, CCAP1085/3 (CCAL). Both strains had a similar growth rate under continuous light, but growth rate was lower in CTEN than in CCAL under the L:D cycle. Photosynthetic pigments content was higher under the L:D cycle than under continuous light in both strains, and higher pigment content was found in CCAL than in CTEN, indicating different photoacclimation. The lipid content of CTEN did not change markedly with photoperiod or growth phase, unlike CCAL. Both strains had high proportions of essential lipids, particularly n-3 polyunsaturated fatty acids, including EPA and DHA, but these varied less in CTEN than in CCAL. CTEN was richer in DHA (22:6n-3) with a more balanced DHA:EPA ratio. From these results, a potential interest of CTEN for use in aquaculture is discussed, with regard to its nutritional quality (essential lipid content), its growth, and its high-light niche offering possibilities for cultivation in outdoor systems in the Mediterranean area.
(Journal of Applied Phycology, n° 0921-8971, 15/04/2025)
SPE, CNRS, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, UMR MARBEC, IRD, IFREMER, CNRS, UM, LEMAR, IRD, IFREMER, UBO EPE, CNRS, CRO
Modélisation de l’effet des phénomènes de bypass sédimentaire sur l’évolution moyen à long terme du trait de côte
Sous l’effet des courants induits par les vagues, le sable peut contourner les obstacles rocheux naturels ou artificiels présents sur la plage via un phénomène nommé bypass sédimentaire. Le bypass joue un rôle clé dans l’évolution des plages, notamment les plages en baie délimitées par deux obstacles rocheux qui représentent environ la moitié des plages dans le monde. Pourtant, ce phénomène est souvent mal pris en compte dans les modèles d’évolution du trait de côte, voire absent. L’objectif de cette thèse est ainsi d’étendre le champ d’application du modèle à complexité réduite LX-Shore en y implémentant une paramétrisation du bypass sédimentaire. La nouvelle version du modèle, intégrant l’impact du bypass subaquatique, est testée sur une plage en baie idéalisée soumise à diverses conditions de vagues d’incidence variable. Les résultats montrent que la prise en compte du bypass impacte significativement la forme moyenne de la plage et la variabilité spatiale du trait de côte, notamment en termes de rotation, courbure et maximum d’érosion. Des applications sur des plages réelles présentant des épis rocheux (au Danemark et à Fréjus) ou un ouvrage de défense longitudinal (Lacanau) ont permis d’explorer l’influence du bypass à différentes échelles de temps : à l’échelle évènementielle, à l’échelle annuelle et à l’échelle pluri-décennale, sous l’effet de l’élévation du niveau marin. En intégrant pour la première fois une paramétrisation générique du bypass sédimentaire dans un modèle à complexité réduite, ces travaux contribuent à améliorer la compréhension et la modélisation de l’évolution du trait de côte en présence d’obstacles rocheux, offrant ainsi de nouvelles perspectives en termes de gestion des zones côtières.
(15/04/2025)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS