Biological features for a minimum conservation reference size revision – case of Ruditapes philippinarum in Arcachon Bay (French Atlantic coast)
The Minimum Conservation Reference Size (MCRS) for marine resources ensure that individuals can mature and reproduce at least once before being caught. For management purposes, MCRS should be revised for specific populations in given areas. In Arcachon Bay (southwest France), fishers have repeatedly requested a review of the MCRS for R. philippinarum. In 2020, a joint recommendation, supported by France, was addressed to the European Commission suggesting a possible reduction in the MCRS of R. philippinarum from 35 mm to 32 mm for Arcachon Bay. This paper provides an overview of the biological features that need to be considered to support such a review, primarily focusing on sexual maturity, individual growth and natural mortality. The reproductive cycle and size at first maturity, estimated at 26.7 mm for the Bay, were found to be similar to other locations in France and in Portugal. The greatest length at which growth slowdown occurred ranges between 24.0 and 31.5 mm with few differences among sites and no significant differences within each site (at hypsometric levels). The natural mortality coefficients were high with 0.67 yr−1 and 0.51 yr−1 for juveniles and adults, respectively. Regarding productivity (resulting from growth and mortality processes) and all methods combined, the optimal balance between individual growth and natural mortality above 30 mm was found at a mean length of 32.2 mm for the intra-lagoon sites and at a mean length of 36.8 mm for the oceanic sites. Based on available information, reducing the MCRS to 32 mm would not threaten population viability. However, the European Commission has raised warning points, which are discussed in light of current regulations in Arcachon Bay.
(Estuarine, Coastal and Shelf Science. vol. 320, n° 0272-7714, pp. 109288, 24/05/2026)
LMAP, UPPA, CNRS, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS
A new species of Diopatra (Annelida, Onuphidae) from Akanda National Park in Gabon (West Africa)
Several ecological surveys were recently conducted in the Akanda National Park in Gabon. The main objectives of this study were to assess the urban impact on the estuarine ecosystem of Libreville and to document the benthic biodiversity of this ecosystem. Among all the species collected, a new species of Diopatra was discovered in different habitats, including mangroves. This species is described and illustrated in detail, and information on 16S gene is provided. Diopatra ariasi sp. nov. is a medium-sized species and belongs to the D. neapolitana complex, having antennae with long ceratophores and ventral lobes. This species is also characterized by the presence of ceratophores with 9–12 rings on antennae, by sensory buds which are semicircular, by spiraled branchiae from chaetiger 4–5; by bidentate pseudocompound falcigers with moderately long hoods in first four chaetigers; by pectinate chaetae with 11–15 teeth from chaetiger 6–8 and by bidentate subacicular hooks from chaetiger 15–18.
(Marine Biodiversity. vol. 55, n° 1867-1616, pp. 94, 24/05/2026)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, UMR MARBEC, IRD, IFREMER, CNRS, UM
Non-Stationary Model Free Parameter In Equilibrium Shoreline Modelling
The state-of-the-art equilibrium shoreline model proposed by Davidson et al. (2013) is used to hindcast shoreline evolution. A similar approach to the work of Ibaceta et al. ( 2022) is adopted, where they introduced non-stationary model free parameters to improve long term shoreline change predictions. An Ensemble Kalman Filter (EnKF) is implemented to track the temporal variability in model free parameters and explore if their evolution can be linked to the environmental forcing. A correlation between the winter wave energy and the model free parameter φ (beach memory) is identified where high energetic winters are followed by an increase in the parameter suggesting such time variation in beach memory can be parametrized.
(24/05/2026)
UB, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, BRGM, WRL, UNSW
Influence of cockle bioturbation on microphytobenthic primary producers: habitat and density-dependent effects
While the global impact of the edible cockle Cerastoderma edule on microphytobenthos (MPB) dynamics has been extensively studied, some underlying processes remain unknown, such as their non-trophic interactions. For this purpose, a laboratory mesocosm experimental approach was used to quantify the bioturbation generated by C. edule adults and their influence on oxygen and nutrient fluxes, MPB biomass and photosynthetic performance at the sediment-water interface. The effects of sediment properties and cockle densities (0, 288, 720 and 1,297 ind. m−2) were also investigated. Our results showed that cockles exert a net negative density-dependent effect on MPB biomass, with intensity varying according to sediment type. This is mainly due to sediment reworking by cockles and their emergence at the sediment surface, mechanically disrupting MPB biofilms. Nonetheless, the physiological status and photosynthetic performances of the remaining MPB cells were not impacted. This could be explained by cockle bioirrigation which stimulates nutrient fluxes at the sediment surface and cell turnover. In the finest sediment, the stimulation of MPB growth by nutrient fluxes did not compensate algal biomass loss due to burial, leading to a net decrease in MPB biomass. In coarser sediment, no significant impact of cockles on the net total MPB biomass was observed. This indicates a balance between suboptimal sediment condition for MPB, biofilm destruction by cockles, and enhanced bioirrigation rates that increase nutrient availability for MPB biofilms at the sediment-water interface.
(Marine Biology. vol. 172, n° 0025-3162, pp. 70, 24/05/2026)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, MERSEA, UNICAEN, NU, BOREA, UNICAEN, NU, MNHN, IRD, SU, CNRS, UA, UNICAEN, NU, CESAM
En-échelon Rifting and Origin of the Volcanism in the Comoros
Two volcanic provinces have been recently discovered during the SISMAORE oceanographic cruise in the Comoros archipelago in the North Mozambique Channel between Madagascar and East Africa: N'Droundé, along the North-eastern insular slopes of Grande Comores Island and Mwezi, in the abyssal plain, north-east of Mayotte and Anjouan islands. By combining bathymetry and backscatter data, high-resolution seismic reflection and sub-bottom profiles, we have identified and mapped various tectonic (faults, forced folds) and volcanic structures (lava flows, edifices, sills, dykes) at several spatial scales on the seabed and in crosssection within the sedimentary cover. We have characterized the volcano-tectonic structures (geometry, segmentation, and kinematics) to better understand the link (geometry, chronology) between tectonic and volcanic processes. We show that volcanic and tectonic features are controlled by tectonic processes and viceversa. Ridges, volcanic cones and lava flows are set up along fissures and dikes during main rifting events to accommodate a N40°E regional extension within an E-W right lateral shear transfer zone. The volcano tectonic features are Plio-Pleistocene. This transfer zone lies between the offshore branch of the East African rift system and Malagasy grabens and may have formed when the East African rifts propagated offshore. We evidence a major rifting episode in the last Ma. The estimated volume and flux of extruded lavas show that the volcanism of the Comoros could be related to shallow tectonic processes.
(Geochemistry, Geophysics, Geosystems. vol. 26, pp. e2024GC011576, 24/05/2026)
IPGP - UMR_7154, INSU - CNRS, IGN, UR, IPG Paris, CNRS, UPCité, BRGM, LMV, IRD, INSU - CNRS, CNRS, UCA, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, iSTeP, INSU - CNRS, SU, CNRS, CY
Role of aquatic macrophytes on diel evolution of lowland streams nutrient concentrations, pCO2 and d-13DIC
(24/05/2026)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS
Le mystère de la maladie des pêcheurs (2020-2021) sénégalais levé [Note politique AWA]
Il aura fallu quatre années d'investigations, la mobilisation d'une quarantaine de scientifiques à travers une vingtaine d'équipes de recherche situées dans une quinzaine de laboratoires à travers le monde, pour venir àbout de l'énigme de la maladie mystérieuse qui a sévit au Sénégal en 2020 et 2021 chez les pêcheurs artisans. Cette maladie mystérieuse a touché plus d'un millier de pêcheurs sénégalais, suscitant l'inquiétude et l'attentioninternationale, est une dermatite aiguë. Les mêmes symptômes sont apparus sur des pêcheurs artisans en Guinée en 2023. Une étude menée par un consortium scientifique international (article publié en février 2025)dévoile l'origine de cette maladie : une toxine, la Portimine A, produite par la microalgue marine Vulcanodinium rugosum, jusqu'ici inconnu au Sénégal et dans sa sous-région CSRP. Cette toxine, qui perturbe les cellules de la peau humaine, déclenche une inflammation sévère. Cette étude met en lumière une problématique plus large : l'impact croissant des toxines environnementales sur la santé humaine, dans un contexte du changementglobal, notamment le changement climatique et l'accroissement des flux de transport maritime qui favorisent la prolifération et la redistribution de certains micro-organismes marins, comme les dinoflagellés toxiques.Le trafic maritime favorise la dissémination d'espèces marines d'un écosystème à un autre, notamment par les eaux de ballast. L'épidémie de dermatite associée à la Portimine A illustre les risques imprévisibles queles transformations subies par les écosystèmes marins peuvent entraîner. Elle souligne également l'urgence de surveiller, de manière coordonnée interdisciplinaire à une échelle sous-régionale, les espèces marinesproductrices de toxines, de comprendre leurs mécanismes d'action et d'adaptation, et de développer des solutions pour prévenir et traiter les menaces qui pèsent sur la santé humaine et les écosystèmes marins.
(pp. 16 p. multigr., 24/05/2026)
LEMAR, IRD, IFREMER, UBO EPE, CNRS, IRD, UCAD, LERBO, COAST, IFREMER, PSMS, URCA, PHYTOX, IFREMER, LBCM, UBS, UBO EPE, IUEM, IRD, INSU - CNRS, UBO EPE, CNRS, CNRS, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, IPBS, CNRS, EPE UT, Comue de Toulouse
Relating estuarine turbidity maxima to tide and river conditions
Tidal rivers and estuaries may experience high levels of suspended particulate matter (SPM), which impacts water quality and ecosystem functioning. The processes controlling the development of estuarine turbidity maxima (ETM) are fairly well understood. However, predicting the maximum SPM concentration in an estuary based on aggregated parameters (estuarine dimensions, river discharge, tidal range) remains, up to now, impossible without extensive in-situ measurements and/or numerical models. This study introduces an approach that links the strength of the ETM to the tidal, river, and morphological characteristics of a system. Using in-situ data from contrasting meso- to macro-tidal estuaries, we found a consistent pattern of maximum SPM concentrations within a two-dimensional parameter space. The resulting turbidity diagram reveals a high SPM hotspot in estuaries with specific forcing conditions, corresponding to intermediate relative tidal amplitudes and freshwater Froude numbers. This multi-site research advances our predictions of ETM intensity in tide-dominated estuaries, offering a straightforward method to explore potential turbidity trajectories under various human pressures.
(Scientific Reports. vol. 16, n° 2045-2322, pp. 3096, 24/05/2026)
DYNECO, IFREMER, IOW, RHITME, Cerema, M2C, UNICAEN, NU, INSU - CNRS, UNIROUEN, NU, CNRS, BAW, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, TU Delft
Dynamics of low and high density microplastics in the world's largest choked coastal lagoon under contrasting meteoceanographic conditions
The contamination by plastic waste in aquatic environments has become a global issue, scientifically reported since 1970. The size and durability of microplastics (MPs, 1 μm > 5 mm) have made these debris widely distributed in aquatic environments. Despite various ongoing initiatives, there is a need to fill gaps in understanding how MPs are transported from their release sources to their final destinations. Therefore, understanding the distribution and dynamics of MPs in coastal areas, such as lagoons and estuaries, which are considered continental sources of MPs to the oceans, is essential to help fill these gaps and propose alternatives for managing what is the environmental problem of the century. In this context, this study aimed to assess the transport patterns of MPs in Patos Lagoon, the largest choked coastal lagoon in the world, considering contrasting meteoceanographic conditions in the system dynamics, such as wind and discharge. Using the hydrodynamic model TELEMAC-3D and the model for plastics particles TrackMPD, simulations were performed using a type of MP polymer (Polypropylene - PP). The simulations of MP transport considered advection, dispersion and the contribution of biofilm in increasing particle density (representing high-density microplastics). The results indicated a gradient of MPs retention from north to south, with higher concentrations of MPs occurring in the northern part of the system. The central region of the lagoon showed a greater tendency for MP export towards the southern region than retention. Meanwhile, the estuary region of Patos Lagoon exhibited a tendency for export of low-density MPs free of biofilm and retention of higher-density MPs, subject to the action of the Plastisphere. Additionally, based on the results obtained from density occurrence maps, it was possible to suggest potential accumulation areas of MPs throughout the lagoon system, reinforcing that the system can act as a sink in specific regions.
(Continental Shelf Research. vol. 285, n° 0278-4343, pp. 105396, 24/05/2026)
FURG, INRAE, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS
Underwater sound data, recorded during a 18-month in situ experiment in Helgoland, Germany
This dataset shows the hourly sound pressure magnitude data measured underwater throughout the 18 months of experiment (11th of May 2023 – 31st of August 2024) in Helgoland (Margate) for different frequencies (10 Hz, 20 Hz, 30 Hz, 40 Hz, 50 Hz, 60 Hz, 70 Hz, 80 Hz, 90 Hz, 100 Hz, 200 Hz, 300Hz, 400 Hz, 500 Hz, 600 Hz, and 700 Hz) recorded by the HFNI valvometer. The mean sound pressure magnitude is also presented. Missing data corresponds to the stop of recording of the valvometer.
(24/05/2026)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, AWI, AWI