The role of advection and density gradients in driving the residual circulation along a macrotidal and convergent estuary with non-idealized geometry
Due to variations in channel depth, width, and lateral bottom profile, estuarine residual flows can exhibit significant variation in magnitude and transverse structure along macrotidal and convergent estuaries. This article explores the along-channel residual flow (magnitude and transverse structure), forcing mechanisms and their variations along the Gironde estuary in France. With emphasis on the role of density gradient and the advective accelerations in the along channel momentum balance, the study outlines the along-channel residual flows and forcing mechanisms over the neap-spring tidal cycle during high and low river discharge conditions. The results demonstrate that the density-driven flow contribution to total residual flows is, approximately, 75% (along-channel averaged) during neap tide and 18% during spring tide for both high and low river discharge scenarios. Owing to the complex lateral variation in the channel depth and the constriction near the mouth, advective accelerations play a major role in altering the residual flow lateral structure. However, the relative importance of advection reduces in the main body of the estuary where the channel is widened with poor lateral variation in the bottom depth. The results suggest advection and the baroclinic pressure gradient produce a laterally sheared along-channel residual flow with inflow in the channel and outflow over the shoals during neap tide. During spring tide, this lateral structure is produced due to advection. The results show that even in a homogenous system, advection can induce a flow with a structure that mimics the density-driven flow. The article shows that along macrotidal estuaries the presence of complex morphological features can affect the residual flow dynamics. As such, the residual flow in these systems should be schematized not only by considering the lateral variation of bathymetry, but also the along channel complexity.
(Continental Shelf Research. vol. 212, n° 0278-4343, pp. 104295, 01/01/2021)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS
Efficiency of benthic diatom-associated bacteria in the removal of benzo(a)pyrene and fluoranthene
We investigated the efficiency of a benthic diatom-associated bacteria in removing benzo(a)pyrene (BaP) and fluoranthene (Flt). The diatom, isolated from a PAH-contaminated sediment of the Bizerte Lagoon (Tunisia), was exposed in axenic and non-axenic cultures to PAHs over 7 days. The diversity of the associated bacteria, both attached (AB) and free-living bacteria (FB), was analyzed by the 16S rRNA amplicon sequencing. The diatom, which maintained continuous growth under PAH treatments, was able to accumulate BaP and Flt, with different efficiencies between axenic and non-axenic cultures. Biodegradation, which constituted the main process for PAH elimination, was enhanced in the presence of bacteria, indicating the co-metabolic synergy of microalgae and associated bacteria in removing BaP and Flt. Diatom and bacteria showed different capacities in the degradation of BaP and Flt. Nitzschia sp. harbored bacterial communities with a distinct composition between attached and free-living bacteria. The AB fraction exhibited higher diversity and abundance relative to FB, while the FB fraction contained genera with the known ability of PAH degradation, such as Marivita, Erythrobacter, and Alcaligenes. Moreover, strains of Staphylococcus and Micrococcus, isolated from the FB community, showed the capacity to grow in the presence of crude oil. These results suggest that a “benthic Nitzschia sp.-associated hydrocarbon-degrading bacteria” consortium can be applied in the bioremediation of PAH-contaminated sites.
(Science of the Total Environment. vol. 751, n° 0048-9697, pp. 141399, 01/01/2021)
UCAR, CBS, CBS, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, MIO, IRD, AMU, INSU - CNRS, UTLN, CNRS, CBS
Impact of the Agulhas Return Current on the oceanography of the Kerguelen Plateau region, Southern Ocean, over the last 40 kyrs
(Quaternary Science Reviews. vol. 251, n° 0277-3791, pp. 106711, 01/01/2021)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, LSCE, UVSQ, INSU - CNRS, CNRS, DRF (CEA), CEA, PALEOCEAN, LSCE, UVSQ, INSU - CNRS, CNRS, DRF (CEA), CEA, CLIMAG, LSCE, UVSQ, INSU - CNRS, CNRS, DRF (CEA), CEA
Contrasted impact of two macrofaunal species (Hediste diversicolor and Scrobicularia plana) on microphytobenthos spatial distribution and photosynthetic activity at microscale
Microphytobenthos is most often the primary source of carbon for coastal soft-sediment communities, especially in intertidal and shallow subtidal environments. The influence of benthic macrofaunal organisms on microphytobenthic biomass, spatial distribution and photosynthetic capacities is not only resulting from their feeding intensity but also indirectly from their bioturbation activity, which regulates nutrient fluxes and sediment mixing. This study compares the impact of two species (Hediste diversicolor and Scrobicularia plana) that dominate macrofaunal communities in estuarine intertidal mudflats on microphytobenthic biomass and photosynthetic activity. Imaging-PAM fluorescence was used to non-invasively map the development of microphytobenthic biomass and to assess its spatial extent. Our results showed that, due to intense deposit feeding, Scrobicularia plana quickly limited microphytobenthos growth and photosynthetic activity, even at low density (<250 ind m(-2)). In contrast, the negative impact of Hediste diversicolor on microphytobenthos development due to direct consumption was very low. Thereby, the stimulation of nutrient fluxes at the sediment-water interface resulting from bioirrigation seems to enhance microphytobenthos growth and photosynthesis.
(Marine Environmental Research. vol. 163, n° 0141-1136, pp. 105228, 01/01/2021)
BOREA, UNICAEN, NU, MNHN, IRD, SU, CNRS, UA, ECOBIO, UR, INEE-CNRS, CNRS, CNRS, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS
Compte rendu de l'atelier national « espèces non indigènes » (ENI), 14.10.2021, MNHN Paris
(pp. 17 pages, 21/04/2026)
PatriNat, MNHN, CNRS, OFB, LERAR, COAST, IFREMER, LOG, INSU - CNRS, ULCO, CNRS, IRD [Ile-de-France], IUEM, IRD, INSU - CNRS, UBO EPE, CNRS, OFB, DYNECO, IFREMER, M2C, UNICAEN, NU, INSU - CNRS, UNIROUEN, NU, CNRS, MTES, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, IFREMER, LIENSs, INSU - CNRS, ULR, CNRS, LERPC, COAST, IFREMER, ECOSEAS, CNRS, UniCA, UICN, CRESCO, MNHN, IFREMER, MIO, IRD, AMU, INSU - CNRS, UTLN, CNRS, UMR ISEM, Cirad, EPHE, PSL, CNRS, UM
Impacts of highway runoff on metal contamination including rare earth elements in a small urban watershed: case study of Bordeaux Metropole (SW France)
High temporal resolution sampling of runoff (15 samples/4 h) and river water (24 samples/24 h) was performed during a major rainstorm (41 mm/4 h) in the Bordeaux Metropole, after a dry and high vehicle-density period. Runoff was sampled at the outlet of one collector draining Northern Bordeaux Highway (NBH; 80,000–93,000 vehicles/day) and river water in the downstream Jalle River. The studied metals, including priority and emergent (Rare Earth Elements [REEs]) contaminants, showed major temporal and spatial variations in the dissolved and particulate concentrations. Hierarchical cluster analyses distinguished metal groups, reflecting different: (i) sources (i.e., automotive traffic: Zn–Cu–Ce and wastewater treatment plant: Cd–Ag–Gd) and/or (ii) processes (i.e., groundwater dilution by rainwater and sorption processes). The contribution of the particulate fraction to total metal fluxes was predominant in the NBH collector (except for Sr and Mo) and highly variable in the Jalle River, where the highest particulate metal loads were due to the export of road dusts exported by the NBH collector. Metal fluxes from the NBH collector represented highly variable fractions of daily fluxes into the Gironde Estuary at the outlet of the Jalle River, depending on elements and partitioning. The resulting relative contributions ranged from: 5% (Sr) to 40% (Cu) for dissolved phases and 30% (As) to 88% (Cu) for particulate phases. The first 40 min of the event accounted for 65% of the suspended particulate matter flux (and associated particulate metals) exported by the NBH collector, whereas the respective water flux contribution was 35%. This finding clearly demonstrates the importance of monitoring the first minutes of rainy events when establishing mass balances in urban systems.
(Archives of Environmental Contamination and Toxicology. vol. 193, n° 0090-4341, pp. 1-21, 21/04/2026)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, I2M-BX, UB, CNRS, INRAE
Inter‐country differences in the cultural ecosystem services provided by cockles
Coastal systems provide many cultural ecosystem services (CES) to humans. Fewer studies have focused solely on CES, while those comparing CES across countries are even rarer. In the case of shellfish, considerable ecosystem services focus has been placed on nutrient remediation, with relatively little on the cultural services provided, despite strong historical, cultural, social and economic links between shellfish and coastal communities. The ecosystem services provided by the common cockle, Cerastoderma edule, have recently been described, yet the cultural benefits from cockles remain mostly unknown. Here, we documented the CES provided by C. edule in five maritime countries along the Atlantic coast of western Europe, classifying evidenced examples of services into an a priori framework. The high-level classes, adapted from the Millennium Assessment and the Common International Classification of Ecosystem Services, were: inspirational, sense of place, spiritual & religious, aesthetic, recreation & ecotourism, cultural heritage and educational. A further 19 sub-classes were defined. We followed a narrative approach to draw out commonalities and differences among countries using a semi-quantitative analysis. Examples of CES provided by cockles were found for all classes in most countries. Cockles supply important and diverse cultural benefits to humans across Atlantic Europe, making it an ideal model species to study CES in coastal areas. Most examples were in cultural heritage, highlighting the importance of this class in comparison with classes which typically receive more attention in the literature like recreation or aesthetics. We also found that the cultural associations with cockles differed among countries, including between neighbouring countries that share a strong maritime heritage. The extent to which cultural associations were linked with the present or past also differed among countries, with stronger association with the present in southern countries and with the past in the north. Understanding the wider benefits of cockles could deepen the recognition of this important coastal resource, and contribute to promoting sustainable management practices, through greater engagement with local communities. This study is an important step towards better integration of CES in coastal environments and could be used as a framework to study the CES of other species or ecosystems.
(People and Nature. vol. 4, n° 2575-8314, pp. 71-87, 21/04/2026)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, BOREA, UNICAEN, NU, MNHN, IRD, SU, CNRS, UA, GEMEL-Normandie
High-resolution, large-scale laboratory measurements of a sandy beach and dynamic cobble berm revetment
(Scientific Data, 21/04/2026)
SBMS, LEGOS, IRD, UT3, Comue de Toulouse, INSU - CNRS, CNES, CNRS, UGent, UGent, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, FZK
Reinterpreting the Bruun Rule in the Context of Equilibrium Shoreline Models
Long-term (>decades) coastal recession due to sea-level rise (SLR) has been estimated using the Bruun Rule for nearly six decades. Equilibrium-based shoreline models have been shown to skillfully predict short-term wave-driven shoreline change on time scales of hours to decades. Both the Bruun Rule and equilibrium shoreline models rely on the equilibrium beach theory, which states that the beach profile shape equilibrates with its local wave and sea-level conditions. Integrating these two models into a unified framework can improve our understanding and predictive skill of future shoreline behavior. However, given that both models account for wave action, but over different time scales, a critical re-examination of the SLR-driven recession process is needed. We present a novel physical interpretation of the beach response to sea-level rise, identifying two main contributing processes: passive flooding and increased wave-driven erosion efficiency. Using this new concept, we analyze the integration of SLR-driven recession into equilibrium shoreline models and, with an idealized test case, show that the physical mechanisms underpinning the Bruun Rule are explicitly described within our integrated model. Finally, we discuss the possible advantages of integrating SLR-driven recession models within equilibrium-based models with dynamic feedbacks and the broader implications for coupling with hybrid shoreline models
(Journal of Marine Science and Engineering. vol. 9, n° 2077-1312, pp. 974, 21/04/2026)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, BRGM, USGS
Pesticide mixture toxicity assessment through in situ and laboratory approaches using embryo-larval stages of the pacific oyster (Magallana gigas)
Worsened state of oysters in French Arcachon Bay, demand an investigation of possible causes. This study evaluated the effects of an environmentally relevant mixture of five common pesticides on the early-life stages of the Pacific oyster (Magallana gigas). Laboratory assays with artificial mixture and in situ transplantation were complementarily used to investigate a series of sublethal endpoints. The laboratory exposure revealed developmental toxicity at 0.32 μg/L, which corresponds to mixture concentrations in Arcachon Bay. Downregulation of some gene transcriptions was observed at environmental level. No difference in larvae development was revealed among the three sites in Arcachon Bay. This study was the first to evaluate locomotion of oyster larvae exposed in situ. Suspected poor water quality in the inner part of Arcachon Bay was reflected by impairment at the molecular level. In conclusion, current concentrations of the tested pesticides in Arcachon Bay hinder larval development and affect several biological functions.
(Marine Environmental Research. vol. 169, n° 0141-1136, pp. 105390, 21/04/2026)
MU / MUNI, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS