Transient dynamics in confined aquifers: Planning horizon impacts on sustainable yield estimations
Confined aquifers challenge current groundwater sustainability concepts due to their long response time scales and the dampening potential of aquitards. Pumping introduces a perturbation that initiates a transient response, which propagates through the confining units towards adjacent aquifers and surface systems. As a result, the planning horizon, which refers to the timeframe over which management decisions are evaluated, becomes a critical factor in sustainability assessments. This work explores how sustainable yield estimations in confined systems are influenced by climatic conditions, the degree of confinement, and the chosen planning horizon. To investigate this, a synthetic cross-section model of a multi-layer aquifer system was developed using MODFLOW6 and FloPy. The sustainable yield was estimated through a constrained optimization approach, by iteratively running a transient model with different constant pumping rates. This analysis was conducted under a range of scenarios, including contrasting recharge rates, varying degrees of confinement, and multiple planning horizons. Additionally, the effect of transient recharge rates was investigated to understand their relevance on the transient response of the system and the impact on estimated sustainable yields. The modelled response times of this type of systems appear to be highly relevant for planning purposes given the typical human timeframes used for management and policy implementations. Our results reveal that sustainable yield is not a single, fixed value but a dynamic variable dependent on the chosen planning horizon. This analysis illustrates that what might be considered a sustainable withdrawal rate over a 25-year horizon could lead to unacceptable or undesirable impacts over a 50-year period, bringing an important question to the debate: which planning horizon to use? We conclude that effective management of confined aquifers requires a paradigm shift away from steady-state thinking: what is considered sustainable fundamentally depends on when we decide to evaluate it. This demands an adaptive, time-dependent approach where sustainability is analysed within a context-specific planning horizon, acknowledging that our decisions today have consequences that might unfold over decades or even centuries. This introduces broader issues of intergenerational equity, emphasizing that sustainability cannot be determined solely by physical indicators and it must also address long-term governance and ethical considerations.
(27/10/2025)
Bordeaux INP, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, CEREGE, IRD, INRA, AMU, CdF (institution), INSU - CNRS, CNRS
Population dynamics of the potentially invasive Asian date mussel, Arcuatula senhousia, in Arcachon Bay, France
Originated from Asia, Arcuatula senhousia has spread globally and is often reported as an invasive species that alters benthic communities and ecosystem functioning. However, very few studies have focused on the population dynamics of this ecosystem-engineering mytilid, partly due to the difficulty in monitoring cohorts of this short-lived, fast-growing species. Through a one-year monthly monitoring of mussel in two distinct locations in Arcachon Bay, France, we observed higher growth performance and P/B ratio at the station closer to the main river mouth, confirming the species preference for brackish, estuarine conditions. Post-recruitment mortality was particularly high, exceeding typical bivalve mortality rates, likely due to the vulnerability of this small species at the sediment surface. Trematode parasites, absent in our samples, were not implicated in mortality. In both locations, the reproductive phenology was similar, with a prolonged spawning season centred in the warmer months. As of 2024, A. senhousia remains a colonizing introduced species in Arcachon Bay with relatively low densities. However, vigilance is necessary, as its population dynamics resemble those observed in the few areas where these data are available and where this species has become invasive.
(Estuarine, Coastal and Shelf Science. vol. 324, n° 0272-7714, pp. 109448, 15/10/2025)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, LERAR, COAST, IFREMER, PatriNat, MNHN, IRD, CNRS, OFB - DSUED, OFB
Aquatic metabolism influences temporal variations of water carbon and atmospheric carbon dioxide fluxes in a temperate salt marsh
Salt marshes are blue carbon (C) ecosystems characterized by intense atmospheric CO2 uptake and C sequestration but also by organic and inorganic C exports through the tide. However, uncertainties about the main biotic factors controlling these vertical and horizontal C fluxes imply studying terrestrial and aquatic metabolisms simultaneously at small timescales (diurnal and tidal) to distinguish their contributions to net ecosystem CO2 exchange (NEE). In a temperate salt marsh, four sampling 24 h cycles were performed to measure all water C biogeochemical parameters (including CO2 partial pressures, pCO2), nutrients, and aquatic metabolism simultaneously to NEE from high tide during marsh immersion (imported coastal waters influenced by the continental shelf) to low tide during marsh emersion (exported channel waters influenced by the marsh drainage). At high tide, water CO2 oversaturation (water pCO2 > air pCO2) due to marsh aquatic heterotrophy and CO2-concentrated water inputs from the coastal end-member induced water–air CO2 emissions during marsh immersion. At low tide, water pCO2 in the channel were also mainly controlled by the marsh aquatic metabolism, inducing a water CO2 oversaturation in winter due to dominant heterotrophy and a water CO2 undersaturation in spring and summer due to dominant autotrophy. In winter, the greatest increases in dissolved inorganic carbon (DIC; from 2354 to 3963 µmol kg−1), total alkalinity (TA; from 2508 to 4016 µmol kg−1) and dissolved inorganic nitrogen (DIN; from 27.7 to 68.4 µM) were measured simultaneously during low tide at night, probably due to intense aerobic/anaerobic microbial respiration of organic matter in channel waters and/or sediments resulting in the greatest water pCO2 increase (from 533 to 1461 ppmv). On the contrary, in spring and summer, large water pCO2 decreases (down to 83 ppmv) and dissolved organic carbon (DOC) increases (up to 1040 µM) from high to low tide could be related to intense autochthonous and allochthonous marsh primary production, including benthic microalgae, phytoplankton and macroalgae. This study suggests that the horizontal exchanges of coastal waters with the salt marsh significantly modify water C dynamics and associated water CO2 sink/source state in the channel due to an intense marsh metabolism (production and respiration). At the daily scale, plant and phytoplankton metabolism rates played a major and a minor role, respectively, in the marsh CO2 sink measured by atmospheric eddy covariance at the ecosystem scale (NEE), even during immersion where emerged plants located on the highest marsh levels can maintain a low CO2 uptake, despite aquatic heterotrophy and associated water–air CO2 emissions.
(Biogeosciences. vol. 22, n° 1726-4170, pp. 5387 - 5411, 08/10/2025)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, LERMPL, COAST, IFREMER, LERPC, COAST, IFREMER, DYNECO, IFREMER, UMR MARBEC, IRD, IFREMER, CNRS, UM, BRGM, ISTO, BRGM, INSU - CNRS, UO, CNRS, UMR ISPA, Bordeaux Sciences Agro, INRAE, BOREA, MNHN, IRD, SU, CNRS, UA
Tipping points in ocean and atmosphere circulations
Abstract. Continued anthropogenic pressures on the Earth system hold the potential to disrupt established circulation patterns in the ocean and atmosphere. In this narrative review, we investigate tipping points in these systems by assessing scientific evidence for feedbacks that may drive self-sustained change beyond critical forcing thresholds, drawing on insights from expert elicitation. The literature provides multiple strands of evidence for oceanic tipping points in the Atlantic Meridional Overturning Circulation (AMOC), the North Atlantic subpolar gyre (SPG), and the Antarctic Overturning Circulation, which may collapse under warmer and “fresher” (i.e. less salty) conditions. A slowdown or collapse of these oceanic circulations would have far-reaching consequences for the rest of the climate system and could lead to strong impacts on human societies and the biosphere. Among the atmospheric circulation systems considered, a few lines of evidence suggest the West African monsoon (WAM) as a tipping system. Its abrupt changes in the past have led to vastly different vegetation states of the Sahara (e.g. “green Sahara” states). Despite multiple potential sources of destabilization, evidence about tipping of the monsoon systems over South America and Asia is limited. Although theoretically possible, there is currently little indication for tipping points in tropical clouds or mid-latitude atmospheric circulations. Similarly, tipping towards a more extreme or persistent state of the El Niño–Southern Oscillation (ENSO) is currently not fully supported by models and observations. While the tipping thresholds for many of these systems are uncertain, tipping could have severe socio-environmental consequences. Stabilizing Earth's climate (along with minimizing other environmental pressures, such as aerosol pollution and ecosystem degradation) is critical for reducing the likelihood of reaching tipping points in the ocean–atmosphere system.
(Earth System Dynamics. vol. 16, n° 2190-4979, pp. 1611-1653, 08/10/2025)
PIK, NOC, CAOS, IISc Bangalore, BCCR, BIO / UiB, UiB, USP, IMAU, KNMI, UNSW, LOCEAN-VARCLIM, LOCEAN, MNHN, IRD, INSU - CNRS, SU, CNRS, IPSL (FR_636), ENS-PSL, UVSQ, CEA, INSU - CNRS, X, CNES, SU, CNRS, UPCité, MOHC, IIASA, LDEO, UQAM, NOCS, LOCEAN-PROTEO, LOCEAN, MNHN, IRD, INSU - CNRS, SU, CNRS, IPSL (FR_636), ENS-PSL, UVSQ, CEA, INSU - CNRS, X, CNES, SU, CNRS, UPCité, CCRC, UNSW, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, IISc
When invasion is faster than science: the long story of the flatworm who travelled across oceans
Both scientific and policy recommendations on marine non-indigenous species agree on the importance of a rapid detection and identification of species, for a rapid action. But sometimes, detection can just be the beginning of a long investigation, longer than the invasion of the species. In 2020, oyster farmers of the Arcachon Bay (France) noted the presence of a polyclad in cultivated oysters (Magallana gigas). Rapidly, special attention was paid to it because of its potential predatory behavior on bivalves. Because of its absence from public barcode databases until 2023 and from available identification keys, it was described as a new species (Idiostylochus tortuosus) while keeping in mind the high probability to be an introduced non-indigenous species. After several months of investigation, mainly based on molecular markers, the presence of this polyclad in Pacific areas (Australia and Japan)supported this status and finally allowed its identification as Postenterogonia orbicularis described from New-Zealand. Meanwhile, the species took the opportunity to proliferate both in terms of spatial expansion and population densities. This poster aimed to detail the investigation about this traveler polyclad and first results of population dynamic in the Arcachon Bay, acquired during two successive projects, RAPSODI (IFREMER) and VISQUEUX (FEAMPA-OFB).
(07/10/2025)
PatriNat, MNHN, IRD, CNRS, OFB - DSUED, OFB, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, IRSTEA, LERAR, COAST, IFREMER, LERPC, COAST, IFREMER, CAPENA
One decade of monitoring the consequences of different forest management alternatives on ecosystem functioning in young plantations
The global demand for wood biomass is increasing, therefore it is necessary to develop forest management alternatives that can, simultaneously, produce large amounts of biomass and maintain ecosystem functions and services in a sustainable way. However, assessing the consequences of silviculture is challenging, as forest ecosystems function slowly over long periods of time. Therefore, in this study, an experimental platform was set up to monitor the long-term effects of several forest management alternatives (FMA) on ecosystem functioning in a pine forest in a temperate region characterised by oligotrophic conditions. In practice, we monitored three contrasting FMA over a decade: (i) wood biomass production (WBP), designed using an approach of very intense forestry (high stand density; seed lot of pines selected to growth fast), (ii) combined objective management (COM; low stand density), aimed at improving pine growth by alleviating any competition by spontaneous vegetation, and (iii) nutrient management (NuM; medium stand density), designed to improve tree nutrition using N-fixers in the stand furrows. Overall, although FMA showed contrasting stand growth and structures, they had modest effects on forest biogeochemistry over a decade of monitoring: FMA showed similar trends regarding atmospheric deposition, soil solution chemistry and water table-ditch chemistry. The main difference observed was a more important role of dissolved organic matter in NuM biogeochemical functioning. Conversely to their effects on biogeochemistry, the FMA appeared to influence the biophysical properties of stands. The WBP management (with high stand density) was shown to be shadier, cooler and wetter than the other FMA. This trend was fairly clear during the summer periods although differences were observed all year-long. An important result regarding biophysical effects was that, in addition to being observed in the topsoil layers, they were also evident in deeper soil layers and in the water table. All in all, our results indicated that contrasting FMA have tended to influence the ecosystem functioning, in particular its biophysical component, but showed no early sign of unsustainable biogeochemical functioning. Nonetheless, this latter result should be confirmed in the long-term through further monitoring.
(06/10/2025)
UMR ISPA, Bordeaux Sciences Agro, INRAE, UEFP, INRAE, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS
Investigation of the combined influence of salinity and particle concentration on the adsorption of anionic and zwitterionic PFAS onto estuarine sediment using the RSM modelling approach
Salinity (S) and suspended particulate matter (SPM) are key factors influencing the sorption of micropollutants in estuaries, due to strong gradients in these ecosystems.
We initially investigated the adsorption kinetics of 11 anionic and zwitterionic PFAS onto estuarine sediment under one S/SPM combination in laboratory-controlled conditions, as well as their adsorption isotherms under two S/SPM combinations. We also determined their distribution coefficients (Kd) across 35 S/SPM combinations covering estuarine conditions. The adsorption kinetics of PFAS could be described by a pseudo-second-order model (equilibrium time <24h). Sorption isotherms were fitted by both linear and Freundlich models; the linear sorption range was in the range 0.12-1.31 nM and Kd varied between 0.6 and 55271 L/kg. Based on response surface modelling, both S and SPM were significant factors, i.e. Kd was positively related to S (salting-out effect), while it was negatively related to SPM concentration (third-phase effect). SPM had a stronger effect than S for short-chain carboxylates, whereas S was the dominant factor for most other compounds. We also provide, for the first time, evidence of a significant negative interaction between these two factors. This study provides a new perspective to model the fate of PFAS at the land-sea interface.
(03/10/2025)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS
Carte morphostructurale sous-marine de la zone Comores-Mayotte-Glorieuses, nord du Canal du Mozambique
Au début de la crise sismo-volcanique de Mayotte (2018-présent), le constat a été fait du manque de connaissances géologiques du domaine immergé du nord du Canal du Mozambique permettant de fournir un contexte géodynamique régional aux évènements en cours. Les campagnes de recherche SISMAORE (Thinon et al., 2020) et SCRATCH (Berthod et al., 2021) et les campagnes de surveillance MAYOBS (Rinnert et al., 2019) ont largement enrichi les jeux de données géologiques et géophysiques. Les données bathymétriques et d’imagerie multifaisceaux acquises ont complété celles plus disparates provenant du SHOM et de l’Ifremer, mais ayant déjà donné lieu à des interprétations morphologiques (Audru et al., 2006 ; Tzevahirtzian et al., 2021). L’ensemble des données multifaisceaux acquises depuis 2004 a ainsi fait l’objet d’une compilation permettant d’obtenir une couverture suffisamment complète pour entreprendre une mise à jour fine de la cartographie à l’échelle du 1/250 000 sur les eaux des ZEE des Glorieuses, de Mayotte, des Comores et des Seychelles, et ce dans le cadre du projet ANR COYOTES. La carte produite sous SIG montre la distribution de plus de 2400 édifices volcanique sous-marins (cônes, fissures), parfois regroupés en chaînes volcaniques (ex : Mwezi-Jumelles, …) ou monts sous-marins (zone Glorieuses). Ces zones volcaniques montrent également des évidences d’intrusions de sills, se traduisant par des plis forcés présentant en surface des morphologies en dômes. De nombreuses failles sont cartographiés sur la plaine abyssale au nord des Comores et de Mayotte, associées notamment à des zones volcaniques orientées N160° (N’Drounde) ou N135° (Mwezi-Jumelles). L’interprétation morphologique permet également de mettre en évidence les processus d’érosion, transport et sédimentation depuis les plateformes carbonatées et les flancs volcaniques, jusqu’aux plaines abyssales. Le transport se fait sur les pentes insulaires ou continentales par le biais de canyons, mais également lors d’évènements gravitaires majeurs comme le montrent les loupes d’arrachements, les lobes, et la présence de milliers de blocs glissés. Le SIG associé à la carte présentée ici dans sa première version, pourra s’enrichir d’informations complémentaires au fil du temps et servir de base à de futures cartes thématiques (structurales s.s., typologie volcanique, âges obtenus sur les volcans sous-marins).
(01/10/2025)
BRGM, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, IPGP - UMR_7154, INSU - CNRS, IGN, UR, IPG Paris, CNRS, UPCité, iSTeP, INSU - CNRS, SU, CNRS, CY, GEO-OCEAN, UBS, IFREMER, INSU - CNRS, UBO EPE, CNRS, LMV, IRD, INSU - CNRS, CNRS, UCA, UPCité
Reactive transport modeling of CO2 and CH4 plumes during a gas-rich water leakage in a shallow carbonate freshwater aquifer
The recent advances in geological carbon capture and storage and the worldwide proliferation of such projects to reach net-zero emissions by 2050 highlight the importance of investigating the risks associated with CO 2 leakage from carbon storage reservoirs into shallow aquifers. A recent experiment indicates that residual CH 4 from legacy hydrocarbon fields could be a potential early indicator of CO 2 leakage. In this study, numerical reactive transport simulations are performed to examine the reasons behind the different behavior of CH 4 in regard to CO 2 as well as its potential and limitations as a monitoring parameter. The base case model was calibrated using a large data set, including a tracer test, major element concentrations, dissolved CO 2 and CH 4 concentrations, and pH monitoring. The results show that the delay of CO 2 with respect to CH 4 is likely related to sorption, which plays a significant role in CO 2 retardation but has a minimal effect on CH 4 transport. The presence of clay minerals (montmorillonite and illite) did not significantly change the delay between the two gases. Furthermore, CO 2 retardation was found to increase in a scenario with a lower natural groundwater CO 2 concentration. The CH 4 oxidation simulation revealed that oxidation decreased the CH 4 concentration below the CH 4 concentrations from baseline water reported in the literature, suggesting that CH 4 oxidation is a critical process able to reduce the efficiency of CH 4 monitoring and should be considered if CH 4 monitoring is implemented.
(Applied Geochemistry. vol. 190, n° 0883-2927, pp. 106495, 01/10/2025)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, IFPEN
A dynamic H2 system with multi-source methane in chromitite-rich ophiolitic settings
The generation and migration of hydrogen and methane in serpentinizing environments represent fundamental processes with implications for deep carbon cycling, the origin of life, and emerging carbon-free energy resources. Here we present an integrated geochemical study of gas emissions from the Bulqizë chromite mine in Albania, where exceptional underground access to depths exceeding 1000 m enables direct investigation of one of Earth's most intense natural hydrogen systems (~200 tones H₂/year). Through a comprehensive analysis of bulk and clumped isotopes, noble gases, molecular compositions, and structural controls, we report a novel occurrence of radiocarbon-bearing methane (3.76 ± 0.06 pMC; ~26 ka) in any ophiolite globally. This discovery, combined with modern water ages (³H = 3.5 TU; ¹⁴C-DIC = 95.8 pMC) yet ancient gas signatures, reveals a dramatically decoupled fluid systems where meteoric water circulates rapidly within the mine while gas migrates slowly from depth. Methane clumped isotopes (Δ¹³CH₃D = 2.52 ± 0.26‰; Δ¹²CH₂D₂ = 9.95 ± 1.6‰) indicate a lack of isotopic equilibrium with H₂ (δD-H₂ = -743.5 ± 1.1‰; ΔDD = 255 ± 35‰) and suggest formation from a single hydrogen source. They also show positive Δ¹²CH₂D₂ deviations likely due to diffusion or mixing, and point to a microbial origin probability of less than 10%. High δ¹³C-CH₄ values (-12.3‰), complete isotopic reversal in C₂-C₄ alkanes, and Volatile Organic Compounds signatures further support a predominantly abiotic synthesis. Noble gas and nitrogen isotopes reveal mixing between atmospheric (80-85%) and crustal (15-20%)
(Geochimica et Cosmochimica Acta. vol. 409, n° 0016-7037, pp. 281-307, 01/10/2025)
ISTerre, IRD, INSU - CNRS, USMB [Université de Savoie] [Université de Chambéry], CNRS, Fédération OSUG, UGA, IPGP - UMR_7154, INSU - CNRS, IGN, UR, IPG Paris, CNRS, UPCité, ISTO, BRGM, INSU - CNRS, UO, CNRS, ISTO, BRGM, INSU - CNRS, UO, CNRS, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, MIO, IRD, AMU, INSU - CNRS, UTLN, CNRS, GET, IRD, INSU - CNRS, CNES, CNRS, EPE UT, Comue de Toulouse