Karst aquifers play a crucial role in global water resources. Characterizing their thermal dynamics is essential for improving our understanding of their functioning. However, monitoring karst systems is challenging due to their strong heterogeneity, anisotropy, and limited accessibility. To address these challenges, we deployed an 800-m-long fiber-optic cable within the unsaturated zone of a karst system in the Jura Mountains (eastern France). The objective was to investigate the spatial and temporal variability of cavity air and underground river water temperatures over a 6-month monitoring period. The results highlight a gradual increase in cavity air temperature (CAT) and cavity river temperature (CRT) over the study period, consistent with the diffusion of surface air temperature (SAT). Superimposed on this long-term influence, short-term temperature fluctuations linked to precipitation events reveal the role of advective heat transfer associated with rapid infiltration and mixing in the main conduit. Temperature and electrical conductivity contrasts between the underground river and a lateral tributary indicate that multiple reservoirs contribute to aquifer recharge.

Abstract. Karst groundwater systems exhibit heterogeneity in recharge, circulation, and discharge, occupying a unique position within groundwater systems. This complexity facilitates rapid responses via the preferential flow routes, making karst systems vulnerable to climatic and anthropogenic pressures. High-altitude karst aquifers are particularly susceptible to shifting climate patterns – specifically rising temperatures, declining snow cover, and increasingly less and inconsistent precipitation – within the Mediterranean climate hotspot. Effective sustainable management of these groundwater systems require robust hydrological modelling; however, the application of such models is often constrained by the availability of high-quality, reliable datasets. This study presents a comprehensive collection of high-resolution karst spring discharge data from major Euro-Mediterranean mountain belts, including the Atlas, Betics, Pyrenees, Jura, Alps, Carpathians, Apennines, Dinarides, Hellenides, Balkans, Taurus, Levant, and Zagros. We compiled a total of 118 discharge time series specifically curated for hydrological modelling. Geographically, the dataset is led by the Alps (approx. 42%), followed by the Dinarides (approx. 10%), with the Apennines, Carpathians, and Zagros each contributing approx. 7%. The Levant and Taurus account for approx. 5% each, while the remaining regions (Atlas, Balkans, Betics, Hellenides, Jura, and Pyrenees) represent less than 5% each. In terms of temporal resolution, 92% of the records are daily, while hourly and monthly data each comprise 4%. The average record length is 19 years, which is led by a 99-year series from Unica Spring, Slovenia (1926–2025). Regional analysis indicates that the Alps, Apennines, Balkans, Betics, Dinarides, Jura, and Levant maintain average record lengths exceeding 20 years, whereas the Atlas, Carpathians, Taurus, and Zagros range between 10 and 20 years. The shortest average records were observed in the Hellenides and Pyrenees (7 and 8 years, respectively), which is still adequate for hydrological modelling applications.

Karst aquifers are a crucial source of water, supplying approximately 10% of the global population and often serving as the sole water resource in certain regions. These aquifers are characterized by highly heterogeneous flow dynamics and exhibit significant temporal variability in both hydrodynamic and physico-chemical conditions. Continuous monitoring of these parameters is essential for advancing our understanding of karst aquifer functioning; however, comprehensive, high-frequency datasets remain limited. We present a comprehensive dataset covering 13 karst springs monitored across nine observatories of the French Karst National Observatory Service (SNO KARST), spanning various hydroclimatic regions (oceanic, mountainous, Mediterranean). The SNO KARST aims to strengthen knowledge-sharing and to promote cross-disciplinary research on karst systems at the national scale. The dataset includes: (1) hydrodynamic data (water level, discharge), and (2) physico-chemical data (water temperature, electric conductivity, pH, dissolved oxygen, turbidity, Total Organic Carbon (TOC), Dissolved Organic Carbon (DOC), nitrate, and organic matter fluorescence). Spanning over a decade of continuous monitoring, such a dataset is required for the analysis of the hydrological and physico-chemical dynamics of karst aquifers, the assessment of their vulnerability to pollution and climate change, and the modeling of hydrodynamic and hydrochemical variables, ultimately aiming to improve the management and preservation of these critical water resources in contrasted contexts.

Peatlands, though covering only 3 % of the global land surface, play an active role in the Critical Zone (CZ) by mediating substantial water and carbon exchanges with adjacent aquifers, surface waters, and the atmosphere. These ecosystems provide key services, such as carbon and water storage and local climate regulation, addressing contemporary challenges related to climate change, biodiversity loss, and water resource management. However, peatlands are increasingly threatened by global pressures, including climate change, and local disturbances, such as drainage for agriculture, forestry, and peat extraction. To mitigate these threats, it is essential to understand the hydrological, biogeochemical, and ecological processes governing peatland dynamics across spatiotemporal scales. To explore the factors controlling greenhouse gases sources, production, and transport in peatlands, an interdisciplinary field campaign was conducted at the Frasne peatland (7 ha, 46.826°N, 6.1754°E, 840 m a.s.l.), a long-term observatory since 2008. The site is part of the French CZ research infrastructure (OZCAR) and the long term ecological research site Jurassian Arc, which focuses on the interaction between human and nature. The campaign was supported by the TERRA FORMA project, which develops smart, connected, low-cost, and low-impact environmental sensors to monitor CZ trajectories in the Anthropocene. The fieldwork integrated microbiological analyses of peat material, including membrane lipid profiling to trace microbial metabolisms, combined with detailed hydrogeochemical investigations of peat pore water along lateral flow and depth gradients. Measurements included physicochemical parameters (temperature, electrical conductivity, pH) and major elements, dissolved organic and inorganic carbon (DOC and DIC), CO₂, and CH₄ concentration, as well as their isotopic characterization (δ¹⁸O, δ²H, δ¹³C) . Additionally, greenhouse gases fluxes were quantified at multiple scales, employing methods such as dissolved gas profiling, chamber measurements, eddy covariance, and UAV-based surveys. This multiscale approach aims to tackle critical challenges in peatland research and management, including three-dimensional quantification of carbon fluxes (lateral and vertical) at the ecosystem scale; characterization of hydrological, biogeochemical, and ecological processes that modulate greenhouse gases and dissolved carbon production and transport; and development of accessible and efficient tools for addressing these pressing environmental issues. three-dimensional quantification of carbon fluxes (lateral and vertical) at the ecosystem scale; characterization of hydrological, biogeochemical, and ecological processes that modulate greenhouse gases and dissolved carbon production and transport; and development of accessible and efficient tools for addressing these pressing environmental issues.

The aim of the present study is to understand the variability and the environmental factors controlling the fluxes of carbonaceous greenhouse gases (GHGs), methane (CH~4~) and carbon dioxide (CO~2~) between a temperate _Sphagnum_-dominated mid-altitude mountain peatland and the atmosphere. We conducted monthly measurements of GHG fluxes over 20 months using the chamber method. Specifically, we assessed the effects of (1) air temperature and (2) water level (WL) on GHG emissions. Open Top Chambers (OTC) were used to simulate a warming effect by passive heating of the air above the soil. To assess the effect of WL, we studied a hydrological gradient along a 35 m long transect from a near-surface “WET” area, through an “INTER” area with an intermediate WL, to a “DRY” area with a lower WL. The WET area featured a higher cover of _Sphagnum_ species while the vegetation cover in the DRY area contained more vascular plants. Although all plots showed the same seasonality of GHG fluxes, considerable variability was observed among them. Raising the temperature using OTCs, which increased annual average air temperature by 0.2 °C to 0.6 °C, did not significantly affect CH~4~ and CO~2~ respiration (Reco) fluxes. In contrast, hydrological conditions played an important role in explaining flux variability. CH~4~ fluxes were significantly higher in the WET and INTER areas (median [95 % CI] values: 17.5 [14.2, 29.0] and 20.0 [14.8, 30.4] nmol m^-2^ s^-1^) compared to the DRY area (3.4 [1.9, 9.4] nmol m^-2^ s^-1^) during all hydrological periods, i.e., humid spring, humid summer and dry summer. Reco did not vary significantly along the hydrological gradient overall, but the fluxes were lower in the WET area under humid spring (0.4 [0.3, 0.6] µmol m^-2^ s^-1^) and summer (1.7 [1.25, 2.75] µmol m^-2^ s^-1^) conditions compared to the DRY area (1.6 [1.3, 2.0] µmol m^-2^ s^-1^ in spring and 3.8 [2.7, 4.6] µmol m^-2^ s^-1^ in summer). Conversely, greater fluxes (by ~ 0.5 µmol m^-2^ s^-1^) were observed in the WET area during summer drought. Given that Reco emissions are expected to be higher during droughts in the DRY area, we hypothesise a possible threshold effect, such as inhibition of phenoloxidase activity and/or other enzymatic activities, which would limit organic matter decomposition. Moreover, increasing WL in the WET and INTER areas led to a drastic drop in gross primary production (GPP) corresponding to _Sphagnum_ immersion.

Continental hydrosystems and in particular peatlands play an important role in the carbon cycle of the Critical Zone (CZ). Peatlands are important sinks for organic carbon and have therefore been extensively studied. However, peatlands are not only important for the fate of organic carbon, but they also affect the cycle of Dissolved Inorganic Carbon (DIC) of the peatland and the surrounding watershed. The fate of DIC is particularly complex in peatlands in limestone-dominated regions, because bicarbonate concentrations in surface and groundwater are high and the interaction between peatlands and surrounding hydrosystems are facilitated by the presence of highly permeable karst aquifers. In the present paper we study the origin and the fractionation of DIC in a peatland located on top of a karst aquifer. The study is based on hydrochemical and isotopic (delta C-13(DIC)) data from samples recovered during 2 campaigns (low flow, high flow) at various depths within the Forbonnet peatland (Jura Mountains, eastern France), at the peatland outlet and at adjacent karst springs representing the underlying aquifer. In order to evaluate secondary fractionation processes, the measured delta C-13(DIC) compositions were compared to modeled values considering the origin of DIC and potentially associated fractionation and speciation processes. The main results are: (1) DIC is lost at the bog surface by CO2 outgassing. (2) The delta(13)C(DIC )compositions of deep catotelm pore waters from the bog were much heavier than the modeled values. We relate this discrepancy to methanogenesis and show that this process is favored by reduced conditions at pH similar to 6 and a HCO3- content of similar to 1 mmol/L, most probably due to punctual groundwater inflows at the base of the bog. Finally, contrasted delta C-13(DIC) compositions between the bog and the fen of the peatland reveal an additional ecohydrological control on DIC speciation.

Unlike surface water reservoirs, that can be easily quantified and monitored, underground conduits in karst systems are often inaccessible, hence challenging to monitor. Seismic noise analysis was proved to be a reliable tool to monitor ground water storage in a fractured rock aquifer (Lecocq et al. 2017). In underground karstic environments, seismic noise monitoring was able to detect hydrological cycles and monitor the groundwater-content variations (Almagro Vidal et al. 2021). The following approach relies on coupling passive seismic wavefield with hydrological data in a machine learning algorithm in order to monitor underground water heights. The studied site is the Fourbanne karst aquifer (Jura Mountains, Eastern France, Jurassic Karst observatory). The underground conduit is accessible through a drilled shaft and instrumented by two 3-component seismological stations, one located underground and the other one at the surface, and a water height probe. We applied a new approach based on the machine learning random forest (RF) algorithm and continuous seismic records (Hibert et al., 2017), to find characteristic signals to predict the underground river water height. The method consists on the computation on a sliding window of seismic signal features (waveform, spectral and spectrogram features) and using the corresponding water height at the same time window to train the algorithm, and then apply it on new data. The RF algorithm is capable of accurately detecting flooding periods and reproduce the groundwater heights with an efficiency exceeding 95% and 53% using the Nash-Sutcliffe criterion for the seismic stations located in the underground conduit and at the surface respectively. The obtained results are a first promising outcome for the remote study of water circulation in karst aquifers using seismic noise.

Peatlands cover only 3 % of emerged lands, but their carbon stock represents about 30 % of the global soil organic carbon. Climate change and local anthropogenic disturbances deeply affect the hydrological functioning of peatlands. This may trigger carbon fluxes to surface waters and the atmosphere, thus leading to a positive feedback for global warming. It is therefore crucial to better estimate carbon fluxes between peatlands and the atmosphere and to delineate their major controlling constraints. To achieve this goal, we studied the functioning of a temperate mid-mountain peatland located in the French Jura Mountains, named the Frasne peatland.The methane (CH4) dynamics of the Frasne peatland appear to be constrained by a range of hydrological, physical, biogeochemical, and biotic factors. From a hydrological point of view, the system is fed by local rainwater and injection of carbonated groundwater at the bottom of the peatland, which provides a major input of dissolved inorganic carbon (DIC) to the system. Values of the δ13CDIC were high (even reaching positive values up to 8.1 ‰) compared to the expected values in a limestone and C3 plant-dominated area such as the Jura Mountains, supporting biotic CH4 production within the peatland. Consistently, high-frequency eddy-covariance monitoring during 2.5 years allowed us to show that the site acted as a source of CH4 to the atmosphere (23.9 ± 0.6 g C m-2 year-1) with interannual, seasonal, and diurnal time scale dynamics. In particular, we found an outstanding diurnal cycle for CH4 with the highest fluxes at night and lower ones at mid-day. In addition, the mid-day fluxes were negative in spring, highlighting larger oxidative processes than CH4 production attributed to photosynthesis activity (i.e., soil oxygen penetration and endosymbiotic methanotrophs of Sphagnum). The range of CH4 emissions was also controlled by the interannual variation in precipitation amounts and by the seasonal temperature variation.This conceptual production-emission model highlights that water-carbon interactions in the peatland depend on local biotic and abiotic factors but also on hydrological processes at the watershed scale. This also highlights the need to further constrain carbon transfers between the production and the emission zones (i.e., peatland-atmosphere interface and surface water exports). For this purpose, we will soon carry out a field campaign to measure the concentrations and isotopic values of dissolved gases in peat pore water along with an upstream downstream and a vertical gradient.

To understand the variability of methane (CH 4 ) fluxes between a temperate mid-altitude Sphagnum- dominated peatland and the atmosphere, we monitored simultaneously eddy covariance, hydrometeorological and physical parameters between April 2019 and December 2021. The site was a CH 4 source for the atmosphere, with a cumulative emission of 23.9 ± 0.6 g C m −2 year −1 . At the interannual scale, deeper water table during vegetation growth periods resulted in lower CH 4 fluxes (FCH4), and reciprocally. Furthermore, the seasonal temperature variation in the anaerobic peat layer was a good predictor for FCH4. However, while the lowest temperatures occurred between December and February, the lowest FCH4 were observed between March and May, with around 30% of negative FCH4. Indeed, the fastest increase in temperature of the aerobic layer likely stimulated methanotrophy at the expense of methanogenesis. Negative FCH4, systematically observed at midday, were concurrent with high photon flux densities, latent heat fluxes and net negative ecosystem CO 2 exchanges, suggesting the control of photosynthesis over CH 4 oxidation. Moreover, our results highlighted marked diurnal cycles with FCH4 maximal at night and minimal at midday for all seasons. This diurnal cyclicity is in opposition to what is typically known for peatlands dominated by vascular plants. Physical parameters, such as soil surface temperature and sensible heat fluxes, likely contribute to this diurnal FCH4 cyclicity and require further investigation. Our study thus demonstrates that diurnal variations in FCH4 must be considered before upscaling to seasonal or annual cycles, along with the effect of vegetation on CH 4 transfer and oxidation processes.

Despite its major role in the Earth’s climate regulation, the evolution of high-latitude ocean dynamics through geological time remains unclear. Around Antarctica, changes in the Southern Ocean (SO) circulation are inferred to be responsible for cooling from the late Eocene and glaciation in the early Oligocene. Here, we present a geochemical study of foraminifera from DSDP Site 277 (Campbell Plateau), to better constrain thermal and redox evolution of the high latitude southwest Pacific Ocean during this time interval. From 56 to 48 Ma, Mg/Ca- and δ18O-paleothermometers indicate high surface and bottom water temperatures (24–26°C and 12–14°C, respectively), while weak negative Ce anomalies indicate poorly oxygenated bottom waters. This is followed by a cooling of ∼4° between 48 and 42 Ma, possibly resulting from a weakening of a proto-EAC (East Australian Current) and concomitant strengthening of a proto-Ross gyre. This paleoceanographic change is associated with better ventilation at Site 277, recorded by an increasing negative Ce anomaly. Once this proto-Ross gyre was fully active, increasing biogenic sedimentation rates and decreasing Subbotina sp. δ13C values indicate enhanced productivity. This resulted in a shoaling of the oxygen penetration in the sediment pile recorded by increasing the foraminiferal U/Ca ratio. The negative Ce anomaly sharply increased two times at ∼35 and ∼31 Ma, indicating enhanced seawater ventilation synchronously with the opening of the Tasmanian and Drake Passage gateways, respectively. The Oligocene glaciation is recorded by a major increase of bottom seawater δ18O during the EOT (Eocene-Oligocene Transition) while Mg/Ca-temperatures remain rather constant. This indicates a significant ice control on the δ18O record.

Les karsts sont autant d’aquifères hétérogènes, résultat de la dissolution des roches carbonatées. Ces aquifères constituent aujourd’hui des ressources en eau stratégiques pour les différents usages. Ils sont en même temps très sensibles aux pressions anthropiques et aux changements climatiques en cours. Pour répondre à cette préoccupation sociétale, la communauté des hydrogéologues karstiques a proposé à l’INSU-CNRS la mise en place d’un service national d’observation des systèmes karstiques (SNO KARST). Rassemblant chercheurs et enseignants-chercheurs, cette structure permet aujourd’hui de mettre à la disposition de la communauté une base de données incluant notamment un suivi temporel en termes de qualité et quantité des eaux de plusieurs systèmes karstiques français. De plus, le SNO KARST constitue un lieu d’échanges scientifiques sur les thèmes des protocoles de mesure et de calibration, du traçage naturel ou artificiel, de l’analyse et du traitement du signal, des signatures hydrologiques et physicochimiques et enfin de la modélisation pluie-niveau-débit. Le SNO KARST est aussi un lieu de formation privilégié pour les étudiants en master et doctorat. Ainsi, depuis 2012, le dispositif SNO KARST a joué un rôle structurant pour la communauté de recherche, et les équipes qui le composent forment aujourd’hui un réseau dynamique sur le plan des échanges scientifiques.

In rapidly growing southern metropolises, climatic, anthropogenic and demographic pressures combined with centralized network deficiencies, favor individual initiatives to access freshwater, e.g., illegal well settlements, pirate connection to the distribution network, rainwater harvesting, and storage in tanks. These strategies are amplified by extreme meteorological events (e.g., droughts) that also trigger cognitive mechanisms, such as denial, opportunism or a kind of “myopic” competition to access the resource without considering (knowing) collateral impacts. From these environmental and social dimensions, this review first evaluates the arguments for the integration of managed aquifer recharge (MAR) in socio-environmental observatories (SEO). SEO are structures concurrently monitoring natural, anthropogenic, and engineered processes but also relationships between stakeholders/managers and end-users. Second, in order to take advantage from the current private (and illegal) strategies, MAR implementation accompanied with a SEO structure is discussed to show how it promotes cognitive, social, economic, and governance conditions required for successful co-management.

Peatlands provide a large panel of socio‐ecosystemic services such as biodiversity, water and carbon storage and amenities. Hydrological and geochemical interactions between peats and their surroundings are expected to be favoured in mountainous areas, which are nowadays increasingly sensitive to climate changes. In order to provide an integrated scheme of potential interactions, this study evaluates spatio‐temporal patterns of environmental tracers ( 87 Sr/ 86 Sr, δ 18 O/δ 2 H, elemental ratios) during high‐ and low‐flow periods in the largest peatland complex of the Jura Mountains (France). Systematically depleted δ 18 O/δ 2 H values in the deepest peat pore waters suggest contrasted dynamics and origins, both compatible with either preferential winter recharge or supply from adjacent high‐elevation areas. Combined with strontium isotopes ( 87 Sr/ 86 Sr), we show that these water fluxes are purveyors of solutes derived from water‐rock interactions, modified by mixing, evapotranspiration and dilution with local meteoric inputs. An end member mixing analysis of the peat pore water solute composition is consistent with a major contribution of carbonates from the regional Cretaceous limestone formations, located beneath fluvio‐glacial Quaternary deposits underlying the peat. This contribution implies a significant upward water flux from the underlying syncline that could reach a sufficient hydraulic head thanks to recharge from an adjacent regional anticline. These multiscale (anticline‐syncline, syncline‐peatland, peatland‐surface) constraints allow us to propose a relevant scheme for the hydrogeochemical functioning of the peatland, enabling an improved understanding of the current high socio‐ecosystemic value of the area, and the potential future evolution of the related services.

Peatlands and associated ecosystem services are sensitive to climate changes and anthropogenic pressures such as drainage. This study illustrates these effects on the Forbonnet bog (7 ha), belonging to the Frasne peatland complex (~300 ha, French Jura Mountain), and shows how they can inform about the ecohydrological functioning of peatlands. The southern part of the Forbonnet bog was restored in 2015–2016 by backfilling of artificial drains dating from the end of the 19th century. Piezometric data from 2014 to 2018 allow to evaluate the restoration effect on the water table depth (WTD) and highlight the reactivation of lateral inflows from the surrounding raised peatland complex. Vertical electrical conductivity (EC) profiles permit to identify three main peat compartments depending on different water supplies arguing for a nested hydrological functioning. This involves (1) one‐off karst groundwater inputs at the substratum/peat interface supplying the deepest peat layer, (2) lateral seepage inputs from the neighbouring raised wooded peatlands sustaining the intermediate peat level and (3) direct rainfall infiltrating the most superficial peat layer. This nested multi‐reservoir model operates at various spatio‐temporal scales and is consistent with the complex seasonal hydrological and physico‐chemical response at the bog outlet, which will be increasingly affected by climate change in the coming decades.

Peatland hydrology forms, together with vegetation cover and carbon dynamics, a sensitive interconnected three-pillar system, which furnishes essential ecosystem services from the local (specific biodiversity, interaction with the watershed) to the global scale (carbon and fresh water storage). The present study focuses on the hydrological function of the Frasne peatland, and especially investigates how restoration of water supplies can be used to mitigate climate change effects on peatland hydrology and sustainability. In this perspective, the Forbonnet bog, belonging to the Frasne peatland complex (300 ha; French Jura Mountains; 46.826 N, 6.1754 E; 850 m a.s.l) is monitored in the framework of the French observatory of peatland (SNO Tourbières) since 2008. The site, restored in 2015 (European program "Life Tourbières"), is located in a wide karstifed syncline overlain by moraine deposits. Between 2009 and 2019, mean annual precipitation and air temperature were respectively 1618 mm and 7 °C. In order to identify and model water supply and transfers at the ecosystem scale, this study combines a range of hydrological, geochemical and reservoir modeling approaches. This enabled us to propose a conceptual scheme of the hydrological functioning that implies a nested organization of 3 water origins: (1) The superficial reservoir (acrotelm) featuring a low mineralization, has a fast (daily) reactivity to precipitation, suggesting a strong dependence to direct atmospheric inputs. In addition, the outlet discharge shows a complex relation with the water level of this layer, highlighting a threshold effect where the saturation degree of the acrotelm seems to be involved. (2) Five years of outlet discharge and electrical conductivity (EC) monitoring highlight a seasonal pattern. During low flow periods (June-Oct.) EC is positively correlated with rainfall recharge of the previous winter (Nov.-May). Furthermore, the bog water budget is loss-making when only considering the topographical watershed. Considering the geological context, these elements argue for groundwater inflows from the surrounding karst aquifer likely occurring at the base of the bog, throughout the permeable or discontinuous moraine layers. Vertical EC profiles show that these inflows supply the mineralized water deep reservoir of the bog. (3) The monitoring of the restoration effects (by backfilling of drainage channels) through panpipe piezometers suggests that lateral seepage from the neighboring wooded, more elevated and mature peatlands supplies a transitional peat reservoir. Moreover, spatial (horizontal and vertical) and temporal EC variability argue for advective water transfers through the bog. This work supports the interest in monitoring over the long-term (several and contrasted hydrological years) for constraining hydrological processes. The three water supplies delineated could have contrasted responses to climate change and then impact both biological and carbon cycles. This work also highlights the importance to integrate hydrological processes beyond the ecosystem scale, to consider climate change and anthropogenic pressure effects on the regional hydrology that probably interact with peatlands in mountainous environments. In this perspective, the current hydrological monitoring is nowadays combined with isotopic (δ18O and δ2H) evaluation to refine this conceptual scheme and quantify the contribution of the 3 identified water flow paths.

Although peatlands occupy only 3 % of the global continental surface, they constitute a Critical Zone’s outstanding compartment. They provide socio-ecosystemic services such as water and hydrochemical regulation, carbon storage and biodiversity conservation. These latter depend directly on the complex interaction between chemical-water fluxes, vegetation cover, and carbon exchange dynamics. Fluvial carbon exports are critical for establishing peatland carbon budgets. In order to evaluate the origin (organic matter mineralization and/or weathering) of inorganic carbon exported from peatlands, we studied the Frasne peatland (French Jura Mountains; 46.826 N, 6.1754 E; 850 m a.s.l), located in a karstified syncline overlain by fluvio-glacial deposits. Rainwater, porewater and outflow waters are sampled monthly since October 2019 and analyzed for physico-chemical parameters (T, Eh, pH, electrical conductivity), major elements, DOC, DIC and isotopic signatures ( δ 18 O H2O , δ 2 H H2O , δ 13 C DIC ). Preliminary results show that outflow water presents signature close to recent local rainfall ( δ 18 O = -7.6 ‰ VSMOW; δ 2 H = -50 ‰ VSMOW) suggesting a direct link between local inputs and outflow during high Water Level Period (WLP). In contrast, pore