Budget of methane emissions from soils, livestock and the river network at the regional scale of the Seine basin (France)
We used various approaches to establish a comprehensive budget of methane (CH4) emissions from the Seine basin, including direct emissions from livestock and soils as well as emissions from the drainage network. For the direct emissions from livestock, we used official livestock census numbers and emission factors (CH4 emitted by each animal species per head per year) available in the literature. For the emissions from soils, we based our estimates on experimental measurements in closed chambers installed on different agricultural plots, forest, and grasslands in 2008 and 2009. The results were extrapolated to the whole Seine basin, including grassland, cropland, and forest soil distributions in the Seine basin. The CH4 emissions from the Seine drainage network were also based on measurements of sampled waters in various rivers and streams (from headwaters to estuary) during different seasons in 2007, 2008, and 2010. After chemical analysis of CH4 concentrations in the water samples using a gas chromatographic technique and calculation of the CH4 supersaturation by stream order in rivers of the Seine basin (from 1 to 8) and by season we could estimate the CH4 emissions for the whole water surface area of the Seine drainage network. The livestock of the Seine basin produce CH4 emissions amounting to 166 × 106 kg C year−1, among which cattle are responsible for 85 %. The total CH4 emission from the Seine drainage network was estimated at 0.3 × 106 kg C year−1, large rivers being responsible for the largest proportion. Ebullition could account for an additional 0.2 × 106 kg C year−1. Soils of the Seine basin are a net sink for CH4 (9.4 × 106 kg C year−1). The water and soils fluxes are low with regard to emissions by livestock, but domestic waste, through landfills, could contribute an additional 40 × 106 kg C year−1.
(Biogeochemistry. vol. 116, n° 0168-2563, pp. 199-214, 25/06/2026)
SISYPHE, UPMC, EPHE, PSL, PSL, CNRS, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, EGC, INRA
Estimation of a time varying extreme quantile with application to the measurement of the activity of bivalves in an environmental contex
(25/06/2026)
LMBA, UBS, UBO EPE, CNRS, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS
Deglacial and Holocene vegetation and climatic changes in the southern Central Mediterranean from a direct land–sea correlation
Despite a large number of studies, the long-term and millennial to centennial-scale climatic variability in the Mediterranean region during the last deglaciation and the Holocene is still debated, including in the southern Central Mediterranean. In this paper, we present a new marine pollen sequence (core MD04-2797CQ) from the Siculo-Tunisian Strait documenting the regional vegetation and climatic changes in the southern Central Mediterranean during the last deglaciation and the Holocene. The MD04-2797CQ marine pollen sequence shows that semi-desert plants dominated the vegetal cover in the southern Central Mediterranean between 18.2 and 12.3 ka cal BP, indicating prevailing dry conditions during the deglaciation, even during the Greenland Interstadial (GI)-1. Across the transition Greenland Stadial (GS)-1 -Holocene, Asteraceae-Poaceae steppe became dominant till 10.1 ka cal BP. This record underlines with no chronological ambiguity that even though temperatures increased, deficiency in moisture availability persisted into the early Holocene. Temperate trees and shrubs with heath underbrush or maquis expanded between 10.1 and 6.6 ka, corresponding to Sapropel 1 (S1) interval, while Mediterranean plants only developed from 6.6 ka onwards. These changes in vegetal cover show that the regional climate in southern Central Mediterranean was wetter during S1 and became drier during the mid-to late Holocene. Wetter conditions during S1 were likely due to increased winter precipitation while summers remained dry. We suggest, in agreement with published modeling experiments, that the early Holocene increased melting of the Laurentide Ice Sheet in conjunction with weak winter insolation played a major role in the development of winter precipitation maxima in the Mediterranean region in controlling the strength and position of the North Atlantic storm track. Finally, our data provide evidence for centennial-scale vegetation and climatic changes in the southern Central Mediterranean. During the wet early Holocene, alkenone-derived cooling episodes are synchronous with herbaceous composition changes that indicate muted changes in precipitation. In contrast, enhanced aridity episodes, as detected by strong reduction in trees and shrubs, are recorded during the mid-to late Holocene. We show that the impact of the Holocene cooling events on the Mediterranean hydroclimate depend on baseline climate states, i.e. insolation and ice sheet extent, shaping the response of the mid-latitude atmospheric circulation.
(Climate of the Past. vol. 9, n° 1814-9324, pp. 767-787, 25/06/2026)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, LSCE, UVSQ, INSU - CNRS, CNRS, DRF (CEA), CEA, PALEOCEAN, LSCE, UVSQ, INSU - CNRS, CNRS, DRF (CEA), CEA, FSS, BTP, LOCEAN, IPSL, ENS-PSL, UVSQ, UPMC, CEA, INSU - CNRS, X, CNES, CNRS, MNHN, IRD, UPMC, INSU - CNRS, CNRS, LCE, CNRS, UMLP, UBFC, GEOPS, UP11, CNRS, CNRS
Vulnerability of sandy coasts to climate variability
The main objective of the VULSACO (VULnerability of SAndy COasts to climate change and anthropic pressure) project was to investigate present day and potential future vulnerability of sandy coasts at the 2030 horizon, i.e. on a time scale related to climate variability. The method, based on a multidisciplinary approach bringing together geologists, geographers, physicists, social psychologists, engineers and stakeholders, was structured around 4 axes: field data analysis; numerical modelling; analysis of governance and stakeholder perceptions; and development of vulnerability indexes. This approach was designed to investigate vulnerability at a local scale and was applied to 4 contrasting beaches located in France: Sète Lido (Mediterranean Sea), Truc Vert and La Tresson beaches (Atlantic Ocean), and Dewulf (English Channel). The results focus on decadal and multi-annual beach trends at the Truc Vert beach site. There is almost no trend in beach volume at Truc Vert beach, although there is a variation in this parameter on a cycle of 2 to 3 yr, with variations related to wave energy and probably to indexes of climate variability. Numerical modelling identified the sensitivity of beach responses to changes in wave height and direction, especially in terms of subtidal morphology and the potential development of shoreline instability. Together with the observed offshore wave angle at the Biscay Buoy, these model results suggest that a potential change in wave angle due to climate variability could significantly modify the bars’ morphology. The combination of data analysis and numerical modelling contributed to the development of vulnerability indexes designed for sandy coasts, which take into account climate-dependant variables such as waves. This allowed the differentiation of the sites in terms of vulnerability to erosion: Sète Lido and Truc Vert beach were the most and least vulnerable sites, respectively. These indexes help in identifying the dominant components of beach vulnerability, and provide potential for the study of how anthropogenic factors affect vulnerability. The study of stakeholder perceptions and decision-making with regard to climate-related risk also highlighted potential anthropogenic effects on beach vulnerability, and identified possible site-specific outcomes.
(Climate Research. vol. 57, n° 0936-577X, pp. 19-44, 25/06/2026)
BRGM, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, UAG, INSU - CNRS, UM, CNRS, UPC, CEFREM, UPVD, INSU - CNRS, CNRS, LETG, UNICAEN, NU, UA, EPHE, PSL, UBO EPE, UR2, CNRS, IGARUN, UN, UC / UniCan, LOG, INSU - CNRS, ULCO, CNRS, IRD [Ile-de-France], ULCO, LEGI, UJF, Grenoble INP, CNRS
Variation patterns in individual fish responses to chemical stress among estuaries, seasons and genders: the case of the European flounder (Platichthys flesus) in the Bay of Biscay
The objective was to describe and model varia- tion patterns in individual fish responses to contaminants among estuaries, season and gender. Two hundred twenty- seven adult European flounders were collected in two sea- sons (winter and summer) in four estuaries along the Bay of Biscay (South West France), focusing on a pristine system (the Ster), vs. three estuaries displaying contrasted levels of contaminants (the Vilaine, Loire and Gironde). Twenty-three variables were measured by fish, considering the load of contaminants (liver metals, liver and muscle persistent organic pollutants, muscle polycyclic aromatic hydrocar- bons); the gene expression (Cyt C oxydase, ATPase, BHMT, Cyt P450 1A1, ferritin); the blood genotoxicity (Comet test); and liver histology (foci of cellular alteration-tumour, steatosis, inflammation, abnormal glycogen storage). Ca- nonical redundancy analysis (RDA) was used to model these variables using gender, season and estuary of origin as explanatory variables. The results underlined the homo- geneity of fish responses within the pristine site (Ster) and more important seasonal variability within the three contam- inated systems. The complete model RDA was significant and explained 35 % of total variance. Estuary and season respectively explained 30 and 5 % of the total independent variation components, whilst gender was not a significant factor. The first axis of the RDA explains nearly 27 % of the total variance and mostly represents a gradient of contami- nation. The links between the load of contaminants, the expression of several genes and the biomarkers were ana- lysed considering different levels of chemical stress and a possible multi-stress, particularly in the Vilaine estuary.
(Environmental Science and Pollution Research. vol. 20, n° 0944-1344, pp. 738-48, 25/06/2026)
LEMAR, IRD, IFREMER, UBO EPE, CNRS, LEHNA IPE, LEHNA, UCBL, ENTPE, CNRS, Cedre, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, PAnTher, Oniris VetAgroBio, INRAE
Mercury bioaccumulation along food webs in temperate aquatic ecosystems colonized by aquatic macrophytes in south western France
Mercury (Hg) is considered as an important pollutant for aquatic systems as its organic form, methylmercury (MeHg), is easily bioaccumulated and bioamplified along food webs. In various ecosystems, aquatic periphyton associated with macrophyte was identified as an important place for Hg storage and methylation by microorganisms. Our study concerns temperate aquatic ecosystems (South Western France) colonized by invasive macrophytes and characterized by high mercury methylation potentials. This work establishes original data concerning Hg bioaccumulation in organisms (plants, crustaceans, molluscs and fish) from five contrasting ecosystems. For low trophic level species, total Hg (THg) concentrations were low (from 277 2 ng THg g À 1 dw in asiatic clam Corbicula fluminea to 418 7 114 ng THg g À 1 dw in crayfish Procambarus clarkii). THg concentrations in some carnivorous fish (high trophic level) were close to or exceeded the International Marketing Level (IML) with values ranging from 10497 220 ng THg g À 1 dw in pike perch muscle (Sander lucioperca) to 3910 7 1307 ng THg g À 1 dw in eel muscle (Anguilla Anguilla). Trophic levels for the individuals were also evaluated through stable isotope analysis, and linked to Hg concentrations of organisms. A significant Hg biomagnification (r 2 ¼ 0.9) was observed in the Aureilhan lake, despite the absence of top predator fish. For this site, Ludwigia sp. periphyton, as an entry point of Hg into food webs, is a serious hypothesis which remains to be confirmed. This study provides a first investigation of Hg transfer in the ecosystems of south western France and allows the assessment of the risk associated with the presence of Hg in aquatic food webs.
(Ecotoxicology and Environmental Safety. vol. 91, n° 0147-6513, pp. 180-187, 25/06/2026)
IPREM, UPPA, INC-CNRS, CNRS, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, IMS, UB, CNRS, UPPA
Comparaison de méthodes basées sur SIR pour des cas sous-déterminés (n < p)
(pp. 1-6, 25/06/2026)
IMB, UB, Bordeaux INP, CNRS, CQFD, IMB, UB, Bordeaux INP, CNRS, Inria, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, INSERM
Changes in the distribution of copepods in the Gironde estuary: A warming and marinisation consequence?
The Gironde is the largest estuary of South-West Europe and is one of the best monitored estuarine systems in the world. This macrotidal estuary is characterized by a low biodiversity in both oligo- and mesohaline zones. Its zooplankton community is constituted by only five major species, three calanoid copepods (including one invasive species) and two mysids. Retrospective analyses have already documented a warming associated to a phenomenon of marinisation. Here, we investigate the influence of both marinisation and warming on the spatial distribution and the abundance of copepods (i.e. Eurytemora affinis, Acartia bifilosa and neritic species) in the Gironde estuary. We modelled the environmental envelope of the copepods as a function of salinity and temperature to demonstrate that the alteration of their longitudinal distribution in the estuary between 1975 and 2003 was the result of both changing temperature and salinity. Although the upstream movement of neritic species was mostly related to salinity, we show that the augmentation of both temperature and salinity was at the origin of the upstream progression of both A. bifilosa and E. affinis. These results suggest that the distribution of copepods can be affected by both anthropogenic forcing and climatic change, which modulate the physic-chemistry of the Gironde estuary.
(Estuarine, Coastal and Shelf Science. vol. 134, n° 0272-7714, pp. 150-161, 25/06/2026)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, UR EPBX, IRSTEA, LOG, INSU - CNRS, ULCO, CNRS, IRD [Ile-de-France]
The acceleration of oceanic denitrification during deglacial warming
Over much of the ocean’s surface, productivity and growth are limited by a scarcity of bioavailable nitrogen. Sedimentary δ15N records spanning the last deglaciation suggest marked shifts in the nitrogen cycle during this time, but the quantification of these changes has been hindered by the complexity of nitrogen isotope cycling. Here we present a database of δ15N in sediments throughout the world’s oceans, including 2,329 modern seafloor samples, and 76 timeseries spanning the past 30,000 years. We show that the δ15N values of modern seafloor sediments are consistent with values predicted by our knowledge of nitrogen cycling in the water column. Despite many local deglacial changes, the globally averaged δ15N values of sinking organic matter were similar during the Last Glacial Maximum and Early Holocene. Considering the global isotopic mass balance, we explain these observations with the following deglacial history of nitrogen inventory processes. During the Last Glacial Maximum, the nitrogen cycle was near steady state. During the deglaciation, denitrification in the pelagic water column accelerated. The flooding of continental shelves subsequently increased denitrification at the seafloor, and denitrification reached near steady-state conditions again in the Early Holocene. We use a recent parameterization of seafloor denitrification to estimate a 30–120% increase in benthic denitrification between 15,000 and 8,000 years ago. Based on the similarity of globally averaged δ15N values during the Last Glacial Maximum and Early Holocene, we infer that pelagic denitrification must have increased by a similar amount between the two steady states.
(Nature Geoscience. vol. 6, n° 1752-0894, pp. 579-584, 25/06/2026)
EPS, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS
Using data assimilation to investigate the causes of Southern Hemisphere high latitude cooling from 10 to 8 ka BP
From 10 to 8 ka BP (thousand years before present), paleoclimate records show an atmospheric and oceanic cooling in the high latitudes of the Southern Hemisphere. During this interval, temperatures estimated from proxy data decrease by 0.8 • C over Antarctica and 1.2 • C over the Southern Ocean. In order to study the causes of this cooling, simulations covering the early Holocene have been performed with the climate model of intermediate complexity LOVECLIM constrained to follow the signal recorded in climate proxies using a data assimilation method based on a particle filtering approach. The selected proxies represent oceanic and atmospheric surface temperature in the Southern Hemisphere derived from terrestrial, marine and glacio-logical records. Two mechanisms previously suggested to explain the 10-8 ka BP cooling pattern are investigated using the data assimilation approach in our model. The first hypothesis is a change in atmospheric circulation, and the second one is a cooling of the sea surface temperature in the Southern Ocean, driven in our experimental setup by the impact of an increased West Antarctic melting rate on ocean circulation. For the atmosphere hypothesis, the climate state obtained by data assimilation produces a modification of the meridional atmospheric circulation leading to a 0.5 • C Antarctic cooling from 10 to 8 ka BP compared to the simulation without data assimilation, without congruent cooling of the atmospheric and sea surface temperature in the Southern Ocean. For the ocean hypothesis, the increased West Antarctic freshwater flux constrainted by data assimilation (+100 mSv from 10 to 8 ka BP) leads to an oceanic cooling of 0.7 • C and a strengthening of Southern Hemisphere westerlies (+6 %). Thus, according to our experiments, the observed cooling in Antarctic and the Southern Ocean proxy records can only be reconciled with the reconstructions by the combination of a modified atmospheric circulation and an enhanced freshwater flux.
(Climate of the Past. vol. 9, n° 1814-9324, pp. 887-901, 25/06/2026)
UCLouvain, BAS, NERC, TECLIM, ELI, UCLouvain, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, VU, LSCE, UVSQ, INSU - CNRS, CNRS, DRF (CEA), CEA, GLACCIOS, LSCE, UVSQ, INSU - CNRS, CNRS, DRF (CEA), CEA