CAFEZH - CArtographie des Fonctions Ecologiques des Zones Humides de la vallée estuarienne de la Seine
Bien que les fonctions écologiques rendues par les zones humides soient aujourd'hui admises par les gestionnaires et les citoyens, la connaissance de leurs dynamiques spatio-temporelles le long de l'estuaire de la Seine reste méconnue. Pourtant, des approches de cartographie des fonctions basées sur l'analyse de données de télédétection ont été développées sur des milieux alluviaux, mais leur transférabilité à des milieux estuariens reste à évaluer. Les objectifs de ce projet sont au nombre de trois : 1. Délimiter et caractériser les zones humides de l’estuaire de la Seine à échelle fine, 2. Suivre les dynamiques intra- et inter-annuelles de la végétation et de l'hydrologie, 3. Évaluer et cartographier les fonctions biogéochimiques (stockage de carbone, dénitrification) des zones humides à partir d’indicateurs dérivés de données de télédétection. Ces objectifs sont ambitieux tant sur le plan scientifique que quant à leur portée thématique. Des méthodes issues de la littérature sont adaptées à notre domaine d’application. Dans ce projet, la méthode d'évaluation des fonctions de dénitrification et de stockage de carbone repose sur l'analyse de données à haute résolution spatiale et temporelle (Sentinel) ainsi que sur des données multispectrales à très haute résolution spatiale (SPOT-6/7), et tri-dimensionnelle (LiDAR). Un effort spécifique d’observation terrain a été mené pour calibrer et évaluer la performance de ces approches dans le cadre du projet CAFEZH. Plus précisément, l'intensité des fonctions est évaluée pour deux années (2022 et 2023) selon une analyse multicritère basée sur des indicateurs issus des données de télédétection. Une campagne de mesures saisonnière étalée sur une année visant à étudier la dynamique de la matière organique et des principaux éléments associés (carbone et azote) permet d'évaluer la fiabilité de la méthode. Concrètement, le projet se déroule en 3 phases à savoir (i) la collecte de donnée comprenant deux campagnes de levée de données terrain, (ii) la cartographie de déterminants du fonctionnement biogéochimique et (iii) la cartographie des fonctions biogéochimiques [FIGURE 1]. Les résultats comprennent un ensemble conséquent de données en open data à savoir des relevés terrain, des variables dérivées de télédétection, des indicateurs et des cartes d’évaluation des fonctions dénitrification et stockage de carbone pour chacune des deux années. Ces données sont utilisables pour le suivi écologique, la planification territoriale et plus précisément d'identifier les sites à enjeux de gestion et de comprendre l'effet des modes de gestion et des événements naturels sur les processus fonctionnels. Porté par un consortium pluridisciplinaire, ce projet ouvre des perspectives méthodologiques (intégration de l’intelligence artificielle, nouvelles séries temporelles à très haute résolution, développement d’indicateurs innovants) et thématiques (protection et restauration des écosystèmes, gestion des usages, prévention des risques), constituant une avancée importante pour la cartographie opérationnelle et la gestion durable des zones humides.
(01/09/2025)
i-Sea, LETG, UBO EPE, UR2, CNRS, Nantes Univ - IGARUN, Nantes Univ, UMR TETIS, Cirad, CNRS, INRAE, OZHM, METIS, EPHE, PSL, INSU - CNRS, SU, CNRS, ECOBIO, UR, INEE-CNRS, CNRS, CNRS, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS
Upstream moisture sources and circulation patterns controls Asian monsoon hydroclimate over the past 20,000 years
Speleothem oxygen isotope records (δ18O) from caves in the Asian monsoon region have been widely utilized to reconstruct paleo-monsoon variability. However, interpreting these records remains challenging due to conflicting hypotheses about their relationship with Asian Summer Monsoon (ASM) strength and regional rainfall patterns. In this study, we analyzed 15 cave stalagmite δ18O records collected across East and South Asia, covering the last 20,000 years. Our analysis focuses on key climatic events, including Heinrich Stadial 1 (HS1), the Bølling-Allerød warm period (BA), and the Younger Dryas (YD), to explore the driving force of Asian summer monsoons from both high-latitude North Atlantic climate and lower-latitudes atmospheric circulation patterns. The results revealed that speleothem δ18O variations were predominantly influenced by shifts in upstream moisture sources, particularly from low-latitude regions in the Indian and Pacific Oceans, as evidenced by both observational data and model simulations. We demonstrated that δ18O records from Chinese caves reflect not only local rainfall dynamics but also broader influences from upstream moisture sources.
(Quaternary Science Reviews. vol. 363, n° 0277-3791, pp. 109438, 01/09/2025)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, UCLouvain, UMR ISPA, Bordeaux Sciences Agro, INRAE, CAGS, MLR
Lower competition in grasslands and higher facilitation in forests as potential drivers of the higher species richness of calcareous than siliceous communities
We tested the hypothesis that, in calcareous and siliceous ecosystems from the wet temperate climate of southwest France, competition primarily explains differences in community composition and species richness in grasslands but that facilitation is more determinant in forests. In a first experiment, we transplanted, in dry and wet years, grass species of contrasting light requirements in gaps and forest understories to compare on the two bedrocks the effects of herbaceous neighbors in gaps to the effects of adult trees on understory species. In a second experiment, we manipulated light and soil nutrient fertility in the same system and transplanted six understory species to disentangle the direct drivers of the positive effect of trees for understory species. In the first experiment, competition was higher in gaps of siliceous than calcareous bedrocks during wet years and facilitation by canopy trees was higher on calcareous than siliceous bedrocks during dry years. In addition, facilitation in calcareous forests was very intense for species from the shadiest origins, while competition was only significant for species from the sunniest origins. In the second, experiment we found that both higher microclimates buffering ability of forest canopies and higher soil fertility explained the higher facilitation found in calcareous forests. Synthesis: the higher importance of competition in grasslands and facilitation in forests is mostly due to the contrasting adaptations to light conditions of grassland and understory species. The higher facilitation in calcareous forests appeared to be due to higher buffering effect of tree canopies and higher soil fertility in calcareous than siliceous soils. The major role of facilitation in forest communities from favorable conditions has been strongly overlooked in the literature, although it might explain the higher species richness of calcareous than siliceous forests.
(Oikos. vol. 2025, n° 0030-1299, 01/09/2025)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS
Comparison of sedimentary ancient DNA (sedaDNA) extraction and shotgun metagenomic library preparation techniques
Sedimentary ancient DNA (sedaDNA) is an emerging field, increasingly being applied to the study of past aquatic ecosystems. However, several sedaDNA extraction methods from deep-ocean sediment matrices and sequencing library preparation have recently been developed, which may complexify results comparison and interpretations. We present a sedaDNA interlaboratory comparison study to assess the impact of extraction and library preparation protocols on metagenomic results. We applied three extraction protocols to four samples from two sediment cores from the Northern Antarctic Peninsula: (1) a ‘combined’ protocol using ethylenediaminetetraacetic acid (EDTA) and silica-in-solution to isolate DNA, (2) a high-guanidine protocol involving long cold centrifugation to remove polymerase chain reaction (PCR) inhibitors, and (3) a commercial kit, the DNeasy PowerSoil Pro Kit. We also compared two library preparation protocols, both optimised versions from Meyer and Kircher (2010). Using a blind approach relying on k-mer similarity assessment, greater variability was observed between individual samples than between protocols. An in-depth analysis of eukaryotic and (highly abundant) diatom community composition revealed that all protocols recovered eukaryotic sedaDNA, with minor differences between extraction and library protocols on sequence composition. However, the different DNA extraction and library preparations influenced the DNA read length, potentially resulting in selective targeting of organisms with variable sedaDNA preservation. This study highlights the importance of selection and standardisation of protocols to ensure reproducibility and comparability of past ecosystem reconstructions, particularly at lower taxonomic levels, e.g. diatoms. Although complete standardisation across research projects is challenging, this study shows that data remain reasonably comparable when processed consistently.
(Marine Micropaleontology. vol. 200, n° 0377-8398, pp. 102498, 01/09/2025)
IBENS, IBENS, ENS-PSL, PSL, INSERM, CNRS, INSERM, CNRS, GOSEE, UPVD, EPHE, PSL, AMU, CEA, UEVE, UTLN, INSERM, SU, CNRS, IRD [Ile-de-France], ENS Paris Saclay, EMBL, Nantes Univ - ECN, Nantes Univ, IMAS, UTAS, EA 7206, MNHN, CNRS, Bordeaux INP, IACT, CSIC, UGR, AWI, MARUM, IGME, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, EPHE, PSL
Relationship between REE signatures and biological traits of marine benthic fauna in a temperate mud patch: Application of multivariate analyses
The increasing contamination of coastal environments by Rare Earth Elements (REEs) necessitates a thorough understanding of the dynamics of these elements in ecosystems under anthropogenic pressure. Sedimentary bodies influenced by large rivers, such as the West Gironde Mud Patch (WGMP), are among these pressured ecosystems. REE analyses in seven benthic marine species and ambient media (i.e., dissolved fraction of bottom water, sediments) of this mud patch has provided REE signatures (i.e., REE concentrations and shape of normalized patterns) using one concentration descriptor (i.e., ∑ REE) and six descriptors of pattern shapes (i.e., La/La*; Ce/Ce*; Eu/Eu*; Pr/Lu; Pr/Gd; Gd/Lu). A robust procedure of multivariate analyses (i.e., PERMDISP, PERMANOVAs, PCO) was applied to study the controlling factors of REE signatures in these species.
Assessment of the within-and between-species variability suggests that differences in REE concentrations and shapes of normalized patterns between species were related to the ambient media's geochemical processes and the fauna's ecological and biological traits. REE concentrations in the fauna document trophic dilution, reflected by elevated concentrations in pure microphages and reduced concentrations in pure carnivores. The predominance of calcareous skeletons in bivalves and brittle stars results in a dilution effect on REE concentrations at the whole-organism level. The chitinous exoskeleton of crabs and shrimps is subject to adsorption processes for REEs present in the sediment.
(Marine Pollution Bulletin. vol. 222, n° 0025-326X, 31/08/2025)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, CNRS, Bordeaux INP, L3I, ULR, UB, OASU, UB, INSU - CNRS, ULR, CNRS, INRAE
Changes in the Strength of Associations Between Tree Seedlings and Understory Shrubs Along a Regional Drought Gradient in Lebanese Coniferous Forests
ABSTRACT Aims Do the effects of an understory shrub on woody seedlings explain the distributions of relict conifer trees at a regional scale? Location Three natural Cedrus libani reserves from Lebanon. Methods Using an observational approach, we quantified associations of recruits of woody species at the center and periphery of the spiny shrub Juniperus oxycedrus in forests and gaps along a north–south climatic gradient of both winter rainfall continentality and summer drought. We quantified the associations of woody seedlings with shrubs using the Relative Interactions Index (RII) calculated for recruits of all species together (community scale) and for four groups of functionally different species. We then analyzed the variation of RIIs along different treatments. Vapor Pressure Deficit (VPD) was quantified in each treatment combination, and its relationship with species‐group RIIs and abundance was evaluated. Results At the community‐scale, shrubs showed likely higher negative effects on woody seedlings at their center than at their periphery. In contrast, there were contrasting responses at the species‐group level, with overall negative associations for Cedrus , positive associations for a group including Abies cilicica , and intermediate responses for two other groups. Positive associations strongly varied along the drought gradient and with the canopy treatment, while negative associations only slightly increased from forests to gaps. Positive associations varied together with VPD, peaking at an intermediate position along the drought gradient coinciding with the southernmost limit of Abies and declining at the dry extreme of the gradient where Cedrus is still present. Main Conclusions VPD appeared as a crucial driver of tree species occurrence and likely facilitation. Although manipulative experiments are needed to confirm the real occurrence of facilitative and competitive effects of the shrub, our study highlights the potential role of facilitation in explaining tree species distribution at regional scales.
(Journal of Vegetation Science. vol. 36, n° 1100-9233, 04/08/2025)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS
Contrasting Scenarios for Upper Ocean Temperature Changes at the Last Glacial Maximum Inferred From Inorganic and Organic Paleothermometers: A Case Study From the Eastern Tropical Indian Ocean
Reconstructing paleo seawater temperatures is essential for understanding past climate changes, yet different paleotemperature proxies can yield divergent signals with opposing climatic interpretations. This study reconstructs the upper ocean thermal structure in the eastern tropical Indian Ocean offshore southwest Sumatra across two 2‐kyr periods during the Last Glacial Maximum (LGM, 19–21 ka) and the Late Holocene (LH, 0–2 ka). Our multiproxy approach combines updated, published results from organic paleothermometers (, TEX 86 ), published and newly generated Mg/Ca data from four species of surface and thermocline dwelling planktic foraminifera, alongside new data from clumped isotope analysis (Δ 47 ) on the same foraminiferal species. The new Δ 47 data suggest surface dwellers experienced more pronounced cooling (6.1°C; 95% confidence interval 4.7–7.5°C) than the thermocline dwellers (1.6°C; 1.1–2.1°C) during the LGM compared to the LH, resulting in a weaker LGM vertical temperature gradient in the upper ocean and a deeper thermocline. While this weaker thermal gradient is generally consistent with previous Mg/Ca reconstructions, our new Δ 47 data for the LH suggest a higher thermocline temperature than the Mg/Ca‐based data, which may have been affected by dissolution effects as indicated by the correlation between Mg/Ca values and shell weights of thermocline dwellers. In contrast, paired and TEX 86 suggest a stronger or similar upper ocean thermal gradient during the LGM. Based on our analysis of modern data, we propose that the apparent discrepancy between the foraminiferal and biomarker approaches might have stemmed from proxies reflecting different depths with different sensitivities to upwelling dynamics.
(Paleoceanography and Paleoclimatology. vol. 40, n° 2572-4525, 04/08/2025)
NTU, NTOU, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, BCCR, BIO / UiB, UiB, NTU, NTU
New insights in benthic biodiversity of the saya de Malha Bank
(Deep Sea Research Part II: Topical Studies in Oceanography. vol. 222, n° 0967-0645, pp. 105500, 01/08/2025)
ISYEB, MNHN, EPHE, PSL, SU, CNRS, UA, AIM (UMR_7158 / UMR_E_9005 / UM_112), CEA, INSU - CNRS, CNRS, UPCité, LECOB, SU, CNRS, OOB, SU, CNRS, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, PSI
A coupling approach for long-term 3D morphological evolution of sandy coasts under sea-level rise
This study presents a modular modeling framework for simulating medium- to long-term (decadal to centennial) coastal evolution, focusing on shoreface translation under the combined effects of sea-level rise (SLR) and waves. On these timescales, short-term storm-driven processes are treated as noise superimposed on longer-term trends. We couple the one-dimensional ShoreTrans model, which simulates SLR-driven profile adjustment, with the two-dimensional reduced-complexity model LX-Shore, which captures longshore sediment transport gradients. This coupling enables efficient simulation of three-dimensional morphological change across diverse sandy coastal settings, including environments with dunes, barriers, and hard structures. The framework is first applied to synthetic test cases to explore sensitivity to coupling strategies, then tested on a 5-km beach-dune system in southwest France fronted by a 1.2-km seawall. Results show reasonable agreement with observed shoreline evolution and demonstrate the value of the coupled approach in capturing morphodynamic feedbacks and trajectory shifts not reproduced when shoreline and shoreface processes are modeled independently
(Environmental Modelling and Software. vol. 193, n° 1364-8152, pp. 106624, 01/08/2025)
BRGM, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, BW-CGC
Hydrodynamic and Geomorphological Responses of Tidal Flats to Extreme Climate Events
The fate of tidal flats under global climate change is closely tied to ecosystem services and socio-economic development. Nonetheless, there is still a limited understanding of how tidal flats respond to the increasingly frequent and intense extreme weather events. In this study, we conducted a comprehensive hydrodynamic and geomorphological field survey on the Lingang tidal flat in Shanghai during Typhoon In-fa (No. 2106), which allowed us to explore the mechanisms of tidal flat evolution under typhoon and propose insights for sustainable coastal management. Spatially, the vegetation shadow area showed notable sediment deposition, while the windward side of the vegetated zone experienced considerable vegetation loss. Undeveloped channels and depressions acted as sediment sinks, with wider and shallower channels erased by typhoon. Temporally, the differences in tidal flows during the typhoon were closely correlated with changes in wind direction and speed across different typhoon phases. Sediment transport rates during the typhoon were nearly an order of magnitude higher than under calm weather. Based on conceptual model of hydrodynamic and geomorphological processes during typhoons and previous research, we recommend (1) seasonal harvesting of salt marsh vegetation to enhance ecological sustainability while maintaining its wave attenuation function, and (2) spatial planning of artificial salt marsh zones with due consideration of local hydrodynamic patterns to limit vegetation expansion and migration, which could increase maintenance costs. Our findings provide new insights into how tidal flats respond to extreme events and underscore the importance of understanding these geomorphic responses in sustainable coastal management.
(Journal of Hydrology. vol. 656, n° 0022-1694, pp. 133024, 01/08/2025)
ECNU, LOCEAN, MNHN, IRD, INSU - CNRS, SU, CNRS, IPSL (FR_636), ENS-PSL, PSL, UVSQ, CEA, INSU - CNRS, X, IP Paris, CNES, SU, CNRS, UPCité, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS