Radiolarian and Phaeodarian high-rank assemblage change through time in the Scotia Sea: A paleo-genomics approach (IODP Exp. 382)
Radiolaria and Phaeodaria are single-celled eukaryotic zooplankton that inhabit diverse marine environments. While the sedimentary fossil record reveals their ancient origins and morphological diversity, recent advancements in metagenomics and sedimentary ancient DNA (sedaDNA) techniques have highlighted the significant contributions of rarely preserved taxa (e.g., those that are only lightly silicified or soft-bodied) to marine biodiversity and the carbon cycle. Using a paleo-genomic approach, we produced a sedaDNA-based time series of the Radiolarian and Phaeodarian community from the Scotia Sea covering the last 500 kyr. We compared the use of two reference databases, one Radiolarian-and Phaeodarian-specific (RPD) and one more comprehensive eukaryote database (PR 2 ), to assess the validity of a small, taxa-specific database. We determined that the two databases produced comparable results, showing that the overall assemblage changes at the glacial-interglacial scale were similar. At the Class level, Radiolarian and Phaeodarian assemblages appear to have experienced compositional changes during termination events and warm Interglacial periods. This study produced the first Radiolarian-and Phaeodarian-specific reference database. We showed that the Class-level changes that occurred over the last 500 kyr were associated with glacial-interglacial (G-I) cycles, and no permanent shifts away from the natural variation associated with the G-I cycles were found.
(Marine Micropaleontology. vol. 200, n° 0377-8398, pp. 102500, 01/09/2025)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, UTAS, UTAS, LOG, INSU - CNRS, ULCO, CNRS, IRD [Ile-de-France], ULCO, UNIBE, ANU
Effect of H2-rich water percolation in porous limestone core: simulation of a leakage in a shallow carbonate freshwater aquifer
Underground Hydrogen Storage (UHS) builds on existing underground storage technologies used for town gas and CO 2 and involves storing hydrogen in various geological structures underground. However, some questions remain regarding this storage method, particularly concerning safety: an untight UHS site could lead to a hydrogen leak to the surface, where the gas could be intercepted by an overlying freshwater aquifer. H 2 would dissolve in the water, and this fluid could react with the surrounding rock. This study investigates the effects of hydrogen-saturated water flow through carbonate rock cores to simulate such an H 2 leakage in a near subsurface freshwater aquifer. Core flooding experiments were conducted on two carbonate facies, a grainstone and a boundstone, using a Hassler cell. Petrophysical and geochemical changes were monitored throughout the experiments. Results indicate that hydrogen remains largely non-reactive in its dissolved form when in contact with calcite. However, the water flow itself induces mechanical pore clogging, leading to significant permeability reduction without affecting the total porosity. A slight calcite precipitation within the pore network is also suggested. Additionally, a loss of dissolved H 2 is observed, likely due to fluid degassing rather than chemical consumption. These findings highlight the importance of considering mechanical processes in UHS scenarios and emphasize the need for further research on the long-term behavior of hydrogen saturated water in carbonate freshwater aquifers.
(International Journal of Hydrogen Energy. vol. 171, n° 0360-3199, 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
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
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
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