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
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, UCL, UMR ISPA, Bordeaux Sciences Agro, INRAE, CAGS, MLR
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
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
Biological features for a minimum conservation reference size revision – case of Ruditapes philippinarum in Arcachon Bay (French Atlantic coast)
The Minimum Conservation Reference Size (MCRS) for marine resources ensure that individuals can mature and reproduce at least once before being caught. For management purposes, MCRS should be revised for specific populations in given areas. In Arcachon Bay (southwest France), fishers have repeatedly requested a review of the MCRS for R. philippinarum. In 2020, a joint recommendation, supported by France, was addressed to the European Commission suggesting a possible reduction in the MCRS of R. philippinarum from 35 mm to 32 mm for Arcachon Bay. This paper provides an overview of the biological features that need to be considered to support such a review, primarily focusing on sexual maturity, individual growth and natural mortality. The reproductive cycle and size at first maturity, estimated at 26.7 mm for the Bay, were found to be similar to other locations in France and in Portugal. The greatest length at which growth slowdown occurred ranges between 24.0 and 31.5 mm with few differences among sites and no significant differences within each site (at hypsometric levels). The natural mortality coefficients were high with 0.67 yr−1 and 0.51 yr−1 for juveniles and adults, respectively. Regarding productivity (resulting from growth and mortality processes) and all methods combined, the optimal balance between individual growth and natural mortality above 30 mm was found at a mean length of 32.2 mm for the intra-lagoon sites and at a mean length of 36.8 mm for the oceanic sites. Based on available information, reducing the MCRS to 32 mm would not threaten population viability. However, the European Commission has raised warning points, which are discussed in light of current regulations in Arcachon Bay.
(Estuarine, Coastal and Shelf Science. vol. 320, n° 0272-7714, pp. 109288, 01/08/2025)
LMAP, UPPA, CNRS, 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
Depth-Dependent isotope dynamics in karst reservoirs: Multi-Decadal monitoring insights from French caves
Understanding the stable oxygen isotope (δ18O/δD) compositions in rainwater and cave drip water within karst systems is essential for past climatic reconstructions all over the world. However, the relationship between cave drip water isotopes and upper karst infiltrated water and reservoirs remains unclear. Over twenty years, we monitored eight caves in France, from North to South: Arcy-sur-Cure, Villars, Cussac, Pech-Merle, Chauvet, Orgnac, Niaux, and Clamouse, collecting 3,000 dripping water samples from 32 drip points to measure δ18O and δD isotopes. As already observed in many cave sites, the isotopic composition of drip waters shows temporal stability with a Coefficient of Variation (CV) below 7 %, suggesting effective rainfall mixing during infiltration period. However, putting all these data on cave vertical cross sections, we observed subtle decreasing gradients in the averaged dripping δ18O values. For the first time in a multi-cave study, a clear logarithmic decrease of δ18O and δD with depth is found. Deeper sites show more negative isotopic values, especially in shallower zones (<50 m). In order to better understand these gradients, we used the hydrologic KarstFor model which revealed the importance of overflow mechanisms and of evapotranspiration (ETP) in driving this depth-dependent isotopic effect. These findings emphasize the significance of incorporating depth-dependent reservoir dynamics when analyzing isotopes in cave environments, advocating for a nuanced understanding of karst hydrological processes in affecting stalagmite δ18O.
(Journal of Hydrology. vol. 656, n° 0022-1694, pp. 133028, 01/08/2025)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, LSCE, UVSQ, INSU - CNRS, CNRS, DRF (CEA), CEA, GLACCIOS, LSCE, UVSQ, INSU - CNRS, CNRS, DRF (CEA), CEA, GEOTRAC, LSCE, UVSQ, INSU - CNRS, CNRS, DRF (CEA), CEA
In situ analysis of single secondary organic aerosol from the ozonolysis of α-pinene using laser trapping and Raman spectroscopy
To form secondary organic aerosols (SOAs) from volatile α-pinene via ozone oxidation reactions, the generation of low-vapor pressure compounds capable of acting as condensation nuclei is essential. Both laboratory and field studies have identified low-volatile dimers as key components in SOA formation. Although mechanisms involving stabilized Criegee intermediates and peroxy radicals have been proposed for dimer formation in the gas phase, the detailed processes of SOA formation remain widely debated due to the high diversity of reaction products and the inherent complexity of their formation mechanisms. To clarify certain steps of the SOA formation mechanism from ozone-initiated oxidation of α-pinene, a laser trapping technique coupled with Raman spectroscopy was employed for in situ analysis of individual SOA particles. In this study, single micrometer-sized α-pinene SOA particles were successfully trapped in air. To our knowledge, this represents the first successful application of laser trapping of α-pinene SOA particles directly in air. An intense Raman peak observed at about 852 cm−1 was attributed to the O–O stretching vibration of peroxides. This finding provides direct evidence for the presence of peroxy functional groups in the dimers, likely formed via stabilized Criegee intermediates. These results demonstrate the capability of laser trapping combined with Raman spectroscopy to detect specific molecular features, such as peroxide bonds, within α-pinene-derived SOAs in air.
(Chemosphere. vol. 385, n° 0045-6535, pp. 144581, 29/07/2025)
HU, ISM, UB, INC-CNRS, CNRS, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS