Orbital-scale competition of biogenic carbonate and opal production and its implication on carbon cycle at Del Caño Rise in the Indian sector of the Southern Ocean
Geochemical properties measured in core MD19-3575CQ, collected from the Del Ca˜no Rise within the Subantarctic Zone in the Indian sector of the Southern Ocean, provide evidence of orbital-scale changes over eccentricity, obliquity, and precession cycles in phytoplankton productivity and its influence on the organic matter burial over the last 235 kyr. CaCO3 and biogenic opal contents varied oppositely with high CaCO3 and low biogenic opal contents during the interglacial periods and vice versa during the glacial periods. During the glacial periods, the biogenic opal production by diatoms increased as a result of more silica supply when the Subantarctic Front shifted northward across the Del Ca˜no Rise. In addition, Fe-bearing dust and remobilized sediments likely enhanced diatom productivity. In contrast, biogenic carbonate production by coccolithophores and foraminifera was reduced during the glacial periods because of cold ocean temperature and competition for nutrients between coccolithophores and diatoms. More organic carbon was buried at the core site during the glacial periods than during the interglacial periods, probably in relation to a greater export efficiency by diatoms relative to coccolithophores as well as a better preservation of the organic matter when the Circumpolar Deep Water was less ventilated during the glacial periods.
(Palaeogeography, Palaeoclimatology, Palaeoecology. vol. 679, n° 0031-0182, pp. 113290, 15/09/2025)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS
Lateglacial and Holocene mountain glacier fluctuations near Cape Farewell South Greenland inferred from 10 Be moraine dating
ABSTRACT We report 43 new 10 Be exposure ages and six 26 Al/ 10 Be measurements from replicates from a small piedmont mountain glacier located at Cape Farewell (south Greenland) and temperature anomalies estimated from equilibrium‐line altitude (ELA) changes derived from 3D glacier reconstruction carried out using the ‘GlaRe’ toolbox. Both ELA‐derived temperature estimations and climate conditions documented from the transient simulation TraCE‐21ka help us to explore the causes of glacier changes during the investigated period. Exposure ages span from the Oldest Dryas to the Late Holocene, revealing that the GrIS retreat in this valley permitted the individualisation or formation of a mountain glacier early in the Lateglacial. Interestingly, four of the six 26 Al/ 10 Be ratios come from samples located on the oldest moraines do not reveal inheritance. The two other ratios suggest inheritance up to 6 ka. The oldest moraine combining a frontal and a lateral remain is dated to 18.4 ± 0.8 ka. Between 18 ka and ~14.7 ka, the glacier experienced a significant retreat interrupted by at least three minor advances or stillstands. We did not find any moraine formed either during the Younger Dryas, or during the Early and the Mid Holocene. The largest Holocene glacier advance occurred ~4.4 ka. Two other younger moraines were formed at ~2.9 ka and probably during the LIA. Temperatures of 3.3°C and 1.7°C colder than today may explain the glacier extent during the Lateglacial and the Holocene, respectively. Complementary dry regional climate conditions estimated from TraCE‐21ka simulations during the Early Holocene may explain why the glacier was smaller than during the Late Holocene.
(Journal of Quaternary Science, n° 0267-8179, 14/09/2025)
CEREGE, IRD, AMU, CdF (institution), INSU - CNRS, CNRS, INRAE, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS
Bridging the gap: oxygen and nutrient budgets in the Loire estuary using a benthic-pelagic box model
In hypoxic estuaries, sediment feedback is clearly a key factor in nutrient and oxygen cycling, favouring nutrient enrichment and oxygen depletion in the water column. It is crucial to understand these mechanisms to implement effective management strategies for these coastal systems. In this study, a coupled benthic-pelagic box model was developed to assess the impact of sediment and water column processes on nutrient and dissolved oxygen stocks in a hypoxic estuary. The model integrates physical and biogeochemical processes, focusing on the sediment-water column interaction during two contrasting hydrological contexts sampled in 2021: a winter flood and a summer low discharge period. The model reproduces the main processes well, despite some discrepancies with the observed data due to the underlying assumptions, which are discussed. The winter flood caused substantial erosion of upstream sediments, resulting in a strong redox gradient and high sediment-water exchange. The short residence time of the water prevented solutes accumulation, minimising their influence on oxygen and nutrient stocks. In summer, under low flow conditions, benthic recycling to the water column is intensified, resulting in an increase in ammonium concentration of up to 91%, compared to 67% from pelagic processes. In contrast, phosphate release remains modest (around 4%), particularly from the sediments underneath the Turbidity Maximum Zone (TMZ), where benthic exchange is limited by the presence of an oxide-rich sediment layer that acts as a barrier. However, phosphate availability in summer is primarily driven by pelagic desorption from suspended particles, notably in the TMZ. The results clearly highlight a decoupling between nitrogen and phosphorus recycling, which is promoting nitrogen enrichment and potentially favouring harmful algal blooms and hypoxia. The proposed simplified modelling approach is a crucial step in identifying the estuarine processes controlling oxygen and nutrient dynamics and can be easily applied to any estuary.
(Science of the Total Environment. vol. 1000, n° 0048-9697, pp. 180446, 11/09/2025)
LPG, UM, UA, INSU - CNRS, CNRS, Nantes univ - UFR ST, Nantes Univ, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, IPREM, UPPA, INC-CNRS, CNRS, CHROME, UNIMES, LERMPL, COAST, IFREMER
Exploring Future Shoreline and Nearshore Evolution Under Sea-Level Rise Projections: Application of the LX-ST Model to Lacanau
This study applies the reduced-complexity model LX-ST to simulate the future evolution of the shoreline and nearshore morphology of Lacanau, a wave-dominated, erosion-prone coastal site in southwest France. By coupling longshore transport with shoreface translation processes, the model evaluates changes under various IPCC sea-level rise scenarios through 2100. Results highlight significant spatial variability in erosion, with pronounced downdrift retreat near coastal defenses. The findings demonstrate the utility of LX-ST for informing long-term coastal adaptation strategies.
(01/09/2025)
BRGM, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS
A small increase in temperature could rapidly expand the latitudinal range and pathogenicity of the marine trematode parasite Curtuteria arguinae
The phenology and transmission dynamics of the marine trematode Curtuteria arguinae were investigated, a parasite whose recently elucidated life cycle involves oystercatchers (Haematopus ostralegus), needle snails (Bittium reticulatum), and edible cockles (Cerastoderma edule). To assess the influence of temperature and light on cercarial emergence, infected B. reticulatum were exposed to temperatures ranging from 15 °C to 27 °C under both light and dark conditions. Cercarial emergence peaked under warm and illuminated conditions, showing strong temperature dependence, and, to a lesser extent, light dependence. Emergence occurred significantly at temperatures ≥21 °C, with median emergence rates of 12–47 cercariae.day−1, and the positive influence of light was overruled at higher temperatures. A 22-year dataset from Arcachon Bay (France) was also analyzed to determine the timing of first infections in cockles relative to sea and air temperatures, as well as cockle shell size, across ten cohorts. First infections of cockles were consistently observed in late summer, with a mean sea temperature of 20.8 °C, placing cercarial transmission once a thermal threshold is reached. This thermal dependency explains the parasite's current southern distribution. With climate warming, its range is likely to expand northward along the northeastern Atlantic coast, in areas where all hosts are already present. Expansion may also be supported by the northward extension of B. reticulatum. In areas where the parasite is already established, rising temperatures may enhance cercarial output and infection intensity, increasing pathogenic effects on both intermediate hosts and posing a growing threat to ecosystem functioning and cockle fisheries.
(Estuarine, Coastal and Shelf Science. vol. 326, n° 0272-7714, pp. 109541, 01/09/2025)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, OASU, UB, INSU - CNRS, ULR, CNRS, INRAE, SU, SBR, SU, CNRS, ECOMAP, AD2M, SU, CNRS, SBR, SU, CNRS
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