Role of manganese oxides and oxyhydroxides in phosphate sequestration in natural aquatic environments
Excessive inputs of phosphorus (P) to aquatic environments can lead to eutrophication. Adsorption of phosphate on Fe oxides is one of the main process that can limit P availability. Oxidized forms of Mn have also been suggested to play a role in P trapping. However, although a considerable number of studies have shown the relationships between the geochemistry of Fe and that of phosphates, few studies have attempted to show the direct links between Mn and P. In the present study, we studied the adsorption of phosphate on synthetized Mn(III) and Mn(IV) oxides placed under natural conditions. The aim was to compare the role of Fe and Mn oxides in phosphate adsorption. Two muddy sediments were collected in a river bed at the edge of a large agricultural area. A sandy sediment was collected downstream. A muddy and a sandy sample were taken in a coastal environment. The experiments on phosphate adsorption by sediment and Mn oxides were carried out in slurries containing in situ waters spiked with 10 μM phosphate. Control experiments without Mn-oxide addition showed that the natural sediments tested still had the capacity to adsorb phosphate, in particular due to the presence of reactive Fe(III) oxides, extractable by an ascorbate solution. The addition of Mn(III) and Mn(IV) oxides in much larger quantities than the initial quantity of Fe oxides had little impact on the rate of phosphate adsorption. For both Mn(III) and Mn(IV) oxides, the Mn/P ratio between added particulate Mn and adsorbed P was very high, with values between 260 and 1000. The Fe/P ratio of the iron oxides contained in the slurries was between 6 and 20. On average, the P adsorption capacity of the Fe oxides was 50 times greater than that of the Mn oxides. Manganese oxides are generally less abundant than iron oxides in natural environments. Mn oxides therefore play a minor role in P sequestration compared with Fe oxides. Even if there are environments where Mn oxides can concentrate, the reduction of Mn oxides and subsequent liberation of adsorbed P does not represent a major risk for eutrophication of aquatic ecosystems.
(Chemical Geology. vol. 662, n° 0009-2541, pp. 122231, 01/09/2024)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS
Biogeochemical cycling of manganese and iron in a macrotidal and hyperturbid estuary subject to flow-driven sedimentation
The study of manganese (Mn) and iron (Fe) cycling in early diagenetic processes in estuaries is crucial for understanding the functioning of these vital ecosystems and predicting their responses to environmental change. The present study investigates the dynamic interplay of Mn and Fe in early diagenetic processes at highly contrasted hydrosedimentary conditions in the Loire estuary, which is very rare and allows a comprehensive framework to understand diagenetic processes in a very dynamic environment. One campaign took place in the Brillantes intertidal mudflat in March 2015 (PV1), while 3 others took place in a muddy riverbed along the navigation channel off the city of Paimboeuf during a decennial flood in February (RR1–4), under moderate discharge in June (RRK-4) and low in August 2021 (RR2–4). The monitored riverbed station was upstream, under and downstream the maximum turbidity zone, respectively. By combining sequential extraction techniques for Mn and Fe in solid phases and pore-water analysis, the study provides insights into the behaviour of these elements in sedimentary environments and reveals their speciation and association with specific mineral phases and forms during different diagenesis stages. The remobilization of Mn and Fe in the surface sediments of the Brillantes mudflat (PV1) allows iron sulphide formation within the upper 50 cm of the sediment column (above the sulphate penetration depth). The deeper layers show other authigenic phases formation, such as the probable precipitation of vivianite below the sulphate depletion depth and progressive precipitation of carbonate at depth, leading to definitive burial and accumulation. At the muddy riverbed, following the exceptional flood in February 2021 (RR1–4), significant sediment erosion occurred unveiling to the water column old and reduced sediments. Sharp pore-water gradients for dissolved Mn, Fe and sulphate indicated the sudden exposure of the old 7Be-free and anoxic sediment to low-salinity, well‑oxygenated water. Despite its dark colour, this sediment showed no authigenic FeS/FeS2 phases. Four months later, changes in the estuarine environment (low river discharge) and the presence of a maximum turbidity zone (TMZ) led to a new deposition of a sediment layer (RRK-4) triggering transient diagenetic reactions. The freshly deposited sediment layer developed important recycling of dissolved Mn, Fe and sulphate above the precedent sediment water interface (SWI) generating a double peak, accompanied by consistently low concentrations of solid Mn and Fe phases specially FeS/FeS2 and Mn bound to FeS/FeS2 compared to PV1. Six months after the flood event, in August (RR2–4), the discernible attenuation of dissolved Mn and Fe peaks and sulphate concentration, indicated a gradual recovery of characteristic sediment profiles with the well-known redox layer succession. Overall, despite important sulphate reduction within sediments from both the river and its adjacent mudflats, pyritization is not a major process for Mn and Fe burial. The intense hydrodynamics of the mid estuary prevents thermodynamical equilibrium between pore-water chemistry and solid phases not allowing pyrite formation while in the calmer conditions of intertidal mudflats, pyrite accumulates in intermediate depths but carbonates and phosphates seem to be the preferential phases of burial probably related to methane production and phosphate availability.
(Chemical Geology. vol. 661, n° 0009-2541, pp. 122182, 01/09/2024)
LPG, UM, UA, INSU - CNRS, CNRS, Nantes univ - UFR ST, Nantes Univ, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, ISTOM, IPREM, UPPA, INC-CNRS, CNRS, CHROME, UNIMES
ZooCAMNet : plankton images captured with the ZooCAM
Plankton was sampled with a Continuous Underway Fish Egg Sampler (CUFES, 315µm mesh size) at 4 m below the surface, and a WP2 net (200µm mesh size) from 100m to the surface, or 5 m above the sea floor to the surface when the depth was < 100 m, in the Bay of Biscay. The full images were processed with the ZooCAM software and the embedded Matrox Imaging Library (Colas et a., 2018) which generated regions of interest (ROIs) around each individual object and a set of features measured on the object. The same objects were re-processed to compute features with the scikit-image library http://scikit-image.org. The 1, 286, 590 resulting objects were sorted by a limited number of operators, following a common taxonomic guide, into 93 taxa, using the web application EcoTaxa http://ecotaxa.obs-vlfr.fr. For the purpose of training machine learning classifiers, the images in each class were split into training, validation, and test sets, with proportions 70%, 15% and 15%. The archive contains : taxa.csv.gz Table of the classification of each object in the dataset, with columns : objid : unique object identifier in EcoTaxa (integer number). taxon_level1 : taxonomic name corresponding to the level 1 classification lineage_level1 : taxonomic lineage corresponding to the level 1 classification taxon_level2 : name of the taxon corresponding to the level 2 classification plankton : if the object is a plankton or not (boolean) set : class of the image corresponding to the taxon (train : training, val : validation, or test) img_path : local path of the image corresponding to the taxon (of level 1), named according to the object id features_native.csv.gz Table of morphological features computed by ZooCAM. All features are computed on the object only, not the background. All area/length measures are in pixels. All grey levels are in encoded in 8 bits (0=black, 255=white). With columns : area : object's surface area_exc : object surface excluding white pixels area_based_diameter : object's Area Based Diameter: 2 * (object_area/pi)^(1/2) meangreyobjet : mean image grey level modegreyobjet : modal object grey level sigmagrey : object grey level standard deviation mingrey : minimum object grey level maxgrey : maximum object grey level sumgrey : object grey level integrated density: object_mean*object_area breadth : breadth of the object along the best fitting ellipsoid minor axis length : breadth of the object along the best fitting ellipsoid majorr axis elongation : elongation index: object_length/object_breadth perim : object's perimeter minferetdiam : minimum object's feret diameter maxferetdiam : maximum object's feret diameter meanferetdiam : average object's feret diameter feretelongation : elongation index: object_maxferetdiam/object_minferetdiam compactness : Isoperimetric quotient: the ration of the object's area to the area of a circle having the same perimeter intercept0, intercept45 , intercept90, intercept135 : the number of times that a transition from background to foreground occurs a the angle 0ø, 45ø, 90ø and 135ø for the entire object convexhullarea : area of the convex hull of the object convexhullfillratio : ratio object_area/convexhullarea convexperimeter : perimeter of the convex hull of the object n_number_of_runs : number of horizontal strings of consecutive foreground pixels in the object n_chained_pixels : number of chained pixels in the object n_convex_hull_points : number of summits of the object's convex hull polygon n_number_of_holes : number of holes (as closed white pixel area) in the object roughness : measure of small scale variations of amplitude in the object's grey levels rectangularity : ratio of the object's area over its best bounding rectangle's area skewness : skewness of the object's grey level distribution kurtosis : kurtosis of the object's grey level distribution fractal_box : fractal dimension of the object's perimeter hist25, hist50, hist75 : grey level value at quantile 0.25, 0.5 and 0.75 of the object's grey levels normalized cumulative histogram valhist25, valhist50, valhist75 : sum of grey levels at quantile 0.25, 0.5 and 0.75 of the object's grey levels normalized cumulative histogram nobj25, nobj50, nobj75 : number of objects after thresholding at the object_valhist25, object_valhist50 and object_valhist75 grey level symetrieh :index of horizontal symmetry symetriev : index of vertical symmetry skelarea : area of the object skeleton thick_r : maximum object's thickness/mean object's thickness cdist : distance between the mass and the grey level object's centroids features_skimage.csv.gz Table of morphological features recomputed with skimage.measure.regionprops on the ROIs produced by ZooCAM. See http://scikit-image.org/docs/dev/api/skimage.measure.html#skimage.measure.regionprops for documentation. inventory.tsv Tree view of the taxonomy and number of images in each taxon, displayed as text. With columns : lineage_level1 : taxonomic lineage corresponding to the level 1 classification taxon_level1 : name of the taxon corresponding to the level 1 classification n : number of objects in each taxon group map.png Map of the sampling locations, to give an idea of the diversity sampled in this dataset. imgs Directory containing images of each object, named according to the object id objid and sorted in subdirectories according to their taxon.
(SEANOE = Sea scientific open data publication, n° 2491-1836, 01/09/2024)
DECOD, IFREMER, INRAE, Institut Agro, Institut Agro, ENS Paris Saclay, DYNECO, IFREMER, LIENSs, INSU - CNRS, ULR, CNRS, RDT, IFREMER, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, IFREMER, LOV, INSU - CNRS, SU, CNRS, IMEV, INSU - CNRS, SU, CNRS
Neanderthal subsistence strategies within their hunting grounds at Teixoneres Cave (Spain) and Pié Lombard rock shelter (France)
(28/08/2024)
ArScAn, UP1, UP8, UPN, MCC, CNRS, IPHES-CERCA, URV, LAMPEA, AMU, CNRS, MC, EPHE, PSL, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, UNIROMA, GReNES, CEPAM, UNS, CNRS, UniCA, CEPAM, UNS, CNRS, UniCA, UniCA, IIIPC, UC / UniCan, ICArEHB, PACEA, UB, CNRS, EHESS, ICREA
Seasonal Variations and Controls on Triple Oxygen and Hydrogen Isotopes in Precipitation—A Case Study From Monitoring in Southwest China
AbstractPrecipitation δ18O has offered valuable insights into the evolution of the Asian monsoon. Recent researches focusing on precipitation Δ′17O has enhanced our understanding by offering new perspectives beyond those of δ18O, revealing insights into vapor sources and continental recycling. Nevertheless, there remains a lack of interannual triple oxygen isotope data, particularly in the Asian monsoon region. In this study, we analyzed the triple oxygen isotopes and hydrogen isotopes in monthly precipitation samples collected from Chongqing in Southwest China between 2019 and 2022 A.D. Seasonal variations in δD, δ18O, δ17O, and d‐excess values were observed, with lower values during the rainy season and higher values during the dry season, highlighting the impact of changes in moisture sources and local meteorological conditions on seasonal shifts in δD, δ18O, and δ17O. While, mean Δ′17O values were higher in rainy season and lower in dry season. Notably, during rainy season, there is a negative correlation between monthly Δ′17O values and the RH of the vapor source area, as well as a positive correlation with d‐excess. Recalculated Δ′17O values based on RH of oceanic moisture source, are higher than the measured values for this period, indicating the contribution of terrigenous moisture to precipitation in SW China. Precipitation Δ′17O values provide a more precise reflection of changes in moisture source, continental recycling, and evapotranspiration processes that drive water cycling compared Integrating modeling works in future will facilitate the use of precipitation Δ′17O values to quantify the impact of different moisture source on precipitation.
(Journal of Geophysical Research: Atmospheres. vol. 129, n° 2169-897X, 26/08/2024)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS
Three new species of Capitellidae (Annelida) from France
Sampling in shallow sediments of Bay of Biscay up to 70 m has yielded three undescribed capitellids. Mediomastus biscayensis sp. nov. is distinct from its congeners by a combination of characters that includes the presence of bilimbate thoracic capillaries, thoracic and abdominal hooks similar in shape and length and distinct Methyl Green staining pattern with chaetigers 5–9 having sparse green speckles and chaetigers 10–11 with dense green speckles. Notomastus hutchingsae sp. nov. is a very distinct Notomastus species because of the presence of two achaetous segments in the thoracic region and the shape of the thoracic segments with a constriction after segment 4, and after segment 6 segments becoming distinctly separated and bi-annulated. The newly proposed Peresiella ellae sp. nov. is most similar to its Atlantic congener P. spathulata Ewing, 1984 by the absence of eyespots and presence of modified spatulate chaetae on chaetiger 4–11, but differing by the presence of two peristomial annuli, shape of thoracic and abdominal segments, number of spatulate chaetae per tori and dentition of hooded hooks. All species are fully described, illustrated and commented on according to their closest congeners.
(Zootaxa. vol. 5496, n° 1175-5326, pp. 273-289, 19/08/2024)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS
Contribution of soil particles and preferential flow to the leaching of PFAS from an AFFF-contaminated soil: simulated rainfall series on undisturbed soil cores
Aqueous fire-fighting foams (AFFF) contain a high variety of per- and polyfluoroalkyl substances (PFAS). The soil at firefighting training sites is therefore highly contaminated with PFAS and acts as a source of contamination for groundwater and the soil biota. Previous studies investigating the leaching of PFAS from contaminated soils have considered model experimental situations, ranging from batch experiments to repacked soil columns. In essence, these experiments disregard processes that are known to contribute to the transport of contaminants in real soil: preferential, gravity-driven flow in soil macropores of biological or physical origin, and colloid-facilitated transport, a mechanism relevant for contaminants having a strong affinity for soil constituents. Actually, the possible transport of PFAS adsorbed onto mobile colloidal soil particles has been overlooked until recently, when 17% of PFOA leached from a previously spiked repacked soil column was found to be adsorbed onto colloidal soil particles. In our study, we further explored the contribution of colloidal particles to the mobility of PFAS in soils during a series of rainfalls simulated on four undisturbed soil columns excavated from an abandoned firefighter training site. As both rainfall intensity and the duration of the dry period before a rain have been found to affect the mobilization of colloidal soil particles, we studied the impact of these factors on PFAS leaching. The four cores had contrasting hydrodynamic behavior, ranging from matrix flow to preferential macropore flow. Although their mobility in soil is expected to be low, long chain PFAS were present in the leachates, both in the liquid phase and adsorbed to soil particles. Surprisingly, colloid-mediated leaching of PFAS was more important in cores where water transfer was dominated by matrix-flow. Regardless of the hydrodynamic behavior, the experimental results suggest that the leaching of PFAS molecules with C-chain length ≤ 8 was controlled by diffusion. Overall, these results show that quantifying PFAS concentration in both the liquid and the colloidal-phase —in the leachates of transport experiments or in groundwater— will help understand the contribution of soil particles to the transport of PFAS in the vadose zone.
(18/08/2024)
GERS-LEE, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, EMMAH, AU, INRAE, IRSTV, BRGM, UA, ULR, Cerema, CNRS, INSIS - CNRS, IMT Atlantique, IMT, Nantes Univ, Nantes Univ - ECN, Nantes Univ, Nantes Univ - ENSA Nantes, Nantes Univ, Institut Agro
Global assessment of aquatic Isoëtes species ecology
Isoëtes are iconic but understudied wetland plants, despite having suffered severe losses globally mainly because of alterations in their habitats. We therefore provide the first global ecological assessment of aquatic Isoëtes to identify their environmental requirements and to evaluate if taxonomically related species differ in their ecology. The assessment resulted in an extensive new database on aquatic Isoëtes, ecological niche analyses, and descriptive species accounts. We compiled a global database that includes all known environmental data collected from 1935 to 2023 regarding aquatic Isoëtes. We then evaluated the environmental drivers of 16 species using 2,179 global records. Additionally, we used hypervolume analysis to quantify the ecological niches of the two species with the greatest number of records, finding significant differences and evidence that Isoëtes echinospora occupies a wider ecological niche than Isoëtes lacustris. Fifty-nine species (30% of the c. 200 Isoëtes species known today) were categorised as aquatic and were mainly reported in the Americas and northern Europe. About 38% of the aquatic species are threatened with extinction or are endemic to a small region, according to the International Union for Conservation of Nature's.
(Freshwater Biology. vol. 69, n° 0046-5070, pp. 1420 - 1437, 17/08/2024)
UNIROMA, UNIPR, ROMA TRE, CEAB, CSIC, UR EABX, INRAE, ECLA, USMB [Université de Savoie] [Université de Chambéry], INRAE, OFB, RAS, ITV, BIOLOGY CENTRE CAS, BIOLOGY CENTRE CAS, CAS, IBER, UW-La Crosse, UNITUS, NIVA, UCPH, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, USC, IUCN, RSHU
Coral Sr/Ca-SST reconstruction from Fiji extending to ~1370 CE reveals insights into the Interdecadal Pacific Oscillation
The southwestern tropical Pacific is a key center for the Interdecadal Pacific Oscillation (IPO), which regulates global climate. This study introduces a groundbreaking 627-year coral Sr/Ca sea surface temperature reconstruction from Fiji, representing the IPO’s southwestern pole. Merging this record with other Fiji and central tropical Pacific records, we reconstruct the SST gradient between the southwestern and central Pacific (SWCP), providing a reliable proxy for IPO variability from 1370 to 1997. This reconstruction reveals distinct centennial-scale temperature trends and insights into Pacific-wide climate impacts and teleconnections. Notably, the 20th century conditions, marked by simultaneous basin-scale warming and weak tropical Pacific zonal-meridional gradients, deviate from trends observed during the past six centuries. Combined with model simulations, our findings reveal that a weak SWCP gradient most markedly affects IPO-related rainfall patterns in the equatorial Pacific. Persistent synchronous western and central Pacific warming rates could lead to further drying climate across the Coral Sea region, adversely affecting Pacific Island nations.
(Science Advances, n° 2375-2548, 14/08/2024)
UNAM, UNSW, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, UABC
Water-accommodated fractions of heavy and light oils impact DNA integrity, embryonic development, and immune system of Japanese medaka at early life stages
Polycyclic aromatic hydrocarbons (PAHs) are ubiquitous contaminants generally found in complex mixtures. PAHs are known to cause pleiotropic effects on living organisms, including developmental defects, mutagenicity, carcinogenicity and immunotoxicity, and endocrine disruptions. The main goal of this study is to evaluate the toxicity of water-accommodated fractions (WAFs) of oils in two life stages of the Japanese medaka, larvae and juveniles. The deleterious effects of an acute exposure of 48 h to two WAFs from Arabian light crude oil (LO) and refined oil from Erika (HO) were analyzed in both stages. Relevant endpoints, including ethoxy resorufin-O-deethylase (EROD) activity, DNA damage (Comet assay), photomotor response, and sensitivity to nervous necrosis virus (NNV) infection, were investigated. Larvae exposed to both oil WAFs displayed a significant induction of EROD activity, DNA damage, and developmental anomalies, but no behavioral changes. Deleterious effects were significantly increased following exposure to 1 and 10 μg/L of LO WAFs and 10 μg/L of HO WAFs. Larval infection to NNV induced fish mortality and sharply reduced reaction to light stimulation. Co-exposure to WAFs and NNV increased the mortality rate, suggesting an impact of WAFs on fish defense capacities. WAF toxicity on juveniles was only observed following the NNV challenge, with a higher sensitivity to HO WAFs than to LO WAFs. This study highlighted that environmentally realistic exposure to oil WAFs containing different compositions and concentrations of oil generated high adverse effects, especially in the larval stage. This kind of multi-marker approach is particularly relevant to characterize the toxicity fingerprint of environmental mixtures of hydrocarbons and PAHs. © The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature 2024.
(Environmental Science and Pollution Research. vol. 31, n° 0944-1344, pp. 50916-50928, 06/08/2024)
ANSES, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, VIMEP, ANSES, Cedre