Artemisia sieberi shrubs have contrasting specific effects on understory species in Iranian steppes
Questions: (a) Are there contrasting short- and long-term effects of shrubs on understorey species that may balance at the community level? (b) Are these effects due to the responses of different understorey species groups? (c) Are these effects contributing to community composition?. Location: An Artemisia steppe community in Golestan National Park (North-East Iran). Methods: We used both the removal and observational methods to separate short- from long-term effects of Artemisia sieberi Besser on the cover of 18 subordinate species and the relative interaction index (RII) to calculate species’ responses. We conducted a principal components analysis (PCA) on species RII and grouped species with a cluster analysis depending on their responses to the shrubs. Another PCA on understorey composition plots was conducted to assess the consequences of shrub effects for community composition. Results: Artemisia had negative short-term and positive long-term community-level effects that balanced each other to produce neutral net effects. Short- and long-term effects were due to the responses of different species groups, dominantly annuals and perennial grasses, respectively. Although balancing at the community level, the different shrub effects significantly contributed to explain community composition. Conclusions: Our study highlights that a dominant foundation shrub may have contrasting short- and long-term effects on different groups of understorey species that contribute to explain community composition, although balancing at the community level. © 2021 International Association for Vegetation Science
(Journal of Vegetation Science. vol. 32, n° 1100-9233, 31/07/2021)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS
Cockle as Second Intermediate Host of Trematode Parasites: Consequences for Sediment Bioturbation and Nutrient Fluxes across the Benthic Interface
Trematode parasites are distributed worldwide and can severely impact host populations. However, their influence on ecosystem functioning through the alteration of host engineering behaviours remains largely unexplored. This study focuses on a common host parasite system in marine coastal environments, i.e., the trematode Himasthla elongata, infecting the edible cockle Cerastoderma edule as second intermediate host. A laboratory experiment was conducted to investigate the indirect effects of metacercarial infection on sediment bioturbation and biogeochemical fluxes at the sediment water interface. Our results revealed that, despite high parasite intensity, the sediment reworking and bioirrigation rates, as well as nutrient fluxes, were not impacted. This finding was unexpected since previous studies showed that metacercarial infection impairs the physiological condition of cockles and induces a mechanical obstruction of their feet, thus altering their burrowing capacity. There are several explanations for such contrasting results. Firstly, the alteration of cockle behavior could arise over a longer time period following parasite infection. Secondly, the modulation of cockle bioturbation by parasites could be more pronounced in older specimens burying deeper. Thirdly, the intensity of the deleterious impacts of metacercariae could strongly vary across parasite species. Lastly, metacercarial infection alters cockle fitness through an interaction with other biotic and abiotic environmental stressors.
(Journal of Marine Science and Engineering. vol. 9, n° 2077-1312, pp. 749, 06/07/2021)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS
Influence of transient processes on organic carbon remineralization pathways and rates in the West Gironde Mud Patch (Bay of Biscay, Northeast Atlantic)
At the global scale, it is estimated that 50 to 80% of continental organic matter inputs to the ocean are remineralized on continental margins. Characterizing their functioning is therefore essential to improve the understanding of global biogeochemical cycles in a changing ocean. The West Gironde Mud Patch is a mid-shelf silty clay area located in the Bay of Biscay (Northeast Atlantic) where sedimentary processes are influenced by Gironde fluvial inputs, hydrodynamics (waves, tidal currents), bottom trawling and bioturbation. All these processes are likely to modify sedimentary organic carbon remineralization pathways and rates. To determine the intensity of these degradation processes and factors controlling their spatiotemporal variabilities, profiles of porosity, grain-size, particulate (reactive Fe and Mn, organic carbon (OC), pigments) and dissolved (O2, NO3-, NH4+, Fe(II), Mn(II), SO42-) chemical species were measured at five stations along a cross-shelf transect between 2016 and 2018 (four JERICObent cruises, French Oceanographic Fleet). Our results indicate that the main organic carbon degradation pathways are aerobic respiration and sulfate reduction. Despite a high intra-station variability (from 14 to 75%), aerobic respiration tends to be higher at the most distal site (up to 76 mgOC m-2 d-1). On the contrary, the intensity of sulfate reduction decreases from 20 to 3 mgOC m-2 d-1 seaward. The highest sulfate reduction rate, assessed at the shallowest site, is related to a decimeter-thick transient sandy layer overlying relic muddy sediments within which sulfate is the main available oxidant. At the other sites, changes in remineralization intensity appear associated with the quantity and quality of particulate organic matter as well as with biomixing activities. At seaward sites, depth profiles of reactive Fe and Mn along with the large number of burrows suggest that bioirrigation activities could cause transient redox oscillations, thus promoting suboxic degradation processes, which are therefore likely underestimated. In April 2018, an increase of total remineralization rates (i.e. all degradation pathways confounded) from 40 to 160% according to sites was triggered by fresh organic matter inputs related to the spring bloom. We attribute this stimulation of remineralization processes in part to priming effects.
(04/07/2021)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, CHROME, UNIMES, UFRJ
Early diagenetic processes in an eutrophic estuarine system: indices of sediment contribution to summer hypoxia of the Loire?
(04/07/2021)
LPG, UA, UN UFR ST, UN, INSU - CNRS, CNRS, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, CHROME, UNIMES
Development of global temperature and pH calibrations based on bacterial 3-hydroxy fatty acids in soils
Gram-negative bacteria produce specific membrane lipids, i.e. 3-hydroxy fatty acids with 10 to 18 C atoms. They have been recently proposed as temperature and pH proxies in terrestrial settings. Nevertheless, the existing correlations between pH or temperature and indices derived from 3-OH FA distribution are based on a small soil dataset (ca. 70 samples) and only applicable regionally. The aim of this study was to investigate the applicability of 3-OH FAs as mean annual air temperature (MAAT) and pH proxies at the global level. This was achieved using an extended soil dataset of 168 topsoils distributed worldwide, covering a wide range of temperatures (5 to 30 ∘C) and pH (3 to 8). The response of 3-OH FAs to temperature and pH was compared to that of established branched glycerol dialkyl glycerol tetraether (GDGT)-based proxies (MBT'5Me/CBT). Strong linear relationships between 3-OH-FA-derived indices (RAN15, RAN17 and RIAN) and MAAT or pH could only be obtained locally for some of the individual transects. This suggests that these indices cannot be used as palaeoproxies at the global scale using simple linear regression models, in contrast with the MBT'5Me and CBT. However, strong global correlations between 3-OH FA relative abundances and MAAT or pH were shown by using other algorithms (multiple linear regression, k-NN and random forest models). The applicability of the three aforementioned models for palaeotemperature reconstruction was tested and compared with the MAAT record from a Chinese speleothem. The calibration based on the random forest model appeared to be the most robust. It generally showed similar trends with previously available records and highlighted known climatic events poorly visible when using local 3-OH FA calibrations. Altogether, these results demonstrate the potential of 3-OH FAs as palaeoproxies in terrestrial settings.
(Biogeosciences. vol. 18, n° 1726-4170, pp. 3937 - 3959, 01/07/2021)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, METIS, EPHE, PSL, INSU - CNRS, SU, CNRS, UNINA, UCSC, EDYTEM, USMB [Université de Savoie] [Université de Chambéry], CNRS, Fédération OSUG, PITT
Systematic investigation of skill opportunities in decadal prediction of air temperature over Europe
Decadal Climate Predictions (DCP) have gained considerable attention for their potential utility in promoting optimised plans of adaptation to climate change and variability. Their effective applicability to a targeted problem is nevertheless conditional on a detailed evaluation of their ability to simulate the near-term climate evolution under specific conditions. Here we explore the performance of the IPSL-CM5A-LR DCP system in predicting air temperature over Europe, by proposing a systematic assessessment of the prediction skill for different time windows (periods of the calendar time, forecast years and months/seasons). In this framework, we also compare raw and de-biased hindcasts, in which the temperature outputs have been corrected using a quantile matching method. The systematic analysis allows to discern certain conditions conferring larger predictability, which we find to be intermittent in time. The predictions appear more skilful around the 1960s and after the 1980s, in coincidence with large shifts of the Atlantic Multidecadal Variability, which are well reproduced in the hindcasts. Averages on longer forecast periods also generally imply better prediction skill, while the best predicted months appear to be mainly those between late spring and early autumn. Moreover, we find an overall added value due to initialisation, while de-biased predictions significantly outperform raw predictions only for a few specific time windows. Finally, we discuss the potential implications of the proposed systematic exploration of skill opportunities in DCPs for integrated applications in climate sensitive sectors.
(Climate Dynamics. vol. 57, n° 0930-7575, pp. 3245-3263, 01/07/2021)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, LOCEAN-VARCLIM, LOCEAN, MNHN, IRD, INSU - CNRS, SU, CNRS, IPSL (FR_636), ENS-PSL, UVSQ, CEA, INSU - CNRS, X, CNES, SU, CNRS, UPCité
The SPHERE infrared survey for exoplanets (SHINE) II. Observations, data reduction and analysis, detection performances, and initial results
Context. In recent decades, direct imaging has confirmed the existence of substellar companions (exoplanets or brown dwarfs) on wide orbits (>10 au) around their host stars. In striving to understand their formation and evolution mechanisms, in 2015 we initiated the SPHERE infrared survey for exoplanets (SHINE), a systematic direct imaging survey of young, nearby stars that is targeted at exploring their demographics.Aims. We aim to detect and characterize the population of giant planets and brown dwarfs beyond the snow line around young, nearby stars. Combined with the survey completeness, our observations offer the opportunity to constrain the statistical properties (occurrence, mass and orbital distributions, dependency on the stellar mass) of these young giant planets.Methods. In this study, we present the observing and data analysis strategy, the ranking process of the detected candidates, and the survey performances for a subsample of 150 stars that are representative of the full SHINE sample. Observations were conducted in a homogeneous way between February 2015 and February 2017 with the dedicated ground-based VLT/SPHERE instrument equipped with the IFS integral field spectrograph and the IRDIS dual-band imager, covering a spectral range between 0.9 and 2.3 μm. We used coronographic, angular, and spectral differential imaging techniques to achieve the best detection performances for this study, down to the planetary mass regime.Results. We processed, in a uniform manner, more than 300 SHINE observations and datasets to assess the survey typical sensitivity as a function of the host star and of the observing conditions. The median detection performance reached 5σ-contrasts of 13 mag at 200 mas and 14.2 mag at 800 mas with the IFS (YJ and YJH bands), and of 11.8 mag at 200 mas, 13.1 mag at 800 mas, and 15.8 mag at 3 as with IRDIS in H band, delivering one of the deepest sensitivity surveys thus far for young, nearby stars. A total of sixteen substellar companions were imaged in this first part of SHINE: seven brown dwarf companions and ten planetary-mass companions.These include two new discoveries, HIP 65426 b and HIP 64892 B, but not the planets around PDS70 that had not been originally selected for the SHINE core sample. A total of 1483 candidates were detected, mainly in the large field of view that characterizes IRDIS. The color-magnitude diagrams, low-resolution spectrum (when available with IFS), and follow-up observations enabled us to identify the nature (background contaminant or comoving companion) of about 86% of our subsample. The remaining cases are often connected to crowded-field follow-up observations that were missing. Finally, even though SHINE was not initially designed for disk searches, we imaged twelve circumstellar disks, including three new detections around the HIP 73145, HIP 86598, and HD 106906 systems.Conclusions. Nowadays, direct imaging provides a unique opportunity to probe the outer part of exoplanetary systems beyond 10 au to explore planetary architectures, as highlighted by the discoveries of: one new exoplanet, one new brown dwarf companion, and three new debris disks during this early phase of SHINE. It also offers the opportunity to explore and revisit the physical and orbital properties of these young, giant planets and brown dwarf companions (relative position, photometry, and low-resolution spectrum in near-infrared, predicted masses, and contrast in order to search for additional companions). Finally, these results highlight the importance of finalizing the SHINE systematic observation of about 500 young, nearby stars for a full exploration of their outer part to explore the demographics of young giant planets beyond 10 au and to identify the most interesting systems for the next generation of high-contrast imagers on very large and extremely large telescopes.
(Astronomy & Astrophysics - A&A. vol. 651, n° 0004-6361, pp. A71, 01/07/2021)
CRAL, ENS de Lyon, UCBL, INSU - CNRS, CNRS, OAPD, INAF, IPAG, INSU - CNRS, CNES, CNRS, Fédération OSUG, UGA, LESIA, INSU - CNRS, CNRS, PSL, SU, CNRS, UPCité, UNIGE, UMich, IPA, D-PHYS, ETH Zürich, MPIA, CSH, UNIBE, LAM, AMU, INSU - CNRS, CNES, CNRS, LAGRANGE, UNS, INSU - CNRS, UniCA, CNRS, UniCA, OAB, INAF, CEDETE, UO, LabHC, IOGS, UJM, UJM EPE, CNRS, LBMC UMR T9406, UCBL, LaSIE, ULR, CNRS, LESIA, UPMC, INSU - CNRS, CNRS, PSL, UPD7, CNRS, AP-HP, SU, AP-HP, SU, FIZEAU, UNS, INSU - CNRS, UniCA, CNRS, OAC, INAF, IMAPP, ESO, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, OACT, INAF, GSFC, CH Avignon
Environnement & Conchyliculture : étude des effets des microplastiques et pesticides chez l’huître creuse, Crassostrea gigas, des Pertuis Charentais
Les microplastiques (MP) sont largement répandus dans les zones côtières et les océans du monde entier. Les MP sont préoccupants sur le plan environnemental en raison de leurs impacts potentiels sur un large éventail d’organismes marins, de sorte que l'évaluation de leur impact sur les écosystèmes est devenue une priorité de recherche. En complément, les substances phytosanitaires utilisées régulièrement en agriculture se déversent dans les milieux côtiers, par ruissellements. Ces travaux de thèse se sont focalisés sur (i) une étude exploratoire d’un site pilote des Pertuis Charentais (PC) afin d’évaluer l’importance de la contamination plastique et pouvoir évaluer leur toxicité sur (ii) les stades précoces et (iii) tardifs de développement de l’huître creuse, Crassostrea gigas. Ces travaux fournissent une première investigation de l’état de contamination plastique (macro et micro) d’un site d’étude littoral des PC, où la présence de plastiques ostréicoles ainsi que des concentrations élevées en MP dans les sédiments de plage ont été identifiés. De plus, les expérimentations menées en conditions de laboratoire contrôlées, nous informent sur le caractère toxique des MP de PE et des pesticides sur les stades précoces de développement (embryo-larvaire) de l’huitre creuse. Les pesticides dosés dans les eaux des PC ont montré des effets significatifs à des concentrations proches de l’environnement naturel alors que les MP s’avèrent toxiques pour des concentrations plus fortes. Ces effets apparaissent sur le développement, la croissance et le comportement natatoire des larves d’huitre creuse. Des expérimentations complémentaires, effectuées sur des stades plus tardifs, notamment les naissains d’huitre creuse, ont permis de montrer un comportement valvaire modifié suite à une exposition de 25 jours aux MP de type PE et au Chlortoluron, en conditions de laboratoire. Les effets intergénérationnels ont pu être observés avec l’utilisation de MP environnementaux (cocktail de PE, PP et PVC), vieillis aux abords des concessions ostréicoles. La qualité et le succès de fécondation ont été modifiés ainsi que le développement et le comportement de nage des larves-D issues de parents préalablement exposés durant deux mois. Ces premiers résultats permettront de renforcer les connaissances de la communauté scientifique et d’informer les professionnels et acteurs conchylicoles sur les risques des contaminants émergents, tels que les MP et les pesticides. Des adaptations des pratiques conchylicoles seront nécessaires afin d’éviter une probable dégradation de la qualité des eaux littorales dans les PC.
(30/06/2021)
LIENSs, INSU - CNRS, ULR, CNRS, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS
Evidence of deleterious effects of microplastics from aquaculture materials on pediveliger larva settlement and oyster spat growth of Pacific oyster, Crassostrea gigas
(Science of the Total Environment. vol. 794, n° 0048-9697, pp. 148708, 29/06/2021)
LIENSs, INSU - CNRS, ULR, CNRS, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS
Peer Community in Ecotoxicology and Environmental Chemistry
Les Peer Community In… (PCI, https://peercommunityin.org/) sont un processus éditorial de science ouverte. Il s'agit de communautés spécialisées effectuant une évaluation scientifique par les pairs et à la demande des auteurs, de preprints déposés sur des serveurs appropriés. Dans chaque PCI, les recommandeurs, qui sont les équivalents des éditeurs scientifiques de revues, constituent une équipe de reviewers qui réalisent une évaluation détaillée de l’article. S’ensuit une décision éditoriale qui mène soit au rejet, soit à la demande de corrections, soit à la validation de l’article scientifique...
(28/06/2021)
ECOSYS, INRAE, IFREMER, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS