Human activity and climate change triggered the expansion of rocky desertification in the karst areas of Southwestern China
It is conducive to the sustainable development of human beings in karst regions to research the mechanism of karst rocky desertification (KRD) expansion. Whether the large-scale KRD in southwestern China is caused by climate change or human activities is still controversial. In this study, the evolution of the KRD in southwestern China over the past 2000 years was reconstructed through the high-precision δ13C record of stalagmites from Shijiangjun (SJJ) Cave, Guizhou Province, China. The δ13C of the stalagmites from SJJ Cave exhibited heavy values from the Medieval Warm Period (MWP) to the Little Ice Age (LIA). Furthermore, the δ13C records of other stalagmites and tufa from southwestern China also showed the same significant heavy trend. Because the stalagmite δ13C could record the change of ecological environment, it indicated that the consistent change of the stalagmites δ13C may record the process of KRD expansion in the karst regions of southwestern China. During the MWP, the stronger Asian summer monsoon and the northward movement of the rain belt led to a dry period in southwestern China and a wet period in northern China. In contrast, it was wet in southwestern China and dry in northern China during the LIA. In addition, after the Jing-Kang event (JK event, AD1127) occurred at the end of the Northern Song dynasty, the political and economic center of China migrated to southern China for the first time, which changed the population distribution pattern of larger population in the north and smaller population in the south. Therefore, the expansion of KRD in southwestern China was exacerbated in the MWP due to the change of climate in southwestern China, the migration of a large number of people, wars, the large-scale reclamation of arable land, and the cultivation of large areas of crops.
(Science China Earth Sciences. vol. 64, n° 1674-7313, pp. 1761-1773, 09/08/2021)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS
Subchronic exposure to high-density polyethylene microplastics alone or in combination with chlortoluron significantly affected valve activity and daily growth of the Pacific oyster, Crassostrea gigas
Nowadays, pesticides and microplastics (MPs) are commonly found in coastal waters worldwide. Due to their widespread use, their persistence and toxicity, they may induce adverse effects on physiology and behaviour of marine organisms such as the Pacific oyster (Crassostrea gigas). This study explored the growth and valve activity of juvenile oysters exposed for 24 days to two frequently detected pollutants in the Pertuis Charentais (South West, France): a herbicide (chlortoluron, 85 µg.L−1) and high-density polyethylene microparticles (HDPE 20-25 µm, 112 MP.mL−1) alone or in combination (cocktail condition; 97 µg.L−1 of chlortoluron + 108 MP. mL−1). The valve activity of juvenile oysters recorded by using a High Frequency and Non-Invasive valvometer (HFNI) was characterized by three parameters: the number of valve micro-closures (VMC), the Valve Opening Amplitude (VOA), and the Valve Opening Duration (VOD). Additionally, daily shell growth and the oyster daily rhythm were assessed. The exposure to MPs of oysters led to a significant increase of VMC and a decrease of VOD and shell growth. The exposure to chlortoluron showed a significant increase of VOA and a decrease of VMC. In combination with MPs, chlortoluron still increased VOA and decreased VMC but also reduced the shell growth. Chronobiological analysis did not reveal any effects on the daily rhythm of both contaminants. This work highlighted significant effects of high environmental concentrations of MPs and Chlortoluron on the behaviour and growth of the Pacific oyster
(Aquatic Toxicology. vol. 237, n° 0166-445X, pp. 105880, 01/08/2021)
LIENSs, INSU - CNRS, ULR, CNRS, Cedre, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS
Environmentally Relevant Mixture of Pesticides Affect Mobility and DNA Integrity of Early Life Stages of Rainbow Trout (Oncorhynchus mykiss)
The aim of this study was to analyze the impact of three concentrations of a pesticide mixture on the first development stages of rainbow trout (Oncorhynchus mykiss). The mixture was made up of three commonly used pesticides in viticulture: glyphosate (GLY), chlorpyrifos (CPF) and copper sulfate (Cu). Eyed stage embryos were exposed for 3 weeks to three concentrations of the pesticide mixture. Lethal and sub-lethal effects were assessed through a number of phenotypic and molecular endpoints including survival, hatching delay, hatching success, biometry, swimming activity, DNA damage (Comet assay), lipid peroxidation (TBARS), protein carbonyl content and gene expression. Ten target genes involved in antioxidant defenses, DNA repair, mitochondrial metabolism and apoptosis were analyzed using real-time RT-qPCR. No significant increase of mortality, half-hatch, growth defects, TBARS and protein carbonyl contents were observed whatever the pesticide mixture concentration. In contrast, DNA damage and swimming activity were significantly more elevated at the highest pesticide mixture concentration. Gene transcription was up-regulated for genes involved in detoxification (gst and mt1), DNA repair (ogg1), mitochondrial metabolism (cox1 and 12S), and cholinergic system (ache). This study highlighted the induction of adaptive molecular and behavioral responses of rainbow trout larvae when exposed to environmentally realistic concentrations of a mixture of pesticides.
(Toxics. vol. 9, n° 2305-6304, pp. 174, 01/08/2021)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, UB, CNRS
Peer Community in Ecotoxicology & Environmental Chemistry, un nouveau média ouvert, transparent et gratuit pour la valorisation et la diffusion de vos recherches
Les Peer Community In… (PCI, https://peercommunityin.org/) sont des communautés scientifiques qui organisent des processus éditoriaux 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 de preprints ou des archives ouvertes institutionnelles. 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, éventuellement après plusieurs rounds d'évaluation. Dans ce dernier cas, le recommandeur écrit un texte de recommandation dans lequel il explique pourquoi il a validé l’article. L’ensemble de la communauté scientifique a ainsi accès gratuitement au contenu validé de l'article et aux évaluations/recommandations...
(01/08/2021)
ECOSYS, INRAE, IFREMER, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, UMR CBGP, Cirad, UM, IRD [Occitanie], INRAE, Institut Agro, ISA, UNS, CNRS, INRAE, UniCA, UMR PVBMT, Cirad, IRD, UR, INRAE, DipSO, INRAE
Sediment reworking by the burrowing polychaete Hediste diversicolor modulated by environmental and biological factors across the temperate North Atlantic. A tribute to Gaston Desrosiers
Particle mixing and irrigation of the seabed by benthic fauna (bioturbation) have major impacts on ecosystem functions such as remineralization of organic matter and sediment-water exchange. As a tribute to Prof. Gaston Desrosiers by the Nereis Park association, eighteen laboratories carried out a collaborative experiment to acquire a global snapshot of particle reworking by the polychaete Hediste diversicolor at 16 sites surrounding the Northern Atlantic. Organisms and soft sediments were collected during May – July at different geographical locations and, using a common laboratory protocol, particulate fluorescent tracers (‘luminophores’) were used to quantify particle transport over a 10-day period. Particle mixing was quantified using the maximum penetration depth of tracers (MPD), particle diffusive coefficients (Db), and non-local transport coefficients (r). Non-local coefficients (reflecting centimeter scale transport steps) ranged from 0.4 to 15 yr−1, and were not correlated across sites with any measured biological (biomass, biovolume) or environmental parameters (temperature, grain size, organic matter). Maximum penetration depths (MPD) averaged ~10.7 cm (6.5–14.5 cm), and were similar to the global average bioturbation depth inferred from short-lived radiochemical tracers. MPD was also not correlated with measures of size (individual biomass), but increased with grain size and decreased with temperature. Biodiffusion (Db) correlated inversely with individual biomass (size) and directly with temperature over the environmental range (Q10 ~ 1.7; 5–21 °C). The transport data were comparable in magnitude to rates reported for localized H. diversicolor populations of similar size, and confirmed some but not all correlations between sediment reworking and biological and environmental variables found in previous studies. The results imply that measures of particle reworking activities of a species from a single location can be generally extrapolated to different populations at similar conditions.
(Journal of Experimental Marine Biology and Ecology. vol. 541, n° 0022-0981, pp. 151588, 01/08/2021)
LEFE, INEE-CNRS, CNRS, UT3, Comue de Toulouse, CNRS, Toulouse INP, Comue de Toulouse, SDU, SoMAS, SBU, SUNY, ISMER, UQAR, ULaval, ISMAR, ISMAR, CNR, SAMS, MIO, IRD, AMU, INSU - CNRS, UTLN, CNRS, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, GU, MMS UCO, UCO, UNAM, NOC, NORDCEE, UCPH, GU, LEMAR, IRD, IFREMER, UBO EPE, CNRS, NIWA, AWI, PML
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