Résumé
Interactions between parasites and their hosts are shaped by ecological context, yet how anthropogenic pollution modifies these coevolved relationships remains poorly understood. Freshwater ecosystems are particularly exposed to chronic contamination by pesticides, which can affect host physiology, immunity, and behavior, as well as parasite development and transmission. Disentangling the independent and interactive effects of these stressors requires controlled experimental approaches. Here, 109 individuals of the freshwater fish Squalius cephalus were experimentally infected each with 15 acanthocephalan parasites Pomphorhynchus laevis. These infections were followed by 6 exposure to carbendazim, a widely used fungicide, (at a dose of 0.75 μg per gram of fish across a 1 month period. Carbendazim exposure alone altered immune profiles and body coloration. Experimental infections successfully enhanced parasites number in hosts, which in turn modified fish behavior and pigmentation. Importantly, we also detected interactive effects between enhanced parasitism and pollutant exposure: pollutant-induced alterations were reduced in European chubs with enhanced acanthocephalan load compared to fish with natural parasite load. These results suggest that parasites can modulate host responses to chemical stress, potentially by reducing pollutant bioavailability or host metabolic and immune pathways. Parasite fitness, however, appeared largely unaffected by pollutant exposure. Our findings support the hypothesis that pollutants can mediate a shift from parasitism to mutualism and highlight the need to explicitly incorporate host-parasite dynamics into predictions of ecological and evolutionary responses to pollution.
Auteurs, date et publication :
Auteurs Léa Lorrain-Soligon , Constance Warnier de Wailly , Alexandre Bauer , Thierry Rigaud , Jean-Emmanuel Rollin , Simon Agostini , Beatriz Decencière , Alexis Millot , Aurélie Goutte
Publication : Environmental Pollution
Date : 2026
Pages : 127921
Catégorie(s)
#CNRS #ENS #PLANAQUARésumé
Soils play a key role in mitigating global warming due to their capacity to sequester CO₂, a process likely impacted by the efficiency with which microbial communities transform organic matter into biomass. The activity of microbes is affected by the conditions they find themselves in (moisture, oxygen, etc.). Soils are characterized by a network of pores of different sizes, which create a variety of microenvironments that can influence resource availability, microbial activity and soil C dynamics. However, the influence of conditions at the pore-scale on microbial carbon use efficiency remains poorly quantified. In this study, we conducted short-term incubations using a mixture of 13C-labelled compounds to assess the carbon use efficiency of microbial communities residing in pores with maximum neck diameters between 15 and 30 μm and between 75 and 200 μm. The study was carried out in an agricultural soil (Eutric Cambisol) under three different management practices and a grassland (Sandy Cambisol) in order to have a range of pore structures, C contents, pH and different microbial communities. Our findings show that microbial mineralization of added substrate was higher in the large pores but that the carbon utilization efficiency was lower. The differences across pore sizes were likely due to the different constraints at the microenvironment scale (moisture, predation, available space, substrate abundance, etc.). These results suggest that microbes adopt distinct carbon processing strategies and functional roles, depending on pore size.
Auteurs, date et publication :
Auteurs Maëlle Maestrali , Xavier Raynaud , Haotian Wu , Steffen A. Schweizer , Ines Guillot , Thomas Lerch , Stéphane Paolillo , Naoise Nunan
Publication : Applied Soil Ecology
Date : 2026
Volume : 219
Pages : 106771
Catégorie(s)
#CNRS #Ecotron IleDeFranceRésumé
Pyrogenic carbon (PyC) is the carbonaceous solid residue of incomplete combustion of biomass. It is a continuum of mostly condensed and aromatic molecules. PyC persists for longer in soils relative to non-PyC organic carbon. However, estimates of PyC residence time vary greatly. The time and spatial scales investigated are not always adapted to the long-residence time and vertical and lateral mobility of PyC in the soil profile and the landscape. In addition, agricultural land-use and shallow slopes are under-represented in the PyC literature.
We measured the concentrations and stocks of PyC down to 60 cm along three toposequences in a small agricultural catchment with shallow slopes and homogeneous soil parent material in the west of France. We used two methods (chemo-thermal oxidation – CTO and hydropyrolysis – HyPy) of PyC quantification that cover the intermediate to highly condensed part of the PyC continuum, and also measured the radiocarbon values in both total soil organic carbon (SOC) and the PyC fraction. There was likely little persistent PyC inputs to the catchment in the last 150 years which gave us access to the resultant, long term PyC distribution in the landscape. In particular, we aimed to investigate whether the vertical and horizontal distribution of PyC were similar or differed from SOC and whether they were affected by the soil types along the slope.
Topographic position was not the main driver of PyC stocks in this landscape. The stock of PyCCTO to 60 cm depth averaged 2.5 ± 0.22 t ha−1 across topographic positions. PyC stocks were the highest in a Solimovic Cambisol at the toeslope (3.3 ± 0.26 t ha−1), likely formed following changes in erosion dynamics with land-use. Contrary to previous reports, erosion redistributed already aged PyC without enrichment or depletion. PyCHyPy concentrations in the topsoil decreased from upslope (median = 1.6, IQR = 0.22 g C kg−1 soil) to downslope positions (median = 1.10, IQR = 0.40 g C kg−1 soil), which we tentatively attribute to PyCHyPy leaching following the destabilisation of mineral associations with iron oxides in the water-table affected portion of the transects. The subsoil (30–60 cm) represented between 37 % and 51 % of the PyCCTO stock. PyCHyPy proportion in SOC increased with depth and reached an average of 11 ± 3.3 % at 50–60 cm depth. PyCHyPy had an uncalibrated radiocarbon age of 2520 to 9600 years BP at this depth, significantly older than bulk SOC at the same depth and than PyCHyPy at 0–10 cm (1530 to 2630 years BP). These results confirm the long persistence of PyC in soils and point to a slow advection of PyC towards the soil depth under the pedoclimatic conditions of our study area.
Future studies should assess whether erosion modalities and age and quality of PyC affect its fate during erosion events. Identifying the proportion of PyC produced which is quickly transported away from the watershed and that which remains and is stabilised in soils for millennia after a fire is an important knowledge gap that still needs to be investigated to close the terrestrial PyC budget.
Auteurs, date et publication :
Auteurs Johanne Lebrun Thauront , Philippa Ascough , Sebastian Doetterl , Negar Haghipour , Pierre Barré , Christian Walter , Samuel Abiven
Publication : Biogeosciences
Date : 2026
Volume : 23
Issue : 1
Pages : 155-179
Catégorie(s)
#CNRS #Ecotron IleDeFranceRésumé
Mutualisms shape root traits and carbon cycling under global change
Auteurs, date et publication :
Auteurs Arnaud M , Rumpel C , Abiven S
Publication : The New phytologist
Date : 2026
Volume : 249
Issue : 2
Catégorie(s)
#CNRS #Ecotron IleDeFranceAuteurs, date et publication :
Auteurs J.M. Carpentier , S. A. P Derocles , S. Chéreau , B. Marquer , J. Linglin , L. Lebreton , F. Legeai , N. Vannier , A.M. Cortesero , C. Mougel
Publication : mSystems
Date : 2025
Pages : e01269-25
Catégorie(s)
#CNRS #EcoGenO #Université de RennesRésumé
Tropical forests, which cover 6% of Earth's land surface, are essential for global biodiversity and carbon storage. In French Guiana, where forests account for over 97% of the territory, sustainable forest management represents a critical challenge for both conservation and economic development. The French National Forest Office (ONF) manages 6 million hectares, seeking to balance timber extraction with ecosystem preservation. Remote sensing provides a potential solution for large-scale tree species mapping, thereby supporting evidence-based forest management and reducing the environmental footprint of logging activities. This thesis investigates the challenge of generalizing tree species identification models using airborne hyperspectral imagery in hyperdiverse tropical environments. The study is structured around three scientific questions, analyzed through repeated acquisitions over the Paracou and Nouragues sites in French Guiana. The hyperspectral data, acquired in 2016, cover the 4002500 nm spectral range. First, the analysis quantifies the primary sources of spectral variability : atmospheric conditions, solar geometry, and viewing angles, and demonstrates their significant impact on reflectance stability, even after atmospheric correction. The results indicate that this variability disrupts spectral proxies commonly used in vegetation monitoring, calling into question their reliability under operational conditions. Second, the study evaluates the capacity of self-supervised learning (SSL) to generate spectral representations that are robust to acquisition-related variability. While SSL reduces abiotic noise, it may accentuate intra-individual and site-specific differences, thereby limiting its effectiveness for cross-site species classification. Third, the research assesses domain adaptation (DA) techniques to mitigate spectral shifts between dates and sites. The findings reveal that unsupervised DA methods yield only modest improvements, whereas supervised DA approaches, such as Transfert Learning Adaboost (TrAdaBoost), achieve substantial classification gains even with limited labeled data. However, their success remains contingent on the representativeness of annotated samples and the ecological complexity of the study sites. In conclusion, this work frames spectral variability as a central concept for addressing the complex challenge of transfer learning between study sites and acquisition dates in tropical forest remote sensing. The integration of SSL and DA methods provides a structured approach to managing this variability, enabling the development of more reliable and transferable species identification models in operationally relevant contexts.
Auteurs, date et publication :
Auteurs Colin Prieur
Date : 2025
Catégorie(s)
#CNRS #FORET NouraguesRésumé
Atmospheric dioxygen (O2) concentration and isotopic composition are closely linked to the carbon cycle through anthropic carbon dioxide (CO2) emissions and biological processes such as photosynthesis and respiration. The measurement of the isotopic ratio of O2, trapped in ice core bubbles, brings information about past variation in the hydrological cycle at low latitudes, as well as past productivity. Currently, the interpretation of those variations could be drastically improved with a better (i.e., quantitative) knowledge of the oxygen isotopic fractionation that occurs during photosynthesis and respiration processes. This could be achieved, for example, during experiments using closed biological chambers. In order to estimate the isotopic fractionation coefficient with good precision, one of the principal limitations is the need for high-frequency online measurements of isotopic composition of O2, expressed as δ18O of O2 (δ18O(O2)) and O2 concentration. To address this issue, we developed a new instrument, based on the optical-feedback cavity-enhanced absorption spectroscopy (OF-CEAS) technique, enabling high-temporal-resolution and continuous measurements of O2 concentration as well as δ18O(O2), both simultaneously. The minimum Allan deviation occurred between 10 and 20 min, while precision reached 0.002 % for the O2 concentration and 0.06 ‰ for δ18O(O2), which correspond to the optimal integration time and analytical precision before instrumental drift started degrading the measurements. Instrument accuracy was in good agreement with dual-inlet isotope ratio mass spectrometry (IRMS). Measured values were slightly affected by humidity, and we decided to measure δ18O(O2) and O2 concentration after drying the gas. On the other hand, a 1 % increase in O2 concentration increased the δ18O(O2) by 0.53 ‰. To ensure the good quality of O2 concentration and δ18O(O2) measurements we eventually proposed to measure the calibration standard every 20 min.
Auteurs, date et publication :
Auteurs Clément Piel , Daniele Romanini , Morgane Farradèche , Justin Chaillot , Clémence Paul , Nicolas Bienville , Thomas Lauwers , Joana Sauze , Kévin Jaulin , Frédéric Prié , Amaëlle Landais
Publication : Atmospheric Measurement Techniques
Date : 2024
Volume : 17
Issue : 22
Pages : 6647-6658
Catégorie(s)
#CNRS #Ecotron de MontpellierRésumé
Atmospheric dioxygen (O2) concentration and isotopic composition are closely linked to the carbon cycle through anthropic carbon dioxide (CO2) emissions and biological processes such as photosynthesis and respiration. The measurement of the isotopic ratio of O2, trapped in ice core bubbles, brings information about past variation in the hydrological cycle at low latitudes, as well as past productivity. Currently, the interpretation of those variations could be drastically improved with a better (i.e., quantitative) knowledge of the oxygen isotopic fractionation that occurs during photosynthesis and respiration processes. This could be achieved, for example, during experiments using closed biological chambers. In order to estimate the isotopic fractionation coefficient with good precision, one of the principal limitations is the need for high-frequency online measurements of isotopic composition of O2, expressed as δ18O of O2 (δ18O(O2)) and O2 concentration. To address this issue, we developed a new instrument, based on the optical-feedback cavity-enhanced absorption spectroscopy (OF-CEAS) technique, enabling high-temporal-resolution and continuous measurements of O2 concentration as well as δ18O(O2), both simultaneously. The minimum Allan deviation occurred between 10 and 20 min, while precision reached 0.002 % for the O2 concentration and 0.06 ‰ for δ18O(O2), which correspond to the optimal integration time and analytical precision before instrumental drift started degrading the measurements. Instrument accuracy was in good agreement with dual-inlet isotope ratio mass spectrometry (IRMS). Measured values were slightly affected by humidity, and we decided to measure δ18O(O2) and O2 concentration after drying the gas. On the other hand, a 1 % increase in O2 concentration increased the δ18O(O2) by 0.53 ‰. To ensure the good quality of O2 concentration and δ18O(O2) measurements we eventually proposed to measure the calibration standard every 20 min.
Auteurs, date et publication :
Auteurs Clément Piel , Daniele Romanini , Morgane Farradèche , Justin Chaillot , Clémence Paul , Nicolas Bienville , Thomas Lauwers , Joana Sauze , Kévin Jaulin , Frédéric Prié , Amaëlle Landais
Publication : Atmospheric Measurement Techniques
Date : 2024
Volume : 17
Issue : 22
Pages : 6647-6658
Catégorie(s)
#CNRS #Ecotron de MontpellierRésumé
Atmospheric dioxygen (O2) concentration and isotopic composition are closely linked to the carbon cycle through anthropic carbon dioxide (CO2) emissions and biological processes such as photosynthesis and respiration. The measurement of the isotopic ratio of O2, trapped in ice core bubbles, brings information about past variation in the hydrological cycle at low latitudes, as well as past productivity. Currently, the interpretation of those variations could be drastically improved with a better (i.e., quantitative) knowledge of the oxygen isotopic fractionation that occurs during photosynthesis and respiration processes. This could be achieved, for example, during experiments using closed biological chambers. In order to estimate the isotopic fractionation coefficient with good precision, one of the principal limitations is the need for high-frequency online measurements of isotopic composition of O2, expressed as δ18O of O2 (δ18O(O2)) and O2 concentration. To address this issue, we developed a new instrument, based on the optical-feedback cavity-enhanced absorption spectroscopy (OF-CEAS) technique, enabling high-temporal-resolution and continuous measurements of O2 concentration as well as δ18O(O2), both simultaneously. The minimum Allan deviation occurred between 10 and 20 min, while precision reached 0.002 % for the O2 concentration and 0.06 ‰ for δ18O(O2), which correspond to the optimal integration time and analytical precision before instrumental drift started degrading the measurements. Instrument accuracy was in good agreement with dual-inlet isotope ratio mass spectrometry (IRMS). Measured values were slightly affected by humidity, and we decided to measure δ18O(O2) and O2 concentration after drying the gas. On the other hand, a 1 % increase in O2 concentration increased the δ18O(O2) by 0.53 ‰. To ensure the good quality of O2 concentration and δ18O(O2) measurements we eventually proposed to measure the calibration standard every 20 min.
Auteurs, date et publication :
Auteurs Clément Piel , Daniele Romanini , Morgane Farradèche , Justin Chaillot , Clémence Paul , Nicolas Bienville , Thomas Lauwers , Joana Sauze , Kévin Jaulin , Frédéric Prié , Amaëlle Landais
Publication : Atmospheric Measurement Techniques
Date : 2024
Volume : 17
Issue : 22
Pages : 6647-6658
Catégorie(s)
#CNRS #Ecotron de MontpellierRésumé
Atmospheric dioxygen (O2) concentration and isotopic composition are closely linked to the carbon cycle through anthropic carbon dioxide (CO2) emissions and biological processes such as photosynthesis and respiration. The measurement of the isotopic ratio of O2, trapped in ice core bubbles, brings information about past variation in the hydrological cycle at low latitudes, as well as past productivity. Currently, the interpretation of those variations could be drastically improved with a better (i.e., quantitative) knowledge of the oxygen isotopic fractionation that occurs during photosynthesis and respiration processes. This could be achieved, for example, during experiments using closed biological chambers. In order to estimate the isotopic fractionation coefficient with good precision, one of the principal limitations is the need for high-frequency online measurements of isotopic composition of O2, expressed as δ18O of O2 (δ18O(O2)) and O2 concentration. To address this issue, we developed a new instrument, based on the optical-feedback cavity-enhanced absorption spectroscopy (OF-CEAS) technique, enabling high-temporal-resolution and continuous measurements of O2 concentration as well as δ18O(O2), both simultaneously. The minimum Allan deviation occurred between 10 and 20 min, while precision reached 0.002 % for the O2 concentration and 0.06 ‰ for δ18O(O2), which correspond to the optimal integration time and analytical precision before instrumental drift started degrading the measurements. Instrument accuracy was in good agreement with dual-inlet isotope ratio mass spectrometry (IRMS). Measured values were slightly affected by humidity, and we decided to measure δ18O(O2) and O2 concentration after drying the gas. On the other hand, a 1 % increase in O2 concentration increased the δ18O(O2) by 0.53 ‰. To ensure the good quality of O2 concentration and δ18O(O2) measurements we eventually proposed to measure the calibration standard every 20 min.
Auteurs, date et publication :
Auteurs Clément Piel , Daniele Romanini , Morgane Farradèche , Justin Chaillot , Clémence Paul , Nicolas Bienville , Thomas Lauwers , Joana Sauze , Kévin Jaulin , Frédéric Prié , Amaëlle Landais
Publication : Atmospheric Measurement Techniques
Date : 2024
Volume : 17
Issue : 22
Pages : 6647-6658