Contamination des sols par les résidus de pesticides
(11/03/2025)
Info&Sols, INRAE, InfoSol, INRAE, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, UMR ISPA, INRA, Bordeaux Sciences Agro, AFNOR, LAS, INRAE
Evolution of the Asian summer monsoon and regional karst ecological environment since the middle ages in Southwest China
The frequent droughts and floods, closely associated with the Asian summer monsoon (ASM), has profoundly affected the ecological environment and economy in East Asia. While changes in the ASM are closely related to precipitation patterns, the specific mechanism still requires further investigation. This study utilized stalagmite records from the Feilong Cave in southwest China to reconstruct the evolution of the ASM since the Medieval Warm Period (MWP). The results indicated that the ASM strengthened during the MWP and weakened during the Little Ice Age (LIA), with changes in monsoon intensity primarily driven by solar activity and variations in tropical ocean-atmosphere circulation. Different phase combinations of the Atlantic Multidecadal Oscillation, and the Pacific Decadal Oscillation also influenced on the variations of the ASM. During the MWP, with warming of the northern hemisphere landmasses, the ASM intensified, enhancing the long-range transport of moisture from the southwest (Indian summer monsoon), leading to northward shifts of the rain belt in the eastern monsoon region in China and increased precipitation in northern China. Conversely, during the LIA, cooling of the northern hemisphere landmasses led to a weakening of the ASM and reduced southwest moisture transport, resulting in southward shifts of the rain belt in the eastern monsoon China and increased precipitation in southern China. Additionally, the abnormal southward shift of the Western Pacific Subtropical High led to prolonged retention of the rain belt in southern China, causing an increase in monsoonal rainfall in southern China. Comparison with monsoonal Chinese terrestrial proxy records reveals an antiphase relationship between northern and southern parts of the eastern China. During the MWP, the counterparts showed a "wet north-dry south" pattern, while during the LIA, a "wet south-dry north" pattern emerged. Furthermore, proxy records suggest that human activities exacerbated the deterioration of karst ecological environment in southwest China since the Middle Ages.
(Scientific Reports. vol. 15, 08/03/2025)
IGBMC, INSERM, CNRS, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, IGEC, Xjtu, NTU
Simulated millennial-scale climate variability driven by a convection–advection oscillator
The last glacial period, between around 115 and 12 thousand years before present, exhibited strong millennial-scale climate variability. This includes abrupt transitions between cold and warm climates, known as Dansgaard-Oeschger (D-O) cycles. D-O cycles have been linked to switches in dynamical regimes of the Atlantic Overturning Meridional Circulation (AMOC), but the exact mechanisms behind abrupt climate changes and AMOC regime shifts remain poorly understood. This paper introduces the convection-advection oscillator mechanism to explain the millennial-scale oscillations observed in a set of HadCM3 general circulation model simulations forced with snapshots of deglacial meltwater history. The oscillator can be separated into two components acting on different time scales. The fast convection component responds to changes in vertical stratification in the North Atlantic by activating or deactivating deep water formation sites. The slow advection component regulates the accumulation and depletion of salinity in the North Atlantic. This oscillator mechanism is triggered under specific background conditions and freshwater release patterns. The freshwater perturbation causes an instability that triggers a global salt reorganisation, modifying the North Atlantic stratification. For a given forcing pattern, the system oscillates if the salt transport can lead to an alternating reactivation and deactivation of the AMOC. Otherwise, the climate settles in a warm or cold steady state. This mechanism expands existing theories of millennial-scale variability and provides a general framework for understanding abrupt climate change in general circulation models.
(Climate Dynamics. vol. 63, n° 0930-7575, pp. 150, 07/03/2025)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, UOR
Garonne River Behavior Under Climate Change and the Potential Adaptation Strategies
According to the IPCC reports, the effects of climate change are well present from several decades ago, and it is expected to become even more pronounced during the remainder of the twenty-first century. The river basin system is defined as a complex of interaction between aquatic and terrestrial ecosystems. The interface between these ecosystems results in different responses of the river regime ranging from floods to low flow. The instability of alluvial valley due to geomorphological and fluvial dynamics, represents an additional challenge for the riparian societies face to climate changes. The Garonne River, the third largest French Atlantic River in terms of discharge, flows down in the Garonne Valley, the largest occupied and cultivated alluvial plain in France. This area is influenced by a wide range of Oceanic, Mediterranean, and mountainous climates. Hence, the complex Garonne River regime is influenced by the precipitation generated over the Massif Central and the French and Spanish Pyrenees Mountains. The surrounding alluvial aquifer, which forms an important part of this system, maintains a strong hydraulic connection with the river and sustains its low flow. Consequently, this aquifer is extremely sensitive to meteorological changes and hence to recharge system variation. The inhabitants in this area are strongly depending to the river and its alluvial aquifer. However, the impact of climate changes on socio-economic activities could be significant in this area. The adaptation to these changes creates additional challenges for decision-makers and becomes a major objective of the watershed policy. The trends assessment of the Garonne River's discharge over the last fifty years has shown a decrease in average annual discharges and substantial decrease in low flows. The dry periods are starting earlier and becoming more severe and longer. Upstream, the snow cover shows a decrease in thickness and duration, which has a negative impact on the river’s discharge and consequently on the groundwater recharge ratio. Groundwater measurements show a general decrease in water level. The observations show that most of the wells located close to the river have dried up during the dry periods since the alluvial aquifer drains into the river during these periods. The groundwater level reduction could have a negative impact on agriculture, wetlands, and river ecosystems. Thus, the implementation of adaptation measures has been initiated. The artificial recharge of the alluvial aquifer is considered as an adaptation strategy to address the effect of climate change and sustains the low flow of the river. In addition, this strategy will help to buffer the river temperature during the low flow periods. Several pilot sites in the Garonne Valley are under investigation for testing the artificial recharges. The first site, where artificial recharge has been tested since 2019, is located near the city of Agen, where the runoff is collected in a retention basin and is used to recharge the alluvial aquifer. Groundwater level in the wells near the retention basin have increased by about 1 m following rainfall events. The results of the groundwater modeling show (1) a similar magnitude aquifer response to the induced infiltration and (2) that the infiltrated water would take about 4 months to reach the Garonne River, which is an appropriate time to maintain the river's low flow, since recharge takes place in spring. Another site that has been tested is located near the city of Marmande, where the surface water from the Lateral Canal of the Garonne River has been used as a source to recharge the alluvial aquifer in May 2023. The infiltrated water has created a piezometric dome and the groundwater level has increased by 15 and 33 cm into two boreholes located about 40 m upstream and downstream of the infiltration site respectively. This experiment will be carried out on a larger scale, and further groundwater measurements and modeling will be carried out for this and other selected sites in the near future
(. vol. 114, pp. 235-262, 04/03/2025)
PACEA, UB, CNRS, BRGM, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, ACMG, SMEAG
Bivalve monitoring over French coasts: multi-decadal records of carbon and nitrogen elemental and isotopic ratios (δ13C, δ15N and C:N) as ecological indicators of global change
Recent changes in climate and environment, influenced by both global and local factors, have had profound impacts on coastal ecosystem functioning and trajectories. By examining archived samples from ongoing ecological monitoring efforts, particularly focusing on bivalves like mussels and oysters, we gain a valuable long-term perspective on how ecosystems are responding at various scales. We conducted analyses on carbon and nitrogen elemental and isotopic ratios (C:N, δ13C, δ15N) of mussel and oyster soft tissues collected annually at 33 sites along the French coast from 1981 to 2021. This extensive dataset (https://doi.org/10.17882/100583, Liénart et al., 2024a) offers a comprehensive view spanning multiple decades and ecosystems, allowing to track how coastal ecosystems and marine species record changing climate, physical-chemical environments and organic matter cycles. Additionally, these data are crucial for establishing isotope baselines for studying food webs. Ultimately, this data set provide valuable information for more effective ecosystem conservation and management strategies in our rapidly changing world.
(Earth System Science Data. vol. 17, n° 1866-3508, pp. 799-815, 01/03/2025)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, FTMC, CCEM, IFREMER, DYNECO, IFREMER, BOREA, MNHN, IRD, SU, CNRS, UA
Variations in the morphometric characteristics of Fragilariopsis kerguelensis in the Southwest Pacific sector of the Southern Ocean over the past 40,000 years
High-throughput measurements demonstrated the presence of two morphotypes of Fragilariopsis kerguelensis in the Atlantic sector of the Southern Ocean, the proportions of which in downcore samples may be used to reconstruct past sea-surface temperatures quantitatively. We here measured the mean length, width, area, and rectangularity in core SO136-111 to assess variations in both morphotypes in the Polar Front Zone of the western Pacific sector of the Southern Ocean over the past 40,000 years. Mean length, width, and area increased rapidly at the end of the glacial period when the Polar Front migrated southward to reach the core site, ocean temperature increased, and sea ice was no longer present. In contrast, mean rectangularity decreased at the end of the glacial period, when the proportion of the cold-water, high-rectangularity morphotype declined as the ocean warmed at the core site. Downcore patterns and quantitative values of all morphometric characteristics in the southwest Pacific sector agree well with previous studies from the Atlantic sector, suggesting the presence of a similar population of F. kerguelensis in the open Southern Ocean. Nevertheless, rectangularity-based relationships can ultimately produce unrealistic estimates of sea-surface temperatures in core SO136-111 when the proportion of the high-rectangularity morphotype is too low, indicating that these approaches are now limited to temperatures below 3-4°C.
(Marine Micropaleontology. vol. 195, n° 0377-8398, pp. 102447, 01/03/2025)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS
First and disturbing records of the bivalve molluscs Potamocorbula amurensis (Schrenck, 1861) and Mulinia lateralis (Say, 1822) in the Bay of Biscay (France)
The bivalve mollusc Potamocorbula amurensis, a Corbulidae from the Asian coasts, was recorded for the first time in France in September 2023 in the Gironde estuary, and subsequently in September 2024 in Aiguillon Cove and Aytré Bay. In Aytré Bay, it was accompanied by another non-native bivalve not previously reported from French coasts, Mulinia lateralis, a Mactridae from the western Atlantic coasts. These two species were first recorded in Europe in 2018 in the Westerschelde (Netherlands, Belgium) and are known to be potentially highly invasive. Particular attention should be paid to monitor the spread and the establishment of these two euryoecious species along European coasts.
(An Aod - Les cahiers naturalistes de l’Observatoire marin, n° 2263-5718, 25/02/2025)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, LIENSs, INSU - CNRS, ULR, CNRS, OBIONE, LIENSs, INSU - CNRS, ULR, CNRS, LPO, PatriNat, MNHN, IRD, CNRS, OFB - DSUED, OFB, PatriNat, MNHN, CNRS, OFB, PatriNat, MNHN, CNRS, AFB
A new species of the Thelepus cincinnatus complex from Saint-Pierre and Miquelon Archipelago (NW Atlantic) and genetic diversity of Amphitrite figulus (Dalyell, 1853) (Annelida, Terebelliformia)
During an ecological survey conducted in 2023 around the coastal waters of Saint-Pierre and Miquelon Archipelago, a sub-Arctic archipelago located about 20 km south of Newfoundland (NW Atlantic), two species of Terebelliformia were sampled. The first one is Amphitrite figulus (Dalyell, 1853) a species described from Europe but with a wide distribution across the Northern Atlantic Ocean. The second one, Thelepus recheri n. sp., is a new species characterised by the presence of a wide dorsal branchial gap and the presence of notopodia almost until the end of the body. Molecular studies were performed and two markers were sequenced and analyzed, COI and 16S. These genetic data revealed that (1) Thelepus recheri n. sp. belongs to the T. cincinnatus complex and (2) a clear population structure within A. figulus, with two populations on each side of the Atlantic separated from each other. However, our data are inconclusive in resolving whether these two clusters are two populations within the same species or two distinct species.
(Zootaxa. vol. 5588, n° 1175-5326, pp. 250-268, 14/02/2025)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, LEMAR, IRD, IFREMER, UBO EPE, CNRS, IUEM, IRD, INSU - CNRS, UBO EPE, CNRS, UMS POREA, INSU - CNRS, CNRS, INRAE, UIB
Devenir des PFAS dans un sol structuré : rôle des particules colloïdales et macropores
Les mousses anti-incendie contiennent un mélange de substances per- et polyfluoroalkylées (PFAS). Celles-ci sont persistantes dans l’environnement, et les sites d'entraînement des pompiers constituent une source de contamination pour les sols, leur biota et les eaux souterraines. Le devenir des PFAS dans les sols a été principalement étudié en utilisant des situations expérimentales modèles : sols recompactés, souvent saturés, et contaminés artificiellement avec quelques molécules. Nous avons étudié pour la première fois le devenir des PFAS dans un sol structuré en soumettant des colonnes de sol non perturbé, prélevées sur un ancien site d’entrainement des pompiers, à une série de pluies simulées. Ces expériences ont montré que (i) lorsque la longueur de la chaîne perfluorée nc était ≤ 7, la diffusion était le mécanisme limitant le transport, (ii) les particules colloïdales facilitaient la mobilité de certains fluoro-télomères et acides perfluorés avec n≥8, (iii) les conditions hydrodynamiques, liées à la structure du sol, déterminaient l’étendue du transport en phase colloïdale des PFAS. Ces résultats ont permis de préciser le modèle conceptuel du devenir des PFAS dans le sol et de proposer les mécanismes qu’il conviendrait d’étudier pour l’améliorer.
(04/02/2025)
EMMAH, AU, INRAE, GERS-LEE, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS
Is reducing phosphorus inputs sufficient to reduce hypoxia in estuaries? The example of the Loire estuary
Coastal deoxygenation is mainly attributed to excessive nutrient and organic matter inputs from anthropogenic activities. However, although mitigation strategies have been implemented to reduce nutrient inputs, the recovery of estuarine systems has often been limited. By examining long-term data from the turbid Loire estuary, which is prone to summer hypoxia, we aimed to understand the influence of these initiatives on nutrient and dissolved oxygen levels. The data showed that despite the reduction of dissolved phosphorus in the inner estuary, summer hypoxia persisted. By integrating high spatial resolution datasets, we identified nutrient sources, particularly ammonium, in the estuarine turbidity maximum zone. Nutrient recycling is likely to maintain summer hypoxia and hinder ecosystem recovery from hypoxia. A comprehensive understanding of estuarine geochemistry and internal nutrient cycling is essential to develop targeted remediation strategies and mitigate the ongoing threat of hypoxia.
(Estuarine, Coastal and Shelf Science. vol. 313, n° 0272-7714, pp. 109110, 01/02/2025)
LPG, UM, UA, INSU - CNRS, CNRS, Nantes univ - UFR ST, Nantes Univ, Bordeaux INP, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, IPREM, UPPA, INC-CNRS, CNRS, LPG-ANGERS, LPG, UM, UA, INSU - CNRS, CNRS, Nantes univ - UFR ST