Qu'est-ce qu'une eau de bonne qualité ?
Normes et définitions de la qualité de l'eau vis à vis des usages et limites.
(pp. 212-213, 31/08/2026)
UR ETBX, IRSTEA, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, CNRS
Spatial and seasonal variations of methylmercury in European glass eels (Anguilla anguilla) in the Adour estuary (France) and relation to their migratory behaviour
Overall recruitment of European glass eels (Anguilla anguilla) has decreased significantly since the early 1980s. Due to their long life cycle, benthic/demersal habits and high lipid content, eels might accumulate high concentrations of contaminants, but data concerning glass eels are still scarce. This study provides original data on methylmercury (MeHg) concentrations in glass eels at spatial (marine and estuarine), annual and seasonal scales. The relationship between MeHg concentrations in glass eels and their propensity to migrate up estuaries was also investigated. MeHg data were individually related to the eels’ energetic condition which was estimated by dry weight. Glass eel migratory behaviour was investigated in an experimental flume and related to the MeHg concentration and dry weight at the individual scale. Marine and estuarine glass eels were caught from 2004 to 2011. There was a strong inverse correlation between MeHg concentrations and dry weight. MeHg concentrations increased in marine and estuarine glass eels from 2004 to 2009 and from 2004 to 2010, respectively, and then, both groups decreased in 2011. On a seasonal time scale, MeHg concentrations were higher at the end of the fishing season (April). MeHg bioaccumulation is likely to result from different sources, but the lack of significant differences between marine and estuarine glass eels suggests that direct contamination during estuarine migration is low. Other sources such as maternal transfer or oceanic contamination are discussed
(Environmental Science and Pollution Research. vol. 22, n° 0944-1344, pp. 10721-10732, 31/08/2026)
ECOBIOP, INRA, UPPA, IPREM, UPPA, INC-CNRS, CNRS, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS
The extreme mobility of debris avalanches: A new model of transport mechanism
Large rockslide-debris avalanches, resulting from flank collapses that shape volcanoes and mountains on Earth and other object of the solar system, are rapid and dangerous gravity-driven granular flows that travel abnormal distances. During the last 50 years, numerous physical models have been put forward to explain their extreme mobility. The principal models are based on fluidization, lubrication, or dynamic disintegration. However, these processes remain poorly constrained. To identify precisely the transport mechanisms during debris avalanches, we examined morphometric (fractal dimension and circularity), grain size, and exoscopic characteristics of the various types of particles (clasts and matrix) from volcanic debris avalanche deposits of La Réunion Island (Indian Ocean). From these data we demonstrate for the first time that syn-transport dynamic disintegration continuously operates with the increasing runout distance from the source down to a grinding limit of 500 μm. Below this limit, the particle size reduction exclusively results from their attrition by frictional interactions. Consequently, the exceptional mobility of debris avalanches may be explained by the combined effect of elastic energy release during the dynamic disintegration of the larger clasts and frictional reduction within the matrix due to interactions between the finer particles.
(Journal of Geophysical Research : Solid Earth. vol. 120, n° 2169-9313, pp. 8110–8119, 31/08/2026)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, LMV, UBP, INSU - CNRS, UJM, UJM EPE, CNRS, IRAMAT-CRP2A, IRAMAT, UTBM, UO, UBM, CNRS, LGSR, UR, IPG Paris
Weak evidence of regeneration habitat but strong evidence of regeneration niche for a leguminous shrub
The identification of an ecological niche specific to the regeneration phase has mobilised significant attention. However, the importance of the regeneration niche concept remains unclear. Our main objective was to study the existence of such a regeneration niche for a leguminous shrub, Ulex europaeus. This study was carried out in southwest France in the context of water and nutrient stresses (mainly phosphorus limitation) due to the presence of nutrient-poor sandy soils. We analysed the regeneration of the species from the germination of seeds and emergence of new seedlings until the seedlings reached young shrub size. Our design included a P fertilisation treatment. We also investigated microsite characteristics (micro-topography and vegetation development) as they can interact with meteorological conditions and determine water availability for seeds and seedlings. We found that P availability controlled seedling growth and the time necessary to reach young shrub size. Water availability appeared to impact the species germination and seedlings survival. We also found that P and water availability depended on the interactions between microsite characteristics and climatic variations. Finally we found evidence that P and water availability are important ecological factors shaping the regeneration niche of the species, but we found weak evidence that any microsite would be appropriate for the regeneration of the species in the long term. Future studies regarding regeneration niches need to distinguish more clearly the ecological factors important for regeneration (the regeneration niche per se) and the physical world where the seedlings appear and develop (the regeneration habitat).
(PLoS ONE. vol. 10, n° 1932-6203, pp. 20 p., 31/08/2026)
BioGeCo, INRA, UB, UMR ISPA, INRA, Bordeaux Sciences Agro, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS
Trophic networks: How do theories link ecosystem structure and functioning to stability properties? A review
In the context of present global changes, interest in understanding how systems respond to anthropogenic environmental pressures and stress has increased. Indices that characterize ecosystem state are helpful tools for the interpretation of ecosystem responses. The central question is how to link these responses to ecosystem structure and functioning and to quantify ecosystem persistence, resistance or resilience. Quantification and characterization of trophic networks by ecological network analysis (ENA) indices is proceeding rapidly, especially in the field of coastal ecology. In this contribution, we review several theories that relate ecosystem structure and function to stability. The structure and functioning of ecosystems change during the maturation of ecosystems. In the first section, the maturation of ecosystems is described using thermodynamics. In the second and third parts of this paper, we define some concepts for analysing structure and functioning of food webs and discuss their relation to stability. In the last section, we describe three ENA indices and their link to stability. We demonstrate that ENA provides powerful tools for describing local stability, combining quantitative and qualitative concepts. However, it remains incomplete for describing real conservation cases that combine local and global stability. © 2015 Elsevier Ltd. All rights reserved.
(Ecological Indicators. vol. 52, n° 1470-160X, pp. 458--471, 31/08/2026)
LIENSs, INSU - CNRS, ULR, CNRS, JSC, AWI, DYNECO, IFREMER, AWI, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, IOB, BOREA, UNICAEN, NU, MNHN, IRD, SU, CNRS, UA, CNRS, UNICAEN, NU, NU
Dinoflagellate cyst population evolution throughout past interglacials: Key features along the Iberian margin and insights from the new IODP Site U1385 (Exp 339)
IODP 339 Site U1385 ("Shackleton site", e.g. Hodell et al., 2013a), from the SW Iberian margin, offers the opportunity to study marine microfossil population dynamics by comparing several past interglacials and to test natural shifts of species that occurred across these warm periods, in a subtropical context. Here, more specifically, we present results obtained for the dinoflagellate cyst (dinocyst) population integrated at a regional scale thanks to the addition of data from proximal sites from southern Iberian margin. When possible, observations made using the dinocyst bio-indicator are compared to additional proxies from the same records in order to test the synchronicity of the marine biota response. Pollen data available for some of the compiled marine sequences also offer the opportunity to directly compare marine biota with terrestrial ecosystem responses. This spatio-temporal compilation reveals that, over the last 800 ka, surface waters around Iberia were tightly coupled to (rapid) climate changes and were characterised by coherent dinocyst assemblage patterns, highlighting a permanent connection between Atlantic and Mediterranean waters as evidenced through a continuous exchange of dinocyst populations. Some index species well illustrate the evolution of the regional hydrographic context along time, as for instance Spiniferites and Impagidinium species, together with Lingulodinium machaerophorum, Bitectatodinium tepikiense and heterotrophic brown cysts. They constitute key bio-indicators in context of natural environmental shifts at long and short timescales.
(Global and Planetary Change, n° 0921-8181, pp. in press, 31/08/2026)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, LDO, INSU - CNRS, UBO EPE, CNRS, IPMA, CIMA, UAlg
Complex communities exposed to multiple pollutants: using passive sampler extracts in periphyton ecotoxicology
In rivers, risk assessment requires taking into account both the complexity of contaminations (multiple substances at low concentrations), and the increasing demand for ecologically realistic biological endpoints used in toxicity testing. These issues can be tackled by coupling toxicity assessment using complex communities, such as periphyton (composed of microalgae, bacteria, fungi, protozoa, etc.), and complex contaminants like passive samplers extracts (PSE). Here we propose to review some recent progresses in ecotoxicology allowed by the joint use of PSE from POCIS (Polar Organic Chemical Integrative Samplers) and river periphyton. More specifically, we will present diverse experimental approaches, aiming: at characterizing the “toxic potential” of waters and applying the pollution community induced tolerance –PICT– approach to pesticide mixtures, at identifying the compounds responsible for toxicity in the mixture (effect-directed analyses –EDA), and at increasing the environmental realism in microcosm experiments by performing chronic low dose exposure to mixtures from PSE. We were able to detect PICT in periphyton collected in rivers showing a gradient of increasing pesticide concentrations or at sites with different contamination profiles using toxicity tests with PSE from the field. From a pesticide mixture that proved to be toxic, we performed successive fractionation steps to identify, through an EDA approach, the substance(s) responsible for toxicity. In the mixture we used, however, no individual fraction was found to explain the impacts of the cocktails, whereas combinations of fractions did. This highlights the need to consider the “mixture issue” in environmental risk assessment. One way to improve mixture toxicity assessment is to implement chronic exposure experiments with PSE. We successfully performed artificial channel experiments using of PSE as a complex contaminant at low doses. The environmentally relevant concentrations tested drove community changes, in their structure (biomass, composition) as well as in their functions (enzymatic activities). Altogether, these encouraging results open wide perspectives for a more realistic risk assessment, from both biological and chemical points of view.
(pp. 2, 31/08/2026)
UR EABX, IRSTEA, UR MALY, IRSTEA, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS
Feeding Habitats, Connectivity and Origin of Organic MatterSupporting Fish Populations in an Estuary with a ReducedIntertidal Area Assessed by Stable Isotope Analysis
Stable isotopes (delta13C and delta15N) were used to analyse the food web downstream of the largest estuary on the French coast: the Gironde. The different sources of organic matter supporting the most abundant and commercially important fish species were determined, as well as habitat connectivity for fish. Stable isotope analysis was performed in different producers (marine, freshwater and local sources), primary consumers (zooplankton and macrozoobenthos) and nine fish species (Alosa alosa, Engraulis encrasicolus, Sprattus sprattus, Liza ramada, Pomatoschistus minutus, Platichthys flesus, Solea solea, Dicentrarchus punctatus and Argyrosomus regius) in three habitats of the downstream area of the estuary in June–July 2012. All sources and invertebrates had significantly different isotopic signatures in different habitats. Only sole, S. solea, presented distinct dual isotopic signatures, indicating a higher feeding location fidelity, no other fish species showed significant differences in isotopic signatures. This overlap was interpreted as evidence that fish had not been feeding exclusively in the habitat where they were collected, instead ingesting food with different isotopic signatures, reflecting high habitat connectivity for these fish. As the base of the fish food web significantly differed among habitats, the present study indicated the suitability of stable isotopes in tracing fish movements and their fidelity/connectivity for habitats separated by less than 10 km, particularly estuarine habitats without salinity differences but located on opposite banks. The SIAR mixing model estimations of organic matter contribution to fish diets in the Gironde estuary were quite similar for the fish species investigated. The major organic source was marine-derived POM, with contributions >75 % for each species. Freshwater and local POM (generally indicated as the sources structuring estuarine food webs) contributed little to the overall fish food webs in the Gironde estuary. Only flounder, P. flesus, and shad, A. alosa, migratory amphihaline species, utilised freshwater POM in greater proportion than marine. The observed low freshwater POM-high marine POM contribution to the fish food web seems to be explained by the reduced intertidal surface of the system. This characterization of the trophic base and habitat connectivity for the most important Gironde estuary fish provides a novel insight for future management of the estuary, especially in the current context of global change.
(Estuaries and Coasts. vol. 38, n° 1559-2723, pp. 1431-1447, 31/08/2026)
UR EABX, IRSTEA, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS
Is the toxicity of pesticide mixtures on river biofilm accounted for solely by the major compounds identified?
The study aimed to characterize the effects of long-term and low-dose exposure to pesticides on natural biofilm communities and to evaluate if the effects due to PE exposure could be explained solely by the major compounds identified in the extracts.
(Environmental Science and Pollution Research. vol. 22, n° 0944-1344, pp. 4009-4024, 31/08/2026)
UR EABX, IRSTEA, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, UdG
Evaluation de la sensibilité des jeunes stades d'esturgeons européens aux polluants : chapitre V
Les objectifs de cette étude sont (i) d'évaluer la possibilité de créer artificiellement un sédiment dopé agissant de la même manière qu'un sédiment naturel chez l'esturgeon européen (ii) d'évaluer la sensibilité des jeunes stades d'esturgeon européen à différentes concentrations d'un mélange représentatif des polluants organiques et métalliques rencontrés dans l'environnement (iii) et enfin d'évaluer l'effet combiné de l'exposition aux polluants et à une augmentation de la température.
(pp. 59-70, 31/08/2026)
UR EABX, IRSTEA, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS