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, 23/06/2026)
UR EABX, IRSTEA, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS
Levantine intermediate water hydrodynamic and bottom water ventilation in the northern Tyrrhenian Sea over the past 56,000 years: new insights from benthic foraminifers and ostracods
Foraminifera and ostracods have been quantitatively studied in core MD01-2472, from the upper continental slope (at water depth of 501 m), to evaluate their relationship with bottom water condition variability and decipher the control of the Levantine Intermediate Water (LIW) current on benthic faunas. The occurrence of reworked ostracod species (originating from the continental shelf) and, the presence of shallow water Elphidium/Ammonia benthic foraminifera are used to estimate the degree of along-slope transport at the core site. This has revealed two intervals of along-slope transport also associated with coarse-grained contourite deposits, deposited during the YD and HS2 episodes. Planktonic-benthic foraminiferal and ostracod assemblages reflect climate oscillations. Peaks of the polar planktonic Neogloboquadrina pachyderma (left-coiling S) may be used to identify Heinrich Events. Interstadials are marked by abundant ostracod species such as Paracypris sp., Argilloecia acuminata, and Cytheropteron alatum and the presence of benthic foraminifera like Bulimina marginata, Bulimina costata and Gyroidina altiformis. The B–A and Holocene are characterized by abundant warm water species of planktonic foraminifera and by the ostracod species Polycope sp. We hypothesize that there is relationship between LIW intensification during cold rapid climate events and benthic fauna assemblage variations due to changes in: 1) bottom water ventilation; and 2) the export of nutrients and/or sediment particles by bottom currents.
(Quaternary International, n° 1040-6182, pp. 395-313, 23/06/2026)
CEFREM, UPVD, INSU - CNRS, CNRS, UniPi, GEUS, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, GM, IFREMER
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, 23/06/2026)
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
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, 23/06/2026)
UR EABX, IRSTEA, UR MALY, 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, 23/06/2026)
UR EABX, IRSTEA, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, UdG
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, 23/06/2026)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, LDO, INSU - CNRS, UBO EPE, CNRS, IPMA, CIMA, UAlg
Peut-on améliorer l’élimination des micropolluants des eaux usées en optimisant le procédé à boues activées ?
Cette étude visait à améliorer l'élimination des micropolluants en modifiant les conditions de fonctionnement du procédé boues activées aération prolongée. Cette question a nécessité de mesurer les coefficients de sorption et les constantes de biodégradation (étude pilote), et de décrire la variabilité des concentrations dans les eaux usées brutes et les boues d'une installation vraie grandeur. 53 micropolluants ont été étudiés (11 métaux et 42 substances organiques). Au total, 8 campagnes d’échantillonnage de quelques jours ont été réalisées sur une durée d’un an, pour différentes conditions de fonctionnement de l'installation (concentration en boue, durée de présence d'oxygène, température). Les concentrations dans les eaux usées brutes ont varié de façon importante pour les substances organiques (50 à 100%), mais moindre pour les métaux (30%). Au cours d’une période de 24 heures, des concentrations deux fois plus élevées ont été mesurées dans la journée (6 h à 24 h), par comparaison aux concentrations mesurées la nuit pour plusieurs substances (ex. zinc, plomb, nonylphénol, propranolol, diclofénac). Nous avons démontré que la biodégradation explique l’élimination d’une dizaine de substances (ex. paracétamol, acébutolol, aténolol, ibuprofène, nonyl- et octyl-phénol). La sorption seule explique le transfert dans les boues des HAP lourds et des métaux. La sorption et biodégradation expliquent conjointement l’élimination d’une dizaine d’autres substances (ex. propranolol et quelques HAP). En complément, nous avons démontré que la biodégradation se déroule principalement en condition aérobie, surtout en présence simultanée de DCO et d’azote ammoniacal dans le bioréacteur, et avec une vitesse moindre en présence d’azote seul et très faible en phase endogène. Nous avons mesuré une faible dégradation des micropolluants une fois adsorbés sur les boues (
(TSM. Techniques Sciences Méthodes, n° 0299-7258, pp. 32-50, 23/06/2026)
UR MALY, IRSTEA, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS
Modelling analysis of tidal bore formation in convergent estuaries
(23/06/2026)
CARDAMOM, IMB, UB, Bordeaux INP, CNRS, Inria, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS
Reconciling reconstructed and simulated features of the winter Pacific/North American pattern in the early 19th century
Reconstructions of past climate behavior often describe prominent anomalous periods that are not necessarily captured in climate simulations. Here, we illustrate the contrast between an interdecadal strong positive phase of the winter Pacific/North American pattern (PNA) in the early 19th century that is described by a PNA reconstruction based on tree rings from northwestern North America, and a slight tendency towards negative winter PNA anomalies during the same period in an ensemble of state-of-the-art coupled climate simulations. Additionally, a pseudo-proxy investigation with the same simulation ensemble allows for assessing the robustness of PNA reconstructions using solely geophysi-cal predictors from northwestern North America for the last millennium. The reconstructed early 19th-century positive PNA anomaly emerges as a potentially reliable feature, although the pseudo-reconstructions are subject to a number of sources of uncertainty and deficiencies highlighted especially at multidecadal and centennial timescales. The pseudo-reconstructions demonstrate that the early 19th-century discrepancy between reconstructed and simulated PNA does not stem from the reconstruction process. Instead, reconstructed and simulated features of the early 19th-century PNA can be reconciled by interpreting the reconstructed evolution during this time as an expression of internal climate variability, which is unlikely to be reproduced in its exact temporal occurrence by a small ensemble of climate simulations. However , firm attribution of the reconstructed PNA anomaly is hampered by known limitations and deficiencies of coupled climate models and uncertainties in the early 19th-century external forcing and background climate state.
(Climate of the Past. vol. 11, n° 1814-9324, pp. 939-958, 23/06/2026)
MPI-M, IUAV, GERICS, GKSS, UNIBE, PARVATI, LOCEAN, IPSL, ENS-PSL, UVSQ, UPMC, CEA, INSU - CNRS, X, CNES, CNRS, MNHN, IRD, UPMC, INSU - CNRS, CNRS, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS
Seasonal changes in stable carbon and nitrogen isotope compositions of bat guano (Guadeloupe)
Stable isotope compositions of fossil bat guano have recently been developed as a proxy for reconstructing terrestrial paleoenvironments. However, our understanding of exactly how accurately these isotope compositions reflect seasonal variations remains limited. Here, we present a study of modern guano of phytophagous bats collected monthly over a one-year period at two roosting sites in Guadeloupe. The aim is to assess the degree to which seasonal climate and environmental variations are reflected in carbon and nitrogen isotope compositions from bat guano, as well as to evaluate the potential use of guano from phytophagous bats as a paleoenvironmental record. Our results show that stable isotope compositions vary locally, suggesting that guano of phytophagous bats accurately records local environmental conditions. Additionally, stable isotope compositions reflect seasonal variations influencing bat diet that lead to modifications of up to 2‰ of the carbon isotope compositions from feces. However, these variations are not correlated solely with climate variables as there is no straightforward relationship between climate, vegetation and bat diet over a one-year period. Moreover, these seasonal variations drive one of the bat colonies to occasionally consume insects, which can be traced as a seasonal shift in %N (up to 4.5%) and carbon isotope compositions (up to 5.6‰). Seasonal changes in isotope compositions are still lower than expected variations from fossil feces, confirming the potential use of feces from phytophagous bats as a reliable paleoenvironmental proxy.
(Palaeogeography, Palaeoclimatology, Palaeoecology. vol. 440, n° 0031-0182, pp. 524-532, 23/06/2026)
PACEA, UB, CNRS, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS