Méthodes phytobenthiques cours d’eau (Réunion et Antilles) : Cadre général et méthodologique
Pour favoriser la mise en application de la DCE dans les DOM, des programmes locaux de développement de bio-indicateurs ont été entrepris à partir de 2008 sous la maîtrise d’ouvrage principale des gestionnaires locaux des hydrosystèmes (Offices de l’Eau et DEALs), avec des participations financières complémentaires émanant, selon le cas, du niveau national (Ministère de l’Outre-Mer, ONEMA), de l’Union Européenne (FEDER) et d’une part de financement propre souvent apportée par les équipes participant à la réalisation concrète des programmes. Dans ce cadre, le consortium Asconit-Irstea a pris en charge, entre 2008 et 2013, la réalisation de programmes de mise au point de nouveaux indices diatomiques des cours d’eau à la Réunion et aux Antilles et autofinancé, selon le cas, de 25 à 30 %.du coût total de chacun des projets. Les démarches Réunion et Antilles ont suivi des cheminements méthodologiques relativement parallèles et comparables sur le plan de la démarche biomathématique mise en oeuvre. A partir des données taxonomiques et abiotiques obtenues dans le cadre de 7 à 8 campagnes d’échantillonnage de terrain, des référentiels conséquents, atteignant au final 345 doublets de données exploitables à la Réunion et 607 aux Antilles, ont pu être constitués et faire l’objet de diverses analyses biomathématiques de données. Celles-ci se sont organisées en 5 étapes spécifiques d’investigation : 1) une biotypologie visant, à partir de la composition des assemblages, à repérer leur structuration sous les forçages naturels et sous l’emprise des pressions anthropiques ; 2) Une phase d’analyse exploratoire des données abiotiques (ACP complète ) visant à repérer l’organisation des données et les gradients principaux rencontrés au niveau physico-chimie et chimie de l’eau ; 3) Une analyse canonique des correspondances (ACC complète) visant à repérer la co-structuration des données générales d’environnement et des assemblages floristiques ; 4) une analyse canonique des correspondance restreinte, selon le cas, à 9 ou 10 variables physico-chimiques fortement influencées par les activités anthropiques (ACC restreinte), qui a permis de formaliser un gradient composite multimétrique d’anthropisation (GCMA) assis à la fois sur les données abiotiques et sur la matrice de réponse des assemblages diatomiques ; 5) le calcul du profil de qualité des espèces intervenant dans le calcul des futurs indices diatomiques, après seuillage sur un double critère d’occurrence et d’abondance relative minimale dans au moins un relevé, suivi de la formulation de l’indice. Il a ainsi été mis au point 2 versions successives d’IDR (Réunion) et d’IDA (Antilles) permettant au final de tirer parti de l’ensemble des données devenues mobilisables sur ces DOM à la fin 2013 et de remédier aux défauts de jeunesse diagnostiqués sur leur première version. Ces indices fonctionnent sur un principe général de repérage de taxons d’alerte, qui contribuent à la dégradation de la note d’indice avec un poids différent selon la catégorie à laquelle ils appartiennent. Un système d’évaluation propre à chaque DOM a ensuite été élaboré, conduisant à la proposition d’une grille spécifique d’évaluation, exprimée en EQRs, par grand ensemble naturel de chacun de ces DOM (2 grands ensembles naturels à la Réunion, 2 pour les Antilles regroupées). Ces grilles sont utilisables au relevé et devront faire l’objet d’une adaptation spécifique pour une agrégation temporelle au site. Elles ont été intégrées à un projet de nouvel Arrêté d’Evaluation dont la parution est prévue début 2015.
(pp. 19, 26/10/2026)
UR EABX, IRSTEA, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS
Effets de la qualité des sédiments de frayère sur le développement embryo-larvaire de l'esturgeon européen (Acipenser sturio)
Les embryons et larves d'esturgeon européen ont été exposés aux substrats de 2 frayères situées sur la Dordogne et la Garonne. Les individus exposés au substrat de La Réole (Garonne) présentent une augmentation du taux de malformation, une altération des capacités physiologique et natatoire.
(pp. 15, 26/10/2026)
UR EABX, IRSTEA, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS
Benthic foraminifera from the deep-water Niger delta (Gulf of Guinea): Assessing present-day and past activity of hydrate pockmarks
We present ecological and isotopic (δ18O and δ13C) data on benthic foraminifera sampled from 4 deep-sea stations in a pockmark field from the deep-water Niger delta (Gulf of Guinea, Equatorial Atlantic Ocean). In addition, a series of sedimentological and (bio)geochemical data are shown to back up foraminiferal observations. All stations are located within 1.2km of each other, so prevailing oceanographic conditions can be assumed to be similar at each site. Two of the sites (GMMC-01 and GMMC-02) are located in a pockmark (named "pockmark A") where current methane seepages were recorded by ROV observations. A third station (GMMC-03) is located in the topographic depression interpreted as a collapsed pockmark (named "pockmark B"). The fourth site (GMMC-04) is a reference station, without evidence of past or present seepages. Our observations show that degraded organic matter with low bio-availability is present at all stations with a preferential burial of organic compounds in topographic depressions (GMMC-03 station). Authigenic aragonite is abundant in surface sediments at stations GMMC-01 and -02. Its precipitation is likely related to high rates of methane oxidation during past seep events in episodically active pockmark A. In contrast, the absence of anaerobic methanotrophic Archaea (ANME) during the sampling period (November 2011) suggests that only moderate sulphide and methane oxidation take place close to the sediment-water interface. Compared to the reference site GMMC-04, living foraminifera at the collapsed and episodically active pockmarks show minor changes in terms of diversity, standing stocks and faunal composition. However, the δ13C signal of living and dead (but well-preserved) foraminiferal species (Ceratobulimina contraria, Melonis barleeanus, Uvigerina peregrina) is depleted in the episodically active pockmark A compared to the other stations. Overgrowth of authigenic carbonate on altered foraminifera generates an important shift to lower δ13C values. Dead faunas carry a complex time-averaged message, integrating taphonomic gains and losses related to the temporal variability of gas emission. They reveal major faunal differences that may be useful to detect gas hydrate seepages in different pockmark stages. © 2014 Elsevier Ltd.
(Deep Sea Research Part I: Oceanographic Research Papers. vol. 94, n° 0967-0637, pp. 87-106, 26/10/2026)
BIAF, UA, IPREM, UPPA, INC-CNRS, CNRS, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, EGID, LASIRE, INC-CNRS, CNRS, LEP, EEP, IFREMER, IFREMER, AWI
Competition, facilitation and environmental severity shape the relationship between local and regional species richness in plant communities
Understanding the relative contribution of local and regional processes to local species richness is an important ecological question and a subject of controversy between macroecologists and community ecologists. We test the hypothesis that the contribution of local and regional processes is dependent on environmental conditions and that the eff ect of regional processes should be the highest in communities from intermediate positions along environmental severity gradients due to the importance of facilitation. We used the recently developed log-ratio method to analyze the relationship between local species richness (LSR) and regional species richness (RSR) for 13 plant communities from 4 habitat types of France (coastal sand dunes, oceanic heathlands, alpine grasslands, lowland calcareous grasslands). Each habitat type wassplit in 3 – 4 communities using multivariate analyses to identify the relative importance of stress, disturbance, competition, and facilitation functioning within the 13 communities. We found that the LSR/RSR relationship was highly dependent on environmental conditions with saturated communities occurring more frequently than unsaturated communities highlighting the relative importance of local drivers on species richness. We argued that competition was most likely the main source of community saturation whilst facilitation likely contributed to enhancing the importance of the regional species pool for all habitat types. However, the eff ect of facilitation might be stronger in the disturbed than in the stressed systems because unsaturated curves were only observed in the former conditions. In extreme conditions of disturbance LSR was only controlled by the intensity of disturbance. Th is eff ect was not observed in extreme stress conditions. Our study provides support for the emerging balance theory that both local and regional processes are important in nature with their relative contribution depending on environmental conditions. Additionally, this synthesis strongly suggests that facilitation contributes to an important process – the influence of regional species pool on local species richness.
(Ecography. vol. 37, pp. 1-11, 26/10/2026)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, LECA, UJF, USMB [Université de Savoie] [Université de Chambéry], CNRS, SAJF, UJF, CNRS, ECOBIO, UR, INEE-CNRS, CNRS, CNRS, ONF, IEU, UZH
Abnormal ovarian DNA methylation programming during gonad maturation in wild contaminated fish
There is increasing evidence that pollutants may cause diseases via epigenetic modifications. Epigenetic mechanisms such as DNA methylation participate in the regulation of gene transcription. Surprisingly, epigenetics research is still limited in ecotoxicology. In this study, we investigated whether chronic exposure to contaminants experienced by wild female fish (Anguilla anguilla) throughout their juvenile phase can affect the DNA methylation status of their oocytes during gonad maturation. Thus, fish were sampled in two locations presenting a low or a high contamination level. Then, fish were transferred to the laboratory and artificially matured. Before hormonal treatment, the DNA methylation levels of the genes encoding for the aromatase and the receptor of the follicle stimulating hormone were higher in contaminated fish than in fish from the clean site. For the hormone receptor, this hypermethylation was positively correlated with the contamination level of fish and was associated with a decrease in its transcription level. In addition, whereas gonad growth was associated with an increase in DNA methylation in fish from the clean site, no changes were observed in contaminated fish in response to hormonal treatment. Finally, a higher gonad growth was observed in fish from the reference site in comparison to contaminated fish.
(Environmental Science and Technology. vol. 48, n° 0013-936X, pp. 11688--11695, 26/10/2026)
µVIS X-ray Imaging Centre, LPTC, UB, CNRS, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, UR EABX, IRSTEA, ISM, UB, INC-CNRS, CNRS, BOREA, UNICAEN, NU, MNHN, IRD, SU, CNRS, UA, INRS
Preface "The changing Arctic and Subarctic environment: proxy- and model-based reconstructions of Holocene climate variability in the northern North Atlantic
This special issue originates from the EU FP7-Marie Curie initiative "CASE" (The Changing Arctic and Subarctic Environment), an Initial Training Network (ITN) on marine biotic indicators of recent climate changes in the high latitudes of the North Atlantic (http://caseitn.epoc.u-bordeaux1.fr/). This four-year project (April 2010-March 2014) implemented multidisciplinary research initiatives aiming at assembling palaeoclimate data from the Holocene through recent field programmes in the Nordic Seas, and at integrating palaeoclimate information with modern biological and climate modelling data. Associated objectives were to recruit and train a new generation of European polar scientists with expertise on the Nordic Seas, and to develop a network of European experts in polar research to build structures focused on long-term collaboration in Arctic science. Together with the Arctic Ocean, the Nordic Seas and the Barents Sea have shown unprecedented changes in physical and chemical conditions in recent decades, which directly influence the ecosystem structure and processes. The extreme sensitivity of the northern North Atlantic to climate changes is related to the intricate connection, within this oceanic realm, of cryospheric (ice sheets and sea ice), atmospheric (winds related to strong gradients in sea-level pressures), and oceanic processes (through the opposing poleward flow of Atlantic water and southward flow of polar waters). The recent decline in seasonal sea ice extent is of particular concern as it modulates the reflection of incoming solar radiation, and influences the exchanges of heat and moisture between the surface ocean and the atmosphere. Moreover, sea ice also plays a central role in the efficiency of shelf (brines) and deep ocean convection processes, thus influencing the climate on a global scale. Decadal to millennial scale reconstructions of Holocene climate and environments from archives, such as marine sediment cores, and from palaeoclimate modelling hold keys to a better evaluation of the magnitude and implications of the ongoing warming with regard to the full range natural variability of the climate system. This special issue addresses some of the key questions raised by the CASE project and related to the present polar amplification of climate change: -Is the present global warming and its amplification in the Arctic and Subarctic domains a unique event on the scale of the Earth recent history (last 10 000 years)? -How do past decadal-to centennial-scale natural climate changes, as recorded in marine sediments and ice cores, stand in the context of the present human-induced modulation of climate? -How did Holocene variability in key physical elements affect the structure and diversity of the planktonic ecosystem in the Arctic and Subarctic domains?
(Climate of the Past. vol. 10, n° 1814-9324, pp. 589-590, 26/10/2026)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, UvA, LMD, INSU - CNRS, X, IP Paris, ENPC, SU, CNRS, ENS-PSL, PSL
Tectonics of the Dalrymple Trough and uplift of the Murray Ridge (NW Indian Ocean)
The Dalrymple Trough is a 150-km-long, 30-km-wide basin located at the northern termination of the Owen Fracture Zone (OFZ), which is the present-day active India-Arabia plate boundary. The Dalrymple Trough is closely associated with the Murray Ridge, a complex of prominent bathymetric highs located on its eastern flank. Recent multibeam mapping of the connection between the Dalrymple Trough and the OFZ revealed a horsetail structure, which suggests a close relationship between geological histories of both structures. However, the 3-6 Ma age of initiation of the OFZ contrasts with the commonly accepted Early Miocene emplacement of the Dalrymple Trough. Recent seismic lines document a new tectonic history of the Dalrymple Trough, involving two major episodes of deformation along the India-Arabia plate boundary at ~ 8-10 Ma and ~ 1.9 ± 0.9 Ma. The 8-10 Ma episode is marked by a system of folds linked to the main uplift of the southern Murray Ridge and the first uplift of the northern Murray Ridge. This episode is related to a global plate reorganization event in the Late Miocene, well expressed by intraplate deformation in the Central Indian Ocean. The Dalrymple Trough opened at ~ 1.9 ± 0.9 Ma subsequently to the formation of a stepover at the India-Arabia plate boundary, coeval with the regional M-unconformity in the Oman abyssal plain, which marks a structural reorganization of the Makran accretionary wedge, and the last uplift of the northern Murray Ridge.
(Tectonophysics, n° 0040-1951, pp. 1-49, 26/10/2026)
LGENS, INSU - CNRS, CNRS, ENS-PSL, PSL, iSTeP, UPMC, CNRS, GEC, I-MAT, UCP, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS
Impacts of Mayan land use on Laguna Tusp an watershed (Pet en, Guatemala) as seen through clay and ostracode analysis
Most of the cities built by the Mayas in the Pet en area, in the Central Yucat an Peninsula, were abandoned 1200 to 1000 years ago. The phenomenon is sometimes un-appropriately called " the collapse of the Maya civilization ". Its main causes are still debated, ranging from climatic according to the occurrence of severe or modest droughts, to societal in the form of environmental mismanagement of the environment. In both processes, it is inferred that stress triggered the formation in many Pet en lake sediments of erosional clay deposits, known as 'Maya clays'. This work presents a high resolution, multi-proxy study of 'Maya clays' in lacustrine sediments from Laguna Tusp an, near the archaeological site of La Joyanca. Micropaleontological (ostracodes), mineral-ogical (clay minerals) and geochemical (bulk elemental composition and stable isotopes in organic carbon) records reveal three different phases of soil erosion throughout the last 5300 years. The oldest phase from 5281 to 2998 cal yr BP (i.e. 3331 e 1048 BC) is characterized by successive natural and moderate soil erosion deposits which follow climatic variations recorded in the American tropical belt. The time interval between 2998 and 1281 cal yr BP (i.e. 1048 BC and AD 661) contains four distinct erosional layers which, according to clay mineralogy, are indicative of both increased erosion of the regolith and strong soil loss. The most recent, also the most massive, deposit of Maya clay ends around 1281 cal yr BP (AD 661), that is some 200 years before the so-called 'Maya collapse' in the Pet en area. Recent archeological fieldwork studies indicate that a population mobility took place into the city of La Joyanca from its hinterland by the early Late Classic Period (ca. AD 600), that is, at the end or just after this erosion episode, and well before the occurrence of the Terminal Classic-Postclassic (AD 800e1250) drastic climatic changes. Shifts in environmental management by the local society and timing of urbanization may explain environmental changes better than droughts per se.
(Journal of Archaelogical Science. vol. 49, pp. 372-382, 26/10/2026)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, GEODE, UT2J, Comue de Toulouse, CNRS, LOG, INSU - CNRS, ULCO, CNRS, IRD [Ile-de-France]
Hypoxia tolerance of European sturgeon (Acipenser sturio L., 1758) young stages at two temperatures
European sturgeon sensitivity to oxygen depletion at two different temperatures was evaluated with embryos from fertilization to hatching time that were exposed to 90% O2 saturation (% O2 sat), 50% O2 sat and 30% O2 sat at 20 and 26°C; and three-month-old juveniles (12 cm length, 7.3 g width) exposed to oxygen challenge from 70% O2 sat to 10% O2 sat at 20 and 25°C. Parameters measured included embryonic survival rate (ESR) and hatch rate (HR); in juvéniles the opercular beat frequency (OBF), altered swimming behavior, loss of equilibrium (LOE), and death were recorded. ESR did not differ between oxygen saturation levels for a single temperature but decreased between 20 and 26°C from 60.7 to 21.4% mean survival, respectively. No hatching was observed in embryos exposed to oxygen depletion at 50 and 30% O2 sat, regardless of temperature. The HR was lower at 26°C (15.4% mean) than at 20°C (75.8%) at 90% O2 sat. In embryos, all three oxygen concentrations allowed embryonic survival at the tested temperatures but were insufficient for increased activity such as hatching except at 20°C and 90% O2 sat. In juveniles, OBF peaked at 40% O2 sat at 212 beats per minute at 25°C and at 40–30% O2 sat at 182–183 beats per minute at 20°C. For LOE and death no significant differences were observed with regard to oxygen saturation at 20 and 25°C. Altered swimming behavior appeared at a significantly higher oxygen saturation at 25°C (43.5%) compared to 20°C (34.5%). Anaerobic metabolism was initiated after the OBF peak, which would represent a PO2crit for European sturgeon juveniles under 30 and 40% at 20°C and 25°C, respectively. Temperature increase also adversely affected the threshold of altered swimming behavior, which could be considered as a behavioral indicator of metabolic stress. The probability that the sturgeon embryos are being exposed to harmful temperatures and hypoxic conditions remains a true threat in the Gironde catchment basin.
(Journal of Applied Ichthyology. vol. 30, n° 0175-8659, pp. 1195-1202, 26/10/2026)
UR EABX, IRSTEA, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS
Multi-criteria assessment of advanced tertiary treatments for micropollutants removal
This paper presents the removal of 64 micropollutants from wastewater by 5 tertiary treatment processes: adsorption on activated carbon, ozone, ozone/H2O2, ozone/UV and UV/H2O2. Several validated analytical methods were used and reached very low limits of quantification (ng/L) and limited uncertainties. The tertiary treatments studied in the conditions applied were found efficient for the removal of most of the compounds analyzed in this study, except metals. Activated carbon and ozone allowed the removal over 70% of 2/3 of the organic micropollutants quantified. The addition of hydrogen peroxide to ozone increased the number of substances well removed (Rw>70%), but it did not improve the removal of substances that readily react with ozone. The other AOP (ozone/H2O2 and UV/H2O2) did not improve the number of substances well removed in comparison with ozone alone. The 5 technologies studied were sized at full scale in order to evaluate their investment and operation costs for two sizes of WWTP. According to this study, the implementation of a tertiary treatment on a 60 000 or a 200 000 PE WWTP would increase the water treatment cost by 2 to 20 euros cents per cubic meter treated according to the technology, the list of analyzed compounds and the removal objective.
(pp. 4, 26/10/2026)
IRSTEA, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, UR MALY, IRSTEA