A framework for investigating general patterns of benthic β-diversity along estuaries
The description of major patterns in beta (β) diversity is important in order to understand changes in community composition and/or richness at different spatial and temporal scales, and can interrogate processes driving species distribution and community dynamics. Human impacts have pushed many estuarine systems far from their historical baseline of rich, diverse, and productive ecosystems. Despite the ecological and social importance of estuaries, there has not yet been an attempt to investigate patterns of β-diversity and its partitioning along estuarine systems of different continents. We aimed to evaluate if benthic assemblages would show higher turnover than nestedness in tropical than in temperate systems, if well-known impacted estuaries would show greater nestedness than less polluted systems, and to propose a conceptual framework for studying benthic macrofauna beta diversity along estuaries. We analyzed subtidal benthic macrofaunal data from estuaries in Brazil, USA and France. We estimated alpha (α), beta (β) and gamma (γ) diversity for each sampling time in each system, investigated patterns of β -diversity as multivariate dispersion and the partitioning (nestedness and replacement) of β-diversity along each estuary. There was a decrease in the α-diversity along marine to freshwater conditions at most of the estuaries and sampling dates. Beta diversity as multivariate dispersion showed high variability. Most of the estuaries showed a greater proportion of the β-diversity driven by replacement than nestedness. We suggest a conceptual framework for estuaries where relatively pristine estuaries would have their β-diversity mostly driven by replacement while impacted estuaries subjected to several anthropogenic stressors would show total nestedness or total replacement, depending on the stress.
(Estuarine, Coastal and Shelf Science. vol. 149, n° 0272-7714, pp. 223-231, 05/08/2014)
SJSU, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, LIENSs, INSU - CNRS, ULR, CNRS
Labrador current variability over the last 2000 years
The ice-loaded Labrador Current (LC) is an important component of the western North Atlantic circulation that influences the position and strength of the northern limb of the North Atlantic Current (NAC). This flow of cold and fresh Polar Waters originating from the Arctic has a marked impact on the North Atlantic climate, yet little is known about its variability beyond the instrumental period. In this study, we present the first sub-decadal alkenone-based 2000-year long sea-surface temperature (SST) records from the western Labrador Sea, a climatically crucial region at the boundary between the LC and the NAC. Our results show a clear link between the LC strength and the Northern Annular Mode (NAM), with a stronger NAM and a more vigorous LC during the Medieval Climate Anomaly (MCA). This suggests enhanced LC activity upon future global warming with implications for the Atlantic meridional overturning circulation (AMOC).
(Earth and Planetary Science Letters. vol. 400, n° 0012-821X, pp. 26-32, 01/08/2014)
BTP, LOCEAN, IPSL, ENS-PSL, UVSQ, UPMC, CEA, INSU - CNRS, X, CNES, CNRS, MNHN, IRD, UPMC, INSU - CNRS, CNRS, PALEOCEAN, LSCE, UVSQ, INSU - CNRS, CNRS, DRF (CEA), CEA, GEUS, LOCEAN, IPSL, ENS-PSL, PSL, UVSQ, UPMC, CEA, INSU - CNRS, X, IP Paris, CNES, CNRS, MNHN, IRD, UPMC, INSU - CNRS, CNRS, ULaval, INSU - CNRS, CNRS, LSCE, UVSQ, INSU - CNRS, CNRS, DRF (CEA), CEA, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, PARVATI, LOCEAN, IPSL, ENS-PSL, UVSQ, UPMC, CEA, INSU - CNRS, X, CNES, CNRS, MNHN, IRD, UPMC, INSU - CNRS, CNRS
Regional distributon of mercury in sediments of the main rivers of French Guiana
Use of mercury (Hg) for gold-mining in French Guiana (up until 2006) as well as the presence of naturally high background levels in soils, has led to locally high concentrations in soils and sediments. The present study maps the levels of Hg concentrations in river sediments from five main rivers of French Guiana (Approuague River, Comté River, Mana River, Maroni River and Oyapock River) and their tributaries, covering more than 5 450 km of river with 1 211 sampling points. The maximum geological background Hg concentration, estimated from 241 non-gold-mined streams across French Guiana was 150 ng g-1. Significant differences were measured between the five main rivers as well as between all gold-mining and pristine areas, giving representative data of the Hg increase due to past gold-mining activities. These results give a unique large scale vision of Hg contamination in river sediments of French Guiana and provide fundamental data on Hg distribution in pristine and gold-mined areas.
(SpringerPlus. vol. 3, n° 2193-1801, pp. 11 p., 15/07/2014)
BRGM, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS
Detoxification and recovery capacities of Corbicula fluminea after an industrial metal contamination (Cd and Zn): A one-year depuration experiment
This study aimed to assess the recovery capacity of the freshwater bivalve Corbicula fluminea subjected to industrial metal discharges (Cd, Zn). After a 24-day exposure in a metal-contaminated river, bivalves were transferred and maintained in the laboratory for one year under metal-free conditions. Metal accumulation, metallothionein production and genetic expressions of genes involved in metal stress were studied. Results demonstrated the high persistence of Cd in tissues (only 73% eliminated after 365 days) whereas Zn was rapidly depurated. The Cd half-life was estimated around 240 days. Metallothioneins were strongly induced within the 28 first days of decontamination, then decreased by 45% after 365 days. The metal exposure of bivalves led to a significant gene induction. After 28 days, most of the genes were no longer overexpressed, suggesting that the bivalves may withstand small amounts of non-essential metals in their tissues without showing signs of detrimental effects on the tested genes.
(Environmental Pollution. vol. 192, n° 0269-7491, pp. 74-82, 09/07/2014)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS
L'aléa submersion marine sur la rive interne du Bassin d'Arcachon : exposition actuelle, cartographie prévisionnelle et capacité d'atténuation par la restauration des marais salés
Le programme BARCASUB a porté sur le risque de submersion marine à l'intérieur du bassin d'Arcachon (France) et sur la gestion potentielle de ce risque par une mesure souple de défense : la "dépoldérisation". La communication détaille les méthodes suivies et les résultats obtenus aux différentes étapes de la méthode d'évaluation de la submersibilité: (1) détermination de la hauteur du plan d'eau lors des épisodes tempétueux Klaus et Xynthia, (2) évaluation des niveaux d'eau extrêmes au front des digues de mer en fonction de plusieurs scénarios de tempête et d'élévation du niveau marin, (3) modélisation des niveaux extrêmes « à terre », (4) suivi de l'accrétion sédimentaire et de la dynamique végétale dans les zones dépoldérisées.
(pp. p. 124-134, 03/07/2014)
PRODIG, UP1, IRD, EPHE, PSL, UP4, UPD7, CNRS, LGP, UP1, UPEC UP12, CNRS, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS
Impact d'un sédiment dopé aux nanoparticules d'or ou de sulfure de cadmium sur un invertébré et un poisson d'eau douce
Le but de cette thèse était de déterminer l’impact de deux types de nanoparticules métalliques (sulfure de cadmium – CdS - et or - Au) sur deux organismes aquatiques modèles (vers tubifex et poisson zèbre Danio rerio). L’approche a consisté à doper le sédiment de la Garonne avec les deux types de nanoparticules et caractériser l’effet de cette contamination sur les deux organismes en utilisant plusieurs marqueurs à différents niveaux d'organisation biologique (réponses biochimiques, activité de neurotransmission, génotoxicité, expression génétique et activité de bioturbation). Les effets ont été évalués après exposition aux sédiments contaminés dans des systèmes expérimentaux de types microcosmes durant une vingtaine de jours. Dans un certain nombre de cas, ce travail a révélé un effet des nanoparticules qui n’était pas dû au métal mais aux propriétés nanoparticulaires. En effet, dans le cas des nanoparticules de CdS, nous avons observé des altérations du génome ainsi que la modification de l’activité de bioturbation des vers tubifex en réponse à la contamination aux nanoparticules mais pas à celle de la forme ionique. Dans ce travail nous avons pu observer le relargage des nanoparticules d’or depuis le sédiment vers la colonne d’eau, et sa biodisponibilité potentielle pour les poissons. Ces nanoparticules provoquaient des altérations de l’ADN chez les deux organismes, la modification de l’expression de certains gènes et l’augmentation de l’activité de l’acétylcholinestérase chez le poisson zèbre. Les résultats de bioturbation n’ont pas montré d’effets des nanoparticules d’or sur le mouvement des vers.
(01/07/2014)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS
GLOBEX: Wave dynamics on a shallow sloping beach
As waves approach the shore, their non-linear dynamics becomes increasingly important. Most of our understanding of wave non-linearity has resulted from theoretical work, laboratory experiments and field studies on beaches slopes steeper than about 1:40. There, very strong non-linear processes happen locally and on a short time scale, as demonstrated by narrow surf zones with plunging or collapsing breakers. The non-linearity on gently-sloping beaches, typical of high-energy dissipative environments, has a different character, as it can build up over a long period of time and along an extensive cross-shore area. This contribution serves to introduce the GLOBEX project, during which a high-resolution (in space and time) data set of the cross-shore evolution of short and infragravity waves was collected on a low-sloping (1:80) non-mobile laboratory beach. As non-linear transfers also occur in the vertical from the free-stream flow downwards into the bottom boundary layer, additional flow measurements performed with Laser Doppler Anemometry are also briefly presented.
(01/07/2014)
LEGI, UJF, Grenoble INP, CNRS, IMAU, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, LEGOS, IRD, UT3, Comue de Toulouse, INSU - CNRS, CNES, CNRS, M2C, UNICAEN, NU, INSU - CNRS, UNIROUEN, NU, CNRS, PUC
An 18 000-year pollen and sedimentary record from the cedar forests of the Middle Atlas, Morocco
A new record from the heart of the Moroccan Middle Atlas cedar forests spans the last 18 000 years and provides valuable insight into our understanding of the natural vegetation and environmental changes. The approach is based on the study of pollen content, geochemical elements and grain size analysis. The pollen data indicate that the vegetation was dominated by herbaceous plants until 9000 BP. Such open landscape allowed greater soil erosion and an input of chemical elements from the watershed. After 9000 BP, tree cover, mainly oak, increased slightly and was accompanied by a higher taxonomic diversity. However, several steppe elements remain well represented in the area until 5000 BP, which suggests that the climate was rather dry during the first part of the Holocene. After 6000 BP, the climate became more favourable to expansion of the forest ecosystems, including Cedrus atlantica, thereby reducing erosion. A strong reduction of the tree pollen percentages is recorded after 2000 BP, which may be related to increasing human activities during the Roman period. These forest changes are concomitant with an increase of lead and copper concentrations in the record, probably related to Roman metalworking activities.
(Journal of Quaternary Science. vol. 29, n° 0267-8179, pp. 423-432, 01/07/2014)
UMR ISEM, Cirad, EPHE, PSL, UM, CNRS, UCD, FSTG, UCA, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, UAG, INSU - CNRS, UM, CNRS, UAM, UAM, CNRS-L
Dynamical model identification of population of oysters for water quality monitoring
The measurements of valve activity in a population of bivalves under natural environmental conditions (16 oysters in the Bay of Arcachon, France) are used for a physiological model identification. A nonlinear auto-regressive exogenous (NARX) model is designed and tested. The model takes into account the influence of environmental conditions using measurements of the sunlight intensity, the moonlight and tide levels. A possible influence of the internal circadian/circatidal clocks is also analyzed. Through this application, it is demonstrated that the developed dynamical model can be used for estimation of the normal physiological rhythms of permanently immersed oysters and considered for detection of perturbations of these rhythms due to changes in the water quality, i.e. for ecological monitoring.
(24/06/2014)
NON-A, Inria, CRIStAL, CNRS, IMB, UB, CNRS, SyNeR, CRIStAL, CNRS, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS
Demographic consequences of heavy metals and persistent organic pollutants in a vulnerable long-lived bird, the wandering albatross
Seabirds are top predators of the marine environment that accumulate contaminants over a long life-span. Chronic exposure to pollutants is thought to compromise survival rate and long-term reproductive outputs in these long-lived organisms, thus inducing population decline. However, the demographic consequences of contaminant exposure are largely theoretical because of the dearth of long-term datasets. This study aims to test whether adult survival rate, return to the colony and long-term breeding performance were related to blood mercury (Hg), cadmium (Cd) and persistent organic pollutants (POPs), by using a capture–mark–recapture dataset on the vulnerable wandering albatross Diomedea exulans. We did not find evidence for any effect of contaminants on adult survival probability. However, blood Hg and POPs negatively impacted long-term breeding probability, hatching and fledging probabilities. The proximate mechanisms underlying these deleterious effects are likely multifaceted, through physiological perturbations and interactions with reproductive costs. Using matrix population models, we projected a demographic decline in response to an increase in Hg or POPs concentrations. This decline in population growth rate could be exacerbated by other anthropogenic perturbations, such as climate change, disease and fishery bycatch. This study gives a new dimension to the overall picture of environmental threats to wildlife populations.
(Proceedings of the Royal Society B: Biological Sciences. vol. 281, n° 0962-8452, pp. 20133313, 11/06/2014)
CEBC, INRA, ULR, CNRS, LIENSs, INSU - CNRS, ULR, CNRS, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS