Infragravity-wave modulation of short-wave celerity in the surf zone
The cross-shore evolution of individual wave celerity is investigated using two high-resolution laboratory experiments on bichromatic waves. Individual waves are tracked during their onshore propagation and their characteristics, including celerity, are estimated. The intrawave variability in celerity is low in the shoaling zone but increases strongly after breaking. It is maximum when the infragravity-wave height to water depth ratio is the largest, that is to say close to the shoreline. There the observed range of individual wave celerity can be as large as the mean celerity value. This variability can be largely explained by the variations in water depth and velocity induced by the infragravity waves. The differences in celerity are such that they lead to the merging of the waves in the inner surf zone for most of the wave conditions considered. Again, the location at which the first waves start merging strongly correlates with the infragravity-wave height to water depth ratio. The consequences of these findings for celerity-based depth-inversion techniques are finally discussed. Surprisingly, accounting for the infragravity-wave modulation of the velocity field in the celerity estimate does not significantly improve depth estimation in the surf zone. However, it is shown that the occurrence of bore merging decreases significantly the coherence of the wavefield in the surf zone. This loss of coherence could hamper celerity estimation from pixel intensity time series and explain, at least partly, the relatively poor performance of depth-inversion techniques in the inner surf zone.
(Journal of Geophysical Research. Oceans, n° 2169-9275, 20/10/2015)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, LEGI, UJF, Grenoble INP, CNRS
Etude de la pollution marine par les hydrocarbures et caractérisation de leurs effets biochimiques et moléculaires sur la palourde de Ruditapes sp.
Dans notre étude, la biosurveillance de la lagune de Tunis a été réalisée durant une année enemployant une approche combinant les analyses chimiques et biologiques et en utilisant lapalourde Ruditapes decussatus comme espèce bioindicatrice. Cette approche a permis demettre en évidence la forte contamination de la lagune de Tunis par les métaux traces et leshydrocarbures aromatiques polycycliques (HAPs). La variation saisonnière des niveaux debioaccumulation de ces contaminant par la palourde s’avère être fortement associée auxchangements des paramètres physico-chimiques du milieu et aux processus physiologiques del’animal. L’étude de la réponse biologique basée sur l’utilisation d’une batterie debiomarqueurs d’exposition et d’effet situés à différents niveaux de l’organisation biologique :moléculaire (l’expression de cinq gènes d’intérêt), biochimique (les activités benzo(a)pyrènehydroxylase, glutathion S-transférase, acétylcholinestérase, catalase et taux demalondialdéhyde) et tissulaire (altérations histopathologiques), a permis de mettre enévidence une modulation des processus de défense contre les perturbations induites par lapollution et l’identification des altérations histopathologiques (structurales) au niveau desbranchies et de la glande digestive impliquant un impact sévère des contaminants sur l’état desanté de la palourde. L’étude des interactions spatio-temporelles entre les facteurs abiotiqueset biotiques a permis d’identifier la température et la reproduction comme paramètresprincipaux affectant la réponse biochimique de défense et d’effet. L’analyse en composanteprincipale (ACP), regroupant tous les paramètres analysés pendant le printemps, nous apermis d’identifié le site Z2 comme le site le plus affecté par la pollution. Dans un secondtemps, le benzo(a)pyrène (BaP), déjà identifié dans la lagune de Tunis, a été employé dansdes conditions contrôlées au laboratoire afin de caractériser les réponses moléculaires etbiochimiques chez les bivalves (Ruditapes philippinarum et Crassostrea gigas) face à desexpositions subaiguës et aiguës à ce contaminant. Cette étude nous a permis d’identifier unemodulation des biomarqueurs biochimiques de métabolisation, de stress oxydant et deneurotoxicité et de l’expression des gènes impliqués dans les processus de métabolisation, derespiration mitochondriale, de défense antioxydante, de reproduction et de défenseimmunitaire. L’analyse de l’altération de l’ADN a révélé un pouvoir génotoxique précoce etélevé du BaP chez les deux bivalves.
(06/10/2015)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS
Lateral and vertical distributions of living benthic foraminifera off the Douro River (western Iberian margin): Impact of the organic matter quality
In this study, we assess the impact of the quantity and quality of the organic matter on the distribution of live ben-thic foraminifera on a cross-margin transect off the Douro River (western Iberian margin). Surface sediments from five stations ranging from 50 to 2000 m water depth were collected in March 2011 at the end of the period of maximal river runoff, in order to better evaluate the importance of terrestrial input. Living (stained) benthic foraminiferal assemblages (N 150 μm) and environmental parameters (grain size, total organic carbon (TOC), total nitrogen (TN), C/N ratio, δ 13 C TOC , pigments and amino acids) were investigated. Organic matter amounts follow the sediment grain size pattern with higher concentration in fine sediments and seem to control faunal density , except at the shallowest station where TOC is low and faunal density high. At this coastal site, a massive sandy deposit is identified and associated with very low faunal diversity. Labile organic matter is richest at the shelf stations where benthic foraminifera standing stocks are high. This is particularly evident on the Douro mud patch where both density and diversity are high. Foraminiferal faunas living at the shelf stations are dominated by species (e.g., Nonion scaphum, Ammonia beccari,i Bulimina aculeata and Eggerella scabra) characteristic of the rich trophic conditions, with organic matter of mixed estuarine and marine origin. Very low total standing stocks on the upper slope are associated with coarse sediments, probably resulting from intense bottom currents at this depth resulting in poor trophic conditions. Deeper environments are characterized by species (e.g., Hoeglundina elegans, Uvigerina mediterranea and Reophax scorpiurus) indicative of fairly abundant but low-quality organic matter. Finally, the faunal differences between the shelf stations may reflect different succes-sional stages: an early stage at 50 m water depth where unstable conditions are observed, with faunas dominated by opportunistic species and a more mature fauna in the mud patch where more stable conditions prevail.
(Marine Micropaleontology. vol. 120, n° 0377-8398, pp. 31-45, 01/10/2015)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, NIOZ
POPs in free-ranging pilot whales, sperm whales and fin whales from the Mediterranean Sea: Influence of biological and ecological factors
The pilot whale Globicephala melas, the sperm whale Physeter macrocephalus, and the fin whale Balaenoptera physalus are large cetaceans permanently inhabiting the Mediterranean Sea. These species are subjected to numerous anthropogenic threats such as exposure to high levels of contaminants. Therefore, selected persistent organic pollutants POPs (29 PCBs, 15 organochlorine compounds, 9 PBDEs and 17 PCDD/Fs) were analysed in blubber biopsies of 49 long-finned pilot whales, 61 sperm whales and 70 fin whales sampled in the North Western Mediterranean Sea (NWMS) from 2006 to 2013. Contamination profile and species feeding ecology were then combined through the use of stable isotopes. δ13C, δ15N values and POPs levels were assessed through IR-MS and GC–MS respectively. To assess the toxic potency of the dioxin-like compounds, the TEQ approach was applied. δ15N values were 12.2±1.3‰ for sperm whales, 10.5±0.7‰ for pilot whales and 7.7±0.8‰ in fin whales, positioning sperm whales at higher trophic levels. δ13C of the two odontocetes was similar and amounted to −17.3±0.4‰ for sperm whales and −17.8±0.3‰ for pilot whales; whilst fin whales were more depleted (−18.7±0.4‰). This indicates a partial overlap in toothed-whales feeding habitats, while confirms the differences in feeding behaviour of the mysticete. Pilot whales presented higher concentrations than sperm whales for ΣPCBs (38,666±25,731 ng g−1 lw and 22,849±15,566 ng g−1 lw respectively), ΣPBDEs (712±412 ng g−1 lw and 347±173 ng g−1 lw respectively) and ΣDDTs (46,081±37,506 ng g−1 lw and 37,647±38,518 ng g−1 lw respectively). Fin whales presented the lowest values, in accordance with its trophic position (ΣPCBs: 5721±5180 ng g−1 lw, ΣPBDEs: 177±208 ng g−1 lw and ΣDDTs: 6643±5549 ng g−1 lw). Each species was characterized by large inter-individual variations that are more related to sex than trophic level, with males presenting higher contaminant burden than females. The discriminant analysis (DA) confirmed how DDTs and highly chlorinated PCBs were influential in differentiating the three species. Pollutant concentrations of our species were significantly higher than both their Southern Hemisphere and North Atlantic counterparts, possibly due to the particular Mediterranean geomorphology, which influences pollutants distribution and recycle. Dioxin-like PCBs accounted for over 80% of the total TEQ. This study demonstrated (1) an important exposure to pollutants of Mediterranean cetaceans, often surpassing the estimated threshold toxicity value of 17,000 ng g−1 lw for blubber in marine mammals; and (2) how the final pollutant burden in these animals is strongly influenced not only by the trophic position but also by numerous other factors such as sex, age, body size and geographical distribution.
(Environmental Research. vol. 142, n° 0013-9351, pp. 185-196, 01/10/2015)
IMS, UB, CNRS, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, ULiège
Indian monsoon variations during three contrasting climatic periods: The Holocene, Heinrich Stadial 2 and the last interglacial–glacial transition
In contrast to the East Asian and African monsoons the Indian monsoon is still poorly documented throughout the last climatic cycle (last 135,000 years). Pollen analysis from two marine sediment cores (NGHP-01-16A and NGHP-01-19B) collected from the offshore Godavari and Mahanadi basins, both located in the Core Monsoon Zone (CMZ) reveals changes in Indian summer monsoon variability and intensity during three contrasting climatic periods: the Holocene, the Heinrich Stadial (HS) 2 and the Marine Isotopic Stage (MIS) 5/4 during the ice sheet growth transition. During the first part of the Holocene between 11,300 and 4200 cal years BP, characterized by high insolation (minimum precession, maximum obliquity), the maximum extension of the coastal forest and mangrove reflects high monsoon rainfall. This climatic regime contrasts with that of the second phase of the Holocene, from 4200 cal years BP to the present, marked by the development of drier vegetation in a context of low insolation (maximum precession, minimum obliquity). The historical period in India is characterized by an alternation of strong and weak monsoon centennial phases that may reflect the Medieval Climate Anomaly and the Little Ice Age, respectively. During the HS 2, a period of low insolation and extensive iceberg discharge in the North Atlantic Ocean, vegetation was dominated by grassland and dry flora indicating pronounced aridity as the result of a weak Indian summer monsoon. The MIS 5/4 glaciation, also associated with low insolation but moderate freshwater fluxes, was characterized by a weaker reduction of the Indian summer monsoon and a decrease of seasonal contrast as recorded by the expansion of dry vegetation and the development of Artemisia, respectively. Our results support model predictions suggesting that insolation changes control the long term trend of the Indian monsoon precipitation, but its millennial scale variability and intensity are instead modulated by atmospheric teleconnections to remote phenomena in the North Atlantic, Eurasia or the Indian Ocean.
(Quaternary Science Reviews. vol. 125, n° 0277-3791, pp. 50-60, 01/10/2015)
SCTA, UQAM, EPHE, PSL, IFP, MEAE, CNRS, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, UNH, WHOI
Hydrological pulse regulating the bacterial heterotrophic metabolism between Amazonian mainstems and floodplain lakes
We evaluated in situ rates of bacterial carbon processing in Amazonian floodplain lakes and mainstems, during both high water (HW) and low water (LW) phases (p < 0.05). Our results showed that bacterial production (BP) was lower and more variable than bacterial respiration, determined as total respiration. Bacterial carbon demand was mostly accounted by BR and presented the same pattern that BR in both water phases. Bacterial growth efficiency (BGE) showed a wide range (0.2-23%) and low mean value of 3 and 6%, (in HW and LW, respectively) suggesting that dissolved organic carbon was mostly allocated to catabolic metabolism. However, BGE was regulated by BP in LW phase. Consequently, changes in BGE showed the same pattern that BP. In addition, the hydrological pulse effects on mainstems and floodplains lakes connectivity were found for BP and BGE in LW. Multiple correlation analyses revealed that indexes of organic matter (OM) quality (chlorophyll-a, N stable isotopes and C/N ratios) were the strongest seasonal drivers of bacterial carbon metabolism. Our work indicated that: (i) the bacterial metabolism was mostly driven by respiration in Amazonian aquatic ecosystems resulting in low BGE in either high or LW phase; (ii) the hydrological pulse regulated the bacterial heterotrophic metabolism between Amazonian mainstems and floodplain lakes mostly driven by OM quality.
(Frontiers in Microbiology. vol. 6, n° 1664-302X, pp. 11p / article n°1054, 30/09/2015)
UENF, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, LOG, INSU - CNRS, ULCO, CNRS, IRD [Ile-de-France], ULCO, UFSCar, UFF, UFJF, GET, IRD, UT3, Comue de Toulouse, INSU - CNRS, CNES, CNRS, IPGP - UMR_7154, INSU - CNRS, IGN, UR, IPG Paris, CNRS, UPCité, UNIFESP
Cadmium sulfide nanoparticles trigger DNA alterations and modify the bioturbation activity of tubificidae worms exposed through the sediment
To address the impact of cadmium sulfide nanoparticles (CdS NPs) in freshwater ecosystems, aquatic oligochaete Tubifex tubifex were exposed through the sediment to a low dose (0.52 mg of 8 nm in size of CdS NPs/kg) for 20 days using microcosms. Cadmium (Cd) was released from the CdS NPs-contaminated sediment to the water column, and during this period the average concentrations of Cd in the filtered water fraction were 0.026 ± 0.006 µg/L in presence of oligochaetes. Similar experiments with microparticular CdS and cadmium chloride (CdCl2) were simultaneously performed for comparative purposes. CdS NPs exposure triggered various effects on Tubifex worms compared to control, microsized and ionic reference, including modification of genome composition as assessed using RAPD-PCR genotoxicity tests. Bioaccumulation levels showed that CdS NPs were less bioavailable than CdCl2 to oligochaetes and reached 0.08 ± 0.01 µg Cd/g for CdS NPs exposure versus 0.76 ± 0.3 µg Cd/g for CdCl2 exposure (fresh weight). CdS NPs altered worm’s behavior by decreasing significantly the bioturbation activity as assessed after the exposure period using conservative fluorescent particulate tracers. This study demonstrated the high potential harm of the CdS nanoparticular form despite its lower bioavailability for Tubifex worms.
(Nanotoxicology. vol. 10, n° 1743-5390, pp. 322-331, 29/09/2015)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, LEFE, INEE-CNRS, CNRS, UT3, Comue de Toulouse, CNRS, Toulouse INP, Comue de Toulouse, ICMCB, UB, INC-CNRS, CNRS
Reproduction and offspring defects after exposure to PAHs mixtures.
(13/09/2015)
LPGP, INRA, Biosit : Biologie - Santé - Innovation Technologique, IFREMER, LPTC, UB, CNRS, PAnTher, ONIRIS, INRAE, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, CREMA, IFREMER, CNRS, LRHLR, HGS, IFREMER, HGS, IFREMER, UMR MARBEC, IRD, IFREMER, UM, CNRS
Communautés micro-algales : effets de la matière organique dissoute et des pesticides sur l’activité photosynthétique et la composition taxonomique
Le contexte de changement global pose des questions spécifiques aux milieux aquatiques du littoral Aquitain, liées aux répercussions des modifications climatiques sur les sources et le devenir des substances dissoutes d'origine naturelle (Matière Organique Dissoute, MOD) et anthropique (pesticides), ainsi que leurs impacts sur l'écosystème aquatique. Le projet COMPACT a pour objectif principal d'étudier l'impact écologique des pesticides sur les communautés micro-algales du Bassin d’Arcachon et de son principal tributaire (La Leyre) en fonction des assemblages d’espèces, des saisons et de la composition du milieu en MOD. Malgré la continuité entre écosystèmes aquatiques continentaux et littoraux, très peu d'études se sont attachées jusqu'ici à comparer les réponses des micro-algues dans ces deux écosystèmes. Les travaux relatifs à la réponse des micro-algues aux variations de conditions environnementales pouvant résulter du changement climatique, et notamment à des variations de qualité/quantité de MOD ou pesticides, traitent généralement de conditions d’exposition à des facteurs seuls, souvent dans le cadre de tests standardisés, monospécifiques. Il découle de ces approches mono-facteur et mono-espèce un manque flagrant de réalisme écologique, principalement dû à la difficulté de prendre en compte la multiplicité des facteurs abiotiques et biotiques impliqués, de manière directe et indirecte. Les approches d’écotoxicologie des communautés visent à répondre en partie à ce besoin croissant. Les interactions complexes entre organismes vivants, MOD et contaminants, dans des écosystèmes aquatiques très différents (dulçaquicole versus marin), compliquent la prévision des effets toxiques combinés sur le biote. Selon leur nature, et/ou leur intensité, ces déterminants environnementaux peuvent, d'une part, modifier le comportement et la biodisponibilité des substances chimiques organiques et, d'autre part, produire des effets divergents sur les organismes aquatiques. Dans un contexte de multi-stress, la combinaison de ces facteurs est susceptible de provoquer des effets écotoxicologiques imprévus sur les communautés micro-algales, que le projet COMPACT se propose d'explorer. Ce projet propose une approche pluridisciplinaire originale, couplant chimie, écotoxicologie et biologie, dans le but d’améliorer la compréhension des mécanismes d’interactions MOD/pesticides. Cette approche permettra de faire le lien entre la présence de MOD et de contaminants, et l’impact toxique sur les communautés de micro-algues qui forment la base des réseaux trophiques en milieu aquatique. En plus de la description des réponses structurelles (taxonomie, proportion des différents groupes algaux, quantité de chlorophylle) et fonctionnelles (activité photosynthétique) dans ces communautés aquatiques profondément différentes (mais rarement comparées), ce projet vise à produire des connaissances sur les réponses des micro-algues à des conditions d’exposition chimique complexes, en intégrant les phénomènes d’interaction MOD/pesticides. Cette étude permettra donc de mieux comprendre les effets des pesticides sur les communautés naturelles de micro-algues au sein d’un continuum eau douce / eau marine, tout en tenant compte des interactions chimiques entre contaminants et matière organique. Les expérimentations mises en oeuvre permettront de déterminer si les pesticides ont un effet sur les communautés, et si cet effet est influencé par la présence et le type de matière organique. Les réponses des communautés seront comparées selon les saisons et leur site d’origine, afin de déterminer si la sensibilité des espèces considérées diffère selon l’environnement d’origine des communautés.
(pp. 1, 02/09/2015)
BE, IFREMER, LERAR, COAST, IFREMER, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, UR EABX, IRSTEA
A chemical status predictor. A methodology based on World-Wide sediment samples
As a consequence of the limited resources of underdeveloped countries and the limited interest of the developed ones, the assessment of the chemical quality of entire water bodies around the world is a utopia in the near future. The methodology described here may serve as a first approach for the fast identification of water bodies that do not meet the good chemical status demanded by the European Water Framework Directive (WFD). It also allows estimating the natural background (or reference values of concentration) of the areas under study using a simple criterion. The starting point is the calculation the World-Wide Natural Background Levels (WWNBLs) and World-Wide Threshold Values (WWTVs), two indexes that depend on the concentration of seven elements present in sediments. These elements, As, Cd, Cr, Cu, Ni, Pb and Zn, have been selected taking into account the recommendations of the UNEP (United Nations Environment Programme) and USEPA (United States Environmental Protection Agency), that describe them as elements of concern with respect to environmental toxicity. The methodology has been exemplified in a case study that includes 134 sediment samples collected in 11 transitional water bodies from 7 different countries and 4 different continents. Six of the water bodies considered met the good chemical status demanded by the WFD. The rest of them exceeded the reference WWTVs, at least for one of the elements. The estuaries of the Nerbioi-Ibaizabal (Basque Country) and Cavado (Portugal), the sea inlet of Río San Pedro (Spain), the Sepetiba Bay (Brazil) and the Yucateco lagoon (Mexico) belong to that group.
(Journal of Environmental Management. vol. 161, n° 0301-4797, pp. 21-29, 01/09/2015)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS