Disentangling direct and indirect effects of a legume shrub on its understorey community
Direct and indirect interactions among plants contribute to shape community composition through above- and belowground processes. However, we have not disentangled yet the direct and indirect soil and canopy effects of dominants on understorey species. We addressed this issue in a semi-arid system from southeast Spain dominated by the legume shrub Retama sphaerocarpa. During a year with an exceptionally dry spring, we removed the shrub canopy to quantify aboveground effects and compared removed-canopy plots to open plots between shrubs to quantify soil effects, both with and without watering. We added a grass removal treatment in order to separate direct from indirect shrub effects and quantified biomass, abundance, richness and composition of the forb functional group. With watering, changes in forb biomass were primarily driven by indirect shrub effects, with contrasting negative soil and positive aboveground indirect effects; changes in forb abundance and composition were more influenced by direct shrub soil effects with contrasting species composition between open and Retama patches. As community composition was different between open and Retama patches the indirect effects of Retama on forb species did not concern forbs from the open community but forbs from Retama patches. Indirect effects are, thus, important at the functional group level rather than at the species level. Without watering, there were no significant interactions. Changes in species richness between treatments were weak and seldom significant. We conclude that shrub effects on understorey forbs are primarily due to their influence on soil properties, directly affecting forb species composition but indirectly affecting the biomass of the forbs of the Retama patches, and only with sufficient water.
(Oikos. vol. 124, n° 0030-1299, pp. 1251-1262, 01/02/2015)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS
Anisotropic surfaces detection using intensity maps acquired by an airborne LiDAR emitting in near-IR over coastal environments
(. vol. 8, pp. 727 - 739, 01/02/2015)
M2C, UNICAEN, NU, INSU - CNRS, UNIROUEN, NU, CNRS, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, ISCR, UR, INSA Rennes, INSA, ENSCR, INC-CNRS, CNRS
Papuadocus blodiwai gen. nov., sp. nov. (Crustacea: Amphipoda: Maeridae), a new bathyal species associated with sunken wood in the Bismarck Sea (Papua New Guinea)
A new species belonging to a new genus of Maeridae, Papuadocus blodiwai gen. nov., sp. nov., is described from bathyal bottoms of the Bismarck Sea (Papua New Guinea). This genus/species can be distinguished from most other known maerids by right and left maxillas 1 with asymmetrical palps and by gnathopod 2 not sexually dimorphic. Its closest relative is the genus Bathyceradocus also characterized by asymmetrical maxillas 1, but differing by the presence of gill on coxae 7. These observations lead to the conclusion that the diagnosis of the family Maeridae has to be amended to receive both Bathyceradocus and Papuadocus genera. All the collected specimens lived in association with sunken wood, at 500–580 m depth.
(Zootaxa. vol. 3914, n° 1175-5326, pp. 406, 29/01/2015)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS
Arctic warming will promote Atlantic-Pacific fish interchange
Throughout much of the Quaternary Period, inhospitable environmental conditions above the Arctic Circle have been a formidable barrier separating most marine organisms in the North Atlantic from those in the North Pacific1,2. Rapid warming has begun to lift this barrier3, potentially facilitating the interchange of marine biota between the two seas4. Here, we forecast the potential northward progression of 515 fish species following climate change, and report the rate of potential species interchange between the Atlantic and the Pacific via the Northwest Passage and the Northeast Passage. For this, we projected niche-based models under climate change scenarios and simulated the spread of species through the passages when climatic conditions became suitable. Results reveal a complex range of responses during this century, and accelerated interchange after 2050. By 2100 up to 41 species could enter the Pacific and 44 species could enter the Atlantic, via one or both passages. Consistent with historicalandrecent biodiversity interchanges5,6, this Exchange of fish species may trigger changes for biodiversity and food webs in the North Atlantic and North Pacific, with ecological and economic consequences to ecosystems that at present contribute 39% to global marine fish landings.
(Nature Climate Change. vol. 5, n° 1758-678X, pp. 261-265, 26/01/2015)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS
Etude de la réactivité et l’efficacité de rétention des éléments traces métalliques dans les stations d'épuration de Bordeaux et leurs apports métalliques dans les eaux de la section Garonnaise de l'estuaire de la Gironde
Cette thèse s’intègre dans l’axe 3 du programme « ETIAGE » qui a associé pendant quatre ans (2010-2014) la Lyonnaise des Eaux, la Communauté Urbaine de Bordeaux (CUB), l’AEAG, et le FEDER, région Aquitaine avec l’université de Bordeaux, le CNRS et IRSTEA. L’objectif de l’axe 3 était de documenter les apports métalliques du bassin versant de la CUB aux eaux de la section garonnaise de l’estuaire de la Gironde. Ce vaste estuaire européen est l’un des plus turbides au monde, avec en période d’étiage la présence devant Bordeaux d’une zone de turbidité maximum (ZTM, >1 g.L-1 de MES en surface) qui transporte des particules estuariennes et des éléments traces potentiellement toxiques. Les travaux de cette thèse se sont focalisés sur les apports métalliques via le fonctionnement des deux principales stations d’épuration (STEP) de la CUB. De ce fait, l’objectif de cette recherche est d’analyser en détail les concentrations, les flux et la réactivité de huit contaminants métalliques définis comme prioritaires par l’Union Européenne Cr, Cu, Cr, Hg, Ni, Pb, Zn, As, et le contaminant émergent Ag, des STEP de la CUB. Les taux d’abattement calculés sont importants, de l’ordre de 80 % pour la majorité des métaux, essentiellement lors de l’étape de décantation. Malgré cette efficacité, les apports en éléments traces métalliques (ETM) urbains via les STEP pendant les épisodes orageux et dans des situations de faible débit peuvent augmenter les concentrations et les flux dans l’estuaire fluvial de la Gironde et ainsi avoir des conséquences sur la qualité des eaux estuariennes. Les concentrations en Ag sont supérieures aux concentrations normales de bruit de fond dans l’estuaire fluvial de la Gironde, faisant de Ag un excellent traceur urbain. Le traitement dans les STEP concentre les ETM dans les boues extraites dont les concentrations métalliques restent en-deçà des normes d’épandage. Toutefois, les concentrations en éléments traces peuvent être de 15 (Ag) à 30 (Cu) fois supérieures aux concentrations naturelles du bruit de fond en raison du fort enrichissement des boues en Hg, Ag, Cr, Cu et Zn. De plus, environ 70 % des éléments traces Cd, Ag, Pb, Cu, et Zn contenus dans ces boues sont potentiellement biodisponibles et peuvent avoir un impact néfaste à court et long terme sur les environnements récepteurs. En raison de l’augmentation prévisible de la démographie des villes côtières, les résultats de cette étude participent à l’élaboration de nouveaux concepts et outils (récupération, recyclage, valorisation) pour améliorer quantitativement et qualitativement les rejets urbains solides et liquides.
(23/01/2015)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS
Genomic and gene expression responses to genotoxic stress in PAC2 zebrafish embryonic cell line
PAC2 cell line is, along most of the developed zebrafish cell lines, poorly characterized concerning its response to genotoxicants. To define the PAC2 cell line response to different forms of genotoxic stress, we exposed the cells to model genotoxic agents (benzo[a]pyrene, B[a]P, and ethyl methanesulfonate) and subsequently monitored DNA damage and alterations by using the battery of tests, including the Comet assay, quantitative random-amplified polymorphic DNA and amplified fragment length polymorphism. The expression of several DNA repair (xpc, xpd, hr23b, rad51, msh2) and oxidative stress response (sod (Cu/Zn)) genes was monitored as well. To obtain an indication of the PAC2 cell line metabolizing capacity, the expression of genes belonging to cyp1, cyp2 and cyp3 families was assessed upon exposure to B[a]P. Genotoxic responses were observed in all the used methods, and quantitative random-amplified polymorphic DNA and amplified fragment length polymorphism proved to be more sensitive by revealing DNA alterations even when the Comet assay indicated lack of significant damage. The PAC2 cell line demonstrated basal and B[a]P-induced expression of several cyp genes, suggesting its ability to metabolize indirect acting xenobiotics to a certain point. Based on these results, PAC2 cells seem to be sensitive zebrafish in vitro model in the genotoxicity assessment of the direct acting genotoxicant; however, they are less sensitive toward the indirect acting genotoxicant due to their limited metabolizing properties.
(Journal of Applied Toxicology. vol. 35, n° 0260-437X, pp. 1381-1389, 21/01/2015)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS
Preliminary Assessment of SARAL/AltiKa Observations over the Ganges-Brahmaputra and Irrawaddy Rivers
Radar altimetry has demonstrated strong capabilities for the monitoring of water levels of lakes, rivers and wetlands over the last 20 years. The Indo-French SARAL/AltiKa mission, launched in February 2013, is the first satellite radar altimetry mission to carry onboard a Ka-band sensor. We propose here to evaluate the potential of this new instrument for land hydrology through comparisons with other altimetry-derived stages and discharges in the Ganges-Brahmaputra and Irrawaddy river basins using its first year of data. Due to the lack of concomitant in situ measurements for the current period, Jason-2 data, previously evaluated against in situ gauge records, were used as reference. Comparisons between Jason-2 and SARAL-derived water levels and discharges, and Jason-2 and Envisat (which flew the same orbit as SARAL from 2002 to 2010) –derived ones, was performed. Time-series of only one year of SARAL-derived water levels and discharges present better performances (lower RMSE and higher R, generally greater than 0.95) than the ones derived from Envisat when compared to Jason-2.
(Marine Geodesy. vol. 38, n° 0149-0419, pp. 568-580, 20/01/2015)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS
Ischnomesus harrietae sp. nov., a new benthic asellote (Crustacea: Isopoda: Ischnomesidae) from bathyal bottoms of the southern Bay of Biscay
A new species of Ischnomesidae (Crustacea: Isopoda: Asellota), Ischnomesus harrietae sp. nov. is described from the southern Bay of Biscay. This new species is distinctive due to the presence of numerous pedestal setae arranged in longitudinal rows on pereonite 5. Because of this morphological peculiarity, it can be easily distinguished from the four other Ischnomesus species previously reported from bathyal/abyssal bottoms of the European continental margin. Within its known distributional area, the new species inhabits sandy and muddy bottoms between 619 and 1099 m, with a maximum abundance of 41.8 individuals per 100 m2 recorded at approximately 700 m on the Arcachon Plateau. Another new species is also reported, Ischnomesus sp.1, represented by one specimen only and briefly described. An identification key to European species of Ischnomesus is provided.
(Zootaxa. vol. 3911, n° 1175-5326, pp. 201, 19/01/2015)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS
Elasmopus thalyae sp. nov. (Crustacea: Amphipoda: Maeridae), a new benthic species from soft and hard bottoms of Arcachon Bay (SE Bay of Biscay)
A new species of Elasmopus is described and figured from specimens collected in different benthic communities of Arcachon Bay. It can be distinguished from its closest relative E. rapax by the palmar ornamentation of male gnathopod 2 propodus (shelf and 2 teeth). It preferentially lives on hard bottoms (in mussel fouling of navigation buoys, Sabellaria spinulosa reefs, algal rocky bottoms, Laminaria and Saccorhiza bulbs and as epibiont on the carapace of Maja brachydactyla) but also less abundantly on naked sandy bottoms. An identification key of Atlantic and Mediterranean European species is also given.
(Zootaxa. vol. 3905, n° 1175-5326, pp. 107, 09/01/2015)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, UB
Sedimentary records of past earthquakes in Boraboy Lake during the last ca 600 years (North Anatolian Fault, Turkey)
Multiproxy sedimentological analyses along 4.9 m-long sequence of Boraboy Lake, which is located on the central eastern part of the North Anatolian Fault (NAF), reveal the sedimentary traces of past large earthquakes in the region. The lake has a relatively large catchment area (10 km2) compared to its size (0.12 km2), which renders sedimentation sensitive to heavy rain/storm events. Accordingly, the background sedimentation, which is composed of faintly laminated reddish/yellowish brown clayey silt, is frequently interrupted by organic-rich intercalations probably due to heavy rain/storm events transporting terrestrial plant remains from the densely vegetated catchment. In addition to frequent organic-rich intercalations, the background sedimentation is interrupted by four mass-wasting deposits (MWD) of which thickness range is between 15 and 50 cm. High-resolution ITRAX μXRF data confirms higher homogeneity along the MWDs (E1–E4) compared to the background sedimentation. Based on 137Cs and 210Pbxs dating and radiocarbon chronology, three MWDs detected in Boraboy sequence (E2, E3 and E4) temporally correlate with large historical earthquakes along the NAF; the 1943 Tosya (Ms = 7.6) and/or 1942 Niksar-Erbaa (Ms = 7.1), the 1776 Amasya-Merzifon and the 1668 North Anatolian (Ms = 7.9) earthquakes. The youngest MWD in the sequence (E1), which is dated to early 2000s, does not correlate with any strong earthquake in the region. This MWD was probably a single mass-wasting event due to routine overloading and oversteepening on the delta front formed by the main inlet of the lake. In subaqueous paleoseismology, coevality of multi-location mass-wasting events is used as a criterion to assign a seismic triggering mechanism, and to rule out mass-wasting events due to routine overloading/oversteepening of subaqueous slopes. Within this context, Boraboy sequence provides a valuable example to discuss sedimentological imprints of single- vs. multi-source MWDs.
(Palaeogeography, Palaeoclimatology, Palaeoecology. vol. 433, n° 0031-0182, pp. 1-9, 01/01/2015)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS