Refine search
Results 11-20 of 88
Applications of C and N stable isotopes to ecological and environmental studies in seagrass ecosystems
2004
Lepoint, Gilles | Dauby, Patrick | Gobert, Sylvie | MARE - Centre Interfacultaire de Recherches en Océanologie - ULiège
peer reviewed | Stable isotopes of carbon and nitrogen are increasingly used in marine ecosystems, for ecological and environmental studies. Here, we examine some applications of stable isotopes as ecological integrators or tracers in seagrass ecosystem studies. We focus on both the use of natural isotope abundance as food web integrators or environmental tracers and on the use of stable isotopes as experimental tools. As ecosystem integrators, stable isotopes have helped to elucidate the general structure of trophic webs in temperate, Mediterranean and tropical seagrass ecosystems. As environmental tracers, stable isotopes have proven their utility in sewage impact measuring and mapping. However, to make such environmental studies more comprehensible, future works on understanding of basic reasons for variations of N and C stable isotopes in seagrasses should be encouraged. At least, as experimental tracers, stable isotopes allow the study of many aspects of N and C cycles at the scale of a plant or at the scale of the seagrass ecosystem. (C) 2004 Elsevier Ltd. All rights reserved.
Show more [+] Less [-]Nitrogen dynamics in Posidonia oceanica cuttings: implications for transplantation experiments
2004
Lepoint, Gilles | Vangeluwe, Denis | Eisinger, Michael | Paster, Marcus | van Treeck, Peter | Bouquegneau, Jean-Marie | Gobert, Sylvie | MARE - Centre Interfacultaire de Recherches en Océanologie - ULiège
peer reviewed | A N-15 tracer study was performed during an experimental transplantation trial of natural Posidonia oceanica cuttings. The experiment was done in situ at 17 m depth in the Revellata Bay (Calvi, NW Corsica, France). Despite high survival rates of transplants (>90%) after one year, the weight and the N content of transplants are significantly lower than those of reference plants. In absence of roots, the transplants are not able to meet their N requirement because, leaf uptake is insufficient to replenish the N lost during the natural leaf decay. This could constitute a major cause of long-term failure for transplantation experiments or natural recolonisation processes. The increase of the N-15 content in the roots shows that the plant re-allocates the nitrogen of one organ (i.e. leaves, rhizomes) to ensure the growth of another (i.e. roots). (C) 2003 Elsevier Ltd. All rights reserved. | Novel Marine Technology (NOMATEC)
Show more [+] Less [-]Maintaining viable earthworm populations in frequently inundated river flood plains. Does plasticity in maturation in Lumbricus rubellus promote population survival?
2004
Klok, C. | Zorn, M. | Koolhaas, J.E. | Eijsackers, H.J.P. | Gestel, C.A.M. van
Effects of environmental concentrations of atrazine on hemocyte density and phagocytic activity in the pond snail Lymnaea stagnalis (Gastropoda, Pulmonata)
2004
Russo, Jacqueline | Lagadic, Laurent | Ecosystèmes, biodiversité, évolution [Rennes] (ECOBIO) ; Université de Rennes (UR)-Institut Ecologie et Environnement - CNRS Ecologie et Environnement (INEE-CNRS) ; Centre National de la Recherche Scientifique (CNRS)-Centre National de la Recherche Scientifique (CNRS)-Observatoire des Sciences de l'Univers de Rennes (OSUR) ; Université de Rennes (UR)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Rennes 2 (UR2)-Centre National de la Recherche Scientifique (CNRS)-Institut National de Recherche pour l’Agriculture, l’Alimentation et l’Environnement (INRAE)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Rennes 2 (UR2)-Centre National de la Recherche Scientifique (CNRS)-Institut National de Recherche pour l’Agriculture, l’Alimentation et l’Environnement (INRAE)-Centre National de la Recherche Scientifique (CNRS) | Écologie et santé des écosystèmes (ESE) ; Institut National de la Recherche Agronomique (INRA)-AGROCAMPUS OUEST
Immunotoxicological effects of environmentally relevant concentrations (10, 23, 50, 100 μg/l) of atrazine were studied in Lymnaea stagnalis. Individual hemolymph sampling was performed at 0, 24, 48, 72, 96, 168, 336, 504 and 672 h during exposure. Every atrazine concentration induced a significant increase in the mean number of circulating hemocytes, without any concentration–response relation. A peak (1.6-fold increase) of hemocyte density was observed after 96 h of exposure. After 504 h, the number of hemocytes remained higher only in the snails exposed to the two highest concentrations. Granulocytes contributed most to the increase in hemocyte density in herbicide-exposed snails. Both short- (24 and 96 h) and long-term (504 h) exposures resulted in significant inhibition of hemocyte phagocytic activity upon E. coli. Over the long-term, phagocytosis recovered for the two lowest concentrations. After 504 h of exposure, every herbicide level resulted in a significant reduction of reactive oxygen species production in E. coli-stimulated hemocytes, which was not observed for short-term exposures.
Show more [+] Less [-]Impacts physiologiques de l'ozone sur les arbres
2004
Le Thiec, Didier, | Dizengremel, Pierre,
Heavy Metal Determination in Atmospheric Deposition and Other Fluxes in Northern France Agrosystems
2004
Azimi, Sam | Cambier, Philippe | Lecuyer, Isabelle | Thevenot, Daniel, R. | Centre d'Enseignement et de Recherche Eau Ville Environnement (CEREVE) ; AgroParisTech-École des Ponts ParisTech (ENPC)-Université Paris-Est Créteil Val-de-Marne - Paris 12 (UPEC UP12) | Unité de Sciences du Sol ; Institut National de la Recherche Agronomique (INRA)
International audience | The aim of this study is to assess the annual balance of the fluxes of Cd, Cu, Ni, Pb and Zn within different cropping systems, in an experimental site located near Versailles, France. Four fluxes through the cultivated horizon were considered to assess the annual heavy metal balance in these systems: 1) atmospheric depositions, 2) fertilisers as inputs, 3) crops and 4) leaching water as outputs. The water mass flow was estimated with a model (CERES) while the other parameters were actually measured through field sampling. Some large uncertainties are related to analytical detection limits, specially for Pb which presents very low concentrations in nitrogen fertilisers, in crops and in soil solution. Cd was also close to the detection limits in atmospheric deposition and in soil water, and Zn could not be analysed in soil solution. Nevertheless, the following trends clearly appeared: firstly, atmospheric deposition is the major input way of Cu, Ni, Pb and Zn in the soil, whatever the cropping system, whereas Cd is introduced mainly by fertilisers. Secondly, the uptake of heavy metal by wheat is generally larger than by a pea culture, except for Ni. Finally, the global pattern shows an accumulation of Cd, Ni and Pb in the cultivated horizon while Cu decreased. The annual balances, during the cropping year 2001–2002, represented about 0.33, −0.024, 0.014 and 0.014% of the actual stocks in the cultivated horizon, of Cd, Cu, Ni, and Pb, respectively.
Show more [+] Less [-]Heavy Metal Determination in Atmospheric Deposition and Other Fluxes in Northern France Agrosystems
2004
Azimi, Sam | Cambier, Philippe | Lecuyer, Isabelle | Thevenot, Daniel, R. | Centre d'Enseignement et de Recherche Eau Ville Environnement (CEREVE) ; AgroParisTech-École des Ponts ParisTech (ENPC)-Université Paris-Est Créteil Val-de-Marne - Paris 12 (UPEC UP12) | Unité de Sciences du Sol ; Institut National de la Recherche Agronomique (INRA)
International audience | The aim of this study is to assess the annual balance of the fluxes of Cd, Cu, Ni, Pb and Zn within different cropping systems, in an experimental site located near Versailles, France. Four fluxes through the cultivated horizon were considered to assess the annual heavy metal balance in these systems: 1) atmospheric depositions, 2) fertilisers as inputs, 3) crops and 4) leaching water as outputs. The water mass flow was estimated with a model (CERES) while the other parameters were actually measured through field sampling. Some large uncertainties are related to analytical detection limits, specially for Pb which presents very low concentrations in nitrogen fertilisers, in crops and in soil solution. Cd was also close to the detection limits in atmospheric deposition and in soil water, and Zn could not be analysed in soil solution. Nevertheless, the following trends clearly appeared: firstly, atmospheric deposition is the major input way of Cu, Ni, Pb and Zn in the soil, whatever the cropping system, whereas Cd is introduced mainly by fertilisers. Secondly, the uptake of heavy metal by wheat is generally larger than by a pea culture, except for Ni. Finally, the global pattern shows an accumulation of Cd, Ni and Pb in the cultivated horizon while Cu decreased. The annual balances, during the cropping year 2001–2002, represented about 0.33, −0.024, 0.014 and 0.014% of the actual stocks in the cultivated horizon, of Cd, Cu, Ni, and Pb, respectively.
Show more [+] Less [-]The role of glomalin, a protein produced by arbuscular mycorrhizal fungi, in sequestering potentially toxic elements
2004
Gonzalez-Chavez, M.C. | Carrillo-Gonzalez, R. | Wright, S.F. | Nichols, K.A.
Naturally occurring soil organic compounds stabilize potentially toxic elements (PTEs) such as Cu, Cd, Pb, and Mn. The hypothesis of this work was that an insoluble glycoprotein, glomalin, produced in copious amounts on hyphae of arbuscular mycorrhizal fungi (AMF) sequesters PTEs. Glomalin can be extracted from laboratory cultures of AMF and from soils. Three different experiments were conducted. Experiment 1 showed that glomalin extracted from two polluted soils contained 1.6-4.3 mg Cu, 0.02-0.08 mg Cd, and 0.62-1.12 mg Pb/g glomalin. Experiment 2 showed that glomalin from hyphae of an isolate of Gigaspora rosea sequestered up to 28 mg Cu/g in vitro. Experiment 3 tested in vivo differences in Cu sequestration by Cu-tolerant and non-tolerant isolates of Glomus mosseae colonizing sorghum. Plants were fed with nutrient solution containing 0.5, 10 or 20 μM of Cu. Although no differences between isolates were detected, mean values for the 20 μM Cu level were 1.6, 0.4, and 0.3 mg Cu/g for glomalin extracted from hyphae, from sand after removal of hyphae and from hyphae attached to roots, respectively. Glomalin should be considered for biostabilization leading to remediation of polluted soils.
Show more [+] Less [-]Toxic effect of air pollution on plants : characterization of ozone fluxes and analysis and modelling of ozone impact on photosynthesis
2004
Le Thiec, Didier, | Dizengremel, Pierre, | Bethenod, Olivier, | Castell, Jean-François, | Biolley, J.P. | Leitão, Luís | Cellier, Pierre
Passive capillary pan samplers : an efficient system to monitor in-situ percolation fluxes in soils
2004
Lacas, Jean-Guillaume | Voltz, Marc | Cattan, Philippe | Louchart, X.