Biodiversity and bio-evaluation methods in transitional waters: a theoretical challenge
1 - This paper addresses the question of the weaknesses of the methodologies developed based on the analysis of the composition of benthic invertebrate communities in transitional waters.2 - Benthic communities are an important element of the bio-evaluation methodologies suggested for the Ecological Quality status of the European transitional and coastal waters in the context of the Water Framework Directive. It is argued that the assessment of Ecological Quality status requires both fundamental and applied science.3 - The lack of performance of many biotic indices under varying and highly fluctuating environmental conditions may well be related to weakness in theory supporting marine biodiversity.4 - We propose some possible approaches for future development in the field of biotic indices and marine biodiversity theory.
(Transitional Waters Bulletin, 01/01/2012)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS
The impact of African aridity on the isotopic signature of Atlantic deep waters across the Middle Pleistocene Transition
A high resolution analysis of benthic foraminifera as well as of aeolian terrigenous proxies extracted from a 37 m-long marine core located off the Mauritanian margin spanning the last ~1.2 Ma, documents the possible link between major continental environmental changes with a shift in the isotopic signature of deep waters around 1.0-0.9 Ma, within the so-called Mid-Pleistocene Transition (MPT) time period. The increase in the oxygen isotopic composition of deep waters, as seen through the benthic foraminifera δ 18 O values, is consistent with the growth of larger ice sheets known to have occurred during this transition. Deep-water mass 2 δ 13 C changes, also estimated from benthic foraminifera, show a strong depletion for the same time interval. This drastic change in δ 13 C values is concomitant with a worldwide 0.3‰ decrease observed in the major deep oceanic waters for the MPT time period. The phase relationship between aeolian terrigeneous signal increase and this δ 13 C decrease in our record, as well as in other paleorecords, supports the hypothesis of a global aridification amongst others processes to explain the deep-water masses isotopic signature changes during the MPT. In any case, the isotopic shifts imply major changes in the end-member δ 18 O and δ 13 C values of deep waters.
(Quaternary Research. vol. 77, n° 0033-5894, pp. 182-191, 01/01/2012)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, GEOPS, UP11, CNRS, CLIMAG, LSCE, UVSQ, INSU - CNRS, CNRS, DRF (CEA), CEA, LSCE, UVSQ, INSU - CNRS, CNRS, DRF (CEA), CEA, LOG, INSU - CNRS, ULCO, CNRS, IRD [Ile-de-France], CNRS
A 2500 year record of natural and anthropogenic soil erosion in South Greenland
The environmental impact of the Norse landnám (colonization) in Greenland has been studied extensively. But to date, no study has quantified the soil erosion that Norse agricultural practices are believed to have caused. To resolve this problem, a high resolution sedimentary record from Lake Igaliku in South Greenland is used to quantitatively reconstruct 2500 years of soil erosion driven by climate and historical land use. An accurate chronology, established on 18 AMS 14C, and 201Pb and 137Cs dates, allows for the estimation of detritic fluxes and their uncertainties. Land clearance and the introduction of grazing livestock by the Norse around 1010 AD caused an acceleration of soil erosion up to ∼8 mm century-1 in 1180 AD which is two-fold higher than the natural pre-landnám background. From 1335 AD to the end of the Norse Eastern Settlement (in the mid-fifteenth century), the vegetation began to recover from initial disturbance and soil erosion decreased. After an initial phase of modern sheep breeding similar to the medieval one, the mechanization of agriculture in the 1980s caused an unprecedented soil erosion rate of up to ∼21 mm century-1, five times the pre-anthropogenic levels. Independently, a suite of biological and geochemical proxies (including Ti and diatom concentrations, C:N ratio, δ13C and δ15N of organic matter) confirm that the medieval and modern anthropogenic erosion far exceeds any natural erosion over the last 2500 years. Our findings question the veracity of the catastrophic scenario of overgrazing and land degradation considered to have been the major factor responsible for Norse settlement demise. They also shed light on the sustainability of modern practices and their consequences for the future of agriculture in Greenland.
(Quaternary Science Reviews. vol. 32, n° 0277-3791, pp. 119 - 130, 01/01/2012)
LCE, CNRS, UMLP, BGS, UB, CNRS, ArScAn, UP1, UP8, UPN, MCC, CNRS, ARTeHiS, MCC, UB, CNRS, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, LISA (UMR_7583), INSU - CNRS, UPEC UP12, CNRS, UPCité
The chemokine CCL2 protects against methylmercury neurotoxicity.
Industrial pollution due to heavy metals such as mercury is a major concern for the environment and public health. Mercury, in particular methylmercury (MeHg), primarily affects brain development and neuronal activity, resulting in neurotoxic effects. Because chemokines can modulate brain functions and are involved in neuroinflammatory and neurodegenerative diseases, we tested the possibility that the neurotoxic effect of MeHg may interfere with the chemokine CCL2. We have used an original protocol in young mice using a MeHg-contaminated fish-based diet for 3 months relevant to human MeHg contamination. We observed that MeHg induced in the mice cortex a decrease in CCL2 concentrations, neuronal cell death, and microglial activation. Knock-out (KO) CCL2 mice fed with a vegetal control food already presented a decrease in cortical neuronal cell density in comparison with wild-type animals under similar diet conditions, suggesting that the presence of CCL2 is required for normal neuronal survival. Moreover, KO CCL2 mice showed a pronounced neuronal cell death in response to MeHg. Using in vitro experiments on pure rat cortical neurons in culture, we observed by blockade of the CCL2/CCR2 neurotransmission an increased neuronal cell death in response to MeHg neurotoxicity. Furthermore, we showed that sod genes are upregulated in brain of wild-type mice fed with MeHg in contrast to KO CCL2 mice and that CCL2 can blunt in vitro the decrease in glutathione levels induced by MeHg. These original findings demonstrate that CCL2 may act as a neuroprotective alarm system in brain deficits due to MeHg intoxication.
(Review of Economic Dynamics. vol. 125, n° 1094-2025, pp. 209-18, 01/01/2012)
UPMC, INSERM, CNRS, UNIL, UPMC, INSERM, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, SU, CRICM, UPMC, INSERM, CNRS
Natural and anthropogenic trace metals in sediments of the Ligurian Sea (Northwestern Mediterranean)
(Chemical Geology. vol. 291, n° 0009-2541, pp. 141-151, 01/01/2012)
MIO, IRD, AMU, INSU - CNRS, UTLN, CNRS, IFREMER, LEP, EEP, IFREMER, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, LOV, OOVM, UPMC, INSU - CNRS, CNRS, UPMC, INSU - CNRS, CNRS
Quantitative reconstruction of sea-surface conditions over the last ∼150 yr in the Beaufort Sea based on dinoflagellate cyst assemblages: the role of large-scale atmospheric circulation patterns
Dinoflagellate cyst (dinocyst) assemblages have been widely used over the Arctic Ocean to reconstruct sea-surface parameters on a quantitative basis. Such reconstructions provide insights into the role of anthropogenic vs natural forcings in the actual climatic trend. Here, we present the palynological analysis of a dated 36 cm-long core collected from the Mackenzie Trough in the Canadian Beau-fort Sea. Dinocyst assemblages were used to quantitatively reconstruct the evolution of sea-surface conditions (temper-ature, salinity, sea ice) and freshwater palynomorphs fluxes were used as local paleo-river discharge indicators over the last ∼ 150 yr. Dinocyst assemblages are dominated by au-totrophic taxa (68 to 96 %). Cyst of Pentapharsodinium dalei is the dominant species throughout most of the core, except at the top where the assemblages are dominated by Op-erculodinium centrocarpum. Quantitative reconstructions of sea-surface parameters display a series of relatively warm, lower sea ice and saline episodes in surface waters, alternately with relatively cool and low salinity episodes. Variations of dinocyst fluxes and reconstructed sea-surface conditions may be closely linked to large scale atmospheric circulation patterns such as the Pacific Decadal Oscillation (PDO) and to a lesser degree, the Arctic Oscillation (AO). Positive phases of the PDO correspond to increases of dinocyst fluxes, warmer and saltier surface waters, which we associate with upwelling events of warm and relatively saline water from Pacific origin. Freshwater palynomorph fluxes increased in three phases from AD 1857 until reaching maximum values in AD 1991, suggesting that the Mackenzie River discharge followed the same trend when its discharge peaked between AD 1989 and AD 1992. The PDO mode seems to dominate the climatic variations at multi-annual to decadal timescales in the western Canadian Arctic and Beaufort Sea areas.
(Biogeosciences. vol. 9, n° 1726-4170, pp. 5391 - 5406, 28/10/2026)
ISMER, UQAR, LOCEAN, IPSL, ENS-PSL, PSL, UVSQ, UPMC, CEA, INSU - CNRS, X, IP Paris, CNES, CNRS, MNHN, IRD, UPMC, INSU - CNRS, CNRS, PALEOPROXUS, LOCEAN, IPSL, ENS-PSL, UVSQ, UPMC, CEA, INSU - CNRS, X, CNES, CNRS, MNHN, IRD, UPMC, INSU - CNRS, CNRS, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, ULaval, INSU - CNRS, CNRS
Colonisation et utilisation des habitats estuariens par les poissons migrateurs thalassotoques : approche comparative Seine-Gironde
Ce travail vise à comparer de quelles manières les trois espèces de poissons migrateurs thalassotoques (i.e. qui se reproduisent en mer et vont grandir dans les bassins versants) fréquentant la façade Atlantique : le mulet porc, l'anguille européenne et le flet, colonisent les estuaires de la Seine et de la Gironde et effectue leur croissance. L'hypothèse principale était que leur comportement pouvait être influencé par le niveau de contamination et de pressions anthropiques des estuaires. La démarche retenue pour aborder ces différentes échelles de manière comparative (entre les espèces et entre deux sites situées de manière similaire en Seine et en Gironde) a consisté à examiner : i) la phase de colonisation initiale à un stade très jeune par une approche expérimentale en mésocosme ; ii) la phase de croissance par un suivi en télémétrie acoustique en période estivale ; ii) l'ensemble du cycle vital par une analyse rétrospective à l'aide de la microchimie des otolithes des différents compartiments halins utilisés. Les trois niveaux d'analyse effectués avec des méthodes différentes permettent de dégager des patrons spécifiques (colonisation initiale, phase de croissance, cycle de vie) mais les différences entre les sites ne sont vraiment claires qu'à l'échelle très globale de l'utilisation des différents compartiments. Contrairement à notre hypothèse de départ les jeunes migrateurs thalassotoques parviennent à adopter un comportement spécifique en phase avec un rythme de type circadotidal ou nycthéméral y compris dans une ambiance de type Seine (très chargée en contaminants). Leur comportement est d'ailleurs peu différent dans les ambiances Seine ou Gironde. Il est donc tout à fait possible qu'ils ne soient pas extrêmement perturbés par les contaminants issus des sédiments que ce soit en Seine ou en Gironde. On notera toutefois que les civelles ont construit moins de terriers dans le sédiment de l'ambiance Seine que dans celui de l'ambiance Gironde, on peut imaginer que la plus forte contamination du sédiment de Seine les en dissuade. La fonctionnalité de corridor écologique ne semble donc pas empêchée par la contamination des sédiments. Durant leur phase de croissance en zone tidale d'eau douce les espèces étudiées utilisent des habitats différents selon des patrons temporels spécifiques (par exemple les mulets porcs utilisent les zones intertidales et les bras morts lors des flots de jours ; durant le jour les anguilles demeurent à l'abri dans des enrochements grossiers tandis que durant la nuit elles se déplacent dans des zones profondes à la recherche de leurs proies). Les résultats obtenus sur la Seine sont cohérent avec ceux obtenus sur la Gironde, ainsi dans les deux cas les flets recherchent de zones fraiches (ombre en Gironde, embouchures d'affluents plus frais en Seine), les anguilles présentent une activité principalement nocturne. La réaction des espèces au stress du marquage est très différente selon les espèces. Les mulets quittent très vite le secteur tandis que les anguilles et les flets sont au contraire extrêmement immobiles en "attendant" que leur condition s'améliore. Un épisode hypoxique observé en fin d'été sur la Seine a coïncidé avec un immobilisme des anguilles laissant penser que leur réaction à un stress environnemental pourrait se traduire par le même type de comportement que leur réaction au marquage. Les mulets de la Seine semblent moins inféodés à l'estuaire saumâtre que les mulets de la Gironde, ceci pourrait s'expliquer par la plus grande dimension de l'estuaire de la Gironde. Les anguilles de la Seine et de la Gironde présentent une grande variabilité d'histoires de vie mais on ne peut pas dégager de différences d'utilisation notables des habitats entre la Seine et la Gironde. Chez les flets la contribution des mères ayant utilisé l’eau douce est relativement plus importante en Seine qu'en Gironde. On en déduit une utilisation plus importante des habitats d’eau douce par les flets de Seine en comparaison avec les flets de la Gironde. Il en ressort globalement que les habitats dulcaquicoles de la Seine (trés diversifiés : bathymétrie, substrat, ripisylve…) sont proportionnellement plus utilisés par les espèces thalassotoques que ceux de Gironde. Cela peut s'expliquer par une moindre attractivité (ou une moindre capacité d'accueil) de l'estuaire saumatre de la Seine ou au contraire par une plus grande attractivité (ou une plus grande capacité d'accueil) de l'estuaire dulcaquicole de la Seine. Les comportements mis en évidence sur ces secteurs pourraient servir de référence pour des opérations de restauration.
(pp. 117, 28/10/2026)
UR EPBX, IRSTEA, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, UR HBAN, IRSTEA, CSLN
Les cartes auto-organisantes de Kohonen appliquées à l’étude des communautés de micro-algues des cours d’eau
Depuis une quinzaine d’années, les diatomées sont utilisées en routine afin d'évaluer l'état écologique des hydrosystèmes. Toutefois les indices diatomiques classiques ne permettent pas de diagnostiquer finement les différents types de pollution, et intègrent mal les variations naturelles, temporelles ou spatiales des communautés. Le but de ce travail est donc d'utiliser de nouvelles méthodologies biomathématiques et de tester leur pertinence dans un diagnostic de qualité écologique.
(pp. 43, 28/10/2026)
UR REBX, IRSTEA, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS
Impact of dietary gold nanoparticles in zebrafish at very low contamination pressure: the role of size, concentration and exposure time.
The impact of a daily ration of food containing gold nanoparticles (AuNPs) of two sizes (12 and 50 nm) was investigated in the zebrafish Danio rerio at very low doses (from 36-106 ng gold/fish/day). AuNP exposure resulted in various dysfunctions at the sub cellular scale, and AuNP concentration in food, AuNP size and exposure duration modulated the observed adverse effects. Indeed, we showed alteration of genome composition using a RAPD-PCR genotoxicity test as the number of hybridization sites of the RAPD probes was significantly modified after AuNP exposure. Moreover, the expression of genes involved in DNA repair, detoxification processes, apoptosis, mitochondrial metabolism and oxidative stress was also modulated in response to AuNP contamination. Mitochondrial dysfunctions appeared in brain and muscle for both tested doses (40 and 100 ng gold/fish/day), but gold accumulation in fish tissues could only be observed in the case of the highest exposure dose.
(Nanotoxicology. vol. 6, n° 1743-5390, pp. 144-160, 28/10/2026)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, ICMCB, UB, INC-CNRS, CNRS, IBGC, UB, CNRS
Ring-hydroxylating dioxygenase (RHD) expression in a microbial community during the early response to oil pollution
The early functional response of a bacterial community from the sediments of a chronically oil-polluted retention basin located at the Etang de Berre (France) was investigated just after petroleum addition. After removing hydrocarbon compounds by natural abiotic and biotic processes, the sediments were maintained in microcosms and Vic Bilh petroleum was added. The diversity and the expression of genes encoding ring-hydroxylating dioxygenases (RHD) were examined just after the petroleum addition until 14 days focussing on the first hours following the contamination. RHD gene copy numbers and diversity were maintained throughout all the incubation period; however, transcripts were detected only during the first 2 days. One dominant RHD gene, immediately and specifically expressed in response to petroleum contamination, was related to RHD gene carried by a plasmid found in Pseudomonas spp. The expression of the RHD genes was correlated with high biodegradation levels observed for low molecular weight PAHs at 7 days of incubation. The study shows that the bacterial metabolism induced just after the oil input is a key stage that could determine the bacterial community structure changes. Monitoring the expression of RHD genes, key genes involved in hydrocarbon degradation, may provide useful information for managing bioremediation processes. © 2012 Federation of European Microbiological Societies. Published by Blackwell Publishing Ltd. All rights reserved.
(FEMS Microbiology Ecology. vol. 80, n° 0168-6496, pp. 77-86, 28/10/2026)
IPREM, UPPA, INC-CNRS, CNRS, EEM, IPREM, UPPA, INC-CNRS, CNRS, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS