Spatial and Temporal Variability of Sediment Organic Matter Recycling in Two Temperate Eutrophicated Estuaries
This paper deals with the spatial and seasonal recycling of organic matter in sediments of two temperate small estuaries (Elorn and Aulne, France). The spatio-temporal distribution of oxygen, nutrient and metal concentrations as well as the organic carbon and nitrogen contents in surficial sediments were determined and diffusive oxygen fluxes were calculated. In order to assess the source of organic carbon (OC) in the two estuaries, the isotopic composition of carbon (δ 13C) was also measured. The temporal variation of organic matter recycling was studied during four seasons in order to understand the driving forces of sediment mineralization and storage in these temperate estuaries. Low spatial variability of vertical profiles of oxygen, nutrient, and metal concentrations and diffusive oxygen fluxes were monitored at the station scale (within meters of the exact location) and cross-section scale. We observed diffusive oxygen fluxes around 15 mmol m−2 day−1 in the Elorn estuary and 10 mmol m−2 day−1 in the Aulne estuary. The outer (marine) stations of the two estuaries displayed similar diffusive O2 fluxes. Suboxic and anoxic mineralization was large in the sediments from the two estuaries as shown by the rapid removal of very high bottom water concentrations of NO x − (>200 μM) and the large NH4 + increase at depth at all stations. OC contents and C/N ratios were high in upstream sediments (11-15 % d.w. and 4-6, respectively) and decreased downstream to values around 2 % d.w. and C/N ≤ 10. δ 13C values show that the organic matter has different origins in the two watersheds as exemplified by lower δ 13C values in the Aulne watershed. A high increase of δ 13C and C/N values was visible in the two estuaries from upstream to downstream indicating a progressive mixing of terrestrial with marine organic matter. The Elorn estuary is influenced by human activities in its watershed (urban area, animal farming) which suggest the input of labile organic matter, whereas the Aulne estuary displays larger river primary production which can be either mineralized in the water column or transferred to the lower estuary, thus leaving a lower mineralization in Aulne than Elorn estuary. This study highlights that (1) meter scale heterogeneity of benthic biogeochemical properties can be low in small and linear macrotidal estuaries, (2) two estuaries that are geographically close can show different pattern of organic matter origin and recycling related to human activities on watersheds, (3) small estuaries can have an important role in recycling and retention of organic matter.
(Aquatic Geochemistry. vol. 19, n° 1380-6165, pp. 517-542, 20/11/2013)
UCA, SISYPHE, UPMC, EPHE, PSL, PSL, CNRS, DYNECO, IFREMER, IPGP, INSU - CNRS, UPD7, UR, IPG Paris, CNRS, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, LEMAR, IRD, IFREMER, UBO EPE, CNRS, LSCE, UVSQ, INSU - CNRS, CNRS, DRF (CEA), CEA, OCEANIS, LSCE, UVSQ, INSU - CNRS, CNRS, DRF (CEA), CEA
Development of q-PCR approaches to assess water quality: Effects of cadmium and pesticides on gene expression of diatoms
Periphytic diatoms are valuable tools to determine freshwater rivers quality based on diatoms identifications and distribution and constitute key indices in international standards. Nevertheless, indices currently used for water quality assessment do not take in consideration the diverse nature of contaminants, are time consuming and require important taxonomic knowledge. In this context development of q-PCR approaches have been developed to enhance a better reactivity in the diagnosis of modifications due to pollution conditions and to understand the genetic impact in relation with diatoms species. Through different laboratory experiments (14 days exposure) concerning various contamination (metallic with Cd: 10 and 100 µg/L) or pesticides with diuron: 1 and 10 µg/L), several target genes involved in mitochondrial metabolism (coxI, nad4, 12S), oxidative stress response (sod Mn), detoxification (cyp1A1) and photosynthesis (psaA, d1) have been characterized and their expression levels have been determined.
(pp. 1, 17/11/2013)
UR REBX, IRSTEA, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS
Correlation between perkinsosis and growth in clams Ruditapes spp.
Perkinsosis is one of the most widespread diseases affecting commercially important species of molluscs globally. We examined the impact of Perkinsus spp. on shell growth at the individual scale in 2 clam species: Ruditapes decussatus from Mundaka Estuary (Spain) and R. philippinarum from Arcachon Bay (France). At Arcachon, 2 contrasting sites in terms of environment and Perkinsus olseni presence were chosen: Arguin (disease-free) and Ile aux Oiseaux (infected site). We monitored the dynamics of perkinsosis over the course of the experiment at Mundaka and Ile aux Oiseaux. Prevalences were high (>70%), and intensities were around 105 cells g-1 wet gills at Ile aux Oiseaux, and 106 cells g-1 at Mundaka. No significant differences in prevalence or intensity were observed over time. A 2 yr field growth experiment of tagged-recaptured clams was performed to determine individual clam growth rate, condition index (CI), and Perkinsus spp. infection intensity. Clams were collected at Ile aux Oiseaux and transplanted to Arguin. The growth rate was always significantly and negatively correlated with Perkinsus spp. infection, and positively correlated with CI. CI and Perkinsus spp. infection explained 19% and 7% of the variability of the growth rate at Mundaka and Ile aux Oiseaux, respectively. In experimental clams at Arguin, P. olseni infection explained 26% of the variability of the growth rate at the lower tidal level. Our results suggest that at a concentration of between 105 and 106 cells g-1, perkinsosis affects the physiological functions of the clams, highlighted by its impact on the growth rate.
(Diseases of Aquatic Organisms. vol. 106, n° 0177-5103, pp. 255-65, 06/11/2013)
UQ [All campuses : Brisbane, Dutton Park Gatton, Herston, St Lucia and other locations], UQ [All campuses : Brisbane, Dutton Park Gatton, Herston, St Lucia and other locations], EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, LRHA, HGS, IFREMER, LEMAR, IRD, IFREMER, UBO EPE, CNRS
Transmission of DNA damage and increasing reprotoxic effects over two generations of Daphnia magna exposed to uranium
This study aimed to examine the mechanisms involved in the transgenerational increase in Daphnia magna sensitivity to waterborne depleted uranium (DU) under controlled laboratory conditions. Daphnids were exposed to concentrations ranging from 2 to 50 μg L-1 over two successive generations. Genotoxic effects were assessed using random amplified polymorphic DNA and real time PCR (RAPD-PCR). Effects on life history (survival, fecundity and somatic growth) were monitored from hatching to release of brood 5. Different exposure regimes were tested to investigate the specific sensitivity of various life stages to DU. When daphnids were exposed continuously or from hatching to deposition of brood 5, results demonstrated that DNA damage accumulated in females and were transmitted to offspring in parallel with an increase in severity of effects on life history across generations. When daphnids were exposed during the embryo stage only, DU exposure induced transient DNA damage which was repaired after neonates were returned to a clean medium. Effects on life history remained visible after hatching and did not significantly increase in severity across generations. The present results suggest that DNA damage might be an early indicator of future effects on life history. © 2013 Elsevier Inc.
(Comparative Biochemistry and Physiology - C Toxicology and Pharmacology. vol. 158, pp. 231-243, 01/11/2013)
IRSN/PRP-ENV/SERIS/LECO, IRSN/PRP-ENV/SERIS, IRSN, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, IRSN/PRP-ENV/SERIS/L2BT, IRSN/PRP-ENV/SERIS, IRSN
Evaluation of the sea ice proxy IP25 against observational and diatom proxy data in the SW Labrador Sea
The recent rapid decline in Arctic sea ice cover has increased the need to improve the accuracy of the sea ice component in climate models and to provide detailed long-term sea ice concentration records, which are only available via proxy data. Recently, the highly branched isoprenoid IP25, identified in marine sediments underlying seasonal sea ice, has emerged as a potential sea ice specific proxy for past sea ice cover. We tested the reliability of this biomarker as a sea ice proxy against observational sea ice data (sea ice concentrations from the global HadISST1 database) and against a more established sea ice proxy (sea ice diatom abundance in sediments) in the South-West (SW) Labrador Sea. Furthermore, our study location at the southern margin of Arctic sea ice drift provided a new environmental setting in which to further test the novel PIP25 index. Our two study sites are located North-East (NE) and South-East (SE) of Newfoundland where box cores covering the last ca 100-150 years were collected. IP25 concentrations are nearly an order of magnitude higher and sea ice diatoms more abundant in sediments from NE of Newfoundland, where sea ice prevails 2-4 months per year compared to the sediments SE of Newfoundland, where conditions are generally ice-free year round. The IP25 fluxes NE of Newfoundland agree well with multi-decadal North Atlantic Oscillation (NAO) trends in the study area, which in previous studies have been shown to affect the climatic and sea ice conditions in the region. When assessed against observational sea ice data, IP25 appears to be a more sensitive indicator of sea ice variability in this setting compared to sea ice diatoms and proved to be a robust and reliable proxy for reconstructing low-frequency variability in past sea ice concentrations. The PIP25 index results clearly differ from the observed sea ice data underlining that caution needs to be exercised when using the index in different environmental settings.
(Quaternary Science Reviews. vol. 79, n° 0277-3791, pp. 53-62, 01/11/2013)
LOCEAN, IPSL, ENS-PSL, PSL, UVSQ, UPMC, CEA, INSU - CNRS, X, IP Paris, CNES, CNRS, MNHN, IRD, UPMC, INSU - CNRS, CNRS, LSCE, UVSQ, INSU - CNRS, CNRS, DRF (CEA), CEA, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, IHPST, UP1, DEC, ENS-PSL, PSL, CNRS
Diatoms and biomarkers evidence for major changes in sea ice conditions prior the instrumental period in Antarctic Peninsula
The Antarctic Peninsula (AP) has been identified as one of the most rapidly warming region on Earth. Satellite monitoring currently allows for a detailed understanding of the relationship between sea ice extent and duration and atmospheric and oceanic circulations in this region. However, our knowledge on oceaneiceeatmosphere interactions is still relatively poor for the period extending beyond the last 30 years. Here, we describe environmental conditions in Northwestern and Northeastern Antarctic Peninsula areas over the last century using diatom census counts and diatom specific biomarkers (HBIs) in two marine sediment multicores (MTC-38C and-18A, respectively). Diatom census counts and HBIs show abrupt changes between 1935 and 1950, marked by ocean warming and sea ice retreat in both sides of the AP. Since 1950, inferred environmental conditions do not provide evidence for any trend related to the recent warming but demonstrate a pronounced variability on pluri-annual to decadal time scale. We propose that multi-decadal sea ice variations over the last century are forced by the recent warming, while the annual-to-decadal variability is mainly governed by synoptic and regional wind fields in relation with the position and intensity of the atmospheric low-pressure trough around the AP. However, the positive shift of the SAM since the last two decades cannot explain the regional trend observed in this study, probably due to the effect of local processes on the response of our biological proxies.
(Quaternary Science Reviews. vol. 79, n° 0277-3791, pp. 99-110, 01/11/2013)
LOCEAN, IPSL, ENS-PSL, PSL, UVSQ, UPMC, CEA, INSU - CNRS, X, IP Paris, CNES, CNRS, MNHN, IRD, UPMC, INSU - CNRS, CNRS, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, ULaval, INSU - CNRS, CNRS
Early morphofunctional plasticity of microglia in response to acute lipopolysaccharide
Within the central nervous system (CNS) the traditional role of microglia has been in brain infection and disease, phagocytosing debris and secreting factors to modify disease progression. This led to the concept of “resting” versus “activated” microglia. However, this is misleading because multiple phenotypic and morphological stages of microglia can influence neuronal structure and function in any condition and recent evidence extends their role to healthy brain homeostasis. The present work was thus aimed at reappraising the concept of morphofunctional activity of microglia in a context of peripheral acute immune challenge, where microglial activity is known to be modified, using the new state-of-the-art techniques available. To do so, mice were injected peripherally with lipopolysaccharide, a potent inducer of cerebral inflammation, and we assessed early cytokines production, phenotype, motility and morphology of microglial cells. Our results showed that LPS induced a widespread inflammatory response both peripherally and centrally, as revealed by the quantification of cytokines levels. We also found an alteration of microglial motility that was confirmed by in vivo studies showing an overall reduction of microglial processes length in the hippocampus of LPS-treated animals. Finally, analysis of various surface receptors expression revealed that LPS did not significantly impact microglial phenotype 2 h after the injection but rather induced an increase of CD11b+/CD45high cells. These latter may be at the vasculature, at the CNS vicinity, or may have invaded the CNS.
(Brain, Behavior, and Immunity. vol. 34, n° 0889-1591, pp. 151-158, 01/11/2013)
NutriNeuro, INRA, UB, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS
Anthropogenic sources and biogeochemical reactivity of particulate and dissolved Cu isotopes in the turbidity gradient of the Garonne River (France)
High precision MC-ICP-MS Cu isotope measurements were performed on suspended particulate matter (SPM) and filtered water sampled along the turbidity gradient of the fluvial Gironde Estuary (Garonne Branch), following a summer lasting period of low freshwater discharge. High Cu concentrations (up to ~ 200 μg/g) in particulate organic carbon (POC)-rich (up to ~ 14%) particles upstream from the Maximum Turbidity Zone (MTZ) coincide with the most negative δ65Cu values (down to − 0.39‰). This suggests the preferential uptake of light Cu isotopes by phytoplankton or anthropogenic contamination from CuSO4 fungicides related to intensive wine farming in the area (δ65Cu = − 0.37‰ for vineyard soils). Suspended particulate matter samples in the MTZ exhibit lower Cu concentrations (~ 35 μg/g) and heavier isotopic compositions (δ65Cu = − 0.20‰ in average), as recorded by other samples from the Gironde Watershed. Along the fluvial estuary, dissolved Cu is mostly enriched in heavy isotopes (up to δ65Cu = + 0.21‰), but negative signatures down to δ65Cu = − 0.66‰ occur near the city of Bordeaux. Release of dissolved Cu was attributed to the mineralization of organic matter with a total addition of ~ 600 ng/L in the fluvial estuary. Continuously decreasing amounts of dissolved Cu added with distance suggest that the observed Cu release evolved towards completion in the MTZ and contributed to negative values for dissolved Cu isotopes, as modeled by a Rayleigh process. Urban wastewater effluents probably also contribute to both (i) the dissolved Cu addition (10–20%) in the MTZ and (ii) negative Cu isotope signatures. Further work is necessary to assess the respective roles of anthropogenic sources and biogeochemical fractionation processes. Accordingly, the present study provides new insights into the potential of Cu isotopes for fingerprinting sources and mechanisms involved in the biogeochemical cycle of Cu in temperate aquatic environments impacted by anthropogenic activities.
(Chemical Geology. vol. 359, n° 0009-2541, pp. 125-135, 01/11/2013)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, ULB
Recent discovery of Paranthura japonica Richardson, 1909 (Crustacea: Isopod: Paranthuridae) in European marine waters (Arcachon Bay, Bay of Biscay)
The Asiatic isopod Paranthura japonica Richardson, 1909 was collected in 2007 in Arcachon Bay (SW France), where the species occurs in a variety of habitats, both in the intertidal and at shallow depths. This species, native to the Sea of Japan, may have been accidentally introduced in Arcachon Bay with oyster transfers or as fouling on ship hulls.
(BioInvasions Records. vol. 2, n° 2242-1300, pp. 215-219, 27/09/2013)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS
A bioturbation classification of European marine infaunal invertebrates
Bioturbation, the biogenic modification of sediments through particle reworking and burrow ventilation, is a key mediator of many important geochemical processes in marine systems. In situ quantification of bioturbation can be achieved in a myriad of ways, requiring expert knowledge, technology, and resources not always available, and not feasible in some settings. Where dedicated research programmes do not exist, a practical alternative is the adoption of a trait‐based approach to estimate community bioturbation potential (BPc). This index can be calculated from inventories of species, abundance and biomass data (routinely available for many systems), and a functional classification of organism traits associated with sediment mixing (less available). Presently, however, there is no agreed standard categorization for the reworking mode and mobility of benthic species. Based on information from the literature and expert opinion, we provide a functional classification for 1033 benthic invertebrate species from the northwest European continental shelf, as a tool to enable the standardized calculation of BPc in the region. Future uses of this classification table will increase the comparability and utility of large‐scale assessments of ecosystem processes and functioning influenced by bioturbation (e.g., to support legislation). The key strengths, assumptions, and limitations of BPc as a metric are critically reviewed, offering guidelines for its calculation and application.
(Ecology and Evolution. vol. 3, pp. 3958-3985, 17/09/2013)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, UGent