Consistency in diatom response to metal-contaminated environments
Diatoms play a key role in the functioning of streams, and their sensitivity to many environmental factors has led to the development of numerous diatom-based indices used in water quality assessment. Although diatom-based monitoring of metal contamination is not currently included in water quality monitoring programs, the effects of metals on diatom communities have been studied in many polluted watersheds as well as in laboratory experiments, underlying their high potential for metal contamination assessment. Here, we built large database of river diatoms (comprising more than 600 taxa) that were exposed to various loads of heavy metals in the water was investigated. The samples were collected during field surveys carried out in 6 different countries (France, Spain, Switzerland, Canada, Vietnam, China). After taxonomy harmonization, the patterns in diatom community structure were investigated for 202 samples, all collected from hard substrates in rivers with circumneutral water pH. As the sites were contaminated by a mixture of different metals (mainly Al, As, Cd, Cr, Cu, Fe, Hg, Ni, Pb, Zn) with various loads, metal concentrations were converted into a single score after Clements et al. (2000) in order to classify sites according to potential metal toxicity. Metal contamination proved to be a strong driver of the community structure, and enabled for the identification of tolerant species like Eolimna minima, Surirella angusta, Cocconeis placentula var. euglypta or Pinnularia parvulissima. Traits were also tested: diatom cell size and the occurrence of diatom deformities were found to be good indicators of high metal contamination. This work provides a basis for further use of diatoms as indicators of metal pollution Clements WH, Carlisle DM, Lazorchak JM, Johnson PC, 2000. Heavy metals structure benthic communities in Colorado mountain streams.
(pp. 1, 15/05/2011)
UR REBX, CEMAGREF, IRSTEA, IRSTEA, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, IRSTEA, ICRA, UdG, UdG, GEPV, CNRS
Development of q-PCR approaches to assess water quality: Effects of direct cadmium exposure on gene expression of the diatom Eolimna minima
In regard to the degradation of water quality since the last decades, appropriate diagnostic tools have been implemented. In France, water agencies in collaboration with Cemagref have developed a diatom index to estimate global water quality. The Biological Diatom Index (BDI, Coste et al. 2009) is routinely used for monitoring applications in European territories and has been standardized (NF T 90-354). Nevertheless, indices currently used for water quality assessment don't take in consideration metal contamination in their conception, despite the high bioaccumulation and impact shown on periphytic diatom communities (da Silva et al., 2009, Cunningham et al., 2005, Feurtet-Mazel et al., 2003). Moreover these methods are time consuming and require important taxonomic knowledge. In this context development of q-PCR approaches are of particular interest. In our study we have developed a new RNA extraction method for diatoms, 8 genes of interest for the diatom Eolimna minima have been selected, sequenced and deposited in the GenBank. The responses of the q-PCR tools developed have been tested after Cd exposure on Eolimna minima. Bioaccumulation and population kinetics were also followed.
(pp. 1, 15/05/2011)
UR REBX, CEMAGREF, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS
Sensitivity of beach morphodynamics to climate variability. Application to truc vert beach (France)
Coastal systems should be vulnerable to climate change/variability. The present paper investigates the sensitivity of Truc Vert beach to present day climate conditions as well as possible climate change in the near future. A modeling approach is used, based on three numerical morphodynamic models (MORPHODYN, MARSOUIN, TELEMAC). The first results show an important sensitivity to present day wave classes. Some first indications on the potential influence of wave climate changes are also given, investigating variations of wave classes characteristics. The present work also illustrates the need to go on improving and developing these models.
(06/05/2011)
BRGM, UR OHAX, CEMAGREF, LMA, AMU, ECM, CNRS, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, LEGI, UJF, Grenoble INP, CNRS
Marine diatoms in polar and sub-polar environments and their application to Late Pleistocene paleoclimate reconstruction
(IOP Conference Series: Earth and Environmental Science. vol. 14, n° 1755-1307, pp. 012006, 01/05/2011)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS
Genotoxic damages in zebrafish submitted to a polymetallic gradient displayed by the Lot River (France)
Genotoxic effects of a polymetallic pollution gradient displayed by the Lot River and one of its tributary have been assessed on zebrafish Danio rerio. Three methods were compared: RAPD-PCR, the comet assay, and 8-oxo-7, 8-dihydro-2'-deoxyguanosine (8-oxodG) formation. The fishes were exposed for 14 days to waters collected from three stations: Joanis, a site polluted by cadmium (Cd) and zinc (Zn) (mean concentrations: 15. γg Cd/L and 550. γg Zn/L), Bouillac (mean concentrations: 0.55. γg Cd/L and 80. γg Zn/L), and Boisse-Penchot, a reference station (mean concentrations:<0.05. γg Cd/L and 7. γg Zn/L). The quantitative RAPD-PCR methodology proved to be sensitive enough to unmask metal genotoxicity after 3 and 7 days of exposure to Joanis water and after 14 days to Bouillac water, whereas the comet assay only detected DNA damages at the most contaminated station (Joanis). The 8-oxodG quantification was not sensitive enough to be used in zebrafish under these environmental conditions. © 2011 Elsevier Inc.
(Ecotoxicology and Environmental Safety. vol. 74, n° 0147-6513, pp. 974-983, 01/05/2011)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, ISM, UB, INC-CNRS, CNRS, IRSN/DEI/SECRE/LRE, IRSN/DEI/SECRE, IRSN
Tracing cadmium contamination kinetics and pathways in oysters (Crassostrea gigas) by multiple stable Cd isotope spike experiments
Laboratory experiments using stable Cd isotopes (110 Cd and 112 Cd) were conducted to separately and simultaneously characterize Cd accumulation in different tissues of Pacific oysters (Crassostrea gigas) via the (i) trophic and (ii) direct pathways. For this, we exposed juvenile oysters to 110 Cd-spiked seawater (110 Cd: 2 mg l À 1 ; constant level) and 112 Cd-spiked food (Thalassiossera weissflogii, 112 Cd: 2 mg l À 1 in 35 Â 10 3 cells/oyster/L) in four experimental treatment groups, each containing 6 oysters, for 21 days with constant trophic feeding. These Cd contamination levels were $ 10 times lower than those typically used in experimental accumulation studies. Three oysters per treatment group were dissected every 7 days with separate sampling of the gills, digestive gland and the rest of the body. Metallothioneins were analysed in the digestive gland and gills. Cadmium concentrations and isotope ratios were measured in water (daily) and tissues (weekly) by GF-AAS and ICP-MS. The observed time-dependant evolution in Cd concentrations and 110 Cd/ 114 Cd and 112 Cd/ 114 Cd isotope ratios clearly revealed the bio-accumulation short-term kinetics and pathways of Cd contamination in the different tissues. Under the experimental conditions, significantly changed isotope ratios in gills and the digestive gland of oysters suggested rapid and efficient contamination by 110 Cd derived from direct exposure followed by internal Cd transfer between organs. Trophic contamination became measurable after 14 days of exposure corresponding to a trophic transfer rate of 1%. Constant metallothionein levels during the experiment suggested that the initially present metallothionein levels were sufficient to deal with the experimental Cd exposure.
(Ecotoxicology and Environmental Safety. vol. 74, n° 0147-6513, pp. 600-606, 01/05/2011)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS
Photodegradation of estrone enhanced by dissolved organic matter under simulated sunlight
In the present work the degradation of estrone (E1) a natural estrogenic hormone has been studied under simulated solar irradiation. The photodegradation of E1 has been investigated in the absence and in the presence of 7.7-8.9 mg L(-1) of dissolved organic carbon (DOC), under solar light simulation with irradiance approximating that of the sun. DOC extracts from different origins have been used. Half-lives ranging between 3.9 h and 7.9 h were observed. Results indicated that E1 was photodegraded even in the absence of DOC. The presence of DOC was found to enhance the degradation of E1. Experiments performed with the addition of reactive species scavengers (azide ions and 2-propanol) have shown that these two species play a significant role in the photodegradation. Some experiments have been performed with a DOC previously submitted to solar irradiation. Changes in optical and physico-chemical properties of DOC strongly affect its photoinductive properties, and hence its efficiency on E1 degradation. A part of the study consisted in the investigation of photoproducts structures. Five photoproducts were shown by chromatographic analysis: one arising from direct photolysis and the four others from DOC photoinduced degradation.
(Water Research. vol. 45, n° 0043-1354, pp. 3341-50, 01/05/2011)
LCEE [Poitiers], UP, CNRS, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, LCME [Poitiers], UP, INC-CNRS, CNRS, WDRC, KAUST
The use of Eugenol and electro-narcosis as anaesthetics: Transcriptional impacts on the European eel (Anguilla anguilla L.)
Ecotoxicological studies aim to assess the potential environmental risks of various products. This implies the use of various biological models and tests on live animals. In case of handling fish and mammals, ethical rules have to be respected. The use of anaesthesia is considered to be the best way to ensure animal welfare. Eugenol and electro-narcosis are among the most popular chemical and physical anaesthetics used in fisheries and by field biologists. In this study, the genetic and endocrine impacts of these anaesthetics were assessed in order to establish whether the use of such methods could skew the results of ecotoxicological studies. Twenty yellow European eels (Anguilla anguilla) were submitted to Eugenol (50mg/L) and electro-narcosis until they reached a level of deep anaesthesia, while 20 other eels were kept aware. Five anaesthetized and five unanaesthetized eels were sacrificed and analysed directly after treatment and after 1, 7 and 21 days of recovery. At the brain level, Eugenol triggered an increase in the transcription level of genes encoding proteins involved in oxidative stress responses (catalase expression 2.5-fold, mitochondrial superoxide dismutase expression 3-fold), probably due to a hypoxic event during anaesthesia. Later impacts were detected in muscles 21 days after anaesthesia (ATP synthase subunit 6 3-fold, NADH deshydrogenase subunit 5 4-fold and mitochondrial superoxide dismutase 3-fold increased) revealing oxidative stress from an accrued mitochondrial respiratory metabolism. Hormone dosages showed that the use of Eugenol reduced the release of plasma cortisol during anaesthesia. However, this impact seemed to be reversible within one day. In case of electro-narcosis, no significant variation in transcriptional levels could be detected between anaesthetized and unanaesthetized eels. Our results suggest that the use of Eugenol as an aesthetic in ecotoxicological studies measuring gene expression or plasma cortisol concentration is not appropriate, while electro-narcosis does not seem to have any impact, at least on the parameters taken into consideration in this study.
(Ecotoxicology and Environmental Safety. vol. 74, n° 0147-6513, pp. 1573-1577, 29/04/2011)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS
Assessment of Benthic Ecosystem Functioning Through Trophic Web Modelling : The Example of the Eastern Basin of the English Channel and the Southern Bight of the North Sea
Benthic organisms appear to be accurate proxies for assessing coastal ecosystem structures and changes due to climatic and anthropogenic stresses. Functional studies of benthic systems are relatively recent, mainly because of the difficulties in obtaining the basic parameters for each benthic compartment (i.e. detritus, bacteria, meiofauna and macrofauna). Our study focuses on the eastern basin of the English Channel and the Southern Bight of the North Sea. Trophic web modelling was used to assess the functioning of the three main benthic community assemblages. To test and assess the relative importance of factors assumed to influence trophic structure (geographical environment and sedimentary particle size distribution), the study area was subdivided into divisions defined a priori according to the two main structural factors of community distribution; geographic distribution and sedimentary patterns. Then, a steady state trophic model utilising the inverse method was applied to a diagram composed of eight compartments, including detritus, bacteria, meiofauna, macrobenthos and fish. For each compartment, six physiological parameters were assessed, based on our own data, empirical relationships and literature data. This method allowed estimation of the flux of matter and energy within and between the units of the benthic system and assessment of the amount of trophic energy stored in these units (available mostly to fish). Our results showed that suspension-feeders control most of the matter transfer through the macrobenthic food-web, except in the fine sand community, where deposit-feeders play a dominant role. The results also showed that, whatever the geographic area, trophic structure is strongly linked to the sedimentary conditions. As benthic communities are connected through hydrodynamics, a model of the entire eastern basin of the English Channel would appear to be acceptable. However, the main sediment types must be taken into account when establishing relationships between the functional units
(Marine Ecology. vol. 32, n° 0173-9565, pp. 1-15, 04/04/2011)
LOG, INSU - CNRS, ULCO, CNRS, IRD [Ile-de-France], EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, M2C, UNICAEN, NU, INSU - CNRS, UNIROUEN, NU, CNRS
Evidence for delayed poleward expansion of North Atlantic surface waters during the last interglacial (MIS 5e)
(Quaternary Science Reviews. vol. 30, n° 0277-3791, pp. 934-946, 01/04/2011)
IFM-GEOMAR, CAU, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, LSCE, UVSQ, INSU - CNRS, CNRS, DRF (CEA), CEA, PALEOCEAN, LSCE, UVSQ, INSU - CNRS, CNRS, DRF (CEA), CEA