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Chlordecone is an organochlorine insecticide that has been widely used to control banana weevil in the French West Indies. As a result of this intense use, up to 20,000 ha are contaminated by this insecticide in the French West Indies, and this causes environmental damage and health problems. A scenario of exposure was drawn by French authorities, based on land usage records. Many efforts have been made to monitor the occurrence of chlordecone and its main metabolites using different analytical methods, including GC, GC/MS, LC/MS, and NIRS. Although these different methods allow for the detection and quantification of chlordecone from soils, none of them estimate the bottleneck caused by extraction of this organochlorine from soils with high adsorption ability. In this study, we used C-13(10)-chlordecone as a tracer to estimate chlordecone extraction yield and to quantify chlordecone in soil extracts based on the C-13/C-12 isotope dilution. We report the optimization of C-13(10)-chlordecone extraction from an Andosol. The method was found to be linear from 0.118 to 43 mg kg(-1) in the Andosol, with an instrumental detection limit estimated at 8.84 mu g kg(-1). This method showed that chlordecone ranged from 35.4 down to 0.18 mg kg(-1) in Andosol, Nitisol, Ferralsol, and Fluvisol soil types. Traces of the metabolite beta-monohydrochlordecone were detected in the Andosol, Nitisol, and Ferralsol soil samples. This last result indicates that this method could be useful to monitor the fate of chlordecone in soils of the French West Indies.

The insecticide chlordecone applied for decades in banana plantations currently contaminates 20,000 ha of arable land in the French West Indies. Although the impact of various pesticides on soil microorganisms has been studied, chlordecone toxicity to the soil microbial community has never been assessed. We investigated in two different soils (sandy loam and silty loam) exposed to different concentrations of CLD (D0, control; D1 and D10, 1 and 10 times the agronomical dose) over different periods of time (3, 7, and 32 days): (i) the fate of chlordecone by measuring (14)C-chlordecone mass balance and (ii) the impact of chlordecone on microbial community structure, abundance, and function, using standardized methods (-A-RISA, taxon-specific quantitative PCR (qPCR), and (14)C-compounds mineralizing activity). Mineralization of (14)C-chlordecone was inferior below 1 % of initial (14)C-activity. Less than 2 % of (14)C-activity was retrieved from the water-soluble fraction, while most of it remained in the organic-solvent-extractable fraction (75 % of initial (14)C-activity). Only 23 % of the remaining (14)C-activity was measured in nonextractable fraction. The fate of chlordecone significantly differed between the two soils. The soluble and nonextractable fractions were significantly higher in sandy loam soil than in silty loam soil. All the measured microbiological parameters allowed discriminating statistically the two soils and showed a variation over time. The genetic structure of the bacterial community remained insensitive to chlordecone exposure in silty loam soil. In response to chlordecone exposure, the abundance of Gram-negative bacterial groups (β-, γ-Proteobacteria, Planctomycetes, and Bacteroidetes) was significantly modified only in sandy loam soil. The mineralization of (14)C-sodium acetate and (14)C-2,4-D was insensitive to chlordecone exposure in silty loam soil. However, mineralization of (14)C-sodium acetate was significantly reduced in soil microcosms of sandy loam soil exposed to chlordecone as compared to the control (D0). These data show that chlordecone exposure induced changes in microbial community taxonomic composition and function in one of the two soils, suggesting microbial toxicity of this organochlorine.

Session 5 - Milieux impactés / Impacted mediaSession 5 - Milieux impactés / Impacted media; Objectives: Chlordecone was intensively used in the French West Indies (FWI) to control the banana weewil. Recent surveys showed that arable soils cropped with banana, representing up to 20,000 ha, are contaminated this insecticide with concentrations ranging between 0.2 and 37.4 mg kg−1. Chlordecone was classified as a persistent organic pollutant in May 2009. It is not only contaminating soil resources but also water resources where it is often detected. This insecticide is bioaccumulated in different plant and animals thereby contaminating the food chain causing an important human health. This contaminant is recalcitrant to biodegradation and very few information is available on microbial degradation of chlordecone in soils and almost nothing in the soil of the French West Indies. In this context, the program of research Biodechlord funded by the INRA (National Institute of Agronomical Research) in the framework the National Plan for Chlordecone (PNAC), was aiming at searching for traces of chlordecone microbial degradation in FWI soils. This project relied on a multidisciplinary approach developed by a broad scientific consortium involving researchers from CEA, Ecole Centrale Lyon, INRA, Irstea, Strasbourg and Lyon Universities. This program was made of several approaches consisting in (i) in silico analyses aiming at (ia) classifying chlordecone and its known metabolites using the QSAR Typol in order to define hypotheses on possible degradation pathways (ib) searching for microbial genes coding deshalogenases in genomic databank that could be used to dechlorinate chlordecone; (ii) chemical analyses aiming at (iia) optimizing approaches to quantify chlordecone and its main metabolites in soils, (iib) identify chemical processes (photodegradation and photocatalysis) that can be used to transform chlordecone; (iii) search for microbes tolerant to chlordecone able to grow on it under aerobic or anaerobic conditions; (iv) characterize the impact of chlordecone on soil microbial communities using soil metagenomics. A synthesis of the work carried out in the framework of Biodechlord will be presented. Innovative nature of the proposed topic: Very little information is available on the processes involved in the transformation of chlordecone in the contaminated soils of the French West Indies. Regarding to the environmental and the human health problems caused by the pollutant there is an urgent to document this question. The Biodechlord project proposed to search for chemical and microbial processes possibly involved in chlordecone transformation in the contaminated soils of the French West Indies. Among the results accumulated by the Biodechlord project, results about the isolation of microbial cultures tolerant to chlordecone will be highlighted.

The insecticide chlordecone is a contaminant found in most of the banana plantations in the French West Indies. This study aims to search for fungal populations able to grow on it. An Andosol heavily contaminated with chlordecone, perfused for 1 year in a soil-charcoal system, was used to conduct enrichment cultures. A total of 103 fungal strains able to grow on chlordecone-mineral salt medium were isolated, purified, and deposited in the MIAE collection (Microorganismes d'Intérêt Agro-Environnemental, UMR Agroécologie, Institut National de la Recherche Agronomique, Dijon, France). Internal transcribed spacer sequencing revealed that all isolated strains belonged to the Ascomycota phylum and gathered in 11 genera: Metacordyceps, Cordyceps, Pochonia, Acremonium, Fusarium, Paecilomyces, Ophiocordyceps, Purpureocillium, Bionectria, Penicillium, and Aspergillus. Among predominant species, only one isolate, Fusarium oxysporum MIAE01197, was able to grow in a liquid culture medium that contained chlordecone as sole carbon source. Chlordecone increased F. oxysporum MIAE01197 growth rate, attesting for its tolerance to this organochlorine. Moreover, F. oxysporum MIAE01197 exhibited a higher EC50 value than the reference strain F. oxysporum MIAE00047. This further suggests its adaptation to chlordecone tolerance up to 29.2 mg l(-1). Gas chromatography-mass spectrometry (GC-MS) analysis revealed that 40 % of chlordecone was dissipated in F. oxysporum MIAE01197 suspension culture. No chlordecone metabolite was detected by GC-MS. However, weak amount of (14)CO2 evolved from (14)C10-chlordecone and (14)C10-metabolites were observed. Sorption of (14)C10-chlordecone onto fungal biomass followed a linear relationship (r (2) = 0.99) suggesting that it may also account for chlordecone dissipation in F. oxysporum MIAE01197 culture.

Like other highly urbanized and industrialized estuaries, the Seine estuary (France) has, for decades, received high inputs of polycyclic aromatic hydrocarbons (PAHs). In order to estimate the bioremediation potentials and to identify the bacterial species involved in hydrocarbon degradation, we used microcosms containing seawater from the Seine estuary supplemented with either naphthalene, phenanthrene, fluorene or pyrene. In the microcosms enriched with naphthalene or phenanthrene, hydrocarbon biodegradation was significant within 9 weeks (43% or 46%, respectively), as shown by analyses in GC-MS. In similar microcosms incubated also with naphthalene or phenanthrene, analysis of the 16S rRNA gene sequences (DNA and cDNA) with denaturing gradient gel electrophoresis and clone libraries indicated that the PAH-degrading communities were dominated by Cycloclasticus spp., confirming their universal key role in degradation of low-molecular-weight PAHs in marine environments. However, in contrast to previous studies, we found that Pseudomonas spp. also degraded naphthalene and phenanthrene in seawater; this occurred only after 21 days, as was confirmed by real-time PCR. Although this genus has been abundantly described in the literature as a good PAH-degrading bacterial group in soil or in sediment, to our knowledge, this is the first evidence of a significant fitness in PAH degradation in seawater.