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International audience; Cheliff River is the most important permanent river of North-west Algeria which plays an essential role for irrigation and drinking water supply, but suffers from high anthropogenic pressure. Multi-dimensional and multi-factorial aspects of water pollution in Cheliff River and its tributary Mina River were evidenced during two contrasting climatic seasons. Urban discharges were identified as a major source of water organic pollution. The inputs of untreated sewages were characterized by maximum concentrations of tryptophan-like (5.7 µmol l−1) and tyrosine-like (9.8 µmol l−1) compounds during the dry period, confirming these amino acids as fingerprints of untreated urban discharges. The synchronous monitoring and assessment of physicochemical parameters, fluorescent organic compounds and metallic elements of Cheliff River waters highlighted its global contamination, mainly in its downstream part. Cheliff River was mainly affected by organic pollution with maximum COD (1536 mg O2 l−1) and BOD5 (12 mg O2 l−1) during the wet period, and by metallic contamination with maximum Fe (287 ± 4.4 µg l−1) and Al (422.4 ± 9.4 µg l−1) during the dry period, exceeding the guideline limits. This chronic contamination was related to untreated domestic sewages, agricultural effluents and technical landfill center discharges in this area. Diffuse pollutions were also evidenced, which made the identification of different contamination sources complicated. Mina River was mostly affected by non-treated domestic sewages with maximum COD (3161 mg O2 l−1) during the wet period and maximum BOD5 (12 mg O2 l−1) during the dry period, exceeding the guideline limits. The correlation Li/Sr showed the contribution of natural influence from saline soils of Mina valley, particularly during the dry period.

International audience; N-Acyl homoserine lactone (AHL)-mediated Quorum sensing (QS) is one of the most studied social behavior among Proteobacteria. However, despite the current knowledge on QS-associated phenotypes such as bioluminescence, biofilm formation, or pathogenesis, the characterization of environmental factors driving QS in realistic ecological settings remains scarce. We investigated the dynamics of AHL and AHL-producing Vibrio among 840 isolates collected fortnightly from the Salses-Leucate Mediterranean lagoon in spring and summer 2015 and 2016. Vibrio isolates were characterized by gyrB gene sequencing, Enterobacterial repetitive intergenic consensus polymerase chain reaction, and genome sequencing, and AHL production was investigated by a biosensors-based UHPLC–HRMS/MS approach. Our results revealed, for the first time, a succession of V. mediterranei isolates with different AHL production phenotypes over time and this dynamics was observed in a single genotype (average genomic nucleotide identity >99.9). A multivariate DistLM analysis revealed that 83.4% of the temporal variation of V. mediterranei QS phenotypes was explained by environmental variables. Overall, our results suggest that isolates of a single genotype are able to change their QS phenotypes in response to environmental conditions, highlighting the phenotypic plasticity of bacterial communication in the environment.

In the North West of Algeria, wastes represent a serious problem for environment and a potential risk for the population health.

International audience; The fate of benzo(a)pyrene (BaP), a ubiquitous contaminant reported to be persistent in the environment, is largely controlled by its interactions with the soil organic matter. In the present study, the spectral characteristics of fluorophores present in the physical fractions of the soil organic matter were investigated in the presence of pure BaP solution. After extraction of humic substances (HSs), and their fractionation into fluvic acid (FA) and humic acid (HA), two fluorescent compounds (C1 and C2) were identified and characterized in each physical soil fraction, by means of fluorescence excitation-emission matrices (FEEMs) and Parallel Factor Analysis (PARAFAC). Then, to each type of fraction having similar DOC content, was added an increasing volume of pure BaP solution in attempt to assess the behavior of BaP with the fluorophores present in each one. The application of FEEMs-PARAFAC method validated a three-component model that consisted of the two resulted fluorophores from HSs, FA and HA (C1 and C2) and a BaP-like fluorophore (C3). Spectral modifications were noted for components C2HSs (C2 in humic substances fraction) (λex/λem: 420/490-520 nm), C2FA (C2 in fulvic acid fraction) (λex/λem: 400/487(517) nm) and C1HA (C1 in humic acid fraction) (λex/λem: 350/452(520) nm). We explored the impact of increasing the volume of the added pure BaP solution on the scores of the fluorophores present in the soil fractions. It was found that the scores of C2HSs, C2FA, and C1HA increased when the volume of the added pure BaP solution increased. Superposition of the excitation spectra of these fluorophores with the emission spectrum of BaP showed significant overlaps that might explain the observed interactions between BaP and the fluorescent compounds present in SOM physical fractions.

Fluorescence excitation-emission matrices showed the spectral signature of dissolved organic matter (DOM) downstream in the River Tet at all seasons corresponding to humic substances with maximum fluorescence emission em=420-460nm for excitations of ex=340-360nm and the occasional presence of tryptophan, tracer of anthropogenic pressure, spectroscopically identified by ex/em=310/350nm. A factorial discriminant analysis, performed using the parameters selected (ex/em pairs of wavelength), succeeded in a better discrimination of seasons than stations, and clearly showed the presence of two fluorophores. Fluorophore 1, with two absorption bands: ex=260-320nm and 330-390nm for em=440-500nm, and Fluorophore 2, with one absorption band: ex=300-360nm for em=410nm, which are attributed to humic acid (HA) and fulvic acid (FA), respectively. Variations of DOM relative contents downstream in the River Tet, according to seasons and stations, showed high amounts of DOM (pedogenic character) along the river in the humid period, with the highest value obtained in the mountain section. In contrast, in summer, the DOM contents were low (aquagenic character). Moreover, DOM presents a relatively constant composition with a percentage of FA ranging from 40% at the mountain station to 48% at the mouth river, whatever the season.

In situ colorimetric determination is a useful quantitative and non-destructive contribution for the characterisation of organic and mineral pigments. It is in accordance with regard to the administrative instructions, which privilege the maximal conservation to secure the integrity of art discovered recently in this extraordinary prehistorical sanctuary. This determination connected with technical statements of archaeologists, help us to understand that many red hand paintings drawn with the palm of the right hand of a man and of a woman or adolescent, were made from one unique paint pot and the mode of retouch of black charcoal drawings.

International audience; Environmental characteristics in water and sediments of two contrasted coastal Mediterranean lagoons, Bages-Sigean and Canet-St Nazaire, were measured over a three season survey. The urban pollution (treatment plant discharges) is very important in Canet-St Nazaire lagoon reflecting untreated sewages, while in Bages-Sigean, the northern part appears more impacted due to larger anthropogenic inputs. Dissolved Cd concentrations are on the whole similar in both lagoons, whereas Cu concentrations are by far higher in lagoon Canet-St Nazaire. Cu concentrations appear to be highly dependent on dissolved organic carbon whereas salinity seems to control Cd variations. Concerning the sediments, the confined northern part of lagoon Bages-Sigean shows organic carbon and total nitrogen enrichment whereas lipid concentrations are much higher in the Canet-St Nazaire lagoon. Cu complexation seems to be strongly related to organic matter as evidenced by the two significant positive relationships, on one hand between Cu and organic carbon, and on the other hand, between Cu and lipids. On the contrary, Cd concentrations appear to be mainly controlled by carbonates. PCBs and PBDEs were detected only in sediments and show relatively low concentrations compared to similar lagoon environments. Regarding the sediment quality guidelines, Cd, Cu and PCBs in both lagoons did not exceed any Probable Effect Concentration (PEC).

The tributyltin-based products and organic biocides which are incorporated into antifouling paints have had a negative impact on the marine environment, and the ban on tributyltin-based antifouling products has urged the industry to find substitutes to prevent the development of fouling on ship hulls. Natural antifouling agents could be isolated from marine resources, providing an alternative option for the industry. The effects of different marine seaweed extracts from Sargassum muticum and Ceramium botryocarpum on the growth, pigment content and photosynthetic apparatus of the marine diatom Fragilaria pinnata were compared with those of Diuron, a biocide widely used in antifouling paints. The addition of the macroalgal extracts in the culture medium resulted in an inhibition of the growth of F. pinnata, but this inhibition was lower than that obtained with Diuron. After transfer to a biocide-free medium, F. pinnata cells previously exposed to the macroalgal extracts exhibited normal growth, in contrast to Diuron-treated cells, which died, demonstrating that the effects of the natural antifouling agents were reversible. Macroalgal extracts and Diuron-induced modifications in F. pinnata cellular pigment content. Chlorophyll a, fucoxanthin, and the xanthophyll pool, diadinoxanthin and diatoxanthin, were the most affected. Changes in the structure and function of the photosynthetic apparatus were studied by microspectrofluorimetry, and provided a comprehensive evaluation of the inhibition of the diatom Photosystem II (PSII) by the biocides. This study confirms that natural extracts from the macroalgae studied have the potential to be used as a substitute to commercial biocides in antifouling paints.

NH4+ turnover plays an important role in benthic compartment as source of nutrient for primary production. The intertidal mudflats of the Marennes-Oleron Bay are characterized by high fluctuations of sediment temperature that generally ranges from 10 to 30 degreesC during emersion periods. Influence of sediment temperature on NH4+ processes was investigated. Grass ammonification and NH4+ incorporation kinetics were studied using the N-15 isotope dilution method. The method was first adapted to these very fine sediments and applied to 2 upper sediment layers (0-2 and 2-4 cm) at different incubation times of up to 120 h. The effect of sediment temperature on gross ammonification and NH4+ incorporation rates was investigated at 10, 20 and 30 degreesC. There was a strong increase of both rates as a function of temperature, gross ammonification rates ranged from 0 to 17 mug NH4+-N.g(-1) dw.d(-1) and NH4+ incorporation rates from 2 to 13 mug N.g(-1) dw.d(-1) between 10 and 30 degreesC. This study showed that short-term temperature variations during the emersion period should be taken into account in quantifying NH4+ turnover in intertidal sediments and that benthic regeneration of NH4+ significantly supports benthic and planktonic primary production in Marennes-Oleron Bay. It suggests also that there is no N-limitation for benthic primary production in this bay and that there is up to 44 % of NH4+ produced in surface sediments, which can diffuse to the water column and become available to phytoplankton., La régénération du NH4 + joue un rôle important dans le compartiment benthique comme source de nutriment pour la production primaire. Les vasières intertidales de la baie de Marennes-Oléron sont caractérisées par de fortes fluctuations de la température du sédiment généralement comprises entre 10 et 30 °C durant les périodes d'émersion. L'influence de la température du sédiment sur les processus du NH4 + a été examinée. Les cinétiques d'ammonification brute et d'incorporation du NH4 + ont été étudiées par la méthode de dilution isotopique au 15N. Cette méthode a d'abord été adaptée sur ces sédiments très fins et appliquée à deux couches du sédiment (0¿2 et 2¿4 cm) pendant différents temps d'incubation jusqu'à 120 h. Tous les résultats indiquent clairement que les incubations de 24 h sont les plus fiables pour les calculs des taux. L'effet de la température du sédiment sur les taux bruts d'ammonification et d'incorporation du NH4 + a été étudié à 10, 20 et 30 °C dans le sédiment de surface. Il y avait une forte augmentation des deux taux en fonction de la température, les taux bruts d'ammonification varient de 0 à 17 μg N-NH4 +.g¿1 ss j¿1 et les taux d'incorporation du NH4 + de 2 à 13 μg N.g¿1 ss j¿1 entre 10 et 30 °C. Cette étude montre que les variations de température à court-terme durant l'émersion doivent être prises en compte dans l'estimation de la régénération du NH4 + dans les sédiments intertidaux et que la régénération benthique du NH4 + soutient significativement la production primaire benthique et planctonique dans la baie de Marennes-Oléron. Cela suggère aussi qu'il n'y a pas de limitation par l'azote pour la production primaire benthique dans cette baie et qu'il y a jusqu'à 44 % du NH4 + produit dans les sédiments de surface, qui peut diffuser dans la colonne d'eau et devenir disponible pour le phytoplancton.