Quantitative proteomics reveals the Sox system's role in sulphur and arsenic metabolism of phototroph Halorhodospira halophila.

The metabolic process of purple sulphur bacteria's anoxygenic photosynthesis has been primarily studied in Allochromatium vinosum, a member of the Chromatiaceae family. However, the metabolic processes of purple sulphur bacteria from the Ectothiorhodospiraceae and Halorhodospiraceae families remain unexplored. We have analysed the proteome of Halorhodospira halophila, a member of the Halorhodospiraceae family, which was cultivated with various sulphur compounds. This analysis allowed us to reconstruct the first comprehensive sulphur-oxidative photosynthetic network for this family. Some members of the Ectothiorhodospiraceae family have been shown to use arsenite as a photosynthetic electron donor. Therefore, we analysed the proteome response of Halorhodospira halophila when grown under arsenite and sulphide conditions. Our analyses using ion chromatography-inductively coupled plasma mass spectrometry showed that thioarsenates are chemically formed under these conditions. However, they are more extensively generated and converted in the presence of bacteria, suggesting a biological process. Our quantitative proteomics revealed that the SoxAXYZB system, typically dedicated to thiosulphate oxidation, is overproduced under these growth conditions. Additionally, two electron carriers, cytochrome c551/c5 and HiPIP III, are also overproduced. Electron paramagnetic resonance spectroscopy suggested that these transporters participate in the reduction of the photosynthetic Reaction Centre. These results support the idea of a chemically and biologically formed thioarsenate being oxidized by the Sox system, with cytochrome c551/c5 and HiPIP III directing electrons towards the Reaction Centre.

The use of copper isotopes for understanding metal transfer mechanisms within the continuum mine-river-dam (Huelva Region, Spain).

Mining areas and in particular those containing massive sulfides have left a heavy environmental legacy with soils and hydrographic networks highly contaminated with metals and metalloids as for example in the Iberian Pyrite Belt (Huelva, Spain). Here, we present new data on copper (Cu) isotopic composition of waters and solids collected along a continuum Mine (Tharsis)-River (Meca)-Lake (Sancho) in the Iberian Pyrite Belt. Our results show that the isotopic signature of pit lakes is spatially variable, but remains stable over the seasons; this signature seems to be controlled by water-rock interaction processes. The data obtained on the Meca River imply a number of attenuation processes such as decrease in the metal concentration by precipitation of secondary minerals. This is accompanied by preferential retention of the heavy isotope (65Cu) with a possibility of living organisms (e.g., algae) participation. The terminal Sancho lake demonstrated constant isotopic signature over the entire depth of the water column despite sizable variations in Cu concentrations, which can be tentatively explained by a superposition of counter-interacting biotic and abiotic processes of Cu fractionation. Overall, the understanding of the isotopic variations along the hydrological continuum is useful for a better understanding of metal element transfer within mining environments and surrounding surface waters.

Cu isotope records of Cu-based antifouling paints in sediment core profiles from the largest European Marina, The Port Camargue.

The intensive use of copper (Cu) compounds as an alternative biocide in antifouling paints (APs) has resulted in wide Cu contamination into the marine environment, especially near marina harbor activities. In this work, the applicability of Cu isotopes to discriminate Cu origins related to the use of Cu-based APs in marine environments was tested. To this, Cu isotopes in APs, shipyard sludges, and sediment cores sampled in the Cu-contaminated Mediterranean marina of Port Camargue were determined. APs represent an important dominant anthropogenic source for metals in this site, making it ideal to test Cu isotopes as tracers. The overall isotope composition of four sediment cores and a surface sample varied between -0.13 and 0.44 ‰ (δ65Cu relative to NIST-976). Selected APs brands show a similar Cu concentration ~0.15 % and δ65Cu average of 0.54 ± 0.05 ‰. The plot of δ65Cu vs concentration for all datasets allowed dissociating natural and APs end-members. However, sample isotope systematics were not consistent with a conservative mixing binary source process. Heavily Cu-contaminated sediments show isotope signatures lighter than APs brands. However, the most Cu-contaminated sample, located directly above the careening area, shows a δ65Cu slightly lighter than APs (0.44 ‰ vs 0.54 ‰, respectively). Results suggest the preferential releasing of a heavy isotope pool by APs when these compounds are solubilized in seawater. The isotope fractionation was attributed to potential chemical Cu coordination changes during its elemental partition between paint and marina seawater and the fractionation induced by the organic ligands in the water column, before deposition. Further laboratory experiments are recommended to model the isotope fractionation mechanisms related to Cu release by APs. Because the APs' isotope signature is modified in marine environments, the use of Cu isotopes as tracers of AP in marine environments is challenging and needs more investigation.

Study of passive sampler calibration (Chemcatcher®) for environmental monitoring of organotin compounds: Matrix effect, concentration levels and laboratory vs in situ calibration.

Application of Chemcatcher® to monitor organotin compounds [monobutyltin (MBT), dibutyltin (DBT) and tributlytin (TBT)] in sea water has been little developed. Prior to the measurement of the time-weighted average water concentrations (TWAC), a calibration step is required to determine sampling rates (Rs) which is usually assessed in a flow-through laboratory pilot where experimental conditions are well controlled. This paper investigates the effect of the water matrix (tap water vs real sea water from the harbor of Port Camargue in France) and organotin concentrations on the uptake rates of organotin compounds. Laboratory calibrations provided sampling rates in the range of 66-225 mL.day-1 in high concentration (usually used for laboratory calibrations) and in the range of 30-56 mL.day-1 at low concentrations (environmental range). When the tank is filled with real sea water, sampling rates were found to be in the range of 38-177 mL.day-1. In order to demonstrate the efficiency of Chemcatcher® in real conditions, in situ calibration was done in the harbor of Port Camargue. This calibration has been done in order to replicate environmental conditions: compounds concentrations, hydrodynamic and water matrix effects. To compare the impact of calibration procedures on TWAC determination, Chemcatcher® was deployed in the harbor of Port Camargue and spot sampling was performed to monitor the concentrations of organotins in water throughout the exposure period. Results obtained using the field Rs determined by in situ calibration were more reliable. In this case, TWAC is in agreement with spot sampling concentration.

Contrasting arsenic biogeochemical cycling in two Moroccan alkaline pit lakes.

Pit lakes resulting from the flooding of abandoned mines represent a valuable freshwater reserve. However, water contamination by toxic elements, including arsenic, compromises their use for freshwater supply. For a better management of these reserves, our aim was to gain insight into arsenic cycling in two Moroccan alkaline pit lakes. We first showed that dimethylarsenic dominated in stratified lake ZA whereas in lake ZL1, As(V) was prevailing. Because microbially mediated processes largely contribute to arsenic cycling, the diversity of arsenic-methylating and -oxidizing bacteria was determined through the sequencing of arsM and aioA genes. Diverse arsM-carrying bacteria were thriving in ZA while a low diversity of aioA genes was detected in ZL1. We also determined the structure of the total bacterial communities by fingerprinting (ARISA). Contrasting arsenic speciation and bacterial communities in the two lakes were associated with differences of conductivity, Total Organic Carbon and temperature. In ZA, dissolved oxygen and redox potential were the main factors driving the total bacterial community structure and the ArsM diversity. In ZL1, stable bacterial communities were associated with limited water physico-chemistry variations. Our study provides new insights into the biogeochemical behavior of arsenic and the role of arsenic transforming bacteria in alkaline pit lakes.

Seasonal changes of chemical contamination in coastal waters during sediment resuspension.

The potential of remobilization of pollutants is a major problem for anthropogenic ecosystems, because even when the anthropogenic source of pollution is identified and removed, pollutants stored in sediments can be released into the water column and impact pelagic communities during sediment resuspension provoked by dredging, storms or bottom trawling. The objectives of the present study were to assess the changes observed in the chemical composition of the water column following resuspension of a polluted marine sediment and the consequences for the chemical composition of adjacent marine waters according to season. For that purpose, an experimental sediment resuspension protocol was performed on four distinct occasions, spring, summer, fall and winter, and the changes in nutrients, organic contaminants and inorganic contaminants were measured after mixing sediment elutriate with lagoon waters and offshore waters sampled nearby. Significant seasonal variations in the chemical composition of the contaminated sediments were observed, with a strong accumulation of PAHs in fall, whereas minimum PAH concentrations were observed during winter. In all seasons, sediment resuspension provoked a significant enrichment in nutrients, dissolved organic carbon, and trace metal elements like Ni, Cu, and Zn in offshore waters and lagoon waters, with enrichment factors that were season and site dependent. The most pronounced changes were observed for offshore waters, especially in spring and winter, whereas the chemical composition of lagoon waters was weakly impacted by the compounds supplied by sediment resuspension.

Hydraulic retention time affects bacterial community structure in an As-rich acid mine drainage (AMD) biotreatment process.

Arsenic removal consecutive to biological iron oxidation and precipitation is an effective process for treating As-rich acid mine drainage (AMD). We studied the effect of hydraulic retention time (HRT)-from 74 to 456 min-in a bench-scale bioreactor exploiting such process. The treatment efficiency was monitored during 19 days, and the final mineralogy and bacterial communities of the biogenic precipitates were characterized by X-ray absorption spectroscopy and high-throughput 16S rRNA gene sequencing. The percentage of Fe(II) oxidation (10-47%) and As removal (19-37%) increased with increasing HRT. Arsenic was trapped in the biogenic precipitates as As(III)-bearing schwertmannite and amorphous ferric arsenate, with a decrease of As/Fe ratio with increasing HRT. The bacterial community in the biogenic precipitate was dominated by Fe-oxidizing bacteria whatever the HRT. The proportion of Gallionella and Ferrovum genera shifted from respectively 65 and 12% at low HRT to 23 and 51% at high HRT, in relation with physicochemical changes in the treated water. aioA genes and Thiomonas genus were detected at all HRT although As(III) oxidation was not evidenced. To our knowledge, this is the first evidence of the role of HRT as a driver of bacterial community structure in bioreactors exploiting microbial Fe(II) oxidation for AMD treatment.

Effects of copper and butyltin compounds on the growth, photosynthetic activity and toxin production of two HAB dinoflagellates: The planktonic Alexandrium catenella and the benthic Ostreopsis cf. ovata.

Controlled laboratory experiments were conducted to test the effects of copper (Cu2+) and butyltins (BuT) on the growth, photosynthetic activity and toxin content of two HABs (Harmful Algal Blooms) dinoflagellates, the planktonic Alexandrium catenella and the benthic Ostreopsis cf. ovata. Microalgae were exposed to increasing concentrations of Cu2+ (10-4 to 31 nM) or BuT (0.084 to 84 nM) for seven days. When considering the growth, EC50 values were 0.16 (±0.09) nM and 0.03 (±0.02) nM of Cu2+ for A. catenella and O. cf. ovata, respectively. Regarding BuT, EC50 was 14.2 (±6) nM for O. cf. ovata, while A. catenella growth inhibition appeared at BuT concentrations ≥27 nM. Photosynthetic activity of the studied dinoflagellates decreased with increasing Cu and BuT concentrations. For O. cf. ovata, the response of this physiological parameter to contamination was less sensitive than the biomass. Cu exposure induced the formation of temporary cysts in both organisms that could resist adverse conditions. The ovatoxin-a and -b concentrations in O. cf. ovata cells increased significantly in the presence of Cu. Altogether, the results suggest a better tolerance of the planktonic A. catenella to Cu and BuT. This could result in a differentiated selection pressure exerted by these metals on phytoplankton species in highly polluted waters. The over-production of toxins in response to Cu stress could pose supplementary health and socio-economic threats in the contaminated marine ecosystems where HABs develop.

The environmental legacy of historic Pb-Zn-Ag-Au mining in river basins of the southern edge of the Massif Central (France).

The main rivers (Aude, Orb, Herault) that discharge into the Gulf of Lions and the west bank tributaries of the Rhone River including the Gardon have former non-ferrous metal mines in their upper drainage basin. Using unpublished data and data from the literature, this study provides an integrated overview of the contamination of water and sediment along the continent-sea continuum and of its impacts on the biota and on human health. In the upper part of these basins, water and stream sediments are enriched in metal(-loids) compared to median European concentrations. Arsenic is the main contaminant in the rivers Aude and Gardon d'Anduze, Sb in the Orb and Gardon d'Alès, and Tl in the Herault river. A rapid reduction in dissolved and particulate concentrations was systematically observed along the river due to dilution and precipitation. The high concentrations of metal(-loid)s observed suggest that the former mining activity still represents a potential threat for the environment, but the lack of high temporal resolution monitoring, especially during Mediterranean floods, prevents accurate assessment of metal fluxes from these rivers to the Mediterranean Sea. Studies dedicated to the impacts on human health are too rare, given that studies have shown a higher rate of arsenic-specific cancer near Salsigne mine in the Aude River basin and cases of saturnism in children in the upper Herault River basin. These studies underline the need to take environmental health issues into consideration not only in these watersheds but around the entire Mediterranean basin, which harbors numerous metalliferous ores that have been mined for millennia.

Behaviour of butyltin compounds in the sediment pore waters of a contaminated marina (Port Camargue, South of France).

Despite the ban on tributyltin (TBT) in marine paints, harbour sediments are still highly contaminated by this antifouling agent. Concentrations of TBT and its dealkylated products dibutyltin (DBT) and monobutyltin (MBT) were determined in the pore waters of Port Camargue, a large marina located on the French Mediterranean coast. Pore waters were sampled in the field using peepers deployed in summer 2012 and 2013 and in winter 2012-2013. The winter surveys were characterized by the presence of sulphides in pore waters from a depth of 5 cm, which was not the case in winter. In summer 2013, TBT was shown to be released into pore waters below the sediment-water interface (SWI) at concentrations of up to 70 ngSn L(-1). This release was also observed in sediment anaerobic incubations and was attributed to the mineralization of the sedimentary organic matter, possible stabilization of TBT by complexation with sulphides, and lower debutylation rates in anoxic than in oxic conditions. In summer 2012, a comparatively lower concentration of TBT (around 20 ngSn L(-1) below the SWI) was measured and the presence of methyltin species was detected. We hypothesize that the differences between the two surveys reflect different microbial activity. In winter 2012-2013, marked by Fe-reducing conditions in the sediments, TBT was released into solution at the SWI at concentrations of up to 40 ngSn L(-1). Sediments are thus a continuing source of TBT for the overlying waters despite the ban on its use for boats in France.

Consequences of contaminant mixture on the dynamics and functional diversity of bacterioplankton in a southwestern Mediterranean coastal ecosystem.

Contamination of coastal environments is often due to a complex mixture of pollutants, sometimes in trace levels, that may have significant effects on diversity and function of organisms. The aim of this study was to evaluate the short-term dynamics of bacterioplankton exposed to natural and artificial mixtures of contaminants. Bacterial communities from a southwestern Mediterranean ecosystem, lagoon and the bay (offshore) of Bizerte were exposed to i) elutriate from resuspension of contaminated sediment, and ii) an artificial mixture of metals and herbicides mimicking the contamination observed during sediment resuspension. Elutriate incubation as well as artificial spiking induced strong enrichments in nutrients (up to 18 times), metals (up to six times) and herbicides (up to 20 times) relative to the in situ concentrations in the offshore station, whereas the increases in contaminants were less marked in the lagoon station. In the offshore waters, the artificial mixture of pollutants provoked a strong inhibition of bacterial abundance, production and respiration and significant modifications of the potential functional diversity of bacterioplankton with a strong decrease of the carbohydrate utilization. In contrast, incubation with elutriate resulted in a stimulation of bacterial activities and abundances, suggesting that the toxic effects of pollutants were modified by the increase in nutrient and DOM concentrations due to the sediment resuspension. The effects of elutriate and the artificial mixture of pollutants on bacterial dynamics and the functional diversity were less marked in the lagoon waters, than in offshore waters, suggesting a relative tolerance of lagoon bacteria against contaminants.

Contrasted responses of Ruditapes decussatus (filter and deposit feeding) and Loripes lacteus (symbiotic) exposed to polymetallic contamination (Port-Camargue, France).

The use of symbiotic bivalve species to assess the effect of anthropogenic metal pollution was rarely investigated whereas data on filter feeding bivalves are common. The aim of this study was the exposure of two bivalve species, Ruditapes decussatus and Loripes lacteus to polymetallic pollution gradient, originating from harbor activities (Port-Camargue, south of France). Both bivalves differ by their trophic status, filter and deposit feeder for Ruditapes and symbiotic for Loripes that underlies potential differences in metal sensibility. The bivalves were immerged in July (for Ruditapes during 2 and 8 days) and in August 2012 (for Loripes during 2, 6 and 8 days) in the water column of the harbor, at 3 stations according to pollution gradient. Metal concentrations (Cu, Mn, Zn) in the water column were quantified as dissolved metals (measured by ICP-MS) and as labile metals (measured by ICP-MS using DGT technique). For each exposure time, accumulation of metals in the soft tissue of bivalves ("bioaccumulation") was measured for both species. In addition, specific parameters, according to the trophic status of each bivalve, were investigated: filtering activity (specific clearance rate, SCR) for Ruditapes, and relative cell size (SSC) and genomic content (FL1) of bacterial symbionts hosted in the gills of Loripes. The SCR of Ruditapes drops from 100% (control) to 34.7% after 2 days of exposure in the less contaminated site (station 8). On the other hand, the relative cell size (SSC) and genomic content (FL1), measured by flow cytometry were not impacted by the pollution gradient. Bioaccumulation was compared for both species, showing a greater capability of Cu accumulation for Loripes without lethal effect. Mn, Fe and Zn were generally not accumulated by any of the species according to the pollution gradient. The trophic status of each species may greatly influence their respective responses to polymetallic pollution.

Diversity and spatiotemporal dynamics of bacterial communities: physicochemical and other drivers along an acid mine drainage.

Deciphering the biotic and abiotic factors that control microbial community structure over time and along an environmental gradient is a pivotal question in microbial ecology. Carnoulès mine (France), which is characterized by acid waters and very high concentrations of arsenic, iron, and sulfate, provides an excellent opportunity to study these factors along the pollution gradient of Reigous Creek. To this end, biodiversity and spatiotemporal distribution of bacterial communities were characterized using T-RFLP fingerprinting and high-throughput sequencing. Patterns of spatial and temporal variations in bacterial community composition linked to changes in the physicochemical conditions suggested that species-sorting processes were at work in the acid mine drainage. Arsenic, temperature, and sulfate appeared to be the most important factors that drove the composition of bacterial communities along this continuum. Time series investigation along the pollution gradient also highlighted habitat specialization for some major members of the community (Acidithiobacillus and Thiomonas), dispersal for Acidithiobacillus, and evidence of extinction/re-thriving processes for Gallionella. Finally, pyrosequencing revealed a broader phylogenetic range of taxa than previous clone library-based diversity. Overall, our findings suggest that in addition to environmental filtering processes, additional forces (dispersal, birth/death events) could operate in AMD community.

Fate of Sb(V) and Sb(III) species along a gradient of pH and oxygen concentration in the Carnoulès mine waters (Southern France).

The speciation and behaviour of antimony were investigated in surface waters downstream from the abandoned Pb-Zn Carnoulès mine (Gard, France). These waters exhibit a permanent gradient of oxygen concentration and pH, ranging from acid suboxic in Reigous Creek at the outlet of sulfide tailings impoundment, to near neutral oxygenated at downstream sites along the rivers Amous and Gardon. The concentration of total dissolved (<0.22 µm) antimony, acquired through a seven-year monitoring, decreased from 7.7-409.9 µg L(-1) at the source of Reigous Creek to 0.22-0.45 µg L(-1) in the Gardon River, showing natural Sb attenuation. Speciation analysis carried out during three surveys indicated that Sb(III) represented up to 70% of the total dissolved Sb concentration at the source of Reigous Creek, while Sb(V) represented less than 50%. Field characterization showed that Sb(III) and Sb(V) species were attenuated through dilution and were also removed from the dissolved phase during downstream transport. Speciation analysis in suspended particulate matter extracts gave a distribution of particulate Sb into 70 to 100% of Sb(III) and less than 30% of Sb(V). The removal of Sb(III) and Sb(V) species from the dissolved phase was concordant with the oversaturation of Reigous Creek water relative to Sb(III)- and Sb(V)-oxides and Sb(III)- and Sb(V)-Fe oxides. Sb(III) was more efficiently removed than Sb(V) or As(III) and it was no more detectable in the dissolved phase at downstream sites in the rivers Amous and Gardon. Conversely, the concentration of Sb(V) in the rivers Amous and Gardon still denoted contamination arising from the Carnoulès mine. The range of log Kd values, from 2.4 L kg(-1) to 4.9 L kg(-1), indicated that Sb was mainly transported in the dissolved phase downstream the Reigous Creek input. Altogether, these results give a better understanding of the fate of Sb downstream from sulfide-rich mining wastes.

Trace elements in the sediments of a large Mediterranean marina (Port Camargue, France): levels and contamination history.

The study of trace elements (Cu, Zn, Pb, As, Hg) and butyltin concentrations in the sediments of Port Camargue enabled assessment of the levels and history of the contamination of the largest European marina linked with the use of antifouling paints. Surface sediments near the boat maintenance area were heavily contaminated with up to 1497 µg g(-1) of Cu, 475 µg g(-1) of Zn, 0.82 µg g(-1) of Hg, 94 µg g(-1) of Pb and over 10,000 ngSn g(-1) of tributyltin (TBT). High concentrations of Hg and TBT indicate ongoing sources of these elements despite the ban on their use as biocides in paints. Sediment cores provided records of contamination since 1969. The peak concentrations of As, Hg, Pb and TBT in the sediment profile reflect their presence on boat hulls when the marina was built at the end of the 1960s. Degradation of TBT in the sediments near the boat maintenance area is slow compared to other less contaminated area of the marina.