International audience | Antibiotic use in the early 1900 vastly improved human health but at the same time started an arms race of antibiotic resistance. The widespread use of antibiotics has resulted in ubiquitous trace concentrations of many antibiotics in most environments. Little is known about the impact of these antibiotics on microbial processes or “non-target” organisms. This mini-review summarizes our knowledge of the effect of synthetically produced antibiotics on microorganisms involved in biogeochemical cycling. We found only 31 articles that dealt with the effects of antibiotics on such processes in soil, sediment, or freshwater. We compare the processes, antibiotics, concentration range, source, environment, and experimental approach of these studies. Examining the effects of antibiotics on biogeochemical processes should involve environmentally relevant concentrations (instead of therapeutic), chronic exposure (versus acute), and monitoring of the administered antibiotics. Furthermore, the lack of standardized tests hinders generalizations regarding the effects of antibiotics on biogeochemical processes. We investigated the effects of antibiotics on biogeochemical N cycling, specifically nitrification, denitrification, and anammox. We found that environmentally relevant concentrations of fluoroquinolones and sulfonamides could partially inhibit denitrification. So far, the only documented effects of antibiotic inhibitions were at therapeutic doses on anammox activities. The most studied and inhibited was nitrification (25–100 %) mainly at therapeutic doses and rarely environmentally relevant. We recommend that firm conclusions regarding inhibition of antibiotics at environmentally relevant concentrations remain difficult due to the lack of studies testing low concentrations at chronic exposure. There is thus a need to test the effects of these environmental concentrations on biogeochemical processes to further establish the possible effects on ecosystem functioning

Adding fertiliser to sediments is an established way of studying the effects of eutrophication but a lack of consistent methodology, reporting on enrichment levels, or guidance on application rates precludes rigorous synthesis and meta-analysis. We developed a simple enrichment technique then applied it to 28 sites across an intertidal sandflat. Fertiliser application rates of 150 and 600 g N m−2 resulted in pore water ammonium concentrations respectively 1–110 and 4–580 × ambient, with greater elevations observed in deeper (5–7 cm) than surface (0–2 cm) sediments. These enrichment levels were similar to eutrophic estuaries and were maintained for at least seven weeks. The high between-site variability could be partially explained by the sedimentary environment and macrofaunal community (42%), but only at the high application rate. We suggest future enrichment studies should be conducted in situ across large environmental gradients to incorporate real world complexity and increase generality of conclusions.

Pollution of the oceans by microplastics (<5 mm) represents a major environmental problem. To date, a limited number of studies have investigated the level of contamination of marine organisms collected in situ. For extraction and characterization of microplastics in biological samples, the crucial step is the identification of solvent(s) or chemical(s) that efficiently dissolve organic matter without degrading plastic polymers for their identification in a time and cost effective way. Most published papers, as well as OSPAR recommendations for the development of a common monitoring protocol for plastic particles in fish and shellfish at the European level, use protocols containing nitric acid to digest the biological tissues, despite reports of polyamide degradation with this chemical. In the present study, six existing approaches were tested and their effects were compared on up to 15 different plastic polymers, as well as their efficiency in digesting biological matrices. Plastic integrity was evaluated through microscopic inspection, weighing, pyrolysis coupled with gas chromatography and mass spectrometry, and Raman spectrometry before and after digestion. Tissues from mussels, crabs and fish were digested before being filtered on glass fibre filters. Digestion efficiency was evaluated through microscopical inspection of the filters and determination of the relative removal of organic matter content after digestion. Five out of the six tested protocols led to significant degradation of plastic particles and/or insufficient tissue digestion. The protocol using a KOH 10% solution and incubation at 60 °C during a 24 h period led to an efficient digestion of biological tissues with no significant degradation on all tested polymers, except for cellulose acetate. This protocol appeared to be the best compromise for extraction and later identification of microplastics in biological samples and should be implemented in further monitoring studies to ensure relevance and comparison of environmental and seafood product quality studies.

The effects of polystyrene microbeads (micro-PS; mix of 2 and 6 μm; final concentration: 32 μg L−1) alone or in combination with fluoranthene (30 μg L−1) on marine mussels Mytilus spp. were investigated after 7 days of exposure and 7 days of depuration under controlled laboratory conditions. Overall, fluoranthene was mostly associated to algae Chaetoceros muelleri (partition coefficient Log Kp = 4.8) used as a food source for mussels during the experiment. When micro-PS were added in the system, a fraction of FLU transferred from the algae to the microbeads as suggested by the higher partition coefficient of micro-PS (Log Kp = 6.6), which confirmed a high affinity of fluoranthene for polystyrene microparticles. However, this did not lead to a modification of fluoranthene bioaccumulation in exposed individuals, suggesting that micro-PS had a minor role in transferring fluoranthene to mussels tissues in comparison with waterborne and foodborne exposures. After depuration, a higher fluoranthene concentration was detected in mussels exposed to micro-PS and fluoranthene, as compared to mussels exposed to fluoranthene alone. This may be related to direct effect of micro-PS on detoxification mechanisms, as suggested by a down regulation of a P-glycoprotein involved in pollutant excretion, but other factors such as an impairment of the filtration activity or presence of remaining beads in the gut cannot be excluded. Micro-PS alone led to an increase in hemocyte mortality and triggered substantial modulation of cellular oxidative balance: increase in reactive oxygen species production in hemocytes and enhancement of anti-oxidant and glutathione-related enzymes in mussel tissues. Highest histopathological damages and levels of anti-oxidant markers were observed in mussels exposed to micro-PS together with fluoranthene. Overall these results suggest that under the experimental conditions of our study micro-PS led to direct toxic effects at tissue, cellular and molecular levels, and modulated fluoranthene kinetics and toxicity in marine mussels.

Passive sampling devices (PS) are widely used for pollutant monitoring in water, but estimation of measurement uncertainties by PS has seldom been undertaken. The aim of this work was to identify key parameters governing PS measurements of metals and their dispersion. We report the results of an in situ intercomparison exercise on diffusive gradient in thin films (DGT) in surface waters. Interlaboratory uncertainties of time-weighted average (TWA) concentrations were satisfactory (from 28% to 112%) given the number of participating laboratories (10) and ultra-trace metal concentrations involved. Data dispersion of TWA concentrations was mainly explained by uncertainties generated during DGT handling and analytical procedure steps. We highlight that DGT handling is critical for metals such as Cd, Cr and Zn, implying that DGT assembly/dismantling should be performed in very clean conditions. Using a unique dataset, we demonstrated that DGT markedly lowered the LOQ in comparison to spot sampling and stressed the need for accurate data calculation.

International audience | For herbivore insects, digesting can be somewhat challenging, as the defense mechanisms evolved by plants, including the release of phenolics like the non-protein amino acid l-3,4-dihydroxyphenylalanine (l-DOPA), can cause fitness costs. In addition, industrial and agricultural activities have elevated the amounts of iron that can be found in nature and more particularly FeSO4 that is used as fertilizer. Traces of iron can enhance the auto-oxidation of l-DOPA, in turn, generating reactive oxygen species (ROS) and consequently oxidative stress in insects. We examined the effects of the ion Fe2+ (as FeSO4) and l-DOPA on fifth instars of the desert locust Schistocerca gregaria. We measured the level of oxidative damage occurring to macromolecules (proteins and lipids) from midgut and thoracic tissues and assessed the activities of responsive antioxidant enzymes. Injected l-DOPA and redox-active metal iron generated ROS which caused oxidative damages to proteins and lipids to S. gregaria. The protein carbonyls and lipid peroxides present in tissue homogenates were elevated in treated insects. No synergism was observed when l-DOPA was co-injected with Fe2+. K (m) values of superoxide dismutase (SOD), glutathione reductase (GR), and glutathione peroxidase (GPx) were 4.3, 2.6, and 4.0 mM in thoracic muscles and 5.00, 2.43, and 1.66 mM in whole midgut for SOD, GR, and GPx, respectively, and 8.3 and 3.43 M for catalase (CAT) in the two tissues, respectively. These results suggest higher affinities of GPx and CAT to H2O2 in midgut than in muscles. The time-course changes in activities of antioxidant enzymes and amounts of protein carbonyls and lipid peroxides showed fluctuating patterns, suggesting complex interactions among macromolecules, l-DOPA and FeSO4, and their degradation products. Our results demonstrated the stressful effects of l-DOPA and FeSO4, proving that iron-containing fertilizers are pollutants that can strongly affect S. gregaria.

[Departement_IRSTEA]Ecotechnologies [TR1_IRSTEA]TED | International audience | The German guidelinefor the dimensioning, construction, and operation of constructed wetlands for biological treatment of domestic and municipal wastewater, which last published in March 2006, has recently been revised. The guideline applies to small wastewater treatment systems of less than 50 Person Equivalents (PE), municipal treatment plants up to 1.000 – 3.000 PE (with combined or separated sewers), treatment systems which use constructed wetlands as a polishing step, and small wastewater treatment systems which are operated seasonally (summer months only).The revision is based on a wide range of experience gained in recent years in the use of treatment wetlands in Germany and in Europe. Previous to the revisions, the proposed changes were discussed in a public hearing in Potsdam, Germany in January 2014. The final revisions were released for public review in October 2015. The finalized document is anticipated to be put into effect in April, 2016. A number of constructed wetland designs appear for the first time in the new guideline. Two-stage unsaturated vertical flow gravel filters which receive raw wastewater in the first stage (based on experience in France) as well as two-stage unsaturated vertical flow filters receiving primarytreated wastewater (based on experience in Austria) are now included. The revisions also include new dimensioning for unsaturated vertical flow filters with lava sand as the main treatment media, as well as aerated treatment wetlands, both as secondary treatment steps. Recommendations are also provided for seasonally operated constructed wetlands, as well as constructed wetlands for graywater treatment. With the publication of the new guideline, horizontal subsurface flow constructed wetlands are no longer supported as a secondary treatment stage in Germany, and are recommended only as a tertiary or polishing stage. Existing horizontal subsurface flow wetlands are allowed to continue operation, provided the systems are not hydraulically or organically overloaded, and that they continue to receive routine operations and maintenance. This presentation will outline the key points of the newly revised DWA-A 262 German constructed wetland guideline.

[Departement_IRSTEA]Ecotechnologies [TR1_IRSTEA]TED | International audience | An ion exchange process was assessed to improve ammonium removal by vertical flow filters. Six columns, filled with gravel and zeolite (30cm and 10cm, respectively), were compared with a standard column with 40 cm of gravel. Columns were fed for 3.5 days with semi-synthetic wastewater then rested for 7 days. Each column, filled with zeolite, had different inlet characteristics in order to study the effects of operational parameters pointed out as affecting the ion exchange process. Two columns assessed the impact of concentration (100mgNH4-N.L-1 versus 2000mgNH4-N.L-1) on exchange capacity and performance. The effect of competition with another cation on efficiency and saturation rate was studied at three different concentrations of sodium (0 mg.L-1, 85 mg.L-1 and 300 mg.L-1, respectively). Finally, regeneration of exchange capacity by nitrification as well as its effects on treatment efficiency was studied. Although zeolite showed promising results in the early stages of operation (>80%), performances quickly declined, until reaching similar efficiency as the standard (60%), suggesting insufficient regeneration. Moreover the concentration strongly affected the exchange capacity, the latter one being quite low for the range of ammonium concentrations usually observed in domestic wastewater. The sodium supply did not result in performance reductions for the studied conditions.

International audience | Chlordecone (CLD) is an organochlorine pesticide whose extended use led to the contamination of at least 20 % of agricultural soils from the French West Indies. Livestock reared on polluted areas are involuntary contaminated by CLD and their level of contamination may exceed the threshold values set by the European Union. Thus, characterizing the CLD behaviour in farm animals appear as a real issue in terms of food safety for local populations. The aim of this experiment was (i) to characterize the CLD disappearance in various tissues after exposure cessation and (ii) to evaluate the potential effect of body fatness on this process. Two groups of eight growing goats were submitted to either a basal diet or a high energy diet for 50 days before being intravenously contaminated with 1 mg CLD kg(-1) body weight. Two days after CLD contamination, half of the kids of each experimental group were slaughtered in order to determine pollutant levels in the serum, liver, adipose tissues, and empty carcass. The remaining animals were submitted to a 30-day decontamination period before slaughtering and measurements as described above. The implemented nutritional plan resulted in both groups of kids with significant differences in terms of body fatness. CLD was mainly concentrated in the liver of animals as described in the literature. It was found also in kids' empty carcass and adipose tissues; however its levels in the empty carcass (muscles and bones) were unexpected since they were higher than in fat. These results indicate that the lipophilic pollutant CLD is found mainly in liver but also in muscles and fat. Concerning the animals' depuration, a 30-d decontamination period was sufficient to observe a decrease of CLD levels by more than 75 % in both experimental groups and neither CLD concentrations nor CLD amounts were significantly affected by kids' body fatness.

International audience | In estuarine ecosystems, metallic and organic contaminants are mainly associated with fine grain sediments which settle on mudflats. Over time, the layers of sediment accumulate and are then transformed by diagenetic processes mainly controlled by microbial activity, recording the history of the estuary's chemical contamination. In an environment of this specific type, we investigated the evolution of the chemical contamination and the structure of both total and active microbial communities, based on PhyloChip analysis of a 4.6-m core corresponding to a 40-year sedimentary record. While the archaeal abundance remained constant along the core, a decrease by one order of magnitude in the bacterial abundance was observed with depth. Both total and active microbial communities were dominated by Proteobacteria, Actinobacteria, and Firmicutes in all sediment samples. Among Proteobacteria, alpha-Proteobacteria dominated both total (from 37 to 60 %) and metabolically active (from 19.7 to 34.6 %) communities, including the Rhizobiales, Rhodobacter, Caulobacterales, and Sphingomonadales orders. Co-inertia analysis revealed a relationship between polycyclic aromatic hydrocarbons, zinc and some polychlorobiphenyls concentrations, and the structure of total and active microbial communities in the oldest and most contaminated sediments (from 1970 to 1975), suggesting that long-term exposure to chemicals shaped the structure of the microbial community.