Editorial trend: adverse outcome pathway (AOP) and computational strategy - towards new perspectives in ecotoxicology.

The adverse outcome pathway (AOP) has been conceptualized in 2010 as an analytical construct to describe a sequential chain of causal links between key events, from a molecular initiating event leading to an adverse outcome (AO), considering several levels of biological organization. An AOP aims to identify and organize available knowledge about toxic effects of chemicals and drugs, either in ecotoxicology or toxicology, and it can be helpful in both basic and applied research and serve as a decision-making tool in support of regulatory risk assessment. The AOP concept has evolved since its introduction, and recent research in toxicology, based on integrative systems biology and artificial intelligence, gave it a new dimension. This innovative in silico strategy can help to decipher mechanisms of action and AOP and offers new perspectives in AOP development. However, to date, this strategy has not yet been applied to ecotoxicology. In this context, the main objective of this short article is to discuss the relevance and feasibility of transferring this strategy to ecotoxicology. One of the challenges to be discussed is the level of organisation that is relevant to address for the AO (population/community). This strategy also offers many advantages that could be fruitful in ecotoxicology and overcome the lack of time, such as the rapid identification of data available at a time t, or the identification of "data gaps". Finally, this article proposes a step forward with suggested priority topics in ecotoxicology that could benefit from this strategy.

First assessment of Rare Earth Element organotropism in Solea solea in a coastal area: The West Gironde Mud Patch (France).

Few studies exist on concentration and internal distribution of Rare Earth Elements (REEs) in marine fishes. REEs organotropism was determined in common sole (Solea solea) from the West Gironde Mud Patch (WGMP; N-E Atlantic Coast, France). The highest ∑REEs concentrations occurred in liver (213 ± 49.9 µg kg-1 DW) and gills (119 ± 77.5 µg kg-1 DW) followed by kidneys (57.7 ± 25.5 µg kg-1 DW), whereas the lowest levels were in muscles (4.53 ± 1.36 µg kg-1 DW) of Solea solea. No significant age- or sex-related differences were observed. The organotropism varied among groups of REEs. Light and heavy REEs preferentially accumulated in liver and gills, respectively. All considered organs showed different normalized REEs patterns, suggesting differences in internal distribution processes between organs. Further work should address: (1) baseline levels worldwide, and (2) factors controlling uptake and organ-specific concentration of REEs.

Development of an integrated indicator to assess chemical contamination in different marine species: The case of mercury on the French Atlantic continental shelf.

Good Environmental Status (GES) for Descriptor 8 (D8) of the Marine Strategy Framework Directive (MSFD) is considered to be achieved when concentrations of contaminants are at levels not giving rise to pollution effects. This study proposes a framework to assess GES in marine waters adjacent to France, including four groups of species (bivalves, fish, birds and mammals) living on the continental shelf and covering different dimensions of the marine environment. This framework is applied to mercury (Hg) in the three marine regions along the French Atlantic coast and includes two assessment types: i) an absolute assessment by comparing contamination levels with environmental thresholds, and ii) a relative assessment by comparing contamination levels over time, performed for bivalves and mammals that had long time-series available. Mercury concentrations were higher than environmental thresholds for bivalves and fish in all the three studied regions. Plus, they significantly increased since the 2000s for most bivalve stations and for the common dolphin Delphinus delphis. Our results therefore indicate that Hg concentrations have increased in marine waters and have reached levels possibly giving rise to pollution effects in biota from the three marine regions. The present study also highlighted the complementarity of monitoring Hg concentrations in each group of species and each type of assessment, making it possible to propose a conceptual framework for assessing the environmental pressure of bioaccumulated and biomagnified contaminants over the continental shelf.

Trace elements, dioxins and PCBs in different fish species and marine regions: Importance of the taxon and regional features.

Chemical contaminant concentrations in wild organisms are used to assess environmental status under the European Marine Strategy Framework Directive. However, this approach is challenged by the complex intra- and inter-species variability, and the different regional features. In this study, concentrations in trace elements (As, Cd, Hg and Pb), polychlorinated biphenyls (PCBs), polychlorodibenzo-para-dioxines (PCDDs) and polychlorodibenzofuranes (PCDFs) were monitored in 8 fish species sampled on the continental shelf of three French regions: the Eastern English Channel (EEC) and Bay of Biscay (BoB) in the Northeast Atlantic Ocean, and the Gulf of Lions (GoL) in Western Mediterranean Sea. Our objectives were to identify species or regions more likely to be contaminated and to assess how to take this variability into account in environmental assessment. While concentrations were higher in benthic and demersal piscivores, PCB and PCDD/F concentrations (lipid-weight) were similar in most teleost species. For Cd, Hg and Pb, the trophic group accumulating the highest concentrations depended on the contaminant and region. Concentrations in Hg, PCBs and PCDD/Fs were higher in the EEC and/or GoL than in BoB. Cadmium and Pb concentrations were highest in the BoB. Lipid content accounted for 35%-84% of organic contaminant variability. Lipid normalisation was employed to enhance robustness in the identification of spatial patterns. Contaminant patterns in chondrichthyans clearly differed from that in teleosts. In addition, trophic levels accounted for ≤1% and ≤33% of the contaminant variability in teleost fishes in the EEC and BoB, respectively. Therefore, developing taxa-specific thresholds might be a more practical way forward for environmental assessment than normalisation to trophic levels.

Use of groundwater and reclaimed water for agricultural irrigation: Farmers' practices and attitudes and related environmental and health risks.

Agricultural reuse of treated wastewater (TWW) for irrigation is widely practiced. Its conjunctive use with freshwater is becoming more common to guarantee food security, while the rationale behind and its sustainability are quite arguable. The objective of this study is to better understand the drivers of the conjunctive use of TWW and groundwater (GW) in Nabeul region, Tunisia, and the potential environmental and health impacts taking into account farmers' practices and attitudes toward reuse. TWW used for irrigation exhibited relatively high salinity and high microbiological load. GW has a very high salinity. TWW and GW showed low concentrations of heavy metals (Al, Cd, Co, Cu, Cr, Mn, Ni, Pb, and Zn). Concentrations of pharmaceutical compounds were between Limits of Quantification and 13 µg/L. In GW, values were relatively high, especially for caffeine, carbamazepine, ofloxacin, and ketoprofen. Farmers have a low perception of the polluting load of TWW and GW and of their potential long-term impacts on agricultural environment, human health, and agricultural productivity. GW availability has facilitated its conjunctive use with TWW, either to augment water quantity and/or to improve its quality. Despite its low quality, GW timeliness for irrigation was the main driver to guarantee a better yield and quality of produces. Soil microbial community, bacterial biomass, denitrifying potential and carbon oxidation profiles were similar under TWW, GW and their conjunctive use. Though an effect of the sampling period was observed with a high abundance of denitrifying bacteria in the wet season and a low carbon oxidation activity at the end of the dry season. The conjunctive use of TWW and GW is very likely unsustainable from health and environmental perspectives. Balancing farmers' economic profit against the preservation of agricultural activity, linked to cultural and natural heritage, remains one of the challenges for decision-makers and regional stakeholders.

Differences in chemical contaminants bioaccumulation and ecotoxicology biomarkers in Mytilus edulis and Mytilus galloprovincialis and their hybrids.

The Mytilus mussels are spread all over the world and many related species coexist in several areas and can produce hybrid offspring. Mussels have been used for decades in national and international programs to monitor chemical contamination in the environment. Differences in bioaccumulation and biotransformation abilities between species and their hybrids should be evaluated to assess the comparability of the results obtained within the international biomonitoring programs. The objective of this study was to characterize bioaccumulation abilities and biomarker responses in Mytilus edulis, Mytilus galloprovincialis and their hybrids via an in situ transplantation experimentation on their progenies. Four mussel groups (M. edulis, M. galloprovincialis and two hybrids batches) issued from genetically characterized parents were transplanted for one year in Charente Maritime (France) to ensure their exposure to identical sources of contamination. The bioaccumulation of several families of contaminants (trace metals, polycyclic aromatic hydrocarbons, polybrominated diphenyl ethers, polychlorinated biphenyls), the response of several biomarkers (DNA strand breaks level, lysosomal membrane stability, metallothionein content, acetylcholine esterase activity) and some physiological parameters (growth, mortality, gonadal development), were analyzed. Differences were observed between species, however they were contaminant-specific. Variations in contaminants levels were observed between progenies, with higher levels of Cu, PBDE, PCB in M. edulis, and higher levels of Cd, Hg, Zn in M galloprovincialis. This study demonstrated that variations in contaminant bioaccumulation and different biomarker responses exist between Mytilus species in the field. Data on species or the presence of hybrid individuals (or introgression) is an important additional parameter to add to biomonitoring programs databases.

High inter-species variability in elemental composition of the twilight zone fauna varies implications for predators and exploitation by humans.

While the importance of oceanic micronektonic species in biogeochemical cycles and in the transfer of matter in food webs is globally recognized, specific knowledge on elemental concentrations and their variability within this community is still poorly documented. Here, we report for the first time in the Bay of Biscay, North-East Atlantic, the body composition in various biological parameters and chemical elements of a meso-to bathypelagic micronektonic community. Stable carbon and nitrogen isotope compositions (δ13C, δ15N), C:N ratios, energy density, as well as the concentrations in 6 macro-minerals and 13 trace elements including essential (micro-nutrients) and non-essential elements (undesirables, with no know biological function) were measured in whole organisms of 4 crustacean and 11 fish species caught simultaneously around 800 m depth. The results showed a low variability of δ13C values, confirming that all studied species share the same habitat. On the contrary, large differences were observed among species for several elements. Trace elements showed the greatest variability (i.e. larger range of values), especially silver (Ag), arsenic (As), cadmium (Cd), cobalt and vanadium. Significant differences were also revealed among taxa for Ag, As, Cd, copper and strontium concentrations (with crustaceans > fish), as well as for δ15N values and phosphorus concentrations (with fish > crustaceans). Although concentrations varied greatly among species, they could be grouped according to their energy density and composition in 19 chemical elements, through hierarchical clustering analysis. Six functional groups of species have been thus identified, reflecting contrasted nutritional benefit and/or exposure to undesirables for predators feeding on this deep pelagic community. Finally, the concentrations measured for the potentially toxic trace elements (undesirables) exceeded the existing European thresholds for Cd and to a lesser extent mercury (Hg), which point out potential risks in the perspective of a future exploitation of these deep living resources by humans.

Microbial Transformation of Chlordecone and Two Transformation Products Formed During in situ Chemical Reduction.

Chlordecone (CLD) is a very persistent synthetic organochlorine pesticide found in the French West Indies. Recently published work has demonstrated the potential of zero-valent iron to dechlorinate CLD by in situ chemical reduction (ISCR) in soils under water-saturated conditions, forming mono- to penta-dechlorinated CLD transformation products. These transformation products are more mobile than CLD and less toxic; however, nothing is known about their further degradation, although increasing evidence of CLD biodegradation by bacteria is being found. The present study began with the enrichment from wastewater sludge of a CLD-transforming community which was then inoculated into fresh media in the presence of either CLD or two of the main ISCR transformation products, 10-monohydroCLD (-1Cl-CLD) and tri-hydroCLD (-3Cl-CLD). Carried out in triplicate batches and incubated at 38°C under anoxic conditions and in the dark, the cultures were sampled regularly during 3 months and analyzed for CLD, -1Cl-CLD, -3Cl-CLD, and possible transformation products by gas chromatography coupled to mass spectrometry. All batches showed a decrease in the amended substrates (CLD or hydroCLD). CLD degradation occurred with concomitant formation of a nine-carbon compound (pentachloroindene) and two sulfur-containing transformation products (chlordecthiol, CLD-SH; methyl chlordecsulfide, CLD-SCH3), demonstrating competing transformation pathways. In contrast, -1Cl-CLD and -3Cl-CLD only underwent a sequential reductive sulfidation/S-methylation process resulting in -1Cl-CLD-SH and -1Cl-CLD-SCH3 on the one hand, and -3Cl-CLD-SH, -3Cl-CLD-SCH3 on the other hand. Some sulfur-containing transformation products have been reported previously with single bacterial strains, but never in the presence of a complex microbial community. At the end of the experiment, bacterial and archaeal populations were investigated by 16S rRNA gene amplicon sequencing. The observed diversity was mostly similar in the CLD and -1Cl-CLD conditions to the inoculum with a dominant archaea genus, Methanobacterium, and four OTU affiliated to bacteria, identified at the family (Spirochaetaceae) or genus level (Desulfovibrio, Aminobacterium, and Soehngenia). On the other hand, in the -3Cl-CLD condition, although the same OTU were found, Clostridium sensu stricto 7, Candidatus Cloacimonas, and Proteiniphilum were also present at > 2% sequences. Presence of methanogens and sulfate-reducing bacteria could contribute to sulfidation and S-methylation biotransformations. Overall, these results contribute to increasing our knowledge on the biodegradability of CLD and its transformation products, helping to progress toward effective remediation solutions.

Effect of pesticides and metabolites on groundwater bacterial community.

We assessed the effect of pesticides, especially commonly detected herbicides, on bacterial communities in groundwater. To this end, we used a combined approach with i) triazine-spiked experiments at environmentally relevant concentrations (1 and 10µg/L) in waters with contrasting contamination histories, and ii) in situ monitoring in a rural aquifer, where many additional biotic and abiotic parameters also affect the community. Microbial community was characterized by fingerprinting techniques (CE-SSCP), gene presence (atzA/B/C/D/E/F and amoA genes) and abundance (16S RNA, napA and narG genes). During triazine-spiked experiments, the bacterial community structure in reference water was modified following an exposure to atrazine (ATZ) and/or its metabolite desethylatrazine (DEA) at 1µg/L; in historically-contaminated water, the bacterial community structure was modified following an exposure to 10µg/L ATZ/DEA. Similarly, biodiversity indices and biomass in the reference water appeared affected at lower triazine concentrations than in the historically-contaminated water, though these end-points are less sensitive than the community structure. Our results thus suggest that the history of contamination induced a community tolerance to the tested triazines. ATZ and DEA were not degraded during the experiment and this was consistent with the absence of atz genes involved in their degradation in none of the tested conditions. In field monitoring, triazines that represent a historical and diffuse contamination of groundwater, participate in the microbial community structure, confirming the triazine effect observed under laboratory conditions. Other herbicides, such as chloroacetanilides that are applied today, did not appear to affect the whole community structure; they however induced a slight, but significant, increase in the abundance of nitrate-reducing bacteria. To our best knowledge, this is the first study on the microbial ecotoxicology of pesticides and their metabolites at environmentally relevant concentrations in groundwater.

Relevance of Bacteroidales and F-specific RNA bacteriophages for efficient fecal contamination tracking at the level of a catchment in France.

The relevance of three host-associated Bacteroidales markers (HF183, Rum2Bac, and Pig2Bac) and four F-specific RNA bacteriophage genogroups (FRNAPH I to IV) as microbial source tracking markers was assessed at the level of a catchment (Daoulas, France). They were monitored together with fecal indicators (Escherichia coli and enterococci) and chemophysical parameters (rainfall, temperature, salinity, pH, and turbidity) by monthly sampling over 2 years (n = 240 water samples) and one specific sampling following an accidental pig manure spillage (n = 5 samples). During the 2-year regular monitoring, levels of E. coli, enterococci, total F-specific RNA bacteriophages, and the general Bacteroidales marker AllBac were strongly correlated with one another and with Rum2Bac (r = 0.37 to 0.50, P < 0.0001). Their correlations with HF183 and FRNAPH I and II were lower (r = 0.21 to 0.29, P < 0.001 to P < 0.0001), and HF183 and enterococci were associated rather than correlated (Fisher's exact test, P < 0.01). Rum2Bac and HF183 enabled 73% of water samples that had ≥ 2.7 log(10) most probably number (MPN) of E. coli/100 ml to be classified. FRNAPH I and II enabled 33% of samples at this contamination level to be classified. FRNAPH I and II complemented the water sample classification obtained with the two Bacteroidales markers by an additional 8%. Pig2Bac and FRNAPH III and IV were observed in a small number of samples (n = 0 to 4 of 245). The present study validates Rum2Bac and HF183 as relevant tools to trace fecal contamination originating from ruminant or human waste, respectively, at the level of a whole catchment.

Anionic surfactant linear alkylbenzene sulfonates (LAS) in sediments from the Gulf of Gdansk (southern Baltic Sea, Poland) and its environmental implications.

Linear alkylbenzene sulfonate (LAS) is a group of anionic surfactants employed in the formulation of laundry and cleaning products, with a global production rate of 4 million metric tons. Sediments from the Polish coast of the southern Baltic Sea were collected at ten stations. Total LAS concentrations, measured by high-performance liquid chromatography, were between 0.04 and 0.72 mg LAS·kg(-1) dry weight. Highest LAS concentrations were found in suspended matter collected from the Vistula River, sediment collected close to the Vistula River mouth and from the Gdansk Deep, known as the depositional area. With the obtained environmental LAS concentrations, a risk assessment for this surfactant has been carried out, based on publicly available acute and chronic toxicity data in target organisms. The results indicated that LAS could pose a low risk for the existing benthic community applying worst case scenario assessment. This is the first time that levels of LAS have been measured in environmental samples of the southern Baltic Sea.

Colonized beads as inoculum for marine biodegradability assessment: application to linear alkylbenzene sulfonate.

An innovative biodegradation test system was developed in order to fill the current gap for cost effective and environmentally relevant tools to assess marine biodegradability. Glass beads were colonized by a biofilm in an open flow-through system of seawater with continuous pre-exposure to Linear Alkylbenzene Sulfonate (LAS) (20 microg/L). Thereafter, such colonized beads were added as inoculum in different test systems. [(14)C]-LAS (5-100 microg/L) was added and primary and ultimate biodegradation were assessed. The bacterial density collected on the beads (10(9) bact./mL beads) was ca. 3 orders of magnitude higher than the typical seawater content. The LAS mineralization lag phase duration decreased from 55 to <1 days and the mineralization extent increased from 53 to 90% as the colonized beads volume increased from 10 to 275 mL. This is the first demonstration of marine bacteria's ability to mineralize LAS. On the opposite, less than 13% LAS was mineralized in seawater only. The colonized beads possibly enhanced the probability to encounter the full degraders' consortium in a low volume of seawater (100 mL).

Characterization of biliary metabolites of fluoranthene in the common sole (Solea solea).

Fluoranthene is one of the most abundant polycyclic aromatic hydrocarbon (PAH) pollutants in the environment. Studies of the metabolism of PAHs have highlighted the importance of the gallbladder in concentrating xenobiotics in fish before excretion in feces. Analysis of bile metabolites can be considered useful for monitoring and assessing the exposure of fish to PAHs. Although the fate of several PAHs in marine organisms has been widely investigated, information is lacking regarding the metabolism of fluoranthene in fish. Therefore, we investigated the metabolic pathways of [14C]fluoranthene in the common sole (Solea solea) by identifying bile metabolites using electrospray ionization/mass spectrometry (ESI/MS) and nuclear magnetic resonance (NMR) spectroscopy. [14C]Fluoranthene was administered by intraperitoneal injection to 20 common soles. Groups of animals (n = 5) were killed 1, 2, 3, and 4 d postdosing, and gallbladders were excised for radioactivity counting and bile analysis. Biliary metabolites were separated and quantified by radio-high-performance liquid chromatography, and structure identification was performed by ESI/MS. Isomeric structures were confirmed by NMR analyses. At the end of the experiment, 12.2% of the administered radioactivity was recovered in bile. As expected, hydroxylation and glucuronidation were the predominant metabolic pathways. The 7-O-glucuronide-fluoranthene metabolite (representing 13.3% of total radioactivity found in bile), 8-O-glucuronide-fluoranthene (11.8%), trans-2,3-dihydro-3-hydroxy-2-O-glucuronide-fluoranthene (17.9%), and cis-2,3-dihydro-2-hydroxy-3-O-glucuronide-fluoranthene (13.9%) were the major metabolites observed in bile. Minor metabolites, such as trans-2,3-dihydro-2-hydroxy-3-O-glucuronide-fluoranthene (3.9%) and 2,3-di-O-glucuronide-fluoranthene (6.6%), also were identified. The 2,3-dihydrodiol-fluoranthene metabolite, which is found in bile conjugated to glucuronic acid, would be, after hydrolysis of the conjugates, a suitable biomarker of PAH pollution in the marine environment.