Evaluation of tire tread particle toxicity to fish using rainbow trout cell lines

Tire and road wear particles (TRWP) resulting from tire abrasion while driving raise concerns due to their potential contribution to aquatic toxicity. Our study aimed to assess cryogenically milled tire tread (CMTT) particle toxicity, used as a proxy for TRWP, and associated chemicals to fish using two Rainbow Trout (Oncorhynchus mykiss) cell lines representing the gill (RTgill-W1) and the intestinal (RTgutGC) epithelium. CMTT toxicity was evaluated through several exposure pathways, including direct contact, leaching, and digestion, while also assessing the impact of particle aging. Following OECD TG249, cell viability was assessed after 24 h acute exposure using a multiple-endpoint assay indicative of cell metabolic activity, membrane integrity and lysosome integrity. In vitro EC50 values for the fish cell lines exceeded river TRWP concentrations (2.02 g/L and 4.65 g/L for RTgill-W1 and RTgutGC cell lines, respectively), and were similar to in vivo LC50 values estimated at 6 g/L. Although toxicity was mainly driven by the leaching of tire-associated chemicals, the presence of the particles contributed to the overall toxicity by inducing a continuous leaching, highlighting the importance of considering combined exposure scenarios. Aging and digestion conditions were also found to mediate CMTT toxicity. Thermooxidation resulted in a decreased chemical leaching and toxicity, while in vitro digestion under mimicked gastrointestinal conditions increased leaching and toxicity. Specific chemicals, especially Zn, 2-mercaptobenzothiazole, 1,3-diphenylguanidine, and N-(1,3-dimethylbutyl)-N'-phenyl-p-phenylenediamine (6PPD) were identified as contributors to the overall toxicity. Although 6PPD-quinone was detected in CMTT digestate, cytotoxicity assays with RTgill-W1 and RTgutGC cell lines showed no toxicity up to 6 mg/L, supporting the notion of a specific mode of action of this chemical. This study provides insights into the toxicological mechanisms induced by tire particles and their associated chemicals and can help in the evaluation of potential risks to aquatic life associated with TRWP.

Identification of polar organic chemicals in the aquatic foodweb: Combining high-resolution mass spectrometry and trend analysis

Environmental risk assessment of chemical contaminants requires prioritizing of substances taken up by biota as it is a starting point for potential adverse effects. Although knowledge about the occurrence of known chemical pollutants in aquatic organisms has significantly improved during the last decade, there is still a poor understanding for a broad range of more polar compounds. To tackle this issue, we proposed an approach that identifies bioaccumulative and biomagnifiable polar chemicals using liquid chromatography coupled with electrospray ionization to high resolution tandem mass spectrometry (LC-HRMS/MS) and combine it with trend analysis using hierarchical clustering. As a proof-of-concept, this approach was implemented on various organisms and compartments (sediment, litter leaves, periphytic biofilm, invertebrates and fish) collected from a small urban river. HRMS/MS data measured via data-independent acquisition mode were retrospectively analysed using two analytical strategies: (1) retrospective target and (2) suspect/non-target screening. In the retrospective target analysis, 56 of 361 substances spanning a broad range of contaminant classes were detected (i.e. 26 in fish, 18 in macroinvertebrates, 28 in leaves, 29 in periphyton and 32 in sediments, with only 7 common to all compartments), among which 49 could be quantified using reference standards. The suspect screening approach based on two suspect lists (in-house, Norman SusDat) led to the confirmation of 5 compounds with standards (three xenobiotics at level 1 and two lipids at level 2) and tentative identification of seven industrial or natural chemicals at level 2 and 3 through a mass spectra library match. Overall, this proof-of-concept study provided a more comprehensive picture of the exposure of biota to emerging contaminants (i.e., the internal chemical exposome) and potential bioaccumulation or biomagnification of polar compounds along the trophic chain.

Bioaccessibility of Organic Compounds Associated with Tire Particles Using a Fish In Vitro Digestive Model: Solubilization Kinetics and Effects of Food Coingestion

Tire and road wear particles (TRWP) account for an important part of the polymer particles released into the environment. There are scientific knowledge gaps as to the potential bioaccessibility of chemicals associated with TRWP to aquatic organisms. This study investigated the solubilization and bioaccessibility of seven of the most widely used tire-associated organic chemicals and four of their degradation products from cryogenically milled tire tread (CMTT) into fish digestive fluids using an in vitro digestion model based on Oncorhynchus mykiss. Our results showed that 0.06-44.1% of the selected compounds were rapidly solubilized into simulated gastric and intestinal fluids within a typical gut transit time for fish (3 h in gastric and 24 h in intestinal fluids). The environmentally realistic scenario of coingestion of CMTT and fish prey was explored using ground Gammarus pulex. Coingestion caused compound-specific changes in solubilization, either increasing or decreasing the compounds' bioaccessibility in simulated gut fluids compared to CMTT alone. Our results emphasize that tire-associated compounds become accessible in a digestive milieu and should be studied further with respect to their bioaccumulation and toxicological effects upon passage of intestinal epithelial cells.

Environmental DNA metabarcoding for benthic monitoring: A review of sediment sampling and DNA extraction methods

Environmental DNA (eDNA) metabarcoding (parallel sequencing of DNA/RNA for identification of whole communities within a targeted group) is revolutionizing the field of aquatic biomonitoring. To date, most metabarcoding studies aiming to assess the ecological status of aquatic ecosystems have focused on water eDNA and macroinvertebrate bulk samples. However, the eDNA metabarcoding has also been applied to soft sediment samples, mainly for assessing microbial or meiofaunal biota. Compared to classical methodologies based on manual sorting and morphological identification of benthic taxa, eDNA metabarcoding offers potentially important advantages for assessing the environmental quality of sediments. The methods and protocols utilized for sediment eDNA metabarcoding can vary considerably among studies, and standardization efforts are needed to improve their robustness, comparability and use within regulatory frameworks. Here, we review the available information on eDNA metabarcoding applied to sediment samples, with a focus on sampling, preservation, and DNA extraction steps. We discuss challenges specific to sediment eDNA analysis, including the variety of different sources and states of eDNA and its persistence in the sediment. This paper aims to identify good-practice strategies and facilitate method harmonization for routine use of sediment eDNA in future benthic monitoring.

In Vitro Digestion of Tire Particles in a Fish Model (Oncorhynchus mykiss): Solubilization Kinetics of Heavy Metals and Effects of Food Coingestion

Tire and road wear particles (TRWP) have been shown to represent a large part of anthropogenic particles released into the environment. Nevertheless, the potential ecological risk of TRWP in the different environmental compartments and their potential toxic impacts on terrestrial and aquatic organisms remain largely underinvestigated. Several heavy metals compose TRWP, including Zn, which is used as a catalyst during the vulcanization process of rubber. This study investigated the solubilization potential of metals from cryogenically milled tire tread (CMTT) and TRWP in simulated gastric fluids (SF_GASTRIC) and simulated intestinal fluids (SF_INTESTINAL) designed to mimic rainbow trout (Oncorhynchus mykiss) gastrointestinal conditions. Our results indicate that the solubilization of heavy metals was greatly enhanced by gastrointestinal fluids compared to that by mineral water. After a 26 h in vitro digestion, 9.6 and 23.0% of total Zn content of CMTT and TRWP, respectively, were solubilized into the simulated gastrointestinal fluids. Coingestion of tire particles (performed with CMTT only) and surrogate prey items (Gammarus pulex) demonstrated that the animal organic matter reduced the amount of bioavailable Zn solubilized from CMTT. Contrastingly, in the coingestion scenario with vegetal organic matter (Lemna minor), high quantities of Zn were solubilized from L. minor and cumulated with Zn solubilized from CMTT.

Sediment quality assessment framework for per- and polyfluoroalkyl substances: Results from a preparatory study and regulatory implications

A preparatory study was performed to develop a sediment quality and risk assessment strategy for Switzerland, addressing the following questions: the sediment fraction to be analyzed chemically (< 63 µm, or alternatively < 2 mm); the suitability of using perfluorooctanesulfonic acid (PFOS) as an indicator of per- and polyfluoroalkyl substances (PFAS) contamination in sediments; the availability of data for the derivation of sediment quality guidelines; and the suitability of normalization to total organic carbon (TOC). The results confirmed PFOS as a suitable indicator of PFAS contamination in sediments from small streams, being the most detected and on average with the highest concentrations among the analyzed PFAS. The fine fraction (< 63 µm) was more appropriate to screening for possible sources and studying the compound profiles at the study sites, but the analysis of the < 2 mm fraction and the normalization to a sample consisting of 100% of the < 63 μm fraction was, in principle, feasible for PFOS. Sediment quality guidelines for PFOS aiming to protect benthic invertebrates from generic adverse effects could be derived, but the available toxicity database is still too sparse. It was only possible to derive preliminary values. Sediment quality guidelines to protect wildlife and human health from secondary poisoning, using the equilibrium partitioning approach and simple trophic web models, were also derived. The use of food web models to derive sediment quality guidelines has not been validated, and the available database of Biota-Sediment Accumulation Factors and Trophic Magnification Factors for PFOS remains limited. However, it is still larger than the effect concentrations database based on sediment studies using benthic invertebrates. Normalization to TOC content in the field (0.2%-12.9%) was decisive in the quality assessment outcome. This is a widely accepted practice for hydrophobic organic contaminants, but its endorsement for PFOS would also benefit from validation. Integr Environ Assess Manag 2021;17:716-725. © 2021 SETAC.

Metadata standards and practical guidelines for specimen and DNA curation when building barcode reference libraries for aquatic life

DNA barcoding and metabarcoding is increasingly used to effectively and precisely assess and monitor biodiversity in aquatic ecosystems. As these methods rely on data availability and quality of barcode reference libraries, it is important to develop and follow best practices to ensure optimal quality and traceability of the metadata associated with the reference barcodes used for identification. Sufficient metadata, as well as vouchers, corresponding to each reference barcode must be available to ensure reliable barcode library curation and, thereby, provide trustworthy baselines for downstream molecular species identification. This document (1) specifies the data and metadata required to ensure the relevance, the accessibility and traceability of DNA barcodes and (2) specifies the recommendations for DNA harvesting and for the storage of both voucher specimens/samples and barcode data.

Legacy and alternative halogenated flame retardants in Lake Geneva fish

Legacy (i.e., polybrominated diphenyl ethers (PBDEs) and hexabromocyclododecane (HBCDD)) and alternative halogenated flame retardants (HFRs) were analyzed in 31 whole fish samples from Lake Geneva in 2018. Two fish species, namely, the burbot (Lota lota) and the roach (Rutilus rutilus), were selected, hypothetically representing different habitats, feeding behaviors, and different metabolic capacities. Roach (N = 20) and burbot (N = 11) displayed similar size and mass, but the latter species was overall leaner than the former. The sum of individual PBDE concentrations (0.54-9.86 ng g^-1 wet weight (ww)) was similar in both species, but the respective molecular profiles suggested contrasted metabolic capacities. HBCDD sum of isomer concentrations ranged from non-detected to 3.477 ng g^-1 (ww), also similar in both species. Both PBDEs and HBCDD levels were far below the threshold that indicates a risk to fish predators. Referring to previous surveys, which involved a wider range of species, PBDE concentrations have declined or are stable. HBCDD concentrations remained low, despite the PBDE ban, which could have fostered the consumption of other HFRs. The occurrence of alternative HFRs was also low for most compounds analyzed. Only dechloranes and decabromodiphenyl ethane (DBDPE) had detection rates above 50%. Dechloranes spanned a concentration range between 5 and 10 times the quantification limits (0.002 to 0.005 ng g^-1 wet weight), lower than DBDPE (< 0.005 to 2.89 ng g^-1 wet weight). Quality standards targeting biota are currently missing for these emerging chemicals.

The Foreign Oligochaete Species Quistadrilus multisetosus (Smith, 1900) in Lake Geneva: Morphological and Molecular Characterization and Environmental Influences on Its Distribution

Simple Summary

The presence of the oligochaete species Quistadrilus multisetosus (Smith, 1900), originating from North America, has been mentioned in Europe for some decades and was recently found in Swiss lakes. Here, we report its repartition and abundance in Lake Geneva based on morphological and eDNA surveys and study its ecology and invasive potential in this lake. We also provide an identification key of this species and two closely related species and describe the phylogenetic position of Q. multisetosus within several Tubificinae lineages based on the cytochrome c oxidase marker. Our results showed that this species was restricted to an area close to the outlet of a wastewater treatment plant and to a combined sewer overflow, was highly tolerant to organic matter pollution and had a limited capacity to disseminate in this lake. Even if the trophic status (oligo-mesotrophic) of Lake Geneva seems unfavorable for the development of this species, we recommend continuing monitoring its presence in this lake in the future, as the current warming of waters could contribute to its expansion.

Abstract

The presence of the oligochaete species Quistadrilus multisetosus (Smith, 1900) originating from North America has been mentioned for several decades in Europe, the Middle East and Russia. Its distribution and abundance in Europe is still unknown but it can be considered as potentially invasive. This species was recently discovered in Lake Geneva (Switzerland/France) and three other Swiss lakes. The aims of the present work are to report its repartition and abundance in Lake Geneva, to study its ecology and to determine its invasive potential in this lake. We also provide an identification key for correctly differentiating Q. multisetosus from the closely related species Spirosperma ferox Eisen, 1879 and Embolocephalus velutinus (Grube, 1879), and study the phylogenetic position of Q. multisetosus within several Tubificinae lineages based on the cytochrome c oxidase (COI) marker. Twenty-eight sites have been monitored since 2009 in Lake Geneva. In several sites, the COI sequence corresponding to this species was also searched for in sediment samples using high-throughput sequencing. In addition, we examined specimens collected in this lake before 2009 likely to belong to Q. multisetosus and to have been misidentified. We found that Q. multisetosus was only present in the lake downstream of a wastewater treatment plant and a combined sewer overflow in the Vidy Bay (near Lausanne) and at a site located nearby. These results confirmed the high tolerance of this species to organic matter pollution. Q. multisetosus was already present in this location in 1974 (misidentified as Spirosperma ferox), which suggests that Q. multisetosus has a limited capacity to disseminate in this lake. However, we recommend continuing monitoring its presence in Lake Geneva in the future, especially in the context of warming of waters that could contribute to the expansion of this species.

Retrospective screening of high-resolution mass spectrometry archived digital samples can improve environmental risk assessment of emerging contaminants: A case study on antifungal azoles

Environmental risk assessment associated with aquatic and terrestrial contamination is mostly based on predicted or measured environmental concentrations of a limited list of chemicals in a restricted number of environmental compartments. High resolution mass spectrometry (HRMS) can provide a more comprehensive picture of exposure to harmful chemicals, particularly through the retrospective analysis of digitally stored HRMS data. Using this methodology, our study characterized the contamination of various environmental compartments including 154 surface water, 46 urban effluent, 67 sediment, 15 soil, 34 groundwater, 24 biofilm, 41 gammarid and 49 fish samples at 95 sites widely distributed over the Swiss Plateau. As a proof-of-concept, we focused our investigation on antifungal azoles, a class of chemicals of emerging concern due to their endocrine disrupting effects on aquatic organisms and humans. Our results demonstrated the occurrence of antifungal azoles and some of their (bio)transformation products in all the analyzed compartments (0.1-100 ng/L or ng/g d.w.). Comparison of actual and predicted concentrations showed the partial suitability of level 1 fugacity modelling in predicting the exposure to azoles. Risk quotient calculations additionally revealed risk of exposure especially if some of the investigated rivers and streams are used for drinking water production. The case study clearly shows that the retrospective analysis of HRMS/MS data can improve the current knowledge on exposure and the related risks to chemicals of emerging concern and can be effectively employed in the future for such purposes.

Recycled low-density polyethylene composite to mitigate the environmental impacts generated from coal mining waste in Brazil

Waste materials from coal mining and consumer products can pose significant risks to the environment. Residual coal deposits lead to the formation of acid drainage and release of contaminants, causing negative changes in soil and aquatic systems. Low density polyethylene (LDPE) polymers are an environmental concern due to their high useage, and slow degradation in the environment. In this study both waste materials were used to develop a composite to mitigate the environmental impacts of coal mining waste (CMW). The composite material was produced in different formulations (0-80 % wt CMW), and samples were tested for formation of acid drainage and release of contaminants. Chemical characterisation of the CMW and leachate of the composite materials was performed by X-ray fluorescence and atomic absorption spectrometry. Ecotoxicological effects in soil and water were investigated using standard tests with the earthworm, Eisenia fetida, the collembolan, Folsomia candida and the bacterium, Aliivibrio fischeri. Composites with 20 % wt LDPE showed a 50% increase in the pH value of the leachate compared to the CMW leachate. Iron, aluminium and sulfate concentrations were lower in leachates of the composite materials, and a reduction in the ecotoxicological impact on the tested organisms was observed. The hydrophobic nature of the composite's polymeric matrix as well its physical properties contributed to a better coating of the coal residue particles, blocking the contact with water and reducing the environmental risks of CMW. These results show that the production of composite material is a viable alternative route for treating coal and LDPE waste.

Towards simple tools to assess functional effects of contaminants on natural microbial and invertebrate sediment communities

Surface sediments can accumulate contaminants that affect microorganisms and invertebrates and disturb benthic ecological functions. However, effects of contaminants on ecological functions supported by sediment communities are understudied. Here, we tested the relevance of two simple tools to assess the ecotoxicological effects of metal contamination on natural sediment communities using particulate organic matter breakdown and decomposition as a functional descriptor. To this aim, we performed a 21-day laboratory microcosm experiment to assess the individual and combined effects of Cu and As (nominal concentration of 40 mg kg^-1 dw each) using the bait-lamina method (cellulose, bran flakes, and active coal in PVC strips) as well as artificial tablets (cellulose, bran flakes and active coal embedded in an agar matrix). Sediment toxicity was also evaluated using the standardized ostracod toxicity test. Both the bait-lamina and artificial tablet methods showed low effects of As on organic matter breakdown and decomposition but strong effects of Cu on this important ecological function. Both also showed that the presence of Cu and As in mixture in the sediment induced total inhibition of organic matter breakdown and decomposition. The ostracod toxicity test also showed high toxicity of Cu-spiked and Cu-plus-As-spiked sediments and low toxicity of As-spiked sediments. Besides confirming that artificial organic matter substrates are relevant and useful for assessing the functional effects of contaminants on sediment micro- and macro-organism communities, these results suggest that the proposed methods offer promising perspectives for developing tools for use in assessing functional ecotoxicology in the sediment compartment.

Chromium bioavailability in aquatic systems impacted by tannery wastewaters. Part 2: New insights from laboratory and in situ testing with Chironomus riparius Meigen (Diptera, Chironomidae)

Chromium is widely used as a tanning agent and can become a contaminant of concern in aquatic ecosystems receiving discharges from industrial or artisanal tanning activities. In a companion study, we showed that Cr discharged by tanneries was bioavailable to indigenous chironomids with accumulation via sediment ingestion likely to represent the predominant exposure route. However, Cr accumulation by chironomids did not directly reflect the degree of sediment contamination and the potential adverse effects of Cr accumulation on chironomids were not evaluated. In the present study, chironomids were exposed to homogenised, field-collected sediments in the laboratory and to intact sediments in situ using a customized caging system. Chromium concentrations were assessed in sediments, exposed larvae of laboratory-reared Chironomus riparius and overlying waters of in situ cages. Experimental results of Cr bioaccumulation were compared with expected Cr body burden in chironomids calculated using biodynamic modelling. Our data provided strong support to the hypothesis that Cr bioaccumulation in the field is specifically controlled by the deposition of contaminated suspended particulate matter (SPM) containing a pool of Cr readily bioavailable to surface deposit feeders. Considering freshly deposited SPM as an additional route of exposure for surface deposit feeders leads to a good agreement between the modelling and experimental results. Additionally, a Cr body burden of about 77 μg g^-1 d.w. was identified as a tentative threshold above which effects on the growth of C. riparius may appear. While both laboratory and in situ experiments provide evidence for the availability of Cr in aquatic system impacted by tannery wastewaters, standard laboratory exposure conditions may miss additional exposure routes in the field and underestimate possible adverse effects on benthic organisms.

Chromium bioavailability in aquatic systems impacted by tannery wastewaters. Part 1: Understanding chromium accumulation by indigenous chironomids

The tanning industry uses large quantities of Cr whose contribution to the contaminant burden of aquatic organisms is not yet fully understood. The present study investigated Cr bioaccumulation by indigenous chironomids in a freshwater ecosystem impacted by tannery effluents. Total Cr content in sediments and in chironomids was determined on several occasions. Chromium distribution among sediments and pore waters, and Cr speciation in overlying and pore waters were studied in detail to understand possible factors controlling Cr bioavailability to chironomids. Total chromium concentration ranged from 69 to over 3000 μg g^-1 dry weight in sediments and from negligible to over 300 μg g^-1 dry weight in chironomids (values corrected for sediment gut content). Filterable (<0.45 μm) Cr concentration in overlying waters and pore waters from the surface sediment layers (upper 2 cm) ranged from 3 to 120 μg L^-1, with Cr(VI) representing 0.5-28% of the total filterable Cr. Chromium profiles in pore waters as determined by diffusive equilibration in thin films (DET) and diffusive gradient in thin films (DGT) were comparable. DGT-labile Cr accounted for <2% of the total Cr measured by DET. Although Cr concentrations in sedimentary and aqueous matrices were not directly proportional to Cr levels measured in chironomids, the available findings suggested that Cr inputs from tanneries were bioavailable to resident chironomids. These observations are of particular importance considering that Cr(III), putatively of limited bioavailability and ecotoxicological concern, is the predominant redox form of Cr in bed sediments impacted by tannery discharges. The companion paper provides further insight into Cr bioavailability and effects in tannery impacted ecosystems using a combination of in situ and laboratory approaches.

Simultaneous preservation of the DNA quality, the community composition and the density of freshwater oligochaetes for the development of genetically based biological indices

Introduction

Oligochaetes are recognized as valuable bioindicators of sediment quality in streams and lakes. The development of an oligochaete index based on the identification of specimens using DNA barcodes requires a method for simultaneously preserving the DNA quality and information on the specimen density and oligochaete community composition. Absolute ethanol optimally preserves DNA but fixation of freshwater oligochaetes with this medium can cause disintegration and fragmentation of specimens. Here, we investigated the possibility to preserve oligochaete specimens in low-pH formalin and in neutral buffered formalin for up to four weeks before genetic analyses and tested if the addition of absolute ethanol to formalin-fixed oligochaetes resulted in a loss of specimens and/or species.

Methods

We performed guanidine extraction and polymerase chain reaction (PCR) amplification/sequencing of a fragment of the cytochrome c oxidase I (COI) gene on tissue fragments preserved in low-pH formalin for up to 3 weeks and in neutral buffered formalin for up to 4 weeks. In addition, we compared the density and taxonomic composition of formalin-fixed oligochaetes of several sieved sediment samples before and after the addition of absolute ethanol.

Results

The COI fragment of all oligochaete specimens preserved in neutral buffered formalin for up to 28 days was successfully amplified by PCR and obtained sequences were complete and of high quality. The amplification success rate for low-pH formalin fixed specimens declined after 7 days of storage. The addition of absolute ethanol to formalin-fixed oligochaete communities did not alter density or diversity estimates.

Discussion

Our results indicate that sediment samples can be stored in neutral buffered formalin for up to 4 weeks and the sieved material can then be transferred to absolute ethanol, without affecting DNA quality, density and community composition of oligochaetes. Based on these results, a protocol for preserving freshwater oligochaetes, describing all the steps from collection of sediments to preservation of the biological material in absolute ethanol, is proposed. This method of fixation/preservation is of relevance for establishing DNA barcode reference databases, inventories of genetic diversity and developing genetically based biological indices.

Development and implementation of eco-genomic tools for aquatic ecosystem biomonitoring: the SYNAQUA French-Swiss program

The effectiveness of environmental protection measures is based on the early identification and diagnosis of anthropogenic pressures. Similarly, restoration actions require precise monitoring of changes in the ecological quality of ecosystems, in order to highlight their effectiveness. Monitoring the ecological quality relies on bioindicators, which are organisms revealing the pressures exerted on the environment through the composition of their communities. Their implementation, based on the morphological identification of species, is expensive because it requires time and experts in taxonomy. Recent genomic tools should provide access to reliable and high-throughput environmental monitoring by directly inferring the composition of bioindicators' communities from their DNA (metabarcoding). The French-Swiss program SYNAQUA (INTERREG France-Switzerland 2017-2019) proposes to use and validate the tools of environmental genomic for biomonitoring and aims ultimately at their implementation in the regulatory bio-surveillance. SYNAQUA will test the metabarcoding approach focusing on two bioindicators, diatoms, and aquatic oligochaetes, which are used in freshwater biomonitoring in France and Switzerland. To go towards the renewal of current biomonitoring practices, SYNAQUA will (1) bring together different actors: scientists, environmental managers, consulting firms, and biotechnological companies, (2) apply this approach on a large scale to demonstrate its relevance, (3) propose robust and reliable tools, and (4) raise public awareness and train the various actors likely to use these new tools. Biomonitoring approaches based on such environmental genomic tools should address the European need for reliable, higher-throughput monitoring to improve the protection of aquatic environments under multiple pressures, guide their restoration, and follow their evolution.

Prioritization of substances for national ambient monitoring of sediment in Switzerland

In Switzerland, surface waters are protected by the Swiss Water Protection Ordinance (OEaux; OFEV 1998), which stipulates that the water quality shall be such that the water, suspended matter, and sediments contain no persistent synthetic substances to ensure the protection of aquatic life. Local agencies are in charge of water quality monitoring, using a set of validated methods. Several lists of priority substances have been developed for aquatic microcontaminants for surface water monitoring but not for sediments. Some local agencies have established sediment monitoring programs, but to date, there exists no harmonized methodology for sediment quality assessment in Switzerland. Within the main goal of developing and providing methodologies for monitoring sediment quality in Switzerland, a screening was performed to help prioritize sediment-relevant microcontaminants. The screening approach was largely based on the NORMAN (network of reference laboratories, research centers, and related organizations for monitoring emerging environmental substances) system and was carried out in four steps: (1) identification of candidate substances, (2) selection of sediment relevant substances, (3) classification of substances into different categories based on identified data gaps and envisaged actions, and (4) ranking within each action category. This paper describes the methodology used in the prioritization process for sediment-relevant substances and provides recommendations for monitoring strategies in Switzerland.

Looking at biological community level to improve ecotoxicological assessment of freshwater sediments: report on a first French-Swiss workshop

The first French-Swiss workshop on ecotoxicology of freshwater sediment communities was co-organized by the French Research Institute of Science and Technology for Environment and Agriculture (Irstea) and the Swiss Centre for Applied Ecotoxicology (Ecotox Centre EAWAG-EPFL) in Villié-Morgon (Beaujolais Region, France) on April 27-28, 2017. The workshop brought together scientists working in different fields of expertise (ecotoxicologists, ecologists, environmental chemists…), environmental stakeholder groups and managers, as well as economic players (start-ups and consultancies) to better connect research needs of potential end-users with research outputs. The objectives of this workshop were (i) to establish the state of the art of research in the characterization of sediment contamination and in the evaluation of the effects on sediment-associated biological communities and ecosystem functioning and (ii) to give an overview of the French and Swiss regulations dealing with the assessment of contaminated sediments in freshwater ecosystems. The ultimate goal was to collectively identify research needs and knowledge gaps, as well as to highlight ways to improve the ecotoxicological assessment of sediments in freshwater environments by further considering the structure and functions of associated microbial and invertebrate communities.

Per- and poly-fluoroalkyl compounds in freshwater fish from the Rhône River: Influence of fish size, diet, prey contamination and biotransformation

Pools of aquatic plants and benthic invertebrates were collected along with 47 individuals from three cyprinid fish species (Barbus barbus, Gobio gobio, Rutilus rutilus) at a site in the Rhône River (France). Carbon and nitrogen isotopic ratios (δ¹³C and δ¹⁵N) and a wide range of per- and poly-fluorinated chemicals (PFASs) were analysed in all samples. The sum of PFAS concentrations (ΣPFAS) increased from aquatic plants to fish dorsal muscles; molecular profiles were dominated by C9-C13 perfluorocarboxylic acids (PFCAs), while perfluorooctane sulfonate (PFOS) and perfluorooctane sulfonamide (FOSA) were detected in all samples at lower concentrations. ΣPFAS and especially ΣPFCAs were higher in barbels (B. barbus) than in other species, while roaches (R. rutilus) were less contaminated by PFOS than barbels and gudgeons (G. gobio). Gudgeons accumulated significantly higher FOSA concentrations. Young (small) barbels displayed significantly higher PFOS, perfluorononanoic acid (PFNA) and perfluorodecanoic acid (PFDA) concentrations than did large specimens; conversely, perfluorotetradecanoic acid (PFTeDA) concentrations were significantly higher in large barbels. Multiple linear regressions were performed on the whole set of fish samples with size, mass and isotopic ratios as explicative variables, and several single compounds as explained variables. Regardless of the compound, the regressions did not explain much of the contamination variability. However, adding species as a qualitative variable, i.e. performing analyses of covariance (ANCOVAs) improved the fit greatly, while adding sex did not. Diet (i.e. δ¹³C and δ¹⁵N) was the main factor explaining interspecific differences. Biotransformation was assessed by comparing concentration ratios of PFOS or FOSA to their precursors in the food-web compartments. These ratios increased from invertebrates to fish, and differed among fish species, suggesting that biotransformation occurred but was species-specific. Biomagnification factor calculations showed that C11-C13 PFCAs, PFOS and FOSA were apparently biomagnified in barbels and gudgeons.

Cytochrome c oxidase barcodes for aquatic oligochaete identification: development of a Swiss reference database

Introduction

Aquatic oligochaetes represent valuable indicators of the quality of sediments of watercourses and lakes, but their difficult identification based on morphological criteria compromises their more common use for eco-diagnostic analyses. This issue could be overcome by using DNA barcodes for species identification. A 10% threshold of cytochrome c oxidase (COI) divergence was proposed for differentiating between oligochaete species based on molecular and morphological data. A Swiss database of COI sequences of aquatic oligochaetes was initiated in 2012. The aim of this study is to complement the Swiss oligochaete database of COI sequences and to confirm the relevance of this threshold for species delimitation.

Methods

We sequenced the COI sequence of 216 specimens collected in different regions of Switzerland and ITS2 region of some lineages whose delimitation with COI data was doubtful.

Results

We distinguished 53 lineages, among which 34 were new for Switzerland and 17 sequenced for the first time. All the lineages were separated by more than 10% of COI variation, with the exception of some species within Nais and Uncinais. In these two genera, the threshold was lowered to 8% to be congruent with the morphological analysis. The total number of lineages reported so far for Switzerland is 75, including 59 morphospecies or unidentified species and 16 cryptic species.

Discussion

Our study shows that the threshold of 10% of COI divergence is generally appropriate to distinguish aquatic oligochaete lineages, but that it must be adjusted for some species. The database reported here will be complemented in the future in parallel to the development of genetic oligochaete indices.

DNA barcoding of formalin-fixed aquatic oligochaetes for biomonitoring

BACKGROUND

Oligochaetes are valuable bioindicators of the quality of watercourse and lake sediments. The morphological identification of aquatic oligochaetes is difficult, prompting the development of new molecular oligochaete indices based on DNA barcoding and Next-generation sequencing of sorted specimens. In general, the samples for DNA barcoding are fixed in absolute ethanol. However, in the case of aquatic oligochaetes, this medium is not appropriate as it can induce a modification of specimen abundances and of the composition of communities. Therefore, we investigated the possibility to amplify and sequence aquatic oligochaetes fixed in formalin for a short time. We performed guanidine extraction and polymerase chain reaction (PCR) amplification/sequencing of the cytochrome c oxydase I (COI) gene on tissue fragments fixed in formalin for different periods of time (from 1 h to 1 week) and in ethanol.

RESULTS

The large majority of aquatic oligochaete specimens fixed in formalin for up to 1 week could be successfully amplified and all obtained sequences were of high quality. The amplification and sequencing success rate of formalin-fixed samples and ethanol-fixed samples was similar. These results suggest that formalin fixation of aquatic oligochaete tissues for a short time does not cause serious damages to DNA and inhibit PCR amplification.

CONCLUSION

The possibility to fix aquatic oligochaetes with formalin before genetic analyses is very promising for diversity monitoring, for construction of a comprehensive DNA barcode library and for development of an index based on Next-generation sequencing analysis of samples composed of sorted specimens.

Mercury tissue residue approach in Chironomus riparius: Involvement of toxicokinetics and comparison of subcellular fractionation methods

Along with the growing body of evidence that total internal concentration is not a good indicator of toxicity, the Critical Body Residue (CBR) approach recently evolved into the Tissue Residue Approach (TRA) which considers the biologically active portion of metal that is available to contribute to the toxicity at sites of toxic action. For that purpose, we examined total mercury (Hg) bioaccumulation and subcellular fractionation kinetics in fourth stage larvae of the midge Chironomus riparius during a four-day laboratory exposure to Hg-spiked sediments and water. The debris (including exoskeleton, gut contents and cellular debris), granule and organelle fractions accounted only for about 10% of the Hg taken up, whereas Hg concentrations in the entire cytosolic fraction rapidly increased to approach steady-state. Within this fraction, Hg compartmentalization to metallothionein-like proteins (MTLP) and heat-sensitive proteins (HSP), consisting mostly of enzymes, was assessed in a comparative manner by two methodologies based on heat-treatment and centrifugation (HT&C method) or size exclusion chromatography separation (SECS method). The low Hg recoveries obtained with the HT&C method prevented accurate analysis of the cytosolic Hg fractionation by this approach. According to the SECS methodology, the Hg-bound MTLP fraction increased linearly over the exposure duration and sequestered a third of the Hg flux entering the cytosol. In contrast, the HSP fraction progressively saturated leading to Hg excretion and physiological impairments. This work highlights several methodological and biological aspects to improve our understanding of Hg toxicological bioavailability in aquatic invertebrates.

Bioaccumulation kinetics and effects of sediment-bound contaminants on chironomids in deep waters: new insights using a low-disturbance in situ system

Effective assessment of sediment quality and associated risks requires further integration between laboratory-based studies and field observations. Tools for in situ exposure of laboratory-reared organisms are particularly suitable for this purpose. However, available tools suffer from technical drawbacks that limit their use in deep waters and their general ability to provide results linking laboratory and field observations. To overcome these limitations, we developed a new device (Sediment-Water Interface Study System - S-WISS l) for in situ exposure of fourth instar larvae of Chironomus riparius at depths up to 18 m. S-WISS 1 allows minimum alteration of the sediment natural structure (upon both deployment and recovery) and, in a way analogous to laboratory tests, repeated delivery of food doses to the in situ exposed organisms. Results obtained in situ with S-WISS1 were compared with standard laboratory tests and simple caging systems (large-mouthed bottles partly filled with sand) used as field controlks. A first series of experiments (48 h, no food addition) showed that element bioavailability to chironomids was higher in laboratory settings than on-site or in situ. A second series of experiments (96 h, food addition every 24 h) confirmed that sediments rather than overlying waters acted as the principal source of contaminants and that exposure to field sediments reduced chironomids' growth compared with on-site controls. S-WISSI represents a new family of in situ tools capable of combining the environmental realism associated with field monitoring with the controlled experimental conditions typical of laboratory testing.

Coupling geochemical and biological approaches to assess the availability of cadmium in freshwater sediment

Sediments are considered as a sink for metals, and the assessment of metal bioavailability for benthic organisms represents a great challenge. Diffusive Gradient in Thin films (DGT), developed to measure labile metals in aquatic media, have more recently been applied to sediment. Nevertheless, few studies have determined the relation between measurements from DGT and bioaccumulation in different benthic organisms. The aim of our work was to determine if labile metal measured by DGT in sediment is representative of bioavailable metal for benthic organisms. We focused our work on Cd and chose to use the diversity of ecological traits from different organisms to better understand the measurement given by DGT. We exposed simultaneously DGT and 3 macroinvertebrates species (the chironomid, Chironomus riparius; the amphipod, Gammarus fossarum; the mudsnail, Potamopyrgus antipodarum) to a natural sediment Cd-spiked at environmental relevant concentrations. The nature of sediment-bound Cd was also determined by means of sequential extractions in order to better interpret DGT measurements. Cadmium concentrations were determined in DGT and in the 3 organisms after one week of exposure. Results provided by DGT indicated that Cd was poorly released from particulate phase to pore water, suggesting that Cd measured by DGT was representative of the pore water labile fraction. Sequential extractions showed that the percentage of Cd bound to carbonate fraction increased simultaneously with Cd-spiking level; hence, this Cd fraction was poorly reactive to supply DGT demand. Cadmium accumulation rates were similar between DGT measurements and P. antipodarum, suggesting that labile Cd in pore waters was representative of bioavailable Cd for this species. Cadmium accumulation rates in C. riparius were higher than in DGT, demonstrating that C. riparius can mobilize Cd bound to carbonate phase. G. fossarum showed the lowest Cd accumulation rates, suggesting that they were mainly exposed to Cd from overlaying waters.