Copper Affects Composition and Functioning of Microbial Communities in Marine Biofilms at Environmentally Relevant Concentrations

Copper (Cu) pollution in coastal areas is a worldwide threat for aquatic communities. This study aims to demonstrate the usefulness of the DNA metabarcoding analysis in order to describe the ecotoxicological effect of Cu at environmental concentrations on marine periphyton. Additionally, the study investigates if Cu-induced changes in community structure co-occurs with changes in community functioning (i.e., photosynthesis and community tolerance to Cu). Periphyton was exposed for 18 days to five Cu concentrations, between 0.01 and 10 μM, in a semi-static test. Diversity and community structure of prokaryotic and eukaryotic organisms were assessed by 16S and 18S amplicon sequencing, respectively. Community function was studied as impacts on algal biomass and photosynthetic activity. Additionally, we studied Pollution-Induced Community Tolerance (PICT) using photosynthesis as the endpoint. Sequencing results detected an average of 9,504 and 1,242 OTUs for 16S and 18S, respectively, reflecting the high biodiversity of marine periphytic biofilms. Eukaryotes represent the most Cu-sensitive kingdom, where effects were seen already at concentrations as low as 0.01 μM. The structure of the prokaryotic part of the community was impacted at slightly higher concentrations (0.06 μM), which is still in the range of the Cu concentrations observed in the area (0.08 μM). The current environmental quality standard for Cu of 0.07 μM therefore does not seem to be sufficiently protective for periphyton. Cu exposure resulted in a more Cu-tolerant community, which was accompanied by a reduced total algal biomass, increased relative abundance of diatoms and a reduction of photosynthetic activity. Cu exposure changed the network of associations between taxa in the communities. A total of 23 taxa, including taxa within Proteobacteria, Bacteroidetes, Stramenopiles, and Hacrobia, were identified as being particularly sensitive to Cu. DNA metabarcoding is presented as a sensitive tool for community-level ecotoxicological studies that allows to observe impacts simultaneously on a multitude of pro- and eukaryotic taxa, and therefore to identify particularly sensitive, non-cultivable taxa

Interactions between microplastics and benthic biofilms in fluvial ecosystems: Knowledge gaps and future trends

Plastics, especially microplastics (<5 mm in length), are anthropogenic polymer particles that have been detected in almost all environments. Microplastics are extremely persistent pollutants and act as long-lasting reactive surfaces for additives, organic matter, and toxic substances. Biofilms are microbial assemblages that act as a sink for particulate matter, including microplastics. They are ubiquitous in freshwater ecosystems and provide key services that promote biodiversity and help sustain ecosystem function. Here, we provide a conceptual framework to describe the transient storage of microplastics in fluvial biofilm and develop hypotheses to help explain how microplastics and biofilms interact in fluvial ecosystems. We identify lines of future research that need to be addressed to better manage microplastics and biofilms, including how the sorption and desorption of environmental contaminants in microplastics affect biofilms and how microbial exchange between microplastics and the biofilm matrix affects biofilm characteristics like antibiotic resistance, speciation, biodiversity, species composition, and function. We also address the uptake mechanisms of microplastics by consumers and their propagation through the food web

The use of pulse amplitude modulated fluorescence techniques for metal toxicity assessment in fluvial biofilms

Metal pollution in rivers is in great concern with human activities in the fluvial watershed. This thesis aims to investigate the potential use of chl-a fluorescence parameters as biomarkers of metal toxicity, and to find cause-effect relationships between metal exposures, other environmental factor (i.e. light), and functional and structural biofilm responses. This thesis demonstrates that the use of chl-a fluorescence parameters allows detect early effects on biofilms caused by zinc toxicity, both in the laboratory as in polluted rivers. In microcosm experiments, the use of chl-a fluorescence parameters allows evaluates structural changes on photosynthetic apparatus and in algal groups’ composition of biofilms long-term exposed to zinc. In order to evaluate the effects of chronic metal pollution in rivers, it is recommended the use of biofilm translocation experiments and the use of a multi-biomarker approach.La contaminació per metalls en els rius està principalment lligada a l’activitat humana que té lloc a la conca fluvial. Aquesta tesi té per objectiu principal avaluar l'ús potencial dels paràmetres de fluorescència de la chl-a com a biomarcadors de toxicitat per metalls, i trobar relacions causa-efecte entre l’exposició dels metalls, altres factors ambientals (ex. la llum), i les respostes funcionals i estructurals del biofilms. Aquesta tesi demostra que els paràmetres de fluorescència de la chl-a permeten detectar alteracions ràpides del biofilm causades per la toxicitat del zinc, tan al laboratori com en rius contaminats. En microcosmos, els paràmetres de fluorescència de la chl-a permeten avaluar canvis estructurals en l’aparell fotosintètic i en la composició dels grups algals dels biofilms exposats crònicament al zinc. Per avaluar els efectes de la contaminació crònica per metalls en rius es recomana fer experiments de translocació de biofilms i utilitzar una aproximació de multi-biomarcador

Diatom responses to zinc contamination along a Mediterranean river

Background and aims – Diatom-based water quality management is increasing, and specific indicators are required for the assessment of priority substances such as metals. We tested a variety of features of diatom communities, in a river exhibiting a gradient of zinc contamination (the Riera d'Osor, Spain), to determine the most relevant ones. Key results – Community composition changed over time of exposure, and with the intensity of metal contamination. Species richness was significantly lower at the most contaminated sites. Species composition was more even under background and low exposure levels, but low metal inputs selected for varieties of Cocconeis placentula (var. placentula, euglypta and lineata ). Small taxa ( Eolimna minina, or Achnanthidium minutissimum and A. pyrenaicum ) dominated in the most contaminated sites, and deformed diatom cells were found abundant. Conclusions – Although species composition clearly responded to varied levels of zinc pollution, combining cell size classes or total biovolume of the community and percentages of deformities allowed reliable assessment of the presence, and intensity, of contamination. These descriptors present the major advantage of being independent of regional taxonomic peculiarities, thus providing robust assessment irrespective of the area studied

Utilisation des activités enzymatiques antioxydantes des biofilms comme biomarqueurs de la pollution au zinc dans un système naturel

International audienceThis study aimed to explore the use of antioxidant enzyme activities (AEA) and biofilm metal accumulation capacity in natural communities as effect-based indicator of metal exposure in fluvial systems. To achieve these objectives, an active biomonitoring using fluvial biofilm communities was performed during 5 weeks. Biofilm was colonized over artificial substrata in a non-polluted site. After 5 weeks, biofilms were translocated to four different sites with different metal pollution in the same stream. The evolution of environmental parameters as well as biofilm responses was analysed over time. Physicochemical parameters were different between sampling times as well as between the most polluted site and the less polluted ones, mainly due to Zn pollution. In contrast, AEA and metal accumulation in biofilms allowed us to discriminate the high and moderate metal pollution sites from the rest. Zn, the metal with the highest contribution to potential toxicity, presented a fast and high accumulation capacity in biofilms. According to the multivariate analysis, AEA showed different responses. While catalase (CAT) and ascorbate peroxidase (APX) variability was mainly attributed to environmental stress (pH, temperature and phosphate concentration), glutathione-S-transferase (GST) changes were related to metal pollution. Glutathione reductase (GR) and superoxide dismutase (SOD) responses were related to both stress factors. AEA and metal accumulation are proposed as sensitive effect-based field methods, to evaluate biofilm responses after acute metal exposure (e.g. an accidental spill) due to their capacity to respond after few hours, but also in routinely monitoring due to their persistent changes after few weeks of exposure. These tools could improve the Common Implementation Strategy (CIS) of theWater Framework Directive (WFD) as expert group request

Utilisation des activités enzymatiques antioxydantes du périphyton comme biomarqueurs de contamination métallique

International audienceNowadays high metal loads are still found in watersheds and overall in mining areas. At present there are not many specific biomarkers to detect metal pollution at acute or chronic exposure. Antioxidant enzyme activities (AEA) like SOD, CAT, APX, GR and GST, can be used as early warning systemsbecause they have a functional response and it is expected that functional changes will be detected before than the structural ones used in former investigations. Moreover, these enzyme activities might also be biomarkers of adaptation, since their activation is expected to contribute to metal detoxification under chronic exposure. The main goal of this presentation is to assess the use of AEA as biomarkers of metal pollution under real exposure scenarios: Riou Mort and Osor stream by means of translocation experiments. These translocation studies were carried out in two streams with heavy metal inputs due to natural and anthropogenic sources. The Riou Mort (SW France), and the Osor stream (NE Spain). The experimental design of the Riou Mort (from 0 to 24h) allowed us to assess in situthe effects of short-term exposure (by comparing translocated biofilms) and chronic exposure (by comparing the non-translocated ones) on the AEA responses. And in the Osor stream, the translocation lasted for 5 weeks allowing as to assess in situthe effects of a gradient of metal concentration after short-term (from 0 to 24h) and chronic exposure (up to 5 weeks) on the AEA responses. Metal exposure affected the fluvial biofilm causing transitory physiological responses (short exposure) and structural and functional alterations (chronic exposure). According to this, AEA showed a different response depending on the time of exposure and also depending on water metal concentrations

Diatom responses to zinc contamination along a Mediterranean river

Background and aims – Diatom-based water quality management is increasing, and specific indicators are required for the assessment of priority substances such as metals. We tested a variety of features of diatom communities, in a river exhibiting a gradient of zinc contamination (the Riera d’Osor, Spain), to determine the most relevant ones. Key results – Community composition changed over time of exposure, and with the intensity of metal contamination. Species richness was significantly lower at the most contaminated sites. Species composition was more even under background and low exposure levels, but low metal inputs selected for varieties of Cocconeis placentula (var. placentula, euglypta and lineata). Small taxa (Eolimna minina, or Achnanthidium minutissimum and A. pyrenaicum) dominated in the most contaminated sites, and deformed diatom cells were found abundant. Conclusions – Although species composition clearly responded to varied levels of zinc pollution, combining cell size classes or total biovolume of the community and percentages of deformities allowed reliable assessment of the presence, and intensity, of contamination. These descriptors present the major advantage of being independent of regional taxonomic peculiarities, thus providing robust assessment irrespective of the area studiedSilvia Corcoll kindly mapped the Riera d’Osor watershed. The study was partially by the European project Keybioeffects (MRTN-CT-2006-035695) and the Spanish project FLUVIALMULTISTRESS (CTM2009-14111-C02-01

Variation spatio-temporelle in situ du niveau de tolérance au zinc de communautés périphytiques phototrophes et hétérotrophes

International audiencePollution-induced community tolerance (PICT) uses increased tolerance in populations at contaminated sites as an indicator of contaminant effects. However, given the broad structural and functional complexity that characterizes biological communities, the acquisition of PICT could vary with (i) target community, (ii) intensity of toxicant exposure, (iii) the species succession stage, and (iv) the physicochemical characteristics of the studied site. To assess the spatio-temporal changes of zinc-induced tolerance in fluvial biofilm communities, we conducted an in situ study in Osor River (North-East Catalonia, Spain), which has zinc contamination. Biofilms were developed for 5 weeks in a non-metal-polluted site, and were then transferred to different sites in Osor River with different levels of zinc contamination. The spatio-temporal changes of biofilm PICT to zinc was determined using photosynthetic activity bioassays and respiration-induced aerobic bioassays at T0, and at 1, 3 and 5 weeks of exposure. We also performed physicochemical characterization of the sites, taxonomic analysis of diatoms, bacterial and fungal diversity and profiled pigments of phototrophic communities. We used multivariate ordination to analyze results. In addition to natural species succession, the intensity of metal pollution exerted structural pressure by selecting the most metal-tolerant species, but differently depending on the type of biofilm. Zn-tolerance values indicated that exposure to high levels of zinc had effects that were similar to a longer exposure to lower levels of zinc

Editorial: thematic issue on microbial ecotoxicology

International audienceIma gine you ar e a micr obe and you are exposed to chemical contamination. Will you be at risk? How will you react, and by which means? Just die? Expr ess some form of ada ptation using specific r esistance mec hanisms? Reduce toxicity of c hemicals by degr ading them, or by negative tactic mov ement? Toler ate their pr esence thanks to emergent properties of your surrounding microbial comm unity? Expr ess some other form of r esilience and wait for better times, to return to a functional state after a more or less long period, depending on the intensity and toxicity of the contamination?Alongside these questions that microbial ecotoxicologists are eager to answer, the question "Why do we need to pr eserv e and monitor the integrity of environmental microbes and the communities they form?" has been at the core of the emerging multidisciplinary field of micr obial ecotoxicology. Ov er the last decade, microbial ecotoxicologists have organized through the international EcotoxicoMic network ( https://ecotoxicomic.or g ), whic h now counts 282 members from 46 countries. With three international conferences in 2017 (Ly on, F rance), 2020 (online due to the COVID pandemic), and 2022 (Montpellier, F rance), the netw ork has addressed the interactions , effects , and risks of chemical exposure on microbial and environmental systems and generated new researc h perspectiv es. A forthcoming fourth international Ecotoxi-coMic conference will take place in Gothenburg (Sweden) on 12-14 November 2024 ( https:// ecotoxicomic.org/ ecotoxicomic-2024 ).Micr oor ganisms hav e now become a ppr eciated as k e ystone contributors in numerous ecosystemic processes (Cavicchioli et al. 2019 ), including but not limited to (i) cycling of carbon, nitrogen, phosphorus, iron, and sulfur; (ii) biological control of pathogens; (iii) attenuation of chemical pollution; (iv) production and consumption of greenhouse gases; (v) contribution to soil structure; and (vi) biomass nutrients for higher trophic levels. Micr obial comm unities also constitute the ric hest genetic pool, which can be harnessed by biotechnology. All this very much speaks in favor of the fundamental role that microbial ecotoxicology can play in ecosystem pr eserv ation and functioning today.Indeed, the high diversity, genetic plasticity, adaptability, and r esponses of micr obes to c hemical pollution pr ovides a unique opportunity to discover and quantify chemical effects and associated risks to microbial communities and their crucial ecosystem functions, and to explore the responses of the microbial world, their impact on contaminant eco-dynamics, and associated risks to ecosystems and human health (Fig. 1 ). Thanks to the experimental a ppr oac hes and tec hnologies av ailable today, curr ent r esearc h r anges fr om labor atory studies of the detailed mec hanisms of microbial gene expression linked to exposure to contaminants and their toxic effects in model or ganisms, to integr ativ e studies of the complex responses of envir onmental micr obial comm unities at field scales.Given the high complexity of the investigated interactions, incr easingl y in-depth and integr ativ e explor ation of microbial re- Recei v</div

Catalase in fluvial biofilms: a comparison between different extraction methods and example of application in a metal-polluted river

Antioxidant enzymes are involved in important processes of cell detoxification during oxidative stress and have, therefore, been used as biomarkers in algae. Nevertheless, their limited use in fluvial biofilms may be due to the complexity of such communities. Here, a comparison between different extraction methods was performed to obtain a reliable method for catalase extraction from fluvial biofilms. Homogenization followed by glass bead disruption appeared to be the best compromise for catalase extraction. This method was then applied to a field study in a metal-polluted stream (Riou Mort, France). The most polluted sites were characterized by a catalase activity 4–6 times lower than in the low-polluted site. Results of the comparison process and its application are promising for the use of catalase activity as an early warning biomarker of toxicity using biofilms in the laboratory and in the fiel