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1.
Environ Int ; 139: 105708, 2020 Apr 12.
Artigo em Inglês | MEDLINE | ID: mdl-32294573

RESUMO

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.

2.
Pan Afr Med J ; 34: 63, 2019.
Artigo em Francês | MEDLINE | ID: mdl-31762927

RESUMO

Bleeding during pregnancy may not be due to obstetric causes. Pregnancy is a predisposing factor for some disorders due to physiological changes. These obstetric bleedings are rare but are responsible for high materno-fetal mortality. Prognosis depends on the speed of diagnosis as well as on multidisciplinary management. Splenic artery aneurysm (SAA) rupture during pregnancy is rare with a dreadful prognosis. Common clinical signs including abdominal pain associated with hypotension and anemia are very misleading for the obstetrician who usually suspects retroplacental hematoma or uterine rupture. We report the case of a pregnant patient requiring emergency laparotomy due to the detection of splenic artery aneurysm rupture on imaging test.


Assuntos
Aneurisma Roto/diagnóstico por imagem , Complicações Cardiovasculares na Gravidez/diagnóstico por imagem , Artéria Esplênica/diagnóstico por imagem , Dor Abdominal/etiologia , Adulto , Aneurisma Roto/cirurgia , Feminino , Humanos , Laparotomia/métodos , Gravidez , Complicações Cardiovasculares na Gravidez/cirurgia , Ruptura Espontânea/diagnóstico por imagem , Ruptura Espontânea/cirurgia
3.
FEMS Microbiol Ecol ; 94(10)2018 10 01.
Artigo em Inglês | MEDLINE | ID: mdl-30102345

RESUMO

The enrichment of ecosystems by nutrients such as nitrogen (N) and phosphorus (P) has important ecological consequences. These include effects on plant litter decomposition in forest soils and forested headwater streams, where fungi play a pivotal role. However, our understanding of nutrient relationships on fungal communities associated with decomposing litter remains surprisingly incomplete. We conducted a fully factorial microcosm experiment with known communities of fungal decomposers from streams to assess the importance of dissolved N and P supply, as well as the atomic nutrient ratio (N:P), on fungal community succession, diversity, biomass and reproduction on three leaf-litter species differing in nutrient and lignin concentrations. Fungal biomass accrual and spore production were strongly controlled by external N supply, whereas P supply was much less important. The magnitude of these effects was mediated by litter quality, with stronger effects of dissolved N and P on lignin-poor and high N:P litter. N supply also influenced fungal diversity and species composition, acting as a pacemaker of community succession. Collectively, our data indicate that N was in much greater demand than predicted by standard stoichiometric models. The most parsimonious explanation for this deviation relates to the need of litter fungi to invest large amounts of N into degradative exoenzymes.


Assuntos
Fungos/crescimento & desenvolvimento , Nitrogênio/análise , Fósforo/análise , Folhas de Planta/química , Rios/microbiologia , Biodiversidade , Biomassa , Ecossistema , Fungos/classificação , Fungos/genética , Fungos/metabolismo , Lignina/metabolismo , Folhas de Planta/metabolismo , Folhas de Planta/microbiologia , Rios/química , Esporos Fúngicos/crescimento & desenvolvimento
4.
J Vis Exp ; (136)2018 06 06.
Artigo em Inglês | MEDLINE | ID: mdl-29939166

RESUMO

Biofilms are dynamic consortia of microorganism that play a key role in freshwater ecosystems. By changing their community structure, biofilms respond quickly to environmental changes and can be thus used as indicators of water quality. Currently, biofilm assessment is mostly based on integrative and functional endpoints, such as photosynthetic or respiratory activity, which do not provide information on the biofilm community structure. Flow cytometry and computational visualization offer an alternative, sensitive, and easy-to-use method for assessment of the community composition, particularly of the photoautotrophic part of freshwater biofilms. It requires only basic sample preparation, after which the entire sample is run through the flow cytometer. The single-cell optical and fluorescent information is used for computational visualization and biological interpretation. Its main advantages over other methods are the speed of analysis and the high-information-content nature. Flow cytometry provides information on several cellular and biofilm traits in a single measurement: particle size, density, pigment content, abiotic content in the biofilm, and coarse taxonomic information. However, it does not provide information on biofilm composition on the species level. We see high potential in the use of the method for environmental monitoring of aquatic ecosystems and as an initial biofilm evaluation step that informs downstream detailed investigations by complementary and more detailed methods.


Assuntos
Biofilmes , Monitoramento Ambiental/métodos , Citometria de Fluxo/métodos , Poluentes Químicos da Água/química , Poluentes Químicos da Água/análise
5.
NanoImpact ; 6: 69-80, 2017 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-29057373

RESUMO

Nanotechnology risk management strategies and environmental regulations continue to rely on hazard and exposure assessment protocols developed for bulk materials, including larger size particles, while commercial application of nanomaterials (NMs) increases. In order to support and corroborate risk assessment of NMs for workers, consumers, and the environment it is crucial to establish the impact of biopersistence of NMs at realistic doses. In the future, such data will allow a more refined future categorization of NMs. Despite many experiments on NM characterization and numerous in vitro and in vivo studies, several questions remain unanswered including the influence of biopersistence on the toxicity of NMs. It is unclear which criteria to apply to characterize a NM as biopersistent. Detection and quantification of NMs, especially determination of their state, i.e., dissolution, aggregation, and agglomeration within biological matrices and other environments are still challenging tasks; moreover mechanisms of nanoparticle (NP) translocation and persistence remain critical gaps. This review summarizes the current understanding of NM biokinetics focusing on determinants of biopersistence. Thorough particle characterization in different exposure scenarios and biological matrices requires use of suitable analytical methods and is a prerequisite to understand biopersistence and for the development of appropriate dosimetry. Analytical tools that potentially can facilitate elucidation of key NM characteristics, such as ion beam microscopy (IBM) and time-of-flight secondary ion mass spectrometry (ToF-SIMS), are discussed in relation to their potential to advance the understanding of biopersistent NM kinetics. We conclude that a major requirement for future nanosafety research is the development and application of analytical tools to characterize NPs in different exposure scenarios and biological matrices.

6.
Water Res ; 111: 185-194, 2017 03 15.
Artigo em Inglês | MEDLINE | ID: mdl-28088715

RESUMO

The overarching aim of this field study was to examine causal links between in-situ exposure to complex mixtures of micropollutants from wastewater treatment plants and effects on freshwater microbial communities in the receiving streams. To reach this goal, we assessed the toxicity of serial dilutions of micropollutant mixtures, extracted from deployed passive samplers at the discharge sites of four Swiss wastewater treatment plants, to in situ periphyton from upstream and downstream of the effluents. On the one hand, comparison of the sensitivities of upstream and downstream periphyton to the micropollutant mixtures indicated that algal and bacterial communities composing the periphyton displayed higher tolerance towards these micropollutants downstream than upstream. On the other hand, molecular analyses of the algal and bacterial structure showed a clear separation between upstream and downstream periphyton across the sites. This finding provides an additional line of evidence that micropollutants from the wastewater discharges were directly responsible for the change in the community structure at the sampling sites by eliminating the micropollutant-sensitive species and favouring the tolerant ones. What is more, the fold increase of algal and bacterial tolerance from upstream to downstream locations was variable among sampling sites and was strongly correlated to the intensity of contamination by micropollutants at the respective sites. Overall, our study highlights the sensitivity of the proposed approach to disentangle effects of micropollutant mixtures from other environmental factors occurring in the field and, thus, establishing a causal link between exposure and the observed ecological effects on freshwater microbial communities.


Assuntos
Águas Residuárias , Poluentes Químicos da Água/química , Água Doce
7.
Environ Sci Technol ; 51(4): 2447-2455, 2017 02 21.
Artigo em Inglês | MEDLINE | ID: mdl-28085256

RESUMO

With the accelerated use of silver nanoparticles (AgNP) in commercial products, streams will increasingly serve as recipients of, and repositories for, AgNP. This raises concerns about the potential toxicity of these nanomaterials in the environment. Here we aimed to assess the impacts of chronic AgNP exposure on the metabolic activities and community structure of fungal and bacterial plant litter decomposers as central players in stream ecosystems. Minimal variation in the size and surface charge of AgNP indicated that nanoparticles were rather stable during the experiment. Five days of exposure to 0.05 and 0.5 µM AgNP in microcosms shifted bacterial community structure but had no effect on a suite of microbial metabolic activities, despite silver accumulation in the decomposing leaf litter. After 25 days, however, a broad range of microbial endpoints, as well as rates of litter decomposition, were strongly affected. Declines matched with the total silver concentration in the leaves and were accompanied by changes in fungal and bacterial community structure. These results highlight a distinct sensitivity of litter-associated microbial communities in streams to chronic AgNP exposure, with effects on both microbial functions and community structure resulting in notable ecosystem consequences through impacts on litter decomposition and further biogeochemical processes.


Assuntos
Rios/microbiologia , Prata/toxicidade , Ecossistema , Fungos/efeitos dos fármacos , Nanopartículas , Folhas de Planta/química
8.
Nanotoxicology ; 10(6): 728-35, 2016 08.
Artigo em Inglês | MEDLINE | ID: mdl-26634870

RESUMO

The rapid proliferation of silver nanoparticles (AgNP) in industry and the environment requires realistic toxicity assessments based on approaches that consider the biological complexity of ecosystems. Here we assessed the acute toxicity of carbonate-coated AgNP and, for comparison, AgNO3 (Ag(+)) by using a model system consisting of decomposing plant litter and the associated fungal and bacterial decomposers as central players in the functioning of stream ecosystems. Little variation in size and surface charge during the experiment indicated that the AgNP used were essentially stable. AgNP disrupted bacterial growth (≤83% reduction in protein biosynthesis, EC50 = 0.3 µM), clearly affected fungal growth (≤61% reduction in ergosterol synthesis, EC50 = 47 µM) with both endpoints more sensitive to AgNP than to Ag(+). Fungal reproduction, in contrast, was stimulated by AgNP, but not Ag(+), at concentrations up to 25 µM. Both AgNP and Ag(+ )also stimulated extracellular alkaline phosphatase but reduced leucine aminopeptidase, whereas ß-glucosidase was stimulated by AgNP and reduced by Ag(+). Importantly, the provision of cysteine, a chelating ligand that complexes free Ag(+), failed to alleviate AgNP toxicity to microbial growth, clearly demonstrating particle-mediated toxicity independent of the presence of ionic silver. This contrasts with the observed inhibition of leucine aminopeptidase by Ag(+), which accounted for 2-6% of the total silver in treatments receiving AgNP. These results show that although outcomes of AgNP and Ag(+ )exposure assessed by different functional endpoints vary widely, AgNP strongly interferes with bacterial growth and a range of other microbial processes, resulting in severe consequences for natural microbial communities and ecosystem functioning.


Assuntos
Nanopartículas Metálicas/toxicidade , Consórcios Microbianos/efeitos dos fármacos , Folhas de Planta , Nitrato de Prata/toxicidade , Prata/toxicidade , Cisteína/metabolismo , Ecossistema , Recuperação e Remediação Ambiental , Sedimentos Geológicos/química , Sedimentos Geológicos/microbiologia , Íons , Nanopartículas Metálicas/análise , Modelos Teóricos , Folhas de Planta/química , Folhas de Planta/microbiologia , Prata/análise , Nitrato de Prata/análise , Solubilidade
9.
Environ Sci Technol ; 49(2): 1165-72, 2015 Jan 20.
Artigo em Inglês | MEDLINE | ID: mdl-25513720

RESUMO

Silver nanoparticles (AgNP) are increasingly used as antimicrobials in consumer products. Subsequently released into aquatic environments, they are likely to come in contact with microbial communities like periphyton, which plays a key role as a primary producer in stream ecosystems. At present, however, very little is known about the effects of nanoparticles on processes mediated by periphyton communities. We assessed the effects of citrate-coated silver nanoparticles and silver ions (dosed as AgNO3) on five functional end points reflecting community and ecosystem-level processes in periphyton: photosynthetic yield, respiration potential, and the activity of three extracellular enzymes. After 2 h of exposure in experimental microcosms, AgNP and AgNO3 inhibited respiration and photosynthesis of periphyton and the activities of two of the three extracellular enzymes. Addition of a chelating ligand that complexes free silver ions indicated that, in most cases, toxicity of AgNP suspensions was caused by Ag(I) dissolved from the particles. However, these suspensions inhibited one of the extracellular enzymes (leucine aminopeptidase), pointing to a specific nanoparticle effect independent of the dissolved Ag(I). Thus, our results show that both silver nanoparticles and silver ions have potential to disrupt basic metabolic functions and enzymatic resource acquisition of stream periphyton.


Assuntos
Organismos Aquáticos/efeitos dos fármacos , Nanopartículas Metálicas/toxicidade , Fotossíntese/efeitos dos fármacos , Prata/toxicidade , Poluentes da Água/análise , Quelantes/química , Ecossistema , Exposição Ambiental , Íons , Ligantes , Nanopartículas , Nanotecnologia , Rios , Nitrato de Prata/química , Nitrato de Prata/toxicidade , Unitiol/química
10.
Ecotoxicol Environ Saf ; 103: 82-90, 2014 May.
Artigo em Inglês | MEDLINE | ID: mdl-24378183

RESUMO

This 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 the Water Framework Directive (WFD) as expert group request.


Assuntos
Biofilmes/efeitos dos fármacos , Biomarcadores/análise , Monitoramento Ambiental , Rios/química , Rios/microbiologia , Poluentes Químicos da Água/toxicidade , Zinco/toxicidade , Ativação Enzimática/efeitos dos fármacos , Enzimas/metabolismo , Metais/metabolismo , Metais/toxicidade , Análise Multivariada , Tempo , Poluentes Químicos da Água/análise
11.
Aquat Toxicol ; 136-137: 60-71, 2013 Jul 15.
Artigo em Inglês | MEDLINE | ID: mdl-23643725

RESUMO

This study aims to investigate the potential of antioxidant enzyme activities (AEA) as biomarkers of oxidative stress in freshwater biofilms. Therefore, biofilms were grown in channels for 38 days and then exposed to different concentrations (0-150 µg L(-1)) of the herbicide oxyfluorfen for 5 more weeks. Under control conditions, the AEA of biofilms were found to change throughout time with a significant increase in ascorbate peroxidase (APX) activity during the exponential growth and a more important role of catalase (CAT) and glutathione reductase (GR) activities during the slow growth phase. Chronic exposure to oxyfluorfen led to slight variations in AEA, however, the ranges of variability of AEA in controls and exposed communities were similar, highlighting the difficulty of a direct interpretation of AEA values. After 5 weeks of exposure to oxyfluorfen, no clear effects were observed on chl-a concentration or on the composition of other pigments suggesting that algal group composition was not affected. Eukaryotic communities were structured clearly by toxicant concentration and both eukaryotic and bacterial richness were reduced in communities exposed to the highest concentration. In addition, during acute exposure tests performed at the end of the chronic exposure, biofilms chronically exposed to 75 and 150 µg L(-1) oxyfluorfen showed a higher CAT activity than controls. Chronic exposure to oxyfluorfen provoked then structural changes but also functional changes in the capacity of biofilm CAT activity to respond to a sudden increase in concentration, suggesting a selection of species with higher antioxidant capacity. This study highlighted the difficulty of interpretation of AEA values due to their temporal variation and to the absence of absolute threshold value indicative of oxidative stress induced by contaminants. Nevertheless, the determination of AEA pattern throughout acute exposure test is of high interest to compare oxidative stress levels undergone by different biofilm communities and thus determine their antioxidant capacity.


Assuntos
Biofilmes/efeitos dos fármacos , Biomarcadores/metabolismo , Monitoramento Ambiental/métodos , Enzimas/metabolismo , Água Doce/microbiologia , Herbicidas/toxicidade , Estresse Oxidativo/efeitos dos fármacos , Ascorbato Peroxidases/metabolismo , Catalase/metabolismo , Cromatografia Líquida de Alta Pressão , Eletroforese em Gel de Gradiente Desnaturante , Glutationa Redutase/metabolismo , Éteres Difenil Halogenados , Testes de Toxicidade
12.
J Phycol ; 48(6): 1411-23, 2012 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-27009992

RESUMO

Fluvial biofilms are subject to multistress situations in natural ecosystems, such as the co-occurrence of light intensity changes and metal toxicity. However, studies simultaneously addressing both factors are rare. This study evaluated in microcosm conditions the relationship between short-term light intensity changes and Zn toxicity on fluvial biofilms with long-term photoacclimation to different light conditions. Biofilms that had long-term photoacclimation to 25 µmol photons · m(-2)  · s(-1) (low light [LL] biofilms), 100 µmol photons · m(-2)  · s(-1) (medium light [ML] biofilms), and 500 µmol photons · m(-2)  · s(-1) (high light [HL] biofilms) were characterized by different structural (Chlorophyll-a [Chl-a], total biomass-AFDW, EPS, algal groups, and diatom taxonomy) and physiological attributes (ETR-I curves and photosynthetic pigments). HL biofilms showed higher light saturation intensity and a higher production of xanthophylls than LL biofilms. In contrast, LL biofilms had many structural differences; a higher proportion of diatoms and lower AFDW and EPS contents than ML and HL biofilms. A clear effect of light intensity changes on Zn toxicity was also demonstrated. Zn toxicity was enhanced when a sudden increase in light intensity also occurred, mainly with LL biofilms, causing higher inhibition of both the Φ'PSII and the ΦPSII . A decoupling of NPQ from de-epoxidation reaction (DR) processes was also observed, indicating substantial damage to photoprotective mechanisms functioning in biofilms (i.e., xanthophyll cycle of diatoms) due to Zn toxicity. This study highlights the need to take into account environmental stress (e.g., light intensity changes) to better assess the environmental risks of chemicals (e.g., metals).

13.
Sci Total Environ ; 409(20): 4335-43, 2011 Sep 15.
Artigo em Inglês | MEDLINE | ID: mdl-21840570

RESUMO

Understanding the interactive effects of multiple stressors on ecosystems has started to become a major concern. The aim of our study was therefore to evaluate the consequences of a long-term exposure to environmental concentrations of Cu, Zn and As on the pollution-induced community tolerance (PICT) of lotic biofilm communities in artificial indoor channels. Moreover, the specificity of the PICT was assessed by evaluating the positive and negative co-tolerance between these metals. Photosynthetic efficiency and substrate-induced respiration (SIR), targeting the autotrophic and heterotrophic communities respectively were used in short-term inhibition bioassays with Cu, Zn and As to assess sensitivities of pre-exposed biofilms to the metals tested. Diversity profiles of a phototrophic, eukaryotic and prokaryotic community in biofilms following the different treatments were determined and analyzed with principal component analysis. The results demonstrated that pre-exposure to metals induced structural shifts in the community and led to tolerance enhancements in the phototrophic and heterotrophic communities. On the other hand, whatever the functional parameter used (i.e. photosynthesis and SIR), communities exposed to Cu were more tolerant to Zn and vice versa. Furthermore, only phototrophic communities pre-exposed to As developed tolerance to Cu but not to Zn, whereas no co-tolerance between Cu and As was observed in the heterotrophic communities. Finally, phototrophic and heterotrophic communities exposed to Cu and Zn became more sensitive to As, reflecting a negative co-tolerance between these metals. Overall, our findings support the fact that although the mode of action of the different metals is an important driver for the structure and thus the tolerance of the communities, it appears that the detoxification modes are the most important factors for the occurrence of positive or negative co-tolerance.


Assuntos
Adaptação Fisiológica , Processos Autotróficos/efeitos dos fármacos , Biofilmes/efeitos dos fármacos , Processos Heterotróficos/efeitos dos fármacos , Metais Pesados/toxicidade , Poluentes Químicos da Água/toxicidade , Biofilmes/crescimento & desenvolvimento , Biomassa , Ecotoxicologia , Metais Pesados/análise , Processos Fototróficos/efeitos dos fármacos , Fatores de Tempo , Microbiologia da Água , Poluentes Químicos da Água/análise
14.
Ecotoxicology ; 20(8): 1823-39, 2011 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-21701844

RESUMO

Pollution-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 T(0), 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.


Assuntos
Biofilmes/efeitos dos fármacos , Biota , Rios/microbiologia , Poluentes Químicos da Água/farmacologia , Zinco/farmacologia , Adaptação Fisiológica , Processos Autotróficos , Bactérias/efeitos dos fármacos , Diatomáceas/classificação , Diatomáceas/efeitos dos fármacos , Processos Heterotróficos , Análise Multivariada , Análise de Componente Principal , Espanha
15.
Sci Total Environ ; 409(11): 2102-13, 2011 May 01.
Artigo em Inglês | MEDLINE | ID: mdl-21397296

RESUMO

Aquatic ecosystems face variable exposure to pesticides, especially during floodings which are associated with short bursts of high contaminant concentrations that influence biological systems. A study was undertaken to highlight the impact of the herbicide diuron applied in mixture with the fungicide tebuconazole on natural periphyton during flooding events. Periphyton were grown in two series of two lotic outdoor mesocosms: one series was non-contaminated while the other was exposed to chronic contamination. After 4weeks, one channel of each series was exposed to three successive pulses, with each pulse followed by one week of recovery. Impacts on periphyton were assessed by using Denaturing Gel Gradient Electrophoresis to characterize eukaryotic community structure. At a functional scale, photosynthetic efficiency was quantified during each pulse, and the induced tolerance to diuron was estimated by performing short-term inhibition tests based on photosynthetic efficiency. Moreover, pesticide concentrations in the water column and periphyton matrix were measured. Diuron was adsorbed in the periphyton during each pulse and desorbed 13h after pulse end. The different pulses affected the eukaryotic community structures of the control biofilms, but not of the chronically exposed ones. During the first pulse, photosynthetic efficiency was correlated with pesticide concentration in the water phase, and there was no difference between periphyton from chronically contaminated channels and control channels. However, during the second and third pulses, the photosynthetic efficiency of periphyton chronically exposed to pesticides appeared to be less impacted by the acute pulsed exposure of pesticide. These changes were consistent with the acquisition of induced tolerance to diuron since only after the third pulse that periphyton from chronic channel became tolerant to diuron. Our experimental study indicates that the effects of pulsed acute exposures to pesticides on periphyton depended on whether the communities had previously been exposed to the same stressors or not.


Assuntos
Organismos Aquáticos/efeitos dos fármacos , Diurona/toxicidade , Fungicidas Industriais/toxicidade , Herbicidas/toxicidade , Triazóis/toxicidade , Poluentes Químicos da Água/toxicidade , Animais , Organismos Aquáticos/classificação , Biodiversidade , Biomassa , Diurona/análise , Relação Dose-Resposta a Droga , Meio Ambiente , Inundações , Água Doce/química , Fungicidas Industriais/análise , Herbicidas/análise , Fotossíntese/efeitos dos fármacos , Plâncton/classificação , Plâncton/efeitos dos fármacos , Testes de Toxicidade Aguda , Testes de Toxicidade Crônica , Triazóis/análise , Poluentes Químicos da Água/análise
16.
Environ Pollut ; 159(1): 18-24, 2011 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-20961674

RESUMO

Understanding the ecological status of aquatic ecosystems and the impact of anthropogenic contamination requires correlating exposure to toxicants with impact on biological communities. Several tools exist for assessing the ecotoxicity of substances, but there is still a need for new tools that are ecologically relevant and easy to use. We have developed a protocol based on the substrate-induced respiration of a river biofilm community, using the MicroResp™ technique, in a pollution-induced community tolerance approach. The results show that MicroResp™ can be used in bioassays to assess the toxicity toward biofilm communities of a wide range of metals (Cu, Zn, Cd, Ag, Ni, Fe, Co, Al and As). Moreover, a community-level physiological profile based on the mineralization of different carbon substrates was established. Finally, the utility of MicroResp™ was confirmed in an in-situ study showing gradient of tolerance to copper correlated to a contamination gradient of this metal in a small river.


Assuntos
Biofilmes/efeitos dos fármacos , Bioensaio/métodos , Monitoramento Ambiental/métodos , Metais Pesados/toxicidade
17.
Aquat Toxicol ; 98(2): 165-77, 2010 Jun 10.
Artigo em Inglês | MEDLINE | ID: mdl-20197204

RESUMO

Pollution-induced community tolerance (PICT) concept is based on the assumption that the toxicant exerts selection pressure on the biological communities when exposure reaches a critical level for a sufficient period of time and therefore sensitive species are eliminated. However, induced tolerance of microbial biofilm communities cannot be attributed solely to the presence of toxicants in rivers but also to various environmental factors, such as amount of nutrients. An experimental study was undertaken to highlight the potential impact of a phosphorus gradient on the sensitivity of periphytic microbial community to Cu and diuron. Biofilms were exposed to real-world levels of chronic environmental contamination of toxicants with a phosphorus gradient. Biofilm sensitivity to Cu and diuron was assessed by performing short-term inhibition tests based on photosynthetic efficiency to target photoautotrophs, extracellular enzyme activity (beta-glucosidase and leucine-aminopeptidase) and substrate-induced respiration activity to target heterotrophs. The impact of P-gradient associated to pollution was evaluated by measuring pesticide concentrations in biofilms, biomass parameters (chla, AFDW), bacterial cell density, photosynthetic efficiency and community structure (using 18S and 16S rDNA gene analysis to target eukaryotes and DGGE and HPLC pigment analysis to target bacteria and photoautotrophs). The obtained results show that depending on the studied toxicant and the used structural or functional parameter, the effect of the phosphorus gradient was variable. This highlights the importance of using a range of parameters that target all the biological communities in the biofilm. The PICT method can be regarded as a good tool for assessing anthropogenic environmental contamination, but it is necessary to dissociate the real impact of toxicants from environmental factors.


Assuntos
Bactérias/efeitos dos fármacos , Biofilmes/efeitos dos fármacos , Cobre/toxicidade , Diurona/toxicidade , Farmacorresistência Bacteriana/efeitos dos fármacos , Fosfatos/metabolismo , Poluentes Químicos da Água/toxicidade , Bactérias/crescimento & desenvolvimento , Bactérias/metabolismo , Carga Bacteriana , Biomassa , Cromatografia Líquida de Alta Pressão , DNA Ribossômico/genética , Relação Dose-Resposta a Droga , Farmacorresistência Bacteriana/fisiologia , Ativação Enzimática/efeitos dos fármacos , Ativação Enzimática/fisiologia , Fósforo/metabolismo , Fotossíntese/efeitos dos fármacos , Fotossíntese/fisiologia , Rios , Fatores de Tempo
18.
Aquat Toxicol ; 87(4): 252-63, 2008 May 30.
Artigo em Inglês | MEDLINE | ID: mdl-18387680

RESUMO

An experimental study was undertaken to highlight the potential ecotoxicological impact of the herbicide diuron on biofilms during flooding events in a small river (Morcille) in the Beaujolais vineyard area (France). We investigated the responses of chronically contaminated biofilms exposed to short-term pulses (3 h) of diuron. Biofilms were grown in indoor microcosms that were either non-contaminated or exposed to low-level chronic contamination, and not exposed, or exposed to single or double pulses of two environmental concentrations (7 and 14 microg L(-1)) of diuron. Exposure to pollution and its impact on biofilms were assessed by measuring pesticide concentrations in biofilms, biomass parameters (chl a, AFDW), community structure (using 18S and 16S rDNA gene analysis by DGGE, and HPLC pigment analysis to target eukaryotes, bacteria and photoautotrophs, respectively) and by performing a physiological test. Control biofilms displayed very low diuron concentrations, whereas the herbicide was found in the contaminated biofilms. Nevertheless, diuron concentrations were not higher in the pulsed biofilms than in the non-pulsed ones. AFDW and chl ain vivo fluorescence increased in both microcosms during the experiment and biomass was higher in chronically exposed biofilms than in control ones. The impact on biomass was higher for the control double-pulsed biofilms than for the non-pulsed ones. Carbon incorporation by the chronically exposed biofilms was greater during the first 28 days of growth than during the first 28 days of growth in the control biofilms. Both single and double pulses inhibited carbon incorporation of all biofilm communities, especially of the control ones. Short-term inhibition of photosynthesis was never significantly different in exposed and non-exposed biofilms. Few differences in the pigment structure were found between chronically exposed and control biofilms, but pulses impacted on the pigment structure of all biofilm communities. Bacterial structural differences were observed between single-pulsed and non-pulsed biofilms, but not between double-pulsed and non-pulsed biofilms. The different pulses affected the eukaryotic community structures of the control biofilms, but not of the chronically exposed ones. Unlike the bacterial communities, the control eukaryotic communities were structurally different from the chronically exposed ones. This preliminary experimental study indicates that exposure to environmental concentrations of diuron and other agricultural contaminants and further exposure to diuron can have measurable effects on small river biofilm communities. The effects of a pulsed acute exposure to diuron on biofilms depended on whether the biofilms had previously been exposed to the same stressors or not.


Assuntos
Fenômenos Fisiológicos Bacterianos , Biofilmes/efeitos dos fármacos , Diurona/toxicidade , Eucariotos/fisiologia , Herbicidas/toxicidade , Poluentes Químicos da Água/toxicidade , Biomassa , Carbono/metabolismo , Análise por Conglomerados , Desastres , França , Pigmentos Biológicos/análise , RNA Bacteriano/genética , RNA Ribossômico 16S/genética , RNA Ribossômico 18S/genética , Rios
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