Contrasted effects of an anti-cyanobacterial ultrasound device on the non-target freshwater invertebrate species Gammarus roeseli

International audienceThe aim of this work was to investigate the effects of an anti-cyanobacterial ultrasound device (supplied by an electrical power of 15 W and emitting at 23 and 46 kHz) on the widespread freshwater amphipod species Gammarus roeseli. First, laboratory scale experiments in 8-L glass tanks showed that an ultrasound exposure of 2 h and 40 min was sufficient to produce 50% mortality, along with a 6.5 °C water temperature increase. Avoiding excessive heating by using a water-cooling and recirculation system permitted an exposure time of 29 h for the same mortality rate. A potential relationship between temperature's rise and amphipod mortality was hence highlighted. Moreover, the use of plastic mesh bag (0.5 mm mesh size) as a physical barrier has not shown any lethal effects of ultrasound exposure. Furthermore, the induction of GPx or GST activity as oxidative stress biomarkers was not observed. This could be explained by reduced ultrasound intensity inside the mesh bags. Thus, according to these results, the tested ultrasound system is not expected to be acutely harmful in the field

Réhabilitation de sols pollués par des HAP grâce aux bactéries associées à la rhizosphère de Miscanthus X giganteus

L objectif de cette thèse a été d évaluer les possibilités de réhabilitation de sols dégradés, contaminés par des HAP ou à faible qualité agronomique (parc à cendres volantes), en couplant la bioremédiation de ces sols à la culture de Miscanthus x giganteus (MxG). Dans un premier temps, la mise au point d une série de bioessais in vitro au format microplaque a permis de témoigner de la contribution spécifique des exsudats racinaires de MxG et plus particulièrement de la quercétine (identifié parmi les métabolites secondaires racinaires) dans la biostimulation de bactéries HAP-dégradantes. Afin d appréhender l effet rhizosphérique de MxG sur la qualité des sols, des cultures en microcosmes de sols reconstitués puis de sols de friches ont été menées en laboratoire. D une part, la dissipation significative des HAP à 4 cycles a pu être mesurée dans le compartiment racinaire des sols contaminés. D autre part, l augmentation des teneurs en carbone organique observée dans les cendres volantes, associée à une dynamisation du cycle de l azote suggèrent une accélération des processus pédogénétiques liés au vieillissement du substrat. En outre, le développement d un protocole d extraction et de purification d acides nucléiques a permis de suivre l évolution de la diversité des communautés bactériennes des sols par méthode PCR-TTGE des ADNr 16S microbiens. La sélection de phylotypes bactériens a été mise en évidence au niveau rhizosphérique, en particulier à l interface sol-racine (rhizoplan), soulignant l influence de processus racinaires sur la structuration des communautés bactériennes in vivo. Enfin, un dernier volet, rendant compte d expériences exploratoires sur deux saisons de croissance en champs (sols pollués et parc à cendres), a permis de confirmer l adaptation de MxG à la variété de substrats étudiés, suggérant que sa culture pourrait constituer une alternative d agriculture durable sur sites contaminésThe aim of this work was to investigate the potential of Miscanthus x giganteus (MxG) for PAH polluted soils remediation and fly ash revegetation. In vitro studies through microplate assays demonstrated the contribution of MxG root exudates and particularly of quercetin (following the identification of root secondary metabolites) to the selective biostimulation of PAH-degrading bacteria. To get insights into bioremediation processes and rhizosphere effects on soil quality, microcosm experiments were conducted at a laboratory scale, using artificially reconstituted soils and collected industrial soils. On the one hand, significant dissipations of four-ring PAH were noticed in the rhizosphere of contaminated soils. On the other hand, significant organic carbon and nitrite inputs could be measured in fly ash, indicating a restart of nitrogen cycle and suggesting an enhancement of fly ash weathering processes in the long term. Besides, the development of a soil nucleic acid extraction and purification method permitted to study the evolution of bacterial community diversity in all types of soils, based on PCR-TTGE of eubacterial 16S rDNA. Specific enrichments of bacterial phylotypes could be reported in rhizoplanes, confirming root-associated processes on the selection of soil bacterial communities. Finally, plant adaptation to the broad range of studied substrates in situ lead us to suggest that MxG cultivation could be an effective strategy for a new system of sustainable agricultural activities in wasteland soilsMETZ-SCD (574632105) / SudocSudocFranceF

Sublethal effect assessment of a low-power and dual-frequency anti-cyanobacterial ultrasound device on the common carp (Cyprinus carpio): a field study

International audienc

Arbre de pluie comme (nouveau) dispositif de gestion du ruissellement urbain

International audienc

Storm-water tree as (new) way to manage urban runoff

International audienc

hydrologique des cellules de biorétention -Résultats préliminaires d'un ouvrage pilote

International audienceA pilot bioretention cell with a deep underground storage layer to enhance exfiltration into the underlying clay soil was set up in Sense-City climatic mini city (France). The pilot system is fully equipped with sensors for inflow, outflow, soil moisture and meteorological monitoring. The study involves the uncertainty evaluations of sensors and a 5-month cumulative water balance analysis (16/06/2022 – 22/11/2022). The preliminary results indicate that during the relatively dry summer period (16/06-25/09), the bioretention cell provided a comparatively high percentage of evapotranspiration (40%) and more limited exfiltration (19%), while later in the wet autumn (25/09-22/11), some evidence might suggest groundwater intrusion into the storage/drainage layer at the bottom. Uncertainty evaluations showed high uncertainties on soil water contain measurements, whose impact on the water balance need to be further analysed.Un ouvrage de biorétention expérimental, comportant une couche de stockage souterrain en gravier pour améliorer l'exfiltration vers le sol argileux sous-jacent, a été mis en place dans la mini ville climatique Sense-City (France). Le dispositif pilote est entièrement équipé de capteurs permettant de mesurer les flux entrant et sortant, l'humidité du sol et les paramètres météorologiques. L'étude comprend l'évaluation de l'incertitude de mesure des capteurs et une analyse du bilan hydrique cumulé sur 5 mois (16/6/2022-22/11/2022). Les premiers résultats indiquent un pourcentage comparativement élevé d'évapotranspiration (40%) et plus limité d'exfiltration (20%) pendant la période estivale (16/6-25/9), tandis que plus tard durant la période pluvieuse d'automne (25/9-22/11) une intrusion d'eau souterraine dans le fond de l'ouvrage est mise en évidence. L'évaluation des incertitudes de mesure met en évidence une forte incertitude des mesures de teneur en eau du sol, dont l'incidence sur les bilans volumiques devra être évaluée à l'avenir

Allelopathic potential and ecotoxicity evaluation of gallic and nonanoic acids to prevent cyanobacterial growth in lentic systems: A preliminary mesocosm study

International audienceThe increase in anthropogenic nutrient loading affecting many freshwater ecosystems combined with global warming may lead to cyanobacterial blooms on an increasingly frequent basis. Among the various physicochemical and biological methods which have been proposed to rapidly control blue-green algae growth, the use of plant-derived substances such as allelochemicals has gained great interest as an environment-friendly approach. The primary aim of this work was to evaluate the efficiency of gallic and nonanoic acid application to preemptively inhibit cyanobacterial growth in lentic hydrosystems. In order to address the process feasibility under realistic exposure scenarios, thirteen outdoor freshwater mesocosms (unit volume: 3 m3) were designed, each containing phytoplankton (including local blue-green algae species) and various non-target organisms from higher trophic levels (Physa, Lymnaea, Gammarus, and Scardinius erythrophthalmus). After an 8-week mesocosm stabilization period, a full factorial design based on the presence/absence of gallic acid (GA) and nonanoic acid (NA) (including a control group) was implemented into the exposure tanks. Regular monitoring of major phytoplankton taxa was conducted during a 28-day experiment using an on-line fluorometer. The main results suggested that gallic acid was more efficient than nonanoic acid at limiting cyanobacterial growth at concentrations as low as 1 mg L− 1. Successive gallic acid applications (at 1, 2 and 4 mg L− 1) at the early stages of cyanobacterial growth did not allow the complete elimination of blue-green algae from the mesocosms. However, the specificity of the allelopathic effect of gallic acid towards cyanobacteria was compatible with the maintenance of a primary productivity in the treated tanks as indicated by the photoautotrophic growth of other algal taxa. Finally, no biomarker induction signal could be reported in non-target species. Further gallic acid application trials in lentic systems such as small freshwater ponds may help to design innovative allelopathy-based aquatic ecotechnologies

Influence of Waterborne Gallic and Pelargonic Acid Exposures on Biochemical and Reproductive Parameters in the Zebrafish (Danio rerio)

International audienceGallic and pelargonic acids are biologically derived substances receiving a growing interest as eco-friendly biocides with potential applications in freshwater system management. However, some data gaps remain to address their chronic ecotoxicity issue, particularly for fish. This work aimed at investigating the sublethal effects of a long-term waterborne exposure of zebrafish to these compounds. Mature fish were exposed to gallic or pelargonic acid at the concentrations of 0, 0.05, 0.5 and 5 mg/L during one month under semi-static conditions. Fecundity, hatching rate and median hatching time were regularly evaluated. Circulating sex hormone levels (11 ketotestosterone 211 KT, 17 bestradiol -E2-), plasma vitellogenin (Vtg), and gonad histology were monitored in males and females after exposure. Lactate dehydrogenase (LDH), total glutathione peroxydase (GPx) and glutathione-S transferase (GST) activities were assessed as enzymatic biomarkers of exposure in fish liver. Significant increases of GPx activity were reported in females exposed to both type of chemicals regardless the contamination level. Moreover, 5 mg/L gallic acid induced a decrease in 11-KT levels for males. For fish exposed to pelargonic acid, decreases in circulating hormone levels were reported respectively at 0.05 and 5 mg/L for 11-KT in males, and at 0.5 mg/L for E2 in females. However, no histological alteration in gonads neither significant variation in reproductive performances were detected following zebrafish exposure to gallic or pelargonic acid. Additional investigations concerning the mode of application and the environmental fate of these substances may warrant their further use in freshwater systems at concentrations compatible with biocidal/allelochemical effects

Acute toxicity and sublethal effects of gallic and pelargonic acids on the zebrafish Danio rerio

International audienceGallic and pelargonic acids are naturally found in a variety of plants and food products. Despite their extensive use in man-made applications, little is known regarding their potential risks to aquatic vertebrates. The aim of this work was to assess the acute toxicity of these polyphenolic and fatty acid compounds to the zebrafish. In order to get insights into sublethal effects, the enzyme activity of usual biomarkers related to oxidative stress and biotransformation were also assessed in fish. These latter included total superoxide dismutase, catalase as well as total glutathione peroxidase for antioxidant defence mechanisms and glutathione S-transferase for biotransformation related enzyme. Gallic acid was practically non-toxic (96-h lethal concentration (LC50) > 100 mg/L) whereas pelargonic acid was slightly toxic (96-h LC50 of 81.2 mg/L). Moreover, biomarker analyses indicated enhanced superoxide dismutase activity in fish exposed to 20, 40 and 100 mg/L of gallic acid compared to control. A dose-dependent induction of glutathione peroxidase and glutathione S-transferase was reported following gallic acid exposure at the tested concentrations of 10, 20 and 40 mg/L, with the exception of 100 mg/L of substance where basal activity levels were reported. In the case of pelargonic acid, there was no change in antioxidant enzyme activity while an inhibition of glutathione S-transferase was observed from organisms exposed to 45, 58 and 76 mg/L of test solution. The results concerning sublethal effects on biological parameters of zebrafish highlighted thereby the need for further investigations following chronic exposure to both organic acids