Effect of fulvic acids on lead-induced oxidative stress to metal sensitive Vicia faba L. plant

Lead (Pb) is a ubiquitous environmental pollutant capable to induce various morphological, physiological, and biochemical functions in plants. Only few publications focus on the influence of Pb speciation both on its phytoavailability and phytotoxicity. Therefore, Pb toxicity (in terms of lipid peroxidation, hydrogen peroxide induction, and photosynthetic pigments contents) was studied in Vicia faba plants in relation with Pb uptake and speciation. V. faba seedlings were exposed to Pb supplied as Pb(NO3)2 or complexed by two fulvic acids (FAs), i.e. Suwannee River fulvic acid (SRFA) and Elliott Soil fulvic acid (ESFA), for 1, 12, and 24 h under controlled hydroponic conditions. For both FAs, Pb uptake and translocation by Vicia faba increased at low level (5 mg l−1), whereas decreased at high level of application (25 mg l−1). Despite the increased Pb uptake with FAs at low concentrations, there was no influence on the Pb toxicity to the plants. However, at high concentrations, FAs reduced Pb toxicity by reducing its uptake. These results highlighted the role of the dilution factor for FAs reactivity in relation with structure; SRFA was more effective than ESFA in reducing Pb uptake and alleviating Pb toxicity to V. faba due to comparatively strong binding affinity for the heavy metal

A new cell primo-culture method for freshwater benthic diatom communities

A new cell primo-culture method was developed for the benthic diatom community isolated from biofilm sampled in rivers. The approach comprised three steps: (1) scraping biofilm from river pebbles, (2) diatom isolation from biofilm, and (3) diatom community culture. With a view to designing a method able to stimulate the growth of diatoms, to limit the development of other microorganisms, and to maintain in culture a community similar to the original natural one, different factors were tested in step 3: cell culture medium (Chu No 10 vs Freshwater “WC” medium modified), cell culture vessel, and time of culture. The results showed that using Chu No 10 medium in an Erlenmeyer flask for cell culture was the optimal method, producing enough biomass for ecotoxicological tests as well as minimising development of other microorganisms. After 96 h of culture, communities differed from the original communities sampled in the two rivers studied. Species tolerant of eutrophic or saprobic conditions were favoured during culture. This method of diatom community culture affords the opportunity to assess, in vitro, the effects of different chemicals or effluents (water samples andindustrial effluents) on diatom communities, as well as on diatom cells, from a wide range of perspectives

Use of a fluorescence-based approach to assess short-term responses of the alga Pseudokirchneriella subcapitata to metal stress

This work explores the use of fluorescent probes to evaluate the responses of the green alga Pseudokirchneriella subcapitata to the action of three nominal concentrations of Cd(II), Cr(VI), Cu(II) and Zn(II) for a short time (6 h). The toxic effect of the metals on algal cells was monitored using the fluorochromes SYTOX Green (SG, membrane integrity), fluorescein diacetate (FDA, esterase activity) and rhodamine 123 (Rh123, mitochondrial membrane potential). The impact of metals on chlorophyll a (Chl a) autofluorescence was also evaluated. Esterase activity was the most sensitive parameter. At the concentrations studied, all metals induced the loss of esterase activity. SG could be used to effectively detect the loss of membrane integrity in algal cells exposed to 0.32 or 1.3 mol L1 Cu(II). Rh123 revealed a decrease in the mitochondrial membrane potential of algal cells exposed to 0.32 and 1.3 mol L1 Cu(II), indicating that mitochondrial activity was compromised. Chl a autofluorescence was also affected by the presence of Cr(VI) and Cu(II), suggesting perturbation of photosynthesis. In conclusion, the fluorescence-based approach was useful for detecting the disturbance of specific cellular characteristics. Fluorescent probes are a useful diagnostic tool for the assessment of the impact of toxicants on specific targets of P. subcapitata algal cells.The authors thank the FCT Strategic Project PEst-OE/EQB/LA0023/2013. Manuela D. Machado gratefully acknowledges the post-doctoral grant from FCT (SFRH/BPD/72816/2010)

Effects of Pesticides on Freshwater Diatoms

Effects of Pesticides on Freshwater Diatom

Risques environnementaux liés aux pollutions agricoles et qualité physico-chimique et biologique des cours d'eau : Modélisation de l'impact de ces pollutions. Performance environnementale des activités agricoles : rapport scientifique final du programme INSOLEVIE 2006-2009

Les principaux objectifs de ce projet pluridisciplinaire et interrégional étaient les suivants : - Détermination des zones à risque de pollution par des indicateurs agroenvironnementaux spatialisés suivant la vulnérabilité des milieux, la pression exercée par les acteurs et adaptés aux changements entre les différentes échelles, permettant la déclinaison de programmes d'intervention les plus efficaces : de la politique générale à la mesure de pratique technique à la parcelle. - Caractérisation de l'ambiance chimique siégeant dans les cours d'eau de la zone d'étude par différents principes de mesure et d'échantillonnage plus ou moins intégrateurs, incluant la mise à l'épreuve des capteurs passifs de pesticides (POCIS). - Modélisation des flux géochimiques observés sur les versants (essentiellement nutriments et pesticides) qui doit permettre de mieux affecter la part de la pollution résultant de l'activité agricole. - Appréciation des impacts environnementaux dans les milieux aquatiques à l'aide de bio-indicateurs révélateurs du niveau global de pollution, mais aussi de descripteurs rendant plus spécifiquement compte des effets des pollutions par les produits phytosanitaires (compartiments invertébrés, diatomées, poissons). L'objectif sur ce volet consiste à générer une modélisation des relations entre les descripteurs d'état des cours d'eau et les impacts mesurés sur des maillons biologiques-clés de la DCE. - Elaboration d'une méthode transférable d'évaluation à l'échelle de bassins-versants de la performance environnementale de l'activité agricole traduisant le progrès réalisé suite à des changements de pratiques entre situations avant intervention et situations cibles (normes) sous la contrainte des aptitudes des milieux et de viabilité économique des exploitations agricoles