Seasonal shift in the sensitivity of a natural benthic microalgal community to a herbicide mixture: impact on the protective level of thresholds derived from Species Sensitivity Distributions

International audienceSeasonal changes in the structure and composition of a benthic microalgal community may lead to different responses to herbicide contamination during different seasons. Consequently, the thresholds derived from risk assessment tools such as species sensitivity distributions (SSDs) must allow for these changes. We built a single-substance SSD for each of four herbicides (atrazine, terbutryn, diuron and isoproturon), which was specific to the sensitivity of the benthic diatoms found in Lake Geneva, in order to derive protective thresholds for a mixture of these four herbicides using the concentration addition model. We then investigated (1) the structural parameters of a Lake Geneva benthic microalgal community during two contrasting seasons (summer 2012 and winter 2013), (2) the response of these communities to a herbicide mixture, and (3) the protective levels of the thresholds derived. The winter community was characterized by having greater biomass, diatom species richness, and diversity metrics, and lower non-diatom species richness than the summer community. The differences in the diatom communities composition in these seasons appeared to be primarily driven by the environmental nitrate concentrations and the temperature. Moreover, the species in the winter community were more resistant to herbicides than those found in the summer community. Consequently, the protective threshold for this herbicide mixture obtained in this study was in fact protective for the winter community, but not for the summer community based on their structural parameters. Thus, the protective level against herbicides of the threshold for the benthic microalgal community should take into account changes in the environmental physico-chemical conditions that strongly influence the structure and composition of the community. The fact that the succession of species over time (i.e., over the seasons) is difficult to predict introduces uncertainties into the estimation of protective thresholds and questions their applicability year round

Evaluer la probabilité d'impact significatif des principales pressions anthropiques en cours d'eau via l'outil diagnostique « diatomées »

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Mercury bioaccumulation in the aquatic plant Elodea nuttallii in the field and in microcosm: Accumulation in shoots from the water might involve copper transporters

International audiencePrevious studies suggest that macrophytes might participate in bioaccumulation and biomagnification of toxic mercury (Hg) in aquatic environment. Hg bioaccumulation and uptake mechanisms in macrophytes need therefore to be studied. Amongst several macrophytes collected in an Hg contaminated reservoir in Romania, Elodea nuttallii showed a high organic and inorganic Hg accumulation and was then further studied in the laboratory.Tolerance and accumulation of Hg of this plant was also high in the microcosm. Basipetal transport of inorganic Hg was predominant, whereas acropetal transport of methyl-Hg was observed with apparently negligible methylation or demethylation in planta. Hg concentrations were higher in roots>leaves>stems and in top>middle>bottom of shoots. In shoots, more than 60% Hg was found intracellularly where it is believed to be highly available to predators. Accumulation in shoots was highly reduced by cold, death and by competition with Cu+.Hg in E. nuttallii shoots seems to mainly originate from the water column, but methyl-Hg could also be remobilized from the sediments and might drive in part its entry in the food web. At the cellular level, uptake of Hg into the cell sap of shoots seems linked to the metabolism and to copper transporters. The present work highlights an important breakthrough in our understanding of Hg accumulation and biomagnifications: the remobilization of methyl-Hg from sediments to aquatic plants and differences in uptake mechanisms of inorganic and methyl-Hg in a macrophyte

Promoting Physical Activity and Reducing Sedentary Time Among Tertiary Workers: Position Stand From the French National ONAPS

The modernization of our societies has resulted in a steady increase in service industry occupations tertiarization), which have favored increased sedentary time, while reducing occupational physical activity. In less than 50 years, the United States has increased sedentary professions by about 20%, with a parallel decline in professions requiring physical labor.1 At the same time, French workers spend approximately 10 hours per day sitting without active breaks on work days and about 7.6 hours per day sitting on nonworking days.2 Due to the amount of time that people spend at work, the workplace is now recognized as an opportune setting for promoting an active lifestyle and for developing strategies to reduce sedentary time.3 Although there has been a growing body of literature proposing such strategies over the past 10 years, it is difficult to draw conclusions from this work due to the heterogeneity in research methods and the lack of robust statistical analyses.4,5 Moreover, such workplace intervention strategies appear to suffer from high attrition, as well as a lack of proven sustainability.6,7 Because there is an urgent need to promote physical activity and reduce sedentary time during work time, the French National Conservatory for Physical Activity and Sedentary Behaviors (ONAPS) recently dedicated its annual congress (January 29–30, 2019 in Vichy, France) to this important public health issue. The congress convened an expert panel comprising scientists, public health specialists, occupational physicians, ergonomists, as well as both workers and their employers to examine strategies for improving workplace health. This commentary summarizes the initial conclusions of this expert panel and details the main findings and recommendations regarding the promotion of physical activity and reduction of sedentary time among tertiaryemployees

A meta-analysis of ecotoxicological models used for plant protection product risk assessment before their placing on the market

International audienceBefore their placing on the market, the safety of plant protection products (PPP) towards both human and animal health, and the environment has to be assessed using experimental and modelling approaches. Models are crucial tools for PPP risk assessment and some even help to avoid animal testing. This review investigated the use of modelling approaches in the ecotoxicology section of PPP active substance assessment reports prepared by the authorities and opened to consultation from 2011 to 2021 in the European Union. Seven categories of models (Structure-Activity, ToxicoKinetic, ToxicoKinetic-ToxicoDynamic, Species Sensitivity Distribution, population, community, and mixture) were searched for into the reports of 317 active substances. At least one model category was found for 44 % of the investigated active substances. The most detected models were Species Sensitivity Distribution, Structure-Activity and ToxicoKinetic for 27, 21 and 15 % of the active substances, respectively. The use of modelling was of particular importance for conventional active substances such as sulfonylurea or carbamates contrary to microorganisms and plant derived substances. This review also highlighted a strong imbalance in model usage among the biological groups considered in the European Regulation (EC) No 1107/2009. For example, models were more often used for aquatic than for terrestrial organisms (e.g., birds, mammals). Finally, a gap between the set of models used in reports and those existing in the literature was observed highlighting the need for the implementation of more sophisticated models into PPP regulation

Pollution-induced community tolerance (PICT) as a tool for monitoring Lake Geneva long-term in situ ecotoxic restoration from herbicide contamination

Chemical monitoring revealed a regular decrease in herbicide concentration in Lake Geneva since last decades that may be linked to an ecotoxic restoration of nontarget phytoplanktonic communities. The Pollution-induced community tolerance (PICT) approach was tested as a tool to monitor the ecotoxic restoration of Lake Geneva for herbicides from 1999 to 2011. We conducted monthly assessments in 1999 and in 2011 for the tolerance of the phytoplankton communities to two herbicides (atrazine and copper), using PICT bioassays. The taxonomical composition of the communities was determined on the same collecting dates. The herbicide concentration decrease during the 12 years significantly influenced the composition of communities. The PICT monitoring indicated that a significant tolerance decrease in the community to both herbicides accompanied the herbicide concentration decrease. PICT measurements for atrazine and copper also changed at the intra-annual level. These variations were mainly due to community composition shifts linked to seasonal phosphorus and temperature changes. PICT monitoring on a seasonal basis is required to monitor the mean tolerance of communities. PICT appeared to be a powerful tool that reflected the toxic effects on environmental communities and to monitor ecotoxic ecosystem restoration