Microplastic pollution within the marine environment is of pressing concern globally. Accordingly, spatial monitoring of microplastic concentrations, composition and size distribution may help to identify sources and entry pathways, and hence allow initiating focused mitigation. Spatial distribution patterns of microplastics were investigated in two compartments of the southern North Sea by collecting sublittoral sediment and surface water samples from 24 stations. Large microplastics (500−5000 μm) were detected visually and identified using attenuated total reflection (ATR) Fourier transform infrared (FTIR) spectroscopy. The remaining sample was digested enzymatically, concentrated onto filters and analyzed for small microplastics (11−500 μm) using Focal Plane Array (FPA) FTIR imaging. Microplastics were detected in all samples with concentrations ranging between 2.8 and 1188.8 particles kg−1 for sediments and 0.1–245.4 particles m−3 for surface waters. On average 98% of microplastics were <100 μm in sediments and 86% in surface waters. The most prevalent polymer types in both compartments were polypropylene, acrylates/polyurethane/varnish, and polyamide. However, polymer composition differed significantly between sediment and surface water samples as well as between the Frisian Islands and the English Channel sites. These results show that microplastics are not evenly distributed, in neither location nor size, which is illuminating regarding the development of monitoring protocols.

International audience | Environmentally mediated sensitivity of Lemna minor to copper (Cu) was evaluated for the first time in three experiments: the effects of two levels of nutrient concentration, light irradiance or Cu pre-exposure were tested. Various Cu concentrations (ranging from 0.05 to 0.25 mg/L) were used to assess the sensitivity of L. minor to this metal, using one common strain previously acclimatized to two different levels of light intensity, nutrient enrichment and Cu pre-exposure. Our results showed a phenotypic plastic response of the relative growth rates based on frond number and fresh mass production, and maximum quantum yield of photosystem II (Fv/Fm). Growth was affected by the three environmental conditions both prior and during Cu exposure, whereas Fv/Fm was mostly affected during Cu exposure. Copper significantly influenced all the parameters measured in the three experiments. Environmental conditions significantly modified L. minor sensitivity to Cu in all experiments, with up to twofold difference depending on the treatment. Growth rate was the parameter that was most impacted. Our study revealed for the first time the existence of phenotypic plasticity in L. minor sensitivity to chemical contamination, and implies that environmental context needs to be taken into account for a relevant risk assessment.

International audience | With the actual increasing interest for urban soils, the evaluation of soil contamination by trace elements and the dynamics of this contamination appear mandatory to preserve plant and thereby human health. Street trees and the associated soil placed in pits located nearby roads could represent convenient indicators of urban and vehicle traffic influences on soils and plants. However, data on these soils remain scarce, many studies investigating park soils rather than street tree soils. Furthermore, trace elements could be one of the main factors causing the observed urban tree decline, while practitioners more and more question the possible reuse of these soils after the death of trees as well as tree litter collected in the streets. We evaluated the contamination in anthropogenic trace elements (TE), namely Zn, Pb, and Cd, of street trees (Tilia tomentosa) and their soils distributed all over Paris (France). Street tree soils are imported from rural areas at the plantation of each new tree so that tree age corresponds to the time of residence of the soil within an urban environment allowing the evaluation of temporal trends on TE concentration in soils and trees. The TE concentration revealed an important soil pollution, especially for the older soils (mean age of 80 years old). The consideration of the residence time of trees and soils in an urban environment evidenced an accumulation of Zn and Pb (ca. 4.5 mg kg−1 year−1 and 4 mg kg−1 year−1 for Zn and Pb, respectively). However, leaf concentrations in TE were low and indicate that soil-root transfer was not significant compared to the contamination by atmospheric deposition. These results underlined the necessity to deepen the evaluation of the recycling of urban soils or plants submitted to urban contamination.

International audience | With the actual increasing interest for urban soils, the evaluation of soil contamination by trace elements and the dynamics of this contamination appear mandatory to preserve plant and thereby human health. Street trees and the associated soil placed in pits located nearby roads could represent convenient indicators of urban and vehicle traffic influences on soils and plants. However, data on these soils remain scarce, many studies investigating park soils rather than street tree soils. Furthermore, trace elements could be one of the main factors causing the observed urban tree decline, while practitioners more and more question the possible reuse of these soils after the death of trees as well as tree litter collected in the streets. We evaluated the contamination in anthropogenic trace elements (TE), namely Zn, Pb, and Cd, of street trees (Tilia tomentosa) and their soils distributed all over Paris (France). Street tree soils are imported from rural areas at the plantation of each new tree so that tree age corresponds to the time of residence of the soil within an urban environment allowing the evaluation of temporal trends on TE concentration in soils and trees. The TE concentration revealed an important soil pollution, especially for the older soils (mean age of 80 years old). The consideration of the residence time of trees and soils in an urban environment evidenced an accumulation of Zn and Pb (ca. 4.5 mg kg−1 year−1 and 4 mg kg−1 year−1 for Zn and Pb, respectively). However, leaf concentrations in TE were low and indicate that soil-root transfer was not significant compared to the contamination by atmospheric deposition. These results underlined the necessity to deepen the evaluation of the recycling of urban soils or plants submitted to urban contamination.

The Deepwater Horizon (DWH) disaster released crude oil in the Gulf of Mexico for 87 days, overlapping with the reproductive season and recruitment of the oyster Crassostrea virginica. The pelagic larval life stages of C. virginica are particularly vulnerable to contaminants such as polycyclic aromatic hydrocarbons (PAHs) and oil droplets. Based on their lipophilic properties, PAHs and oil droplets can adsorb onto phytoplankton and filter-feeding C. virginica larvae may be exposed to these contaminants bound to suspended sediment, adsorbed onto algal and other particles, or in solution. This study examined the effects of exposure of C. virginica larvae to algae mixed with DWH oil. In a 14-day laboratory exposure, 5 day-old C. virginica larvae were exposed to Tisochrysis lutea mixed with four concentrations of unfiltered DWH oil (HEWAF) in a static renewal system. Larval growth, feeding capacity, abnormality and mortality were monitored throughout the exposure. Total PAH (n = 50) content of the water medium, in which larvae were grown, were quantified by GC/MS-SIM. Oil droplets were observed bound to algae, resulting in particles in the size-range of food ingested by oyster larvae (1–30 μm). After 14 days of exposure, larval growth and survival were negatively affected at concentrations of tPAH50 as low as 1.6 μg L−1. GC/MS-SIM analysis of the exposure medium confirmed that certain PAHs were also adsorbed by T. lutea and taken up by oyster larvae via ingestion of oil droplets and/or contaminated algae. Long-term exposure to chronic levels of PAH (1.6–78 μg tPAH50 L−1) was shown to negatively affect larval survival. This study demonstrates that dietary exposure of oyster larvae to DWH oil is a realistic route of crude oil toxicity and may have serious implications on the planktonic community and the food chain.

Trace metal contamination in the European sardine and anchovy food web was investigated in the Gulf of Lions, NW Mediterranean Sea, including seawater and size fractions of plankton. The results highlighted: i) higher and more variable concentrations in the smaller plankton size classes for all metals except cadmium; ii) higher concentrations in anchovy versus sardine for all elements except lead; iii) different patterns of metal bioaccumulation through the food web: cobalt, nickel, copper, silver, lead and zinc displayed continuously decreasing concentrations (with the exception of increased zinc in fish only), while mercury concentrations dropped considerably in larger plankton size classes and rose significantly in fish. Lastly, cadmium concentrations were found to be highest in intermediate plankton size classes, with very low levels in fish. The need to efficiently characterize the biological composition of plankton in order to fully identify its role in the mobilization and transfer of metals was highlighted.

International audience | Environmentally mediated sensitivity of Lemna minor to copper (Cu) was evaluated for the first time in three experiments: the effects of two levels of nutrient concentration, light irradiance or Cu pre-exposure were tested. Various Cu concentrations (ranging from 0.05 to 0.25 mg/L) were used to assess the sensitivity of L. minor to this metal, using one common strain previously acclimatized to two different levels of light intensity, nutrient enrichment and Cu pre-exposure. Our results showed a phenotypic plastic response of the relative growth rates based on frond number and fresh mass production, and maximum quantum yield of photosystem II (Fv/Fm). Growth was affected by the three environmental conditions both prior and during Cu exposure, whereas Fv/Fm was mostly affected during Cu exposure. Copper significantly influenced all the parameters measured in the three experiments. Environmental conditions significantly modified L. minor sensitivity to Cu in all experiments, with up to twofold difference depending on the treatment. Growth rate was the parameter that was most impacted. Our study revealed for the first time the existence of phenotypic plasticity in L. minor sensitivity to chemical contamination, and implies that environmental context needs to be taken into account for a relevant risk assessment.

International audience | Today, the environmental awareness is leading to the recovery of the solid organic waste and the use of fossil fuels. Methanisation, or anaerobic digestion, is a solution. This process is the transformation of organic matter by bacteria in the absence of oxygen. It allows both the treatment of organic waste and provides two main products biogas and digestate. Digestate is an improved fertilizer that can be used by spreading or composting. Biogas can be used to produce heat or electricity. Biogas production is currently supported by governments of developed countries. In France, the number of installations is gradually increasing (Club Biogaz ATEE, 2011). However, waste used as raw material can potentially be rich in microorganisms. Currently, some questions arise about the potential spread of micro-organisms by this type of process. Among the among the dispersal pathways, the airborne mode of spread is often poorly explored. During the anaerobic process, a few phases seem to be able to cause the aerosolization of microorganisms, for example, the stock of raw materials or digestate handling. In this context, the EMAMET project was realised to provide data on atmospheric emissions from these processes (Bayle et al, 2016). The objectives of this study are to enumerate and describe the airborne microbial community on anaerobic digestor site caracterized by molecular approach. On a quarterly basis, over a one-year period, of the anaerobic digestion of waste water activated sludge has been monitored. For each campaign, four sampling locations have been investigated; the storage area for raw materials, the raw material preparation area, the digestion reactor and the phase separation zone of the digestate. A fifth simple, an outdoor control sampling point was also included.

International audience

International audience