Single and joint effects of chronic exposure to polyethylene microplastics and chlortoluron on oyster, Crassostrea gigas: biomarkers and metabolomics approaches

, Bringer Arno.

Microplastics (MPs) are a pollutant of increasing environmental concern based on their ubiquitous and persistent nature. Pesticides are widely used in agricultural settings as well as in many homes and residential gardens and may enter estuarine and coastal environments. Microplastics and pesticides are identified as two environmental pollutants that have an adverse impact on the environment. The knowledge about the combined exposure of pesticides and MPs may facilitate further assessment of their ecotoxicity. In this study, a 24-day exposure was set up on juvenile oysters (C. gigas) to various contaminants potentially present in the natural marine environment. Four experimental conditions were tested: control, polyethylene MPs (HDPE 20-25 µm, 10 µg.L-1), chlortoluron (herbicide, 30 µg.L-1) and cocktail mixture (MPs + chlortoluron). Bivalve (juvenile oysters) samples were taken at two sampling dates (D5 and D25) in order to perform various molecular defence biomarker assays: SOD (oxidative stress), GST (detoxification process), MDA (lipid peroxidation), and Laccase (immune reaction). Measures were conducted in the digestive glands due to their bioaccumulation properties. Biochemical analysis showed that the oxidative damage of oysters exposed to the cocktail could be observed on the D25. The condition with MPs alone, on the other hand, shows a higher activity in Laccase in response to environmental stress on the D25. In addition, we propose to evaluate the risk assessment of the effects of MPs and chlortoluron on the bioaccumulation, biomarkers and metabolic profile (metabolic and xenobiotic networks) of juvenile oysters. As part of a modelling approach, various parameters will be assimilated in order to develop sensitive and predictive responses for improving the diagnosis of the quality of the marine environment.

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