Active and passive biomonitoring suggest metabolic adaptation in blue mussels ( Mytilus spp.) chronically exposed to a moderate contamination in Brest harbor (France)

Abstract

Brest harbor (Bay of Brest, Brittany, France) has a severe past of anthropogenic chemical contamination, but inputs tended to decrease, indicating a reassessment of its ecotoxicological status should be carried out. Here, native and caged mussels (Mytilus spp.) were used in combination to evaluate biological effects of chronic chemical contamination in Brest harbor. Polycyclic aromatic hydrocarbon (PAH) contamination was measured in mussel tissues as a proxy of harbor and urban pollution. Biochemical biomarkers of xenobiotic biotransformation, antioxidant defenses, generation of reducing equivalents, energy metabolism and oxidative damage were studied in both gills and digestive glands of native and caged mussels. In particular, activities of glutathione-S-transferase (GST), superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GPx), glutathione reductase (GR), NADP-dependent isocitrate dehydrogenase (IDP), pyruvate kinase (PK) and phosphoenolpyruvate carboxykinase (PEPCK) were measured and lipid peroxidation was assessed by malondialdehyde (MDA) quantification. In addition, a condition index was calculated to assess the overall health of the mussels. Moderate PAH contamination was detected in digestive glands of both native and caged individuals from the exposed site. Modulations of biomarkers were detected in digestive glands of native harbor mussels indicating the presence of a chemical pressure. In particular, results suggested increased biotransformation (GST), antioxidant defenses (CAT), NADPH generation (IDP) and gluconeogenesis (PEPCK), which could represent a coordinated response against chemically-induced cellular stress. Lipid peroxidation assessment and condition index indicated an absence of acute stress in the same mussels suggesting metabolic changes could, at least partially, offset the negative effects of contamination. In caged mussels, only GR was found modulated compared to non-exposed mussels but significant differences in oxidative stress and energy-related biomarkers were observed compared to native harbor mussels. Overall, these results suggested mussels chronically exposed to contamination have set up metabolic adaptation, which may contribute to their survival in the moderately contaminated harbor of Brest. Whether these adaptive traits result from phenotypic plasticity or genetic adaptation needs to be further investigated.

High mortality of mussels in northern Brittany – Evaluation of the involvement of pathogens, pathological conditions and pollutants

“…The river provides more than 63% of the bay's freshwater supply (Auffret, 1983). Lacroix et al (2015) observed differences in physiological responses to contaminants between native Brest Bay and imported mussels. Non-natives were more sensitive and showed more sensitive biomarker responses.…”

Exposure of marine mussels Mytilus spp. to polystyrene microplastics: Toxicity and influence on fluoranthene bioaccumulation

“…Mussels (58.6 ± 9.6 mm, mean ± SD) were collected at the Pointe d'Armorique in the Bay of Brest (48 19'20.29 00 N, Brittany, France), a site known to exhibit low PAH concentrations (Lacroix et al, 2015). The sampling site is located within a zone of overlap between Mytilus edulis and Mytilus galloprovincialis (Bierne et al, 2003), the mussel population is thus considered as a "species complex" (Lacroix et al, 2014a), and is referred to as Mytilus spp.…”

First data on three bivalve species exposed to an intra-harbour polymetallic contamination (La Rochelle, France)

“…The evaluation of the impact of pollutants in the environment is now a major concern, with the aim of reaching a good chemical and ecological state of the littoral zone. Previous studies (Milinkovitch et al, 2015;Lacroix et al, 2015;Luna-Acosta et al, 2011;Breitwieser et al, 2016) showed the risks of chronic chemical contamination and the consequences in the bivalves Mimachlamys varia, Crassostrea gigas and Mytilus edulis in an open coastal environment. In this context, the objective of this project was to assess the impacts of pollution (heavy metals) on the macrofauna of a semi-closed environment: a marina in La Rochelle (France).…”