Influence of particle size on the ecotoxicity of low-density polyethylene microplastics, with and without adsorbed benzo-a-pyrene, in the clam Scrobicularia plana

• Autor(a) principal: Rodrigues, Ana Rita Pereira
• Data de Publicação: 2019
• Tipo de documento: Dissertação
• Idioma: eng
• Título da fonte: Repositório Científico de Acesso Aberto de Portugal (Repositórios Cientìficos)
• Texto Completo: http://hdl.handle.net/10400.1/13900
• topic: Microplástico; Benzo-a pireno; Scrobicularia plana; Dieta mediterrânica; Domínio/Área Científica::Ciências Naturais::Outras Ciências Naturais

Plastic was introduced massively into the world on the beginning of the 1950’s and has accumulated in terrestrial and marine environments since then. Its world-wide production almost reached 350 million tons in 2017. MPs became bioavailable to predatory filter feeding organisms and others at higher trophic levels. This study investigated the ecotoxicological effects in the gills and digestive gland of the clam Scrobicularia plana, exposed to different sizes of low density polyethylene (LDPE) microplastics with and without adsorbed benzo-a-pyrene (BaP), to evaluate the potential effect of different sizes on microplastics accumulation and of microplastics as a source of chemical contamination once ingested. S. plana was exposed to 1 mgL-1 of two different sizes of microplastics, 4-6μm and 20-25 μm, with and without BaP (at environmentally relevant concentrations) for 14 days. To determine the ecotoxicological effects a set of biomarkers were analysed: oxidative stress including the quantification of antioxidant enzymes activities (superoxide dismutase - SOD and catalase - CAT) and biotransformation enzyme activity (glutathione-S-transferases - GST), oxidative damage (lipid peroxidation - LPO), and neurotoxicity (acetylcholinesterase - AChE). The condition index was evaluated to assess the overall health status of the organism. To have a better impact perspective of these contaminants in this bivalve species an integrated biomarker response index (IBR) and a Health Index was applied. All sizes of microplastics were significantly accumulated in MPs exposed clams when compared to control and pre-exposure. In relation to antioxidant enzyme activities, SOD was noted a higher response in the gills for the bigger size of LDPE + BaP MPs. CAT activity is lower in the gills showing a decrease for smaller and bigger + BaP MPs. GST had a significant increase for the bigger size with BaP only on the 7th day. No significant differences either with size or time of exposure for the digestive gland. Oxidative damage was higher in the digestive gland for smaller virgin LDPE MPs with and without BaP. Neurotoxicity showed no inhibition responses during exposure time. Biomarkers alterations are apparently more related to the smaller size in gills and related to the virgin LDPE MPs in the digestive gland according to IBR results. As a final step a health index was performed demonstrating that the digestive gland was more affected by these microplastics.