Toxic effects of paraffin microparticles in Mytilus spp.

• Autor(a) principal: Simões, Maria Inês Santos
• Data de Publicação: 2017
• Tipo de documento: Dissertação
• Idioma: eng
• Título da fonte: Repositório Científico de Acesso Aberto de Portugal (Repositórios Cientìficos)
• Texto Completo: http://hdl.handle.net/10773/21952
• topic: Microplásticos; Ecossistemas marinhos

Plastics are considered one of the main environmental pollutants, especially in aquatic ecosystems. Most plastics are dumped into the environment without any treatment, which contributes to their dispersion, particularly in the form of small particles or fragments (microplastics). The aquatic environment, and in particular the oceans, are the final location for the deposit of large quantities of plastics, of various particles sizes and chemical constituents. Exposure of organisms to microplastics can result in physical (blockage or damage of the digestive tract) and chemical contamination (release of toxic compounds), which can lead to deleterious consequences. The presence of microplastics in the marine environment can also occur by direct introduction in the medium, in the form of microspheres used in cosmetics. Ecotoxicological effects of microplastics have led some cosmetic producers to offer viable alternatives to plastic microspheres, such as paraffin beads. However, the viability of such alternatives requires knowledge of the toxic properties of paraffin particles when in comparison with those posed by microplastic spheres. So, the main objective of this study was to evaluate the potential toxic effects of paraffin microparticles on key physiological processes of the marine mollusc Mytilus spp.. To attain this objective, this work assessed the acute effects of three densities (5, 20 and 80 mg/l) of four size ranges of paraffin particles (100-300 μm, 300-500 μm, 400-850 μm and 800-1200 μm) on mussels exposed for 96 h with and without food. The here-quantified toxicological parameters were the activities of four enzymes involved in metabolism (Glutathione-S-transferases, GSTs), and antioxidant defense (catalase, CAT; glutathione reductase, GRed; and glutathione peroxidase, GPx). In general, smaller microparticles (100-300 μm) caused nearly no effects on the activity of the four enzymes tested. On the contrary, larger particles (800-1200 μm), caused effects on every enzymatic activity. GRed activity was the least affected by the exposure, while GSTs was the most affected parameter. The effect of particle density was mainly observed for the treatment without food supply, and this influence was more significant for the highest particle density (80 mg/l). Overall, data obtained in this work suggest that, in the densities close to those found today in the environment, it is not possible to anticipate toxic effects on redox equilibrium and biotransformation metabolism in mussels.