Microplastics, microfibres and nanoplastics cause variable sub-lethal responses in mussels (Mytilus spp.)

Area of Science:

• Environmental Toxicology
• Marine Biology
• Ecotoxicology

Background:

• Microplastics, microfibers, and nanoplastics are emerging environmental contaminants.
• Understanding the differential toxicity of various plastic particulate sizes is crucial for ecological risk assessment.

Purpose of the Study:

• To compare the toxicological effects of microplastics, microfibers, and nanoplastics on the marine bivalve Mytilus spp.
• To investigate the influence of particle size on the accumulation and biological responses in mussels.

Main Methods:

• Mussels were exposed to polystyrene microplastics (20 μm), polyamide microfibers (10 × 30 μm), and polystyrene nanoplastics (50 nm) at 500 ng/mL for 24 hours and 7 days.
• Biomarkers for immune response, oxidative stress, lysosomal stability, and genotoxicity were analyzed in hemolymph, digestive gland, and gills.
• Statistical analysis (ANOVA) was used to determine significant differences in responses.

Main Results:

• Microplastics and microfibers accumulated in mussel digestive glands, with higher concentrations after 7-day exposure.
• Nanoplastics significantly altered hyalinocyte-granulocyte ratios, indicating an immune response.
• Superoxide dismutase (SOD) activity increased after 24-hour exposure but normalized by 7 days.
• No lysosomal destabilization or genotoxic damage was observed for any plastic type.

Conclusions:

• Plastic particle size is a critical determinant of toxicity in mussels.
• Nanoplastics elicit an immune response, whereas microplastics and microfibers primarily accumulate in tissues.
• Mussels exhibit resilience to lysosomal and genotoxic damage from these plastic types under the tested conditions.