Field and laboratory-based evidence of microplastic ingestion by the Asian green mussel, Perna viridis from the northern Malabar coast of India

Microplastic contamination of aquatic fauna, particularly the filter feeding bivalves, is gaining global attention. Ingestion of microplastics by the commercially important Asian green mussel, Perna viridis (Linnaeus, 1758), from a natural mussel bed situated in the northern part of Kerala (southwest coast of India) and the results of experimental ingestion studies using polystyrene microparticles are discussed. Mussel samples from the inter-tidal zones were severely contaminated by microplastics, mainly constituted by fibre/filament, thin films and beads. Polypropylene was identified as the predominant particle type by Fourier transform infrared (FT-IR) spectroscopy. To confirm the ingestion and to track the fate of microplastics in the digestive tract, organisms were fed with orange fluorescent polystyrene beads of 10 μm size along with algal feed at two different experimental concentrations. Short term impacts of exposure in controlled conditions led to abnormal feeding behavior in mussels. Substantial reduction in algal clearance rate and presence of microplastics in faeces and pseudofaeces confirmed the ingestion. Absence of significant differences in microplastic count in soft tissues post depuration implies possible retention of smaller sized particles. Therefore, ingestion experiments involving environmentally relevant concentrations followed by depuration trials, across a range of mariculture species using particles of various types and dimensions may be necessary to establish safety standards for microplastic contamination in seafood.