Microplastic contamination in Ashtamudi short neck clam Marcia recens and its implications for ecosystem and human health

The escalating concern about microplastics (MPs) stems from their pervasive presence in the environment and potential impacts on human health, wildlife, and ecosystems. Understanding the processes of bioavailability, bioaccumulation, and biomagnification is crucial for assessing the scope of MP pollution’s impact. Because of their wide distribution and filtering ability, bivalves make good bioindicators of MP contamination. Ashtamudi clam, short-neck or yellow-foot clam, Marcia recens (Holten, 1802), is an economically significant bivalve mollusc, a major fishery source, and a much sought-after delicacy thriving in the brackish waters of the designated Ramsar wetland, Ashtamudi Lake, Kollam, on the south-western coast of India. Given the estuary’s critical function in supporting many fishermen and acting as a key source of fisheries goods for both local and international markets, it is imperative to investigate the possibility of MP contamination of the system. Morpho-chemical characterization of MPs ingested by the Ashtamudi short-neck clam, Marcia recens, across different lake zones formed the core of this study. Wet peroxidation, density separation, and filtration techniques were used to remove MPs from the tissue, and a stereomicroscope was used to observe the filtrate. MPs, mostly blue, red, or black of a size range of 0.5-5 mm, were detected in 22.4% of the samples. Four different morphotypes of MPs were observed: fibres (47.5%), fragments (37.6%), pellets (10.8%), and film (3.9%). Attenuated Total Reflectance (ATR) with Fourier Transform Infrared (FTIR) spectroscopy (ATR-FTIR) revealed that polypropylene, polyethylene, and nylon 6,6 were the polymer types in the samples. The study reveals the ingestion of MPs, pointing to their prevalence in the lake. Since thousands of marginalised fishermen depend on these clams as a means of subsistence and many more consume them as a delicacy, the presence of MPs is a cause for alarm, as the consequences of human intake are poorly understood.