Investigation of Microplastic Contamination in Shellfish Harvested from the Cross River Estuary, Cross River State

This study investigates the presence and characterisation of microplastics in shellfish harvested from the Cross River Estuary in Cross River State, South South Nigeria. Shellfish are filter feeders that concentrate microplastic particles from the surrounding water column, making them useful bioindicators of aquatic microplastic pollution and raising direct human health concerns where they form part of the local diet. Oyster, periwinkle, and clam samples were collected from seven harvesting sites distributed along the estuary between Calabar and the mangrove delta fringe. After wet peroxide oxidation to remove organic tissue, the extracted matrices were filtered and examined under a stereomicroscope. Microplastic particles were identified by morphology, colour, and Fourier transform infrared spectroscopy polymer type confirmation for a subset of particles. Microplastic abundances ranged from 3.2 to 11.8 particles per gram wet weight of tissue across all shellfish species and sites, with highest counts near urban riverbank areas. Fibres constitute 61 percent of identified particles, consistent with washing of synthetic textiles as a primary source. Polyethylene and polypropylene are the most frequently identified polymers. Sites near the Calabar urban waterfront show significantly higher contamination than estuarine sites distant from urban areas. The study raises food safety concerns given high per capita shellfish consumption in the region. Recommendations include source reduction interventions targeting urban plastic waste management and further dietary exposure assessment studies. Keywords: microplastics, shellfish contamination, estuary, Cross River, food safety.