Occurrence and Distribution of Microplastics in the Northern Bay of Bengal: A Case Study on the Coast of Sonadia Island

Abstract Microplastic (MP) pollution has become a significant global environmental issue due to its persistence and ecological risks across terrestrial and marine ecosystems. While MPs have been extensively documented in beaches, rivers, and deep-sea sediments, research on island ecosystems, particularly in the Northern Bay of Bengal, remains limited. This study examines the occurrence, distribution, and ecological risk of MPs in Sonadia Island's beach sand, addressing a critical knowledge gap. Beach sand samples were collected from five high-tideline stations on Sonadia Island, with MPs isolated via density separation, filtration, and stereomicroscopic analysis. The mean concentration of possible microplastics (PMPs) was 17.68 ± 7.88 particles/kg, lower than many global beaches but still significant. Fibres were dominant (74%), followed by fragments (18%), films (7%), and foams (1%), with 52% of MPs sized 0.3–1 mm. Transparent particles were most abundant (72%), though colored MPs (red, blue, green, black, and white) were present. Elevated fibre proportions suggest origins from fishing gear and industrial discharge. Contamination Factor (CF) and Pollution Load Index (PLI) values >1 confirmed moderate to considerable pollution. This study provides baseline MP data, revealing moderate contamination dominated by fibres, necessitating improved waste management in fisheries and industries. Recommended mitigation measures include stricter regulations, community clean-ups, and sustained monitoring to reduce ecological risks