Impact of Fengal cyclone on spatial and seasonal variation of microplastics contamination in surface waters along the Ennore Coast, southeast coast of India

Abstract

Microplastic pollution has emerged as a major environmental concern in rapidly urbanising and industrialised ecosystems. This study investigated the spatial and seasonal distribution and ecological risk assessment of microplastics in the Ennore coastal waters of southeast India covering Thalankuppam, Kattupalli, and Ennore Beach across six sampling seasons from monsoon 2024 to post-monsoon 2026. Microplastics were isolated, followed by stereomicroscopic characterisation based on shape, colour, and size. Polymer composition was confirmed using ATR–FTIR spectroscopy, and ecological risk was assessed using the contamination factor (CF), pollution load index (PLI), polymer hazard index (PHI) and potential ecological risk index (PERI). Microplastic abundance ranged from 85 to 215 particles L–1, with the highest seasonal recorded during post-monsoon 2025 (185 particles L–1) and the lowest during summer 2025 (95 particles L–1). Spatially, Kattupalli (110–215 particles L–1) consistently recorded the highest microplastic abundance. Fragments and foam were the dominant morphotypes, while black and blue particles predominated among the colour classes. The 0.5–1 mm size fraction was the most abundant, suggesting extensive secondary fragmentation. ATR–FTIR analysis identified polyethylene (28–32%) and polypropylene (15–18%) as the dominant polymers, indicating packaging materials, fishing gear, and urban plastic waste as major sources. Risk assessment revealed moderate to considerable contamination (CF: 2.12–3.04), low pollution load (PLI: 1.46–1.78), very high polymer hazard (PHI: 5789–7293) and minor ecological risk (PERI: 57.89–72.93). These findings provide baseline information for monitoring microplastic pollution and support effective management strategies for the Ennore coastal ecosystem.