Hydro meteorological and tidal effects on microplastics transport in the Hooghly-Matla estuarine complex, Sundarbans

Abstract

As an emerging category of marine environmental pollutants, microplastics (MPs) have become a critical concern due to their severe impacts on hydro biotic ecosystems and population health. The study investigates the prevalence, properties, and distribution patterns of MPs in the Hooghly-Matla estuarine complex (HMec), considering climatic fluctuations (cyclone and non-cyclone phases), tidal current patterns (ebb and flood), and urban effects. The research recorded an average MPs abundance of 45.42 ± 22.83 items/m³, predominantly constituted of light weight polymers, polypropylene (30.27%), polyethene (23.24%), polyethene terephthalate (8.19%), and polystyrene (8.04%), with a dominance of transparent MPs (33.61%). Climatic analysis reflected substantially higher MPs magnitude during cyclone phase (71.87 ± 26.80 items/m³), compared to non-cyclone phase (57.83 ± 33.98 items/m³), with an average concentration of approximately 24.3% higher during cyclone phase. The tidal regime also affected MPs’ spatial distribution and sedimentation, with the ebb tide showing higher concentrations (41.55 ± 32.21 items/m³) than the flood tide (36.48 ± 22.25 items/m³). Furthermore, the MPs abundance showed a very weak negative correlation (Spearman’s rank correlation coefficient, $\rho$= −0.135) with the distance from the urban centres of the sampling stations, indicating spatially dispersed stations due to the complex geography of the HMec and reflecting the effect of local anthropogenic processes rather than distance. The study recommended aggregating broad-spectrum sampling approaches and incorporating environmental factors into MPs assessments, establishing a framework to strengthen understanding of MPs dispersion and the distribution patterns in the estuarine ecological systems, contributing to SDG 6 and SDG 14.