Microplastics in gastro-intestinal tract of estuarine fish from the mangrove ecosystem of Indian Sundarbans

Mangrove ecosystems all around the globe are affected by microplastic (MPs) pollution. The Sundarban Biosphere reserve, the world’s largest mangrove forest is not an exception. The study aims to identify the occurrence of MPs in the gastro-intestinal tract (GI tract) of estuarine fish from Indian Sundarbans and the relationship between the presence of MPs with the morphology and feeding niche of fish. Total of 13 fish species were collected from the Saptamukhi River near Lothian Island, India and MPs were isolated from GI tract contents. Morphological parameters like body size, mouth aperture length, eyeball diameter and GI tract length of fish were measured. Niche breadths and niche overlapping of these 13 species were analyzed using Levin niche breadth and Pianka niche-overlap indices. The fiber-shaped MPs were ubiquitously detected in all fish species followed by films and fragments. The size of MPs was ranged from 100µm to <5mm. A significant variation (p<0.0001) in respect of the trophic morphology of fish and length of MPs (p<0.05) were found. The length of MPs had a positive correlation with body size and mouth aperture but in the case of GI tract length and eyeball diameter, the correlation was negative. It was noticed that the presences of MPs in GI tract of those 13 estuarine fish species did not bother their niche breadth and niche overlap.