Microplastics in the environment and in commercially significant fishes of mud banks, an ephemeral ecosystem formed along the southwest coast of India.

Microplastic pollution and the impacts they generate on the marine ecosystem and its biota is a major global concern of recent decades. The present study was conducted to evaluate the spatio-temporal distribution of microplastics in the surface waters, sediments, and their subsequent ingestion by the commercially important fishes of Alappuzha Mud banks, a transient ecosystem formed in the littoral zones of the southwest coast of India exclusively during the Indian summer monsoon. Sampling conducted over three periods, Pre-mud bank (Pre-MB), Mud bank (MB), and Post mud bank (Post-MB) extending over three depths (2 m, 5 m and 18 m), along the semi-circular patch of mudbanks revealed marked spatio-temporal variability in microplastic distribution. In both surface water and sediments, microplastic concentration was comparatively high during MB than in Pre-MB and Post-MB periods. Spatially, during MB, the microplastic concentration was high at 5 m where the dampening of waves occurred concomitant to the thick fluid mud formation. In contrast, during Post-MB, with the subsequent dissipation of MB's and less wave dampening, the microplastics aggregated at 5 m were transported to both inshore (2 m) and offshore (18 m), thus raising their concentration at these depths. Likewise, the microplastic ingestion was more in fishes caught during MB (41%) than Post-MB (30%) and Pre-MB (29%) periods indicating increased uptake corresponding to the higher incidences in their ambient environment. Microplastic ingestion was more among pelagic planktivores, S. gibbosa (38%), A. chacunda (20%) and R. kanagurta (13%) compared to the demersal fishes. White coloured fragments of size 1-5 mm of polypropylene were the dominant microplastic in the surface waters, sediment and fishes analysed. The present study indicates the critical role of wind speed, rainfall, wave patterns, and the fluid muddy environment in regulating the microplastics distribution in a transient ecosystem formed along the southwest coast of India.

An assessment of microplastics in the ecosystem and selected commercially important fishes off Kochi, south eastern Arabian Sea, India.

A preliminary report on the abundance of microplastic in the coastal waters in the depth zone 5 to 20 m in the surface waters, sediment and in selected fishes occurring off Kochi, India is presented. Spatial and temporal variation in microplastic abundance was observed with higher abundance in surface water indicating threats to pelagic ecosystem. The relative concentration of microplastic was highest during monsoon season. The major microplastics were fragments of 1-5 mm in white and blue colours. Gut content analysis of 16 species (653 individuals) comprising pelagic (8 species) and demersal (8 species) indicated occurrence (4.6%) of microplastics (fragment>filament>pellet) of size 0.27mm to 3.2 mm in Sardinella longiceps, S. gibbosa, Stolephorus indicus Rastrelliger kanagurta and Cyanoglossus macrostomus. Raman spectroscopy indicated that Polyethylene (PE) and Polypropylene (PP) were the polymer types of microplastics from the fish gut.