Spatiotemporal variations of microplastics in the surface sediments of a tropical mangrove ecosystem in south-western India

Mangroves are crucial ecosystems that play a role in carbon sequestration, shoreline fortification, and provide habitats for diverse species. In developing nations like India, there is a need for more knowledge on the occurrence and distribution of MPs in mangrove forests under changing seasons. Our investigation aimed to fulfil this research gap by studying the seasonal patterns of microplastic distribution within the sediments of the Kota mangroves in south-western India. The mean (± standard deviation) microplastic abundance was 1418.52 (±1404.34) MPs/kg during the wet season and 1414.32 (±1368.65) MPs/kg during the dry season. A consistent pattern in microplastic categories was observed, with fibres being the predominant shape followed by film, fragment, and foam. Microplastics of size 0.1–0.3mm were dominant in all seasons. Fourier Transformed Infrared Spectroscopy (FTIR-ATR) and Raman Spectroscopy analyses revealed the presence of polypropylene, polyethylene, polyethylene terephthalate, and polystyrene. Energy Dispersive Spectroscopy between control and extracted samples revealed adsorption of Cd, Zn, Pb, Fe, and Ni onto the extracted microplastics. The primary contributors to the MP pollution were attributed to fishing related activities, fish meal processing industry, tourism, and local households. This study established a baseline information on the seasonal dynamics governing the distribution of microplastics in sediment of Kota mangroves.