Microplastic Contamination in Indian Mackerel (Rastrelliger kanagurta) and Finletted Mackerel (Megalaspis cordyla): Exploring Occurrence and Variability in Skin and Gill Tissues

Abstract

Two marine fish species: Indian mackerel (Rastrelliger kanagurta) and finletted mackerel (Megalaspis cordyla), were collected from a local fish market near Thiruvalla in Pathanamthitta district, Kerala. Various types of microplastics (such as films, fibres, fragments, and lines) were identified using visual analysis conducted with the aid of light microscopy. This study unveiled a concentration (23%) of microplastics in gill tissues (Rastrelliger kanagurta) when compared to the skin (30%) In fish Rastrelliger kanagurta), indicating different pathways of uptake. Megalaspis cordyla had a greater percentage of microplastics in the skin (25%) than in the gills (22%); also indicating different pathways. There was an abundance of microplastics in the form of film at (25%) than in flake, granules, foam, fibre etc. which all stood at 10%, 10%, 10% and 20% abundance, respectively. Notably, Indian mackerels were found to harbour a more significant microplastic load than finletted mackerels, highlighting the existence of inter-species variations in contamination levels. To confirm the presence of polymers, the identified microplastics underwent Fourier-transform infrared (FTIR) spectroscopy analysis, a method that verified the molecular composition of micro plastics by analysing their infrared absorption spectra. Overall, these findings shed light on the prevalence of microplastic pollution in aquatic ecosystems and underscore the necessity for comprehensive strategies to mitigate its far-reaching repercussions.