Occurrence, Distribution and Ecological Risk of Microplastics in the Lagoon and Coastal Waters of Southwest Nigeria

Abstract

Microplastic pollution has emerged as a pervasive threat to aquatic ecosystems, yet baseline data
for the lagoon and coastal systems of Southwest Nigeria remain scarce. This study assessed the
occurrence, distribution and ecological risk of microplastics across six lagoon and coastal sites.
Surface water, sediment and fish gut samples were collected, treated by wet peroxide oxidation
and density separation, and characterised under microscopy with polymer confirmation by
attenuated total reflectance Fourier transform infrared spectroscopy. Microplastic abundance in
surface water ranged from 2.18 to 4.62 items per litre, with the highest concentrations recorded at
Badagry Creek and Lagos Lagoon. Fragments and fibres were the dominant morphotypes, and
polyethylene and polypropylene were the most prevalent polymers. The pollution load index
classified Lagos Lagoon and Badagry Creek as high risk, while a one way analysis of variance
confirmed significant spatial variation in abundance across sites. The findings establish an
empirical baseline for microplastic contamination in the region and underscore the need for source
directed waste management and continuous monitoring.