Seasonal variation of meso- and micro-plastics in water and sediments of coastal communities in Ondo State, Nigeria

Plastic particles (both meso- and micro-plastics) are ubiquitous in the aquatic environment. They exert profound effects on organisms and may potentially enter the human food chain. Seasonal changes in abundance and types of plastic particles are poorly understood. In this study, plastic particles were determined in five communities along the Atlantic coast of Ondo State, Nigeria. A total of fifty (50) composite water and sediment samples were collected from the communities during each of wet (rainy) and dry seasons of year 2022.The plastic particles were recovered from water samples by filtering through 0.45 μm membrane. Those in sediments were recovered by floatation with supersaturated solution of zinc chloride (ZnCl₂, density 1.5 g/cm³). Polymer identification of sizable particles was performed with attenuated total reflectance − Fourier transform infrared (ATR-FTIR) spectroscopy. The plastic particles were more in the waters during the wet season (10,503) than in the dry season (8,322). For the sediments, the particles were more in the dry season (22,824) compared to the wet season (17,481). Fibre particles were detected most frequently in both seasons. Blue coloured particles (36 %) were predominant in the water samples during the wet season, while white particles (41 %) occurred most frequently in the dry season. Nine (9) plastic polymer types were identified in the sediments, with low-density polyethylene (LDPE, at 64 %) being the dominant plastic material found. Replacement of single-use LDPE “polybags” with reusable alternatives would reduce plastic pollution in the Nigerian coastal area, which connects with the global marine environment.