Microplastic pollution in surface water of Lake Victoria.

Microplastic pollution of aquatic systems is a widely recognised environmental challenge. In this study, the occurrence, abundance, distribution and chemical nature of microplastics within the size range 0.3-4.9 mm, was assessed in the surface water of northern Lake Victoria. Lake surface transects in the sites were sampled using a floating manta net and analysed for microplastics. The various sites examined were grouped into three: Group A- sites in vicinity of fish landing and recreational beaches, and within urban or semi urban setting; Group B - sites in vicinity of only fish landing beaches within a rural community setting, and Group C - Sites in the vicinity of river inflows. Our results show occurrence of microplastics in all sites (range: 2834-329,167 particles/km or 0.02-2.19 particles/m), with the abundance highest in group A (range: 103,333-329,167 particles/km or 0.69-2.19 particles/m) and lowest in group C (range: 2834-20,840 particles/km or 0.02-0.14 particles/m). All the microplastics were secondary in nature being derived from plastic materials utilised by the community. The largest proportion (36%) of microplastic counts were of the size <1 mm which poses a threat to water quality and fisheries of the lake. Analysis of the chemical composition of microplastics indicated dominance by the low density polymers: Polyethylene and Polypropylene across the microplastic types. The occurrence of microplastics derived from degradation of large plastic debris implies that proper plastic waste management measures be implemented in the communities operating on the lake and in its vicinity, in order to safeguard the ecosystem benefits derived from the lake.