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Microplastic Abundance in the Surface Water, Clams (Corbicula fluminea) and Fish Species (Oreochromis niloticus and Coregonus kiyi) from the Gaborone Dam, Botswana
Summary
Researchers investigated microplastic contamination in water, clams, and fish from the Gaborone Dam in Botswana, finding microplastics present across all sample types. Surface water contained 36 to 76 particles per liter, with the highest concentrations near deeper areas of the dam, while fibers were the dominant type found in fish organs. The study suggests that urbanized freshwater environments in southern Africa are accumulating microplastics that are entering aquatic food webs.
Microplastics (< 5 mm) are emerging concern in the aquatic environments with the potential to cause harm to aquatic and human life. Given their small sizes, they become easily ingested by the marine biota and might be transferred to humans through food chain. It is imperative to understand their existence and distribution in freshwaters within the proximity of urbanized areas which are prone to microplastic pollution. We investigated the distribution patterns in the surface water and the quantity ingested by the clams (Corbicula fluminea) and fish species (Oreochromis niloticus and Coregonus kiyi) of the Gaborone Dam. Samples collected were subjected to wet peroxide oxidation and potassium hydroxide. The results showed abundance of microplastics in surface water, ranging from 36.0 to 76.0 particles/L while their weight varied from 760 to 1943 µg/m3. The high abundances were recorded in deep areas (S3 and S6) near the boundary wall of the dam than in shallow areas (S1 and S5). Microplastics recovered in fish species varied from 1.5 to 4.2 count per fish while in clams they varied from 2.2 to 8.0 count per site. Furthermore, microplastics recovered in the fish species and their organs were mostly fibres while film were the least. Overall, translucent and black microplastics were dominant across all samples, with majority being small-sized to medium-sized of ranges 1–2 mm, 2–3 mm and 3–4 mm. The results from this study indicate the accumulation of microplastics in the dam, thus suggesting that the dam may serve as a sink for microplastics.