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Microplastic accumulation in fish and water: a case study from a protected reservoir in a megacity
Summary
Scientists studying a protected drinking water reservoir in Istanbul found tiny plastic particles (microplastics) in both the water and the fish living there—even though this reservoir is supposed to be off-limits to pollution sources. The plastics, mostly tiny fibers, were found in the fish's gills and guts, showing that even "protected" water supplies aren't safe from plastic contamination. This matters because these same fish and water sources can end up on our plates and in our taps, meaning the plastic pollution problem may be harder to avoid than we think, even in areas with strict environmental rules.
Today, microplastics are recognized as a major group of pollutants threatening aquatic ecosystems. While drinking water reservoirs are typically subject to stringent protection-prohibiting direct waste discharge and commercial activities-their vulnerability to microplastic accumulation persists due to the high mobility, size, and low density of the particles. The primary aim of this study is to quantify the microplastic burden within an important drinking water basin in İstanbul-Türkiye's metropolitan city-and to evaluate the degree of accumulation in resident freshwater fish. Seasonal field surveys were conducted between November 2023 and July 2024, focusing on both the water column and three specific fish species: Atherina pontica, Neogobius melanostomus, and Gambusia holbrooki. A total of 217 microplastic particles were identified in the fish samples, with 105 localized in the gills and 112 in the gastrointestinal tract. In addition, 42 microplastic particles were detected in the surface water samples. Morphological classification revealed a clear predominance of fibers over fragments, accounting for 88.9% and 11.1% in fish samples, and 92.9% and 7.1% in water samples, respectively. Among the particles with identifiable polymer compositions, polyethylene (PE) was the dominant polymer type, representing 46.9% of the total. These findings highlight that even protected water bodies are susceptible to microplastic pollution, with significant bioaccumulation occurring in the local ichthyofauna.