Tributaries as reservoirs and vectors of Microplastic pollution within a fluvial network: ecological implications for the Morača river basin

Microplastic (MP) pollution in aquatic ecosystems has become a significant environmental concern worldwide. This study investigates the presence of MP in the main tributaries of the Morača river (Sitnica, Ribnica and Cijevna), the largest river flowing through the capital of Montenegro, aiming to enhance understanding of the presence, distribution, sources, and transport of MP in the Morača river basin. The present study will be covering the entire Morača river basin, yielding crucial data on MP contamination. The MP concentration in the studied rivers varied between mean values of 28.3 ± 12.2 MP/100 g dry sediment for the Sitnica, 24.9 ± 8.1 MP/100 g dry sediment for the Ribnica, and 27.3 ± 14.1 MP/100 g dry sediment for the Cijevna. The identified MPs were mainly fragments and fibers of blue, clear and red color, 0.5-1 mm in size and mainly composed of PE and PP. The results of the pollution load index indicate that the ecological status of the Morača river basin is subject to slight MP contamination, whereas the polymer hazard index results reveal a pronounced potential for adverse ecological effects. The main contribution of this study is a new insight into MP concentration in rivers and its tributaries, where the tributaries were identified as a potential important source of MP on the Morača river. This study represents a significant step towards a comprehensive understanding of the presence, distribution, sources and transport of MP pollution in the entire Morača river basin in Montenegro. The findings of this study will contribute to the growing body of knowledge about MP pollution in freshwater ecosystems, informing future research and the development of effective mitigation strategies to protect the ecological health and biodiversity of the basins.