Microlitter measurement in fish Rutilus rutilus from the Slovenian part of the Mura river basin

Knowledge of the impacts of microlitter pollution on the freshwater environment is still less researched when compared to that of marine environments despite rivers being the main pathway for transport of microlitter pollution to the seas and oceans. To better understand the state of pollution with microplastics in Slovenian freshwater fish, we did the first study of microlitter in freshwater fish, in which 50 specimens of common roach (Rutilus rutilus) caught in the Slovenian part of the Mura river basin were examined for its presence. The gastrointestinal tract was dissected from each specimen and degraded with 10% KOH. Filtered samples were then checked for microlitter using a stereomicroscope and ATR-FTIR spectroscopy. Microlitter was separated into microplastic particles (0.3 – 5 mm) and textile fibres, which can be of synthetic or seminatural origin. Microlitter was found in 94% of specimens, with an average concentration of 5 ± 3 items/specimen. Colourful fragments and textile fibres were found. Fibres were the predominant form (96%) and indicated households as the main source of microlitter in the Mura river. A strong positive correlation between the number of microlitter and the weight of the fish was found (R2 = 0.70). In the future, simultaneous monitoring of microlitter in sediments, water, and fish would be necessary to assess whether Rutilus rutilus is an appropriate species for biomonitoring. Given the growing evidence of the negative effects of microlitter on organisms, it will be important to carry out biomonitoring in terms of assessing environmental status and conditions for human health.