Size-selective microplastic uptake by freshwater organisms: Fish, mussel, and zooplankton

Microplastics, as an emergent pollutant, have garnered substantial attention within aquatic environments, yet a significant knowledge gap persists regarding the interplay of organism size and pollution impacts on microplastic uptake in freshwater ecosystems. The main aim of the current study is to assess the microplastic ingestion by aquatic organisms across diverse trophic levels. To achieve this objective, zooplankton, mussels (Anodonta anatina), and fish (Carassius gibelio) were collected from the highly polluted Susurluk River Basin in Türkiye. The size distribution encompassed 160.8 ± 56.9 μm for the prevailing zooplankton, 6.9 ± 2.2 cm for mussel, and 20.4 ± 3.1 cm for fish, respectively. While no microplastic ingestion was observed among zooplankton, the finding highlights the influence of body-size and pollution on microplastic ingestion. In contrast, A. anatina and C. gibelio contained 617 and 792 microplastic particles, respectively. Predominantly, fibers emerged as the most prevalent microplastic type across trophic levels (except zooplankton) followed by films. Notably, only fish exhibited fragments within their gastrointestinal tract. A substantial correlation emerged between microplastic abundance and mussel size and weight, but no such correlation manifested for fish. The study also revealed a positive link between microplastic count and turbidity (phosphate and high Chl a level), impacting mussel ingestion capacity due to the variability in the food availability and potential shifts in feeding preferences. Conversely, no distinct pattern emerged for fish concerning water quality parameters and ingested microplastics. Consequently, our study underscores diverse microplastic uptake patterns in freshwater ecosystems, with a predominant frequency of microplastics falling with the 0.3 mm-3.0 mm range, emphasizing the significance of size-selective uptake by organisms.