Isolation of microplastics from freshwater macroinvertebrates in the Danube River

Abstract

The study was conducted on the Danube River, within the project Joint Danube Survey 3 (JDS3). The main aim was to estimate the quantity of microplastics in aquatic ecosystems through passive biological monitoring. Three freshwater species were used for microplastic (MP) isolation from different taxonomic groups of organisms: Mollusca, Oligochaeta, and Chironomidae (Diptera), with the following species: Lithoglyphus naticoides (C. Pfeiffer, 1828), Limnodrilus hoffmeisteri (Claparede, 1862), and Chironomus acutiventris (Wülker, Ryser & Scholl, 1983), respectively. The samples were collected from 6 sites along the Danube River where 540 specimens were examined. The samples were digested by alkaline method (incubation in 10% KOH solution at 60 ⁰C for 24 h) and filtered through a mill silk, 10 μm mesh size. Collected particles were categorized as: fibre, hard plastic, nylon, rubber, or miscellaneous. Categories were divided into subcategories based on the coloration of the particles. Particles ingested by organisms were represented mostly by fibres and fragmented hard plastics, within the size range were from 0.03 to 4.87 mm. A total of 678 MP particles were collected with an average of 4.64 ± 1.59; 1.64 ± 0.46 and 1.24 ± 0.34 items/organism isolated from L. hoffmeisteri, L. naticoides and C. acutiventris, respectively. According to results, L. hoffmeisteri, L. naticoides and C. acutiventris could be used as proper bioaccumulators of MP pollution in the Danube River.