Microplastic ingestion and egestion by copepods in the Black Sea

Ingestion and egestion of microplastics by copepods in the Black Sea was assessed for the first time. Composition and concentration of microplastics in the water column was also evaluated. Samples were collected from three stations (river mouth, coastal and open water) in the Southeastern Black Sea over the course of one year. Microplastic concentration in the water column ranged between 0.12 and 7.62 mp·m^-3 (mean 2.04 ± 1.05 mp·m^-3) with significantly higher concentrations in the river mouth. The most common types of microplastics were fibres, followed by films and fragments. A total of 11 colours of microplastics were found, being blue the most common colour. Analysis of 1126 C. euxinus and 1065 A. clausi, resulted in 26 and 9 microplastics being detected, respectively. This resulted in a microplastic ingestion of 0.024 ± 0.020 mp. Calanus^-1 and 0.008 ± 0.006 mp. Acartia^-1. Analysis of 351 faecal pellets, resulted 4 microplastics being found. The average size of ingested microplastics was greater in C. euxinus (0.100 mm ± 0.153 mm) than in A. clausi (0.062 mm ± 0.056 mm). Size of ingested microplastics was in the size range of natural preys of these copepods. Fragments were the most common type of ingested microplastics, followed by films and fibres. The colour of ingested particles was black, blue and red. Our results show that the copepods and the pelagic environment of the Black Sea are contaminated by microplastics. Critical functions of zooplankton in this degraded ecosystem are under risk and zooplankton are likely to act as a vector for the transfer of microplastics and associated toxic chemicals to upper trophic levels including humans in the Black Sea.