Distribution of microplastics and plastisphere communities in the Southeast Black Sea

The distribution, composition and possible sources of microplastics in surface waters were investigated simultaneously with microbial plastisphere communities in the Southeast Black Sea, for the first time. Samples were collected seasonally between July 2019 and June 2020 from the mouth and coastal areas of Sinop Karasu, Samsun Kızılırmak, Yeşilırmak, Ordu Melet, Giresun Aksu, Trabzon Değirmendere and Rize Fırtına rivers. In addition, the formation, diversity, biomass and preferences of microbial plastisphere communities in single used plastics objects including personal protection equipment, which are frequently used during the COVID 19 pandemic, were evaluated by an in situ experimental design. Microplastics were collected from surface waters by manta trawling. Polymers of common microplastics were determined by FTIR, and their surface morphologies and microbial plastisphere communities were visualized by SEM. Microplastic concentration varied between 1,2-132,1 items.m-3 (12,9±22,4 items.m-3) in surface waters. Microplastics were mostly fragments in shape, transparent in colour, 1-2 mm in size, PP and PE in polymers. There was a significant difference between stations in terms of microplastic concentration (F(13, 42)=2,695, P=0,044). A total of 42 species were identified on floating plastisphere communities. A total of 114 species were identified on 10 plastic objects belonging to 6 polymers namely PE, PP, PET, PP+PE, PP+PA and PAN. Among these species, 13 species are reported for the first time from the Turkish coast of the Black Sea, 7 from the Turkish coastal waters and 34 from the plastisphere communities. Additionally, 4 harmful/potentially harmful microalgae species and 1 invasive species were found in the plastisphere. The highest species diversity in the plastisphere was observed in HDPE shopping bag, and the highest biofilm biomass was observed in the PET bottle. Study results show that surface waters in the southeastern Black Sea are contaminated with microplastics. It also reveals the role of plastics as a vector on the transfering invasive/pathogenic/harmful species in the Black Sea.