Diatoms on the PET plastic surfaces near Zmiiniy Island (The Black Sea, Ukraine)

In recent years, there has been an increasing interest in “plastisphere” studies and microalgal communities on plastic surfaces. Diatoms and cyanobacteria are among the primary colonizers of plastics and can affect their decomposition and degradation to smaller fragments. The present study is focused on the species composition of diatoms on polyethylene-terephthalate (PET) surfaces in the Zmiiniy Island area (Northwestern Black Sea, Ukraine) that were exposed in 2018–2020 at a depth of 9 m in the water column. Based on light and scanning electron microscopy, a total of 80 species of diatoms were identified, most of which were common and 12 species rare for the Northwestern Black Sea region and 1 variety new to the Black Sea region. The genus spectrum included 46 genera, among which the most species-rich representatives were: Cocconeis Ehrenb. (6 species), Nitzschia Hassall (6), Navicula Ehrenb. (6), Diploneis Ehrenb. Ex Cleve (4), Halamphora (Cleve) Mereschk. (3), Parlibellus E.J.Cox (3). Two or single species represented other genera. The most common species that were detected in most PET samples included: Cocconeis pseudocostata, Cocconeis scutellum, Cocconeis neothumensis var. marina, Halamphora coffeiformis,
Nitzschia sp., Pseudofallacia tenera and Tabularia tabulata. The comparison of our data with previous floristic data on species composition of diatoms from plankton and benthos revealed 41 species that were not recorded near Zmiinyi Island earlier. This may be due to the fact that plastic may serve as a trap for algal species, raising the chance of rare species detection.