Microphytes assemblages on the neustoplastics from the north Black Sea

Drifted plastics (or so-called neustoplastics) is considered to be colonized by marine organisms that could use the polymers as a substrate, participate in their decomposition, and form unusual biological communities that adapt to severe conditions of the environment in the near-surface layer of water. In this study, we initiated the research of microphytes that may dwell on the plastics on the water surface in the northern part of the Black Sea coastal waters. Two types of neustoplastics were analyzed: polyethylene film (PE-film) with microphytes fouling that was occasionally sampled and polyethylene terephthalate bottle (PET-bottle) that has been exposed to fouling for about six weeks. The microphytes forming fouling on PE-film was represented with 14 taxa of cyanobacteria and 8 species of Bacillariophyta. The most numerous genera were Сalothrix and Mastogloia. Strict hierarchy of the assemblage was noticed, the first layer of microalgae that was located directly on the surface of the PE-film was presented mostly by Mastogloia species that formed capsules (the most abundant M. lanceolata) and three species of Calothrix with short trichomes. C. scopulorum and C. рarietina formed upper layer of the assemblage protecting the microphytes from the aggressive environment. On the surface of PET-bottle assemblage was formed by mosaic scattered spots with different spatial organization. The upper layer was again formed by cyanobacteria Leptolyngbya foveolarum and colonies of the diatom Neosynedra provincialis. Other 10 species of diatoms, 1 dinoflagellate and 7 cyanobacteria were presented in the assemblage. The architecture of both studied assemblages represented the existence of specific adaptations of microphytes that dwell on polymer substrates near the water surface. The assemblage on the PET-bottle was more diverse and with more complicated hierarchical structure.