In this study we used scanning electron microscopy to characterize microbial biofilm communities on the surface of plastics commonly used in daily life and fisheries, namely polyethylene (PE), polypropylene (PP), polyethylene terephthalate (PET), polystyrene (PS), polyamide (PA, nylon) and polyvinylchloride (PVC). For this purpose, we submerged the plastic items in a coastal station in the southeastern Black Sea during five months (February-June 2019) and recorded the evolution of microbial biofilm formation. Diverse microbial communities formed on plastics surface within a month. Diatoms were the most diverse and abundant group of the plastic colonizers represented by 18 genera. Bacteria were also abundant and a diverse group on plastic surface. Dinoflagellates, ciliates, choanoflagellates, auxospores and unidentified organism were also observed. After microbial formation we also observed invertebrate assemblages on plastic. Our experimental results confirm the current concern that plastic is a new pelagic substrate for microorganisms and invertebrates in the Black Sea and that these communities may play an important role in plastic degradation and represent a novel compartment of the ecosystem.