AbstractThe species composition of diatoms and cyanobacteria of the periphyton of experimental synthetic polymer materials, which are anthropogenic waste products and damage marine coastal ecosystems, are presented for the first time. A vertical collector with polymer material samples was exposed in Karantinnaya Bay (the Black Sea) at a depth of 1 to 12 m from August 4 to September 18, 2018. A total of 94 taxa of Bacillariophyta (67) and Cyanobacteria (27) have been found. Two diatom and 15 cyanobacteria species have been detected in the Crimean coastal waters of the Black Sea for the first time. Benthic species are predominant, of which 74% are marine; two major groups are constituted by cosmopolites (58%) and arctic–boreal–tropical species (37%). In total, 32 species–indicators of saprobity are identified; among them, 21% are beta-mesosaprobiont diatoms living in the conditions of moderate organic pollution. The largest number of diatom and cyanobacteria species are detected on the surface of mesh collectors (48/19) and containers (40/7). These organisms actively participate in transforming and reorganizing the architectonics of fouling on the surface of the polymer samples. Thus, it is shown that synthetic materials may obtain novel biochemical properties, which can be used in the future in different areas of science and technology (medicine, biotechnology, etc.).