Species assemblages and spatial organization of phytoperiphyton on the surface of nylon halyards in the Eastern Caspian (Aktau Region, Kazakhstan)

Any objects in natural water bodies are gradually colonized by hydrobionts such as algae and microorganisms. This is how phytoperiphyton is formed. In recent decades, more and more plastic objects have ended up in seas and lakes. They are substrates potentially suitable for colonization by aquatic biota. In the coastal Kazakhstan part of the Caspian Sea, no studies have yet been carried out on the microfouling of artificial polymer substrates. At the same time, as our observations have shown, such fouling can form extensive, clearly visible phenomena on a macroscopic scale. In 2023-2024, we conducted studies of phytoperiphyton foulings on nylon halyards anchored at rocky bottom at a depth of 15 m, at two different locations at distances at least 2 nautical miles from the shore. The 8 mm diameter halyards were stretched from anchors on the bottom to floating buoys at the sea surface, where floating buoys were suspended from them. These two halyards originally served to hold instruments deployed to measure coastal currents (Zavialov et al., 2024). In the first deployment, the halyards were exposed for 8 months (September 2023 - April 2024), in the second one - 4 months (June 2024 - September 2024). In both cases, multi-species phytoperiphyton was formed, whose specific features of composition and spatial organization are described in detail in this article.