Abstract
The coastal zone of the Middle Caspian is currently undergoing significant changes due to falling sea levels. With shallowing, the nature of the influence of water flows on bottom landscapes changes, including the intensification of the impact of storm waves on their surfaces inhabited by bottom communities. The impact of rolling and storm waves on bottom algae is also increasing. Cenoses of bottom macrophyte algae, which was previously growing on underwater rocks, including flat rock platforms, which abound along the eastern coast of the Middle Caspian, at depths of 10-12 m, were previously affected only by particularly strong storm waves. Now their habitats are at a significantly shallower depth (about 7.5-9.5 m), which led to more frequent and massive detachments of macrophyte thalli and their transfer to the pelagic zone. Mass transfer of living thalli of green and red algae to the upper layers of the water column during different seasons of the year led to the formation of communities of a new type, differently structuring the surface layer of the phytopelagic zone. New cenoses are a set of metamorphosed thalli of filamentous algae with a microepiphytic complex abundantly growing on them, live in the surface layer of water for a long time, serve as food for pelagic fish and have a significant impact on coastal landscapes. Mass development of macrophytes on the bottom, and their further intensive development in the pelagic zone, in turn, can be caused by increased eutrophication of the coastal zone in areas of large settlements.