Abstract <p>The relationships between the characteristics of chemical pollution of brown, green, and red macroalgae and organic pollution of the nutrient medium with the transformation of the composition of phytocenoses and morphological characteristics of macrophytes in the coastal zone of the Black Sea coast of Russia near the mouth of the Sochi River (in the valley of which the center of an urban agglomeration of the same name is located) have been established. According to the level of accumulation of chemical elements, macrophyte algae are arranged as follows: brown perennial (<i>Ericaria crinita</i>) &gt; green annual (<i>Cladophora laetevirens</i>) &gt; green annual (<i>Codium fragile</i>) &gt; red annual (<i>Ceramium virgatum</i>). The growth of chemical (mineral) and organic pollution of the ecosystem causes a stable decrease in the following biological parameters of macrophytes: the proportion of the total number and total biomass of the dominant species in the phytocenosis and the total biomass of the wet weight of algae.</p>