Long-term Dynamics of Underwater Landscapesof the Coastal Zone Cape Kosa Severnaya - Cape Tolsty (Sevastopol)
Data on the long-term dynamics of underwater landscapes of the coastal zone at Cape Kosa Severnaya-Cape Tolsty are given for the first time for the period from 1964 to 2017. Landscape maps of the water area are made on the basis of landscape and hydrobotanical studies. The distribution of bottom natural complexes with key Black Sea phytocenoses is shown. It is found that the spatial distribution of underwater landscapes and the qualitative and quantitative indicators of their vegetation component have changed over a period of more than 50 years. It is probably due to both natural factors and increased anthropogenic activity. The bottom natural complexes of the boulder benches and upper shoreface formed by psephitic sediments with dominance of Ericaria crinita and Gongolaria barbata typical of depths of 0.5-5 m have changed the least. These changes concerned only the configuration of their boundaries and the depth of their distribution. Changes were noted in the vegetation component: macrophytobenthos biomass values increased, a high proportion of phytocenosis edificators was identified, epiphytes made a significant contribution, and macrophytes appeared that prefer areas with higher levels of marine eutrophication. The most significant transformation of the bottom natural complexes occurred at a depth of 5-15 m. It was noted that the depth of distribution of the following bottom complexes had changed: 1) that of a gently dipping accumulation plain formed by psammitic deposits with admixed shell fragments and predominated by Phyllophora crispa , and 2) that of the upper shoreface formed by psephitic deposits predominated by Gongolaria barbata with alternation of pebble and gravel deposits and broken shells, where Phyllophora crispa predominates. The vegetation component is characterized by a sharp decrease in the contribution of phytocenosis edificators, substitution of perennial macrophyte species by annual ones, and a vertical decrease of the depth of habitat of deep-water species. This is probably due to a decrease in light exposure.