Spatial-temporal changes of macrophytobenthos in the coastal zone of the Reserve “Karan’sky” (Sevastopol City, Black Sea)

Abstract

For the first time, a comparative analysis of the specific diversity, changes in the biomass of macrophytobenthos in the reserve “Karan’sky” coastal zone from 1964 to 2016 was performed on the basis of a landscape approach. A landscape map of the underwater coastal slope has been drawn up, three bottom natural complexes (BNC) have been identified. The BNC of psephite deposits dominated by C. crinita and Tr. barbata (up to 89.7–78.6% of the total biomass of macrophytes) is the main one. This complex is characterized by high floristic diversity and maximum values of the biomass of macrophytobenthos. The BNC of psephite deposits with C. crinita and Tr. barbata to predominate and with pebble-gravel deposits with broken shells alternate, where Ph. crispa is the dominant species, is characterized by high floristic diversity and a decreased proportion of C. crinite and Tr. barbata, the contribution of Ph. crispa to the total biomass of macrophytes is 14.4%. The BNC of psammitic deposits with Ph. crispa to predominate and with separately randomly located blocks, where Nereia filiformis and Zanardinia typus predominate, is characterized by low floristic diversity, the predominance of Phyllophora crispa (74.3% of the total biomass of macrophytes), and the preservation of perennial species. For more than 50 years, there was a reorganization and degradation of the plant component in all BNC (depth 0.5–10 m), which was probably due to the intensification of anthropogenic activity in the coastal zone. Eudesme virescens, Dictyota dichotoma, Feldmania irrgularis, Dasya baillouviana and Rhodochorton purpureum, which live in clean, open areas of the coast, have disappeared from the bottom vegetation, and macrophytes (Cladophora laetevirens, Ectocarpus siliculosus and C. virgatum), typical for eutrophic waters, have appeared in the duodenum. The biomass of epiphytes has increased (from 0.1 to 42.6% of the total biomass of macrophytes), and the role of dominant species has decreased: C. crinita, Tr. barbata (from 99.9 to 78.6%) and Ph. crispa (from 52.9 to 14.4% of the total biomass of macrophytes). The organization of the “Karan’sky” Reserve contributed to the preservation and partial restoration of the unique natural complex of marine flora and bottom vegetation, which is confirmed by the increased floristic diversity of algaeindicators of clean waters and the increased proportion of the Red Data Book species.