Composition and structure of macrophytobenthos at the coast of the natural monument “Kuchuk-Lambat Stone Chaos” (Crimea, Black Sea)
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Abstract
The Southern Coast of Crimea (SCC) is characterized by a high level of anthropogenic transformation, so the areas preserved in a natural or quasi-natural state have a special nature conservation value. These include the territorial-aquatic complex that unites the geological natural monument “Kuchuk-Lambat Stone Chaos” and the adjacent coastal water area of the Black Sea. The water area has never been studied from the hydrobotanical point of view and is not included in any nature-protected areas. Considering this, the research was carried using 2015 and 2022 data out with the aim of characterizing the species composition, biomass and spatial structure of macrophytobenthos to clarify the data about the distribution and dynamics of the benthic vegetation cover near the SCC and in connection with the prospect for conservation of this water area. It was found that macroscopic vegetation develops on hard and soft substrata, which determines its general nature. In total, 63 species of macrophytes were recorded: Chlorophyta – 14 (22.2%), Ochrophyta – 9 (14.3%), Rhodophyta – 39 (62.0%), Tracheophyta – 1 (1.6%). The total number of species (NS) and the ratio of systematic groups by NS in both years are similar. However, the composition of the flora and the biomass (BM) ratio of dominant species and ecological-floristic groups changed significantly at minimum and maximum depths, which determined the transformation of the vegetation cover. In shallow water, the dynamics, caused by local disturbance and subsequent recovery of macrophytobenthos after the mudflow, have a fluctuating character. At depth, the changes are caused by the invasion of the transformer species Bonnemaisonia hamifera into natural communities. These changes probably have a long-term character, and in order to reveal their degree and reversibility, it is necessary to monitor the spread of the invasive species near the SCC and within the boundaries of the Azov-Black Sea region as a whole. Currently, macrophytes along the surveyed shore form five belt-like communities with BM 0.2–6.0 kg•m-2 and NS 14–27 pcs. The extreme values of these indicators are registered in the sublittoral: maximum values – on hard substrata in the upper and central parts of the Cystoseira belt (Cystoseira s.l. species), minimum values – on soft substrata in the deepest seagrass community (Nanozostera noltei). In general, perennial macrophytes dominate in the BM and short-vegetating macrophytes in the NS; phytobenthos has a pronounced oligosaprobic marine warm-water character. The vegetation cover of the water area demonstrates a high degree of preservation; its spatial distribution, composition and structure (except for changes caused by biological invasion) are typical for the hydrobotanical region of the Black Sea “SCC”. The rare species fraction of the flora includes 12 taxa; biotopes, formed by macrophyte communities, are included in Directive 92/43/EEC. It is expedient to create a complex territorial-aquatic nature reservation, which will unite the existing natural monument and the adjacent water area.