LONG-TERM CHANGES OF MACROPHYTOBENTHOS OF "SUDZHUK LAGOON" NATURAL MONUMENT (BLACK SEA)
The Sudzhuk Lagoon, including Sudzhuk Spit and the adjacent territory, is a unique natural complex of the northeastern part of the Black Sea, that has been studied throughout the last century. In accordance with the environmental importance of lagoon ecosystems, the «Sudzhuk Lagoon» Natural Monument of regional significance was created in 1983, which was included within the network of Protected Areas of the Krasnodarsky Krai. The goal of the present research was to characterise the long-term changes in lagoon’s bottom vegetation from 1921 to 2015, and to reveal the features of species composition and the communities changes. During the investigation period, the number of macrophyte species increased from 16 to 27. Five new species typical for eutrophic water have been found, and more than ten species disappeared. Despite the Sudzhuk Lagoon being included within the protected areas, almost a complete disappearance of the <i>Lamprothamnium papulosum + Chara vulgaris</i> community and a dominance of the <i>Ruppia cirrhosa - Lophosiphonia obscura - Cladophora albida</i> community have been observed. By 2015, the biomass of the opportunistic green alga <i>Ulva intestinalis</i> near the channel, which connect the lagoon with the sea, increased by an order of magnitude compared to 1985. At the present time, intensive transformation has occurred in communities of aquatic vegetation, and the dominance of <i>Phragmites australis</i> and <i>Stuckenia pectinata</i> were found. Almost all research areas of the Sudzhuk Lagoon were in a poor ecological status according to the Ecological Index (EI), except for a few locations in the central and southeastern parts with a moderate ecological status. The lack of a management plan to protect the Sudzhuk Lagoon and intensification of unregulated recreation, along with other natural and anthropogenic factors, can lead to the loss of this unique natural complex. Effective measures aiming at preserving the ecosystem of the Sudzhuk Lagoon with its biological and landscape diversity were proposed.