ТРАНСФОРМАЦИЯ ТАКСОЦЕНА ПОЛИХЕТ МЕЛКОВОДНОЙ ЧАСТИ КАРКИНИТСКОГО ЗАЛИВА В УСЛОВИЯХ ИЗМЕНЕНИЯ СОЛЕНОСТИ

Abstract

The Karkinit Bay is the largest bay of the Black Sea. Since the 1960s, after the construction of the North Crimean Canal, the water in the top of the bay was heavily desalinated by runoff from fish ponds and irrigation systems. In 2014, after the canal was blocked, the salinity of the water increased, and the living conditions of the organisms changed. This work is aimed at the assessment of the change in the species composition and quantitative characteristics of the polychaete taxocene in the shallow zone of the Karkinit Bay in 2018, which resulted from the changes in water salinity, as compared to those in 2008. The studies were carried out in August of 2008 and 2018-in three sampling areas at 17 stations (in 2008 and 2018 alike) at depths of 0.2-1.7 m. Samples of macrozoobenthos were collected using a manual bottom grab with a sample area of 0.04 m2. In the head part of the Karkinit Bay in the first half of the 21st century, 35 species of polychaetes were recorded. Polychaete worms belonging to 19 families have been identified, with the families Phyllodocidae, Syllidae, Nereidae, and Spionidae comprising the largest number of species (4 species each). Three species- Lysidice unicornis , Polyophthalmus pictus , Syllis prolifera- were recorded in the Karkinit Bay for the first time. It is shown that, with the post-2014 increase in salinity, the species richness of the polychaete taxocene in the investigated area has also increased. In 2008, 24 species were found, and in 2018, 32 species. The average abundance of polychaetes in 2008 was 948± 345 ind./m2, and in 2018, it was 417±161 ind./m2. Hediste diversicolor reached the highest abundance in 2008 (average abundance 676±371 ind./m2, maximum abundance 2313 ind./m2). In 2018, Polydora cornuta (600 ind./m2), Platynereis dumerilii (225 ind./m2), and Scolelepis tridentata (450 ind./m2) were characterized by the highest abundance. With an increase in salinity in the range of 1.5-17.8 ‰, a decrease in the density of H. diversicolor was recorded and, conversely, an increase in the density of other Polychaeta species.