Долговременные геоэкологические изменения в малых озерах Сочинского национального парка (диатомовый анализ)

The purpose of the present study is to explore sediment diatom assemblages from two closed lakes in Sochi national park (Krasnodarsky Krai). Both lakes are hydrological objects typical for the area of study. We establish two scenarios of taxonomic structure transformation by using the author’s method of graphical analysis for diatom assemblages. The ecosystem in Lake Zerkal’noe is characterized by only one scenario. It is defined through the outer impact with sufficiently stable inner parameters of the ecosystem. Processes of overgrowing and swamping are not observed in this lake. Two scenarios of taxonomic structure transformation for diatom assemblages were found in Lake Bolshoe. These scenarios correspond to three stages of changes which took place in the lake ecosystem. The earliest stage was completed at the beginning of the 20th century. At this stage the state of ecosystem in Lake Bolshoe was similar to the current ecosystem’s state in Lake Zerkal’noe. The later stages correspond to the second scenario of transformation. It describes progressive processes of swamping and overgrowing of a lake area. These processes are common for the most part of the small lakes in the studied area. Probably, these changes in the lake ecosystem are related to the natural processes of swamping as well as to the increasing anthropogenic impact.