THE HISTORY OF LAKE TRIDTSATKA (MURMANSK REGION) ECOSYSTEM DEVELOPMENT IN THE HOLOCENE BASED ON DIATOM SEDIMENT RECORDS
New data yielded by diatom and lithologic-stratigraphic study of sediments from Lake Tridtsatka, located on the Karelian Coast of the Gulf of Kandalaksha (Murmansk Region), are presented. Based on the results of diatom analysis, lithological and chronometric data, the stages of sedimentation were reconstructed, and the taxonomic composition and structure of diatom complexes were studied. Diatom-inferred ecosystem history in the Holocene was revealed. The initial stage of the sedimentation process occurred within a periglacial freshwater body, with the following change to marine conditions. The lake became fully isolated from the sea at 7060 ± 160 years ago (cal.). The data obtained indicate a rapid isolation of the lake basin from the marine conditions of sedimentation. This is clearly reflected both in the sediment lithology, and in the change of diatom assemblages. Currently, the lake is a typical subarctic oligohalobic freshwater body.