Long-term hydrochemical changes and “Harmful Algal Blooms” in the Arctic Lake Imandra

The large arctic Imandra Lake is located in the industrial Murmansk region, Russia. Since the 2000s it has regular Harmful Algal Blooms. Significant changes in hydrochemical indices were recorded in 1985—2017. The ratio of the main ions has changed, the pH and alkalinity have increased. The indicators of water salinity, the total content of P and N, and their mineral forms have decreased. The concentrations of Zn, Cu, Ni и SO42– have decreased as well. The decrease trends in the content of macronutrients in waters contradict traditional concepts and the role of mineral P and N in the development of HAB. This indicates more complex mechanisms of flowering in this arctic reservoir, which are being discussed.

Lake Imandra depression in the Late Glacial and early Holocene (Kola Peninsula, north-western Russia)

The paper summarizes the evidence of litho-, biostratigraphy and 14C dating of sedimentary sequences studied in natural outcrops and bottom deposits in small lakes, as well as data on coastal morphology in the depressions of Ekostrovskaya and Babinskaya Imandra, the southern sub-basins of Lake Imandra. Lithological, 14C and diatom data suggest that the brackish-water reservoir followed by the fresh-water one existed in the Ekostrovskaya Imandra depression during the Younger Dryas chronozone prior to 11,400cal. yr BP. The Fennoscandian Ice Sheet margin is assumed to have been located in the Lake Imandra basin, covering western Babinskaya Imandra earlier than c. 10,250 cal. yr BP. The early Holocene c. 11,400–8,500 cal. yr BP was marked by a significant westward retreat of the ice margin in the western Lake Imandra depression and adjacent areas, and an extensive fresh-water pra-Imandra Lake basin was formed there. At the end of the Preboreal, earlier than c. 9,210–8,500 cal. yr BP, the pra-Imandra Lake coastline was at least 16–18 m higher than the modern one, as can be assumed according to coastal morphology and lithostratigraphical data. The coastline of that reservoir changed, water square slightly reduced, and isolated small lakes emerged on coasts during the early Holocene.

MODERN BIOLOGICAL CHARACTERISTICS OF WHITEFISH COREGONUS LAVARETUS, EUROPEAN VENDACE C. ALBULA AND EUROPEAN SMELT OSMERUS EPERLANUS FROM THE IMANDRA LAKE

The modern biological characteristics of numerous fish species from the Imandra Lake reaches – white-fish, european vendace and european smelt was investigated. It was shown that under the conditions of the ongoing negative change in the hydrological and hydrochemical regimes of the lake over the past 20 years, there have been multidirectional changes in the population’s structures of these species. If in short-cycle species (smelt, vendace) there is a positive dynamics of a number of indicators, then in whitefish these changes are negative. Euryphagia of smelt from the Imandra Lake, including the transition to preda-tion when reaching a length of 150 mm, combined with an effective breeding strategy and the virtual ab-sence of a predator press, provide him high numbers and successful competition with other species.

Silicon in ultrafresh groundwater: a case study of the Imandra Lake catchment, The Kola Peninsula

The ultrafresh groundwater (with TDS values less than 200 mg/L) of the Imandra Lake catchment, Kola Peninsula, is from an intensive water exchange zone, where the water has a short period of contact with the rock. Therefore, the considered water is at the initial stages of the water–rock interaction. The water is saturated with respect to oxides and hydroxides of aluminium and iron. In the groundwater of the Imandra Lake catchment area, the silicon concentrations significantly exceed the concentrations of magnesium and especially potassium. Nevertheless, water is undersaturated with respect to with respect to silicon oxides. The shown enrichment of water with cations is explained by time of water-rock interaction.

Diatom complexes from bottom sediments of small lakes of the Imandra depression

The study of diatom complexes in the bottom sediments of 2 small nameless lakes on the western coast of Imandra Lake (Murmansk region) was carried out. The features of the historical dynamics of diatom flora in response to changes in the environment and climate in the Holocene are described. Diatom analysis revealed the effects of tectonic activity in the area of the Imandra Lake depression, accompanied by a sharp increase in the water level, which is confirmed by lithological data.