57 PHYSICOCHEMICAL AND BIOLOGICAL PARAMETERS OF DOMBROVSKE PIT LAKE — LEGACY OF OPENCAST POTASSIUM... ISSN 1996-4536 (print) • ISSN 2311-0783 (on-line) • Біологічні Студії / Studia Biologica • 2020 • Том 14/№2 • С. 57–68 Biol. Stud. 2020: 14(2); 57–68 • DOI: https://doi.org/10.30970/sbi.1402.623 www.http://publications.lnu.edu.ua/journals/index.php/biology © 2020 A. Haydyn et al.; Published by the Ivan Franko National University of Lviv on behalf of Біологічні Cтудії / Studia Biologica. This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://www.budapestopenaccessinitiative.org and Creative Commons Attribution 4.0 License), which permits unrestricted reuse, distribution, and reproduction in any medium, provided the original work is properly cited. UDC: 574.5: 556:502.3/.7 PHYSICOCHEMICAL AND BIOLOGICAL PARAMETERS OF DOMBROVSKE PIT LAKE — LEGACY OF OPENCAST POTASSIUM SALT MINE (KALUSH, UKRAINE) A. Haydyn 1 , V. Dyakiv 2 , N. Romanyuk 2 , V. Kozlovskyy 3 * 1 Department of Mining and Chemical Raw Materials, Academy of Mining Sciences of Ukraine 98, Stryiska St., Lviv 79026, Ukraine 2 Ivan Franko National University of Lviv, 4, Hrushevskyi St., Lviv 79005, Ukraine 3 Institute of Ecology of the Carpathians NAS of Ukraine, 4, Kozelnytska St., Lviv 79026, Ukraine *Corresponding author: e-mail: vkozlovskyy@gmail.com Haydyn A., Dyakiv V., Romanyuk N., Kozlovskyy V. Physicochemical and biological parameters of Dombrovske Pit Lake – legacy of opencast potassium salt mine (Kalush, Ukraine). Studia Biologica, 2020: 14(2); 57–68 • DOI: https://doi.org/10.30970/sbi.1402.623 Complex monitoring of physicochemical and biological parameters of water bodies as holistic ecosystems allows developing their right management strategy in future. Dombrovske Pit Lake (49°01′34′′N, 24°19′25′′E) was formed in an abandoned open- cast potassium salt mine in 2008, as a result of ceased mining. The lake is characteri zed as meromictic with the salt gradient of approximately 30 g/L at the surface to 400 g/L at the bottom, with the prevalence of Na + , K + , Mg 2+ , Cl − and SO 4 2− ions. A slight heliother- mal effect occurs during summer (the temperature of the hemocline is approximately 5 °C higher than that of the myxolimnion and monimolimnion). Major anions and cations (Cl – , SO 4 2- , Na + , K + , Mg 2+ , Ca 2+ , HCO 3 − ) profles are very similar to the mineralization curve, the content of microelements (Cd, Ni, Fe, Mn, Zn, Pb, Co) and pH also correlate with salinity. Concentrations of most heavy metals ions in the surface waters of the lake meet the Ukrainian quality standards for drinking and surface water; a small excess of Cd content compared to the Ukrainian standards is expected to disappear along with a decrease in the overall mineralization when the lake is flled to the planned level. Chlo- rophyll concentration (0.5–4 µg/L), pH values (≈ 7.5) and dissolved oxygen content (8– 12 mg/L) point to a high biotic activity within the 0–5 m surface water level. Such con- centrations correspond to oligotrophic lakes with a low plankton level, poor nutrient content and minimal contamination. Chl B constitutes the largest part of the total mass of chlorophyll, which indicates the predominance of green algae representatives. The relatively high proportion of Chl C is due to the considerable biomass of diatoms and dinofagellates, which play a crucial role in the photosynthesis of seas and oceans. Due