RESEARCH ARTICLE Multi-marker study of the responses of the Unio tumidus from the areas of small and micro hydropower plants at the Dniester River Basin, Ukraine Lesya Gnatyshyna 1,2 & Vira Khoma 1 & Olena Mishchuk 3 & Viktoria Martinyuk 1 & Gunta Spriņģe 4 & Oksana Stoliar 1 Received: 11 September 2019 /Accepted: 9 January 2020 # Springer-Verlag GmbH Germany, part of Springer Nature 2020 Abstract The impact of the hydropower plants (HPPs) on the aquatic life is expected, but the biochemical markers of ecotoxicity have not been investigated in relation to HPP proximity. The aim of this study was to compare the responses of mollusk Unio tumidus from the small HPP (reservoir (Ku) and downstream of the dam (Kd)) and micro HPP (upstream (Zu) and downstream of the dam (Zd)). In total, 11 indexes (n) from digestive gland, hemocytes (lysosomal integrity), and gonads (alkali-labile phosphates, ALP) were analyzed. The mollusks from the reservoir demonstrate the typical signs of toxic impact: cholinesterase and glutathione depletion, the highest glutathione S-transferase activity, and ratio of extralysosomal cathepsin D compare to all other groups. The specimens from the micro HPP have the highest levels of glutathione (Zd) and lipid peroxidation (Zu) and lesser Cu/Zn-SOD activity (Zu) than other groups. These indications of stressful conditions may derive from the regular oscillations in the water flow regimes at the micro HPP. For both HPPs, the responses of upstream and downstream groups are distinct. The calculated IBR/n (4.17, 3.85, 3.12, and 0.26 for Ku, Kd, Zu, and Zd correspondingly) gives a quantitative basis for the evaluation of environmental impact of HPPs. Keywords Bivalve mollusk . Hydropower plant . Markers of exposure, oxidative stress, IBR Highlights • Responses of mussels from small and micro hydropower plants (HPPs) first reported. • In the reservoir of small HPP, signs of toxic impact are indicated. • Micro HPP groups suggest oxidative stress. • Responses in groups upstream and downstream of the dam are distinct. Responsible editor: Cinta Porte Electronic supplementary material The online version of this article (https://doi.org/10.1007/s11356-020-07698-4) contains supplementary material, which is available to authorized users. * Oksana Stoliar Oksana.Stolyar@tnpu.edu.ua; http://biochemlab.tnpu.edu.ua Lesya Gnatyshyna gnatyshynall@tdmu.edu.ua Vira Khoma khomav@tnpu.edu.ua Olena Mishchuk mishchuk@rowan.edu Viktoria Martinyuk martynjyk23@ukr.net Gunta Spriņģe gunta.springe@lu.lv 1 Ternopil Volodymyr Hnatiuk National Pedagogical University, Kryvonosa Str 2, Ternopil 46027, Ukraine 2 I.Ya. Horbachevsky Ternopil National Medical University, Ternopil, Ukraine 3 Rowan University, Glassboro, NJ, USA 4 University of Latvia, Institute of Biology, Salaspils, Latvia Environmental Science and Pollution Research https://doi.org/10.1007/s11356-020-07698-4