Abstract <p>This study presents the results of an analysis of the chemical composition of waters in pit lakes formed after the exploitation of the Zavitinskoe lithium–beryllium and Zhipkoshinskoe antimony ore deposits in Transbaikalia. Data on the physicochemical parameters of pit waters, as well as on the concentrations of macro- and microcomponents and their variation with depth, are reported. The waters of the pit lakes are shown to be neutral to slightly alkaline and are predominantly of the sulfate, sulfate–hydrocarbonate, and hydrocarbonate–sulfate magnesium–calcium type. Elevated concentrations of Li, Sr, and Be are observed in the water bodies of the Zavitinskoe deposit, whereas Sb and As are characteristic of the Zhipkoshinskoe deposit. At present, mining operations have ceased, and the pit lakes—particularly those at the Zavitinskoe deposit—are actively used by local residents for recreation and fishing. In this context, the concentrations of selected components in the pit waters have been evaluated against the maximum permissible concentration standards established for fishery water bodies and drinking water. The first data on phytoplankton, macroalgae, macrophytes, and zooplankton in the technogenic water bodies of the studied deposits are presented, and their species composition and abundance are characterized. Low species diversity and low densities of planktonic fauna and macrophytes are observed, which are explained by the lack of suitable biotopes for the development of diverse communities. This limitation is associated with the small catchment area, steep pit slopes, and the resulting absence of shallow zones with aquatic vegetation.</p>