Abstract <p>An analysis of the heavy metal (HM) pollution of surface waters of the middle reaches of the Gazimur River in the area of the Bystrinsky Mining and Processing Plant (Zabaikalsky krai, Russia) is presented. Plants <i>Fontinalis antipyretica</i> Hedw., <i>Ranunculus circinatus</i> Sibt., and the filamentous algae <i>Cladophora fracta</i> (Müll. ex Vahl) Kütz. and <i>Ulothrix zonata</i> (Web. et Mohr) Kütz., as well as the fish <i>Rhynchocypris lagowskii</i> (Dybowski) and <i>Brachymystax lenok</i> (Pallas), are studied as biomonitors of HM pollution. HMs in water and hydrobionts are determined by atomic emission and mass spectral analysis methods. It is found that the values of the HM concentration in the studied organisms are similar to the values from the watercourses of other regions of Zabaikalsky krai. At the same time, high concentrations of HMs in the aquatic moss <i>F. antipyretica</i> are detected for the watercourses of the Gazimur River basin, which is confirmed by calculating the coefficient of biogeochemical activity of the species. The calculation of the total pollution index in the indicator species shows that <i>F. antipyretica</i> has high values for rivers draining catchments with mining sites. For <i>Rh.&#xa0;lagowskii</i>, the highest coefficient values are determined in watercourses remote from mining areas. The results of water biomonitoring studies using hydrobionts make it possible for them to be constantly included in routine monitoring of the state of aquatic ecosystems, along with existing hydrochemical monitoring of surface waters. In the future, attention should be paid to comparing the cumulative properties of aquatic plant species with other aquatic organisms to monitor the spread of HM pollutants through trophic chains.</p>