Complex ecological studies of five small lakes under direct impact of the Monchegorsk site of JSC «Kolskaya GMK» have been conducted. The lakes ecosystems develop under extreme pollution, and characterized by depleted species composition of hydrobionts and low values of their abundance and biomass. Lake Kumuzhye, with the least transformed watershed, is closest to natural environment. Lake Nyudyavr, affecting by cuprum-nikel production sewages is additionally susceptible to anthropogenic eutrophication, which obviously contributes in part to the resistance of hydrobionts to toxic load. It is established that the use of traditional hydrobiological criteria for assessment of water quality and trophic status for the studied water bodies is limited.