The ecosystems of two similar lakes, located at different distances from the Mayak chemical plant, were compared to evaluate the potential ecosystem effects of radiation exposure on hydrobionts (phytoplankton, zooplankton, and zoobenthos). Uruskul Lake, the first lake, experienced significant radiation exposure due to the Kyshtym accident in 1957, while the second lake exhibited radiation levels close to background values. The radiation doses received by the aquatic organisms inhabiting Uruskul Lake are presented, and the long-term effects of irradiation on hydrobionts of this lake are discussed.