Toxicity of silver doped (1% w/w) Ag/TiO2 NCs, (43 nm) to Chodatodesmus mucronulatus and Desmodesmus sp. were determined. The algae cells were exposed to Ag/TiO2 NCs for 72 hours to evaluate the photosynthesis activity, accumulation and oxidative stress induction of the algae. The pigment content, oxidative stress and bioaccumulation responses of the algae cells were determined after Ag/TiO2 NCs exposure. Additionally, the effect of the cellular response at the species level, which was received from the alga cells belonging to the same population, was investigated. When the oxidative stress response of Chodatodesmus mucronulatus and Desmodesmus sp. freshwater algae is considered, ROS formed in both species at significant levels. The highest accumulation for Ag NPs was observed at 0.01 mg/L-1 treatment group in Desmodesmus sp. and 0.1 mg/L-1 in Chodatodesmus mucronulatus. As a result, despite the fact that both of them are freshwater algae, the susceptibility of the cells of both algae to NPs is quite different from each other.