Abstract
The benthic algal composition of Charophyta in the Avusor Great Lake and Koçdüzü Great Lake at the altitude of about 3,000 m a.s.l. was investigated on 21 August 2019. A total of 112 species, belonging to Zygnematophyceae, were identified. The genera Cosmarium (44), Staurastrum (16), Closterium (15), and Euastrum (13) were most abundant. The members of filamentous charophyta were represented by two species. Bioindicator species characterize water in both lakes as clear, Class 2 of water quality and the lakes ecosystem as mesotrophic. The partly unexpected presence of certain desmids taxa, i.e., species characteristic of eutrophic water, was recorded.