Diversity and Ecological Characteristics of Algae in the Water Column in the Subbasin of the Large Danube Lakes During the Autumn-Winter Period (Ukraine)

The paper deals with structural and functional components of algal diversity and ecological characteristics in the water column of the large Danubian lakes, Kahul, Kartal, Yalpuh, Kuhurluy, Katlabukh, and Kytay, in the late autumn-winter of 2019-2020. The water column algal taxonomic diversity comprised of 188 species, represented by 191 infraspecies taxa from 7 divisions, 14 classes, 30 orders, 61 families, and 108 genera. According to the algal species diversity, the lakes can be put in the following order: the Yalpuh (78) > Kytay (76) > Kahul (75) > Kuhurluy (55) > Katlabukh (23) > Kartal (16 ist) Bacillariophyta, Chlorophyta and Cyanobacteria prevailed. According to habitat preference, planktonic forms made up 45%, benthic forms 24%, epiphytic forms 5%, littoral forms 15%, and eurytopic forms 11%. According to salinity preference indifferent species dominated, and according to pH preference alkaliphilic species prevailed. The Sorensen similarity index and Kendall rank correlation indices for leading families were rather low -0.18-0.43 and 0.45-0.57, respectively, which is indicative of significant differences among the algal communities in the lakes under study. The algal cell count amounted to 2,853-360,325 thousand cells · dm-3, the biomass - 0.876-64.113 g · dm-3. According to the quantitative characteristics of planktonic algal communities and Cyanobacteria biomass, the Danubian lakes are eutrophic.