K. Velichkova1*, I. Kiryakov2
1Department of Biology and Aquaculture, Faculty of Agriculture, Trakia University, 6000 Stara Zagora, Bulgaria 2Department of Botany, Faculty of Botany, Paisiy Hilendarski University of Plovdiv, 24 Tzar Assen, 4000 Plovdiv, Bulgaria
Abstract. The cenoses with dominate Homoeothrix varians and Homoeothrix crustaceae in the Veleka River, Bulgaria were studied. The communities were distributed in the four points of the Veleka River. The composition of cenoses with dominant H. varians includes a total of 82 species and intraspecific taxa. Most of them are diatoms (90%). On the second place are blue-green algae (6%), to which it belongs and the dominant species. The rest of the species are green algae – Chlorophyta. About 43% of all established species in cenoses are bioindicators on degree of saprobity. Cenoses with dominant H. crustaceae were developend mainly on rocks in river rapids. We found that coenoses were characteristic of slow-flowing, calcareous waters with ß-mesosaprobic conditions.