Diversity of Benthic Diatoms and Abiotic Patterns in the Headwaters of the Volga River

The Volga is the largest river in Europe and its headwaters comprise reference or least disturbed conditions. In the headwaters of the Volga (445 km) upstream of Tver, 27 diatom samples (18 from the Volga and nine from selected tributaries) were collected in shallow water along the banks from different habitats, wherefrom 270 taxa (244 pennate and 26 centric) were identified. Most benthic taxa were found within Naviculaceae (40 taxa), Fragilariaceae (29 taxa), Bacillariaceae (27 taxa), Achnanthaceae (23 taxa), Gomphonemataceae (19 taxa), Cymbellaceae (17 taxa), and 16 taxa belong to the Amphora-complex. Species richness in the Volga and its tributaries was comparable; the mean value was 46 in the Volga and 50 in the tributaries. Regarding the saprobic index, the source region (reach R1) was characterized by a large proportion of xeno- and oligo-saprobic species, with the proportion of oligo-beta and beta-meso-saprobic species increasing along the continuum. This study provides a first comprehensive checklist of benthic diatoms for the Volga headwaters and analyzes longitudinal changes as well as the interplay between abiotic parameters and the diatom community in the headwaters of the Volga.