Diversity and distribution of testate amoebae (Amoebozoa, Rhizaria) in reservoirs, Northeastern Bulgaria

The aim of the study is to describe the testate amoebae fauna in seven reservoirs in the Northeastern Bulgaria and to investigate the relationship of taxonomic diversity and abundance of these organisms to the some characteristics of the reservoirs. A total of 52 species, varieties and forms belonging to 15 genera were identified in the benthal of the coastal zone. There are significant differences in species richness and abundance between the testacea of different reservoirs. Number of taxa was significantly higher in the Beli Lom (29 species and 12 genera) and Loznitsa (22 species and 13 genera). Most of the reservoirs - Kara Michal, Bogdantsi, Isperih, Lipnik and Brestovene have extremely poor fauna compared to other similar reservoirs. This is confirmed by the low values of the Shannon-Weaver diversity index, which varied between 1.04 and 2.396, as well as by the other indices used to assess the environmental conditions in the reservoirs. The data of the regression analysis showed that a relation between age, surface area and water volume of the reservoirs and the species richness and abundance of testacea is not established.