Benthic Macroinvertebrate Assemblages in Karst Springs Ecosystems in Bulgaria

Ecosystems of karst springs are insufficiently studied in Bulgaria. This study was focused on bottom macroinvertebrate assemblages from this river type. Their taxonomic diversity, community structure and habitat preferences in relation with the environmental factors were examined. During the summer of 2020, seven rivers originating from karst spring areas were sampled at sites being located at different distances from the sources. Diverse communities regarding their taxonomic richness and abundance were found, with 148 taxa enlisted, identified to the lowest possible level (species, genus or family). The strong variability of the number of taxa (S, from 6 to 51), absolute abundance (N, from 351 to 7956 specimens) and the values of the structural parameters (diversity indices, dominance and evenness) proved the highly variable characters of these benthic communities, which predetermined the low level of similarity at the taxon level (less than 21%). The correlation among biota and environmental variables such as altitude, distance to source, substratum type and physical and chemical parameters reflected both abiotic specificities and their impact on the benthic communities at a local and catchment scale.