Abstract
The study aims to present the results obtained from the conducted physicochemical and biological monitoring to establish potential anthropogenic impacts on the biodiversity and ecological state of the freshwater ecosystem of the Krumovitsa River, located in the Eastern Aegean Basin and Southern Bulgaria. The Krumovitsa River belongs to river typeR14c: Sub-Mediterranean, temporary (drying-up) small and medium-sized rivers and streams. The study is conducted in the middle part of the Krumovitsa River catchment, near the town of Krumovgrad, in the spring of 2025. Standard research methods are applied. The main physicochemical quality elements are monitored. The biological diversity of the ichthyologic complexes are described. The main ecological characteristics (distribution, number of species, abundance in percentages (A%), weight (Wg), weight in percentages (W%), and absolute dominance (Di)) are analysed. Biotic indices for ecological assessment are presented as Diversity indices for statistical representations of different aspects of biodiversity (Brillouin’s diversity index (HB), Simpson’s dominance index (S), Pielou’s evenness index (E), etc.). Ichthiocomplexes are represented by two eudominant species (Alburnus alburnus (Linnaeus, 1758), Barbus cyclolepis Heckel, 1837) and one subrecident species (Cobitis elongatoides Băcescu & Mayer, 1969). The parasite component communities and infracommunities of the identified fish species and the indicator significance are discussed. A component species for the parasite communities is Rhabdochona denudata (Dujardin, 1845) Raillet, 1916 (P%=30.62). The ecological assessment is based on a complex analysis of the obtained results and statistical processing of the data.
Keywords: bioindication, bioticindices, physicochemical monitoring, comprehensive assessment, Bulgaria