Longitudinal Distribution of Ephemeroptera Communities for the Sasar River and its

The Sasar River basin is located in the Baia Mare Depression; it covers an area of 311 sq km and it is located in NW Romania. Due to urbanization and industrialization, and to a lesser extent agriculture, Sasar Basin shows a simplification of the biocenosis, more or less brutal, the intensity of pollution.This paper summarizes the results of sampling campaigns that were carried out between 2003-2008, when a total of 10 stations of the investigated basin were identified and analyzed, according to the Normalized Global Biological Index (IBGN) methodology. Subsequent to the systematical study, 20 species belonging to 6 Ephemeroptera families ( Leptophlebiidae, Ephemeridae, Ephemerelllidae, Caenidae, Heptageniidae, Bäetidae  ) were identified. Ephemeroptera is a group of demanding environmental conditions; high specific abundance was recorded in the stations located in areas with minimal and moderate anthropogenic impact (upstream Blidari-10 species; Valley Măriuţii- 10 species, upastream Baia Sprie - 9 species). The number of species is drastically reduced for the stations located downstream of the Baia Sprie and Baia Mare industrial centers (downstream Baia Sprie-3 species, downstream Baia Mare -1 species). Within the communities of Ephemeroptera high frequencies were performed by Bäetis rhodani (90%), considered in terms of the ecological valence, average tolerance to pollution. Pollution-sensitive species had low frequencies: Rhithrogena semicolorata  (40%), Bäetis alpinus (40%).