MACROZOOBENTHIC COMMUNITIES STRUCTURE CHARACTERISTIC OF CERTAIN TRIBUTARIES OF THE SIRET RIVER FROM HARGHITA, MARAMURE AND VRANCEA MOUNTAINS AND MOLDOVEI PLATEAU

35 qualitative macrozoobentonic samples were collected in 2011 from many Siret river tributaries coming from the Harghita Mountains (5 stations), Maramure Mountains (14 stations), Moldavian Plateau (4 stations) and Vrancea Mountains (12 stations). Laboratory analysis of samples revealed the existence of the following 15 groups of benthic invertebrates: Ephemeroptera, Plecoptera, Trichoptera, Oligochaeta, Diptera (Chironomidae, Simuliidae, Ceratopogonidae, Limoniidae), Gastropoda, Bivalva, Coleoptera, Acarina, Odonata, Hirudinea, Isopoda, Heteroptera, Turbellariata and Collembola). Groups that have the highest frequencies were mayflies and dipterans (each with a frequency of 97.1%), followed by caddisflies (80%), amphipods (68.6%), oligochaetes (57.1%) and stoneflies (54.3%). Presence of sensitive groups to water quality degradation (Ephemeroptera, Trichoptera and Plecoptera) with high frequency shows good quality water at most stations investigated.