Analele Științifice ale Universității „Al. I. Cuza” Iași, s. Biologie animală, Tom LV, 2009 THE ECOLOGICAL COMPLEX ROLE OF THE MACROINVERTEBRATE FAUNA FROM THE RIVER CIRIC (IAȘI, ROMÂNIA) Mircea NICOARĂ, Mihai ERHAN, Gabriel PLĂVAN, Ion COJOCARU, Ana DAVIDEANU and Andreea NICOARĂ “Al. I. Cuza” University Iași, Faculty of Biology, Bd. Carol I 20A, 700505 Iași, Romania, mirmag@uaic.ro Abstract. Macroinvertebrate fauna populating lakes Dorobanț, Aroneanu and Veneția (Ciric III) placed on the River Ciric as well as River Ciric (downstream of Lake Venetia) was investigated during the months of year 2006. Samples consisted of nematods, annelid worms (Oligochaeta and Hirudineea), gastropods and bivalves, and arthropods such as: Crustacea (Isopoda and Amphipoda), Acarina, Collembola, and insects belonging to orders: Ephemeroptera, Odonata, Heteroptera, Coleoptera, Trichoptera, and Diptera). Dominant in numbers were insects (larvae especially) and worms (Oligochaeta). Ephemeroptera came in the first place in the lakes. In the River Ciric most numerous were Oligochaeta and Diptera, more resistant to physico-chemical stress supported by the ecosystem. In insects, ratio between imagos and larvae has also been considered. Keywords: ecology, macroinvertebrates, River Ciric. Rezumat. Rolul ecologic complex al faunei de macronevertebrate din Râul Ciric (Iași-România). Fauna de macronevertebrate care populează lacurile Dorobanț, Aroneanu și Veneția (Ciric III) amplasate pe Râul Ciric, dar și cea din Râul Ciric (în aval de Lacul Veneția) a fost investigată în cursul anului 2006. Probele au constat din: nematode, viermi anelizi (Oligochaeta și Hirudineea), moluște gasteropode și bivalve, respectiv artropode: crustacee (Isopoda și Amphipoda), Acarina, Collembola și insecte aparținând ordinelor: Ephemeroptera, Odonata, Heteroptera, Coleoptera, Trichoptera și Diptera). Insectele (în special larve) și viermii (oligochete) au dominat numeric. Efemeropterele au fost cele mai abundente în lacuri. În Râul Ciric, cele mai numeroase au fost oligochetele și dipterele, mai rezistente la stresul fizico-chimic suportat de către ecosistem. La insecte, raportul între adulți și larve a fost luat în considerare de asemenea. Cuvinte cheie: ecologie, macronevertebrate, Râul Ciric. Introduction River Ciric is a left hand tributary of the River Bahlui. Its basin is oblonged and orientated from North-West to South-East with an area of approx. 54 km - ²; its width is between 2 km to 6 km (Barbu & Ungureanu, 1987). On the course of the River Ciric, north from Iasi town are placed the lakes Dorobanț, Aroneanu and Ciric I, II and III. These dam lakes were aimed at preventing floods in Iasi town and neighboured villages but they are also suitable for pisciculture and leisure (Pantazică, 1974). Lakes’ characteristics features are their oblong shape due to the relief conditions as well as the large surface compared to the depth rarely more than 2 m. Besides the practical importance of the lakes, few studies regarding their biology were produced. Vegetation made the object of certain studies: C. Papp (1932), E. Răvăruț (1941), D. Mititelu and Gh. Vițalariu (1967), C. Dobrescu (1966-1969). C. Dobrescu, C. Bârcă and Maria Lazăr (1958) offered a floristic and geo-botanic draft of the Ciric valey, especially referring to the Ciric ponds and forest (Dobrescu et al., 1958; Mititelu & Vițalariu, 1967). Information regarding the biocoenoses of the studied ecosystems is very scarce. Physico-chemical data related to the lake water quality are contained by the paper of P. Gâștescu (1971), the lake being framed within the bicarbonated or mixed class, with Na or -125-