Composition and abundance of oligochaetes (Annelida: Ooligochaeta) in springs of Kraków-Częstochowa Upland (Southern Poland): effect of Spring encasing and environmental factors

Studies were performed on 25 karstic springs located in Southern Poland (50 degrees 10 - 50 degrees 46' N, 19 degrees 17' - 19 degrees 54'E). They are natural or encased, differing also in discharge rate (0.01-15 l s^-1 in the southern part of Kraków-Częstochowa Upland while 20 - 1440 l s^-1 in its northern part) and kind of bottom sediments (fine or coarse). 27 species and l genus representing 5 families were determined, among them Enchytraeidae were represented by the highest number of species whereas Tubificidae (mainly juvenile forms) were the most abundant. Among oligochaetes no crenobionts were found while crenophiles: Rhyacodrilus falciformis Bretscher and Stylodrilus heringianus Claparede were present in a half of the studied springs. In the majority of the studied springs the density of oligochaetes was significantly higher in fine sediments (ranges 200 - 13 200 ind. m^-2) than in coarse ones (ranges 22-7900 ind. m^-2) (P <0.05). The species diversity (H') was also higher in in fine sediments, especially in springs of the southern part of Upland. Oligochaeta were more abundant and diversified in encased springs than in natural ones and they inhabited preferably fine sediments. The discharge and springs localization (in southern or northern part of the studied area) were found to be not of importance for oligochaete composition and abundance.