The aquatic oligochaetes (Annelida: Clitellata) of eight lakes in the Asagi Firat River Basin (Lower Euphrates, Turkey).

The A¸sa˘gı Fırat River is located in the south-eastern Anatolia, Turkey. The water quality of the A¸sa˘gı Fırat River basin has been degrading for some time, primarily as the result of pollutants associated with the discharges from numerous domestic and agricultural point sources. Aquatic macroinvertebrate samples were collected from eight lakes conducted by using both hand-nets and an Ekman-Birge grab sampler during the summer and autumn of 2014, focusing on the species composition and distribution of aquatic oligochaetes in eight lakes of the A¸sa˘gı Fırat River basin, and their relationships with physico-chemical parameters measured in those lakes using Principal Component Analysis. Results of analyses of all identified benthic macroinvertebrates clearly indicate the percent dominance of oligochaetes in benthic samples in the eight dam lakes that were sampled: Hacıhıdır lake (62.9%); Atat¨urk lake (49.6%); ¨U¸c¨oz lake (28.9%); Dumluca lake (22.01%); Seve lake (13.9%); C¸ at lake (8.5%); Karakaya lake (7.8%) and Birecik lake (5%). During this study, 1044 oligochaete specimens representing 10 species of two subfamilies within the family Naididae were identified. The most abundant taxa were Limnodrilus hoffmeisteri (48.94%), Potamothrix hammoniensis (19.3%), Tubifex tubifex (13.1%), Nais simplex (5.2%) and Nais communis (4.1%)