Abstract
The relative abundance of D. polymorpha and other benthic macroinvertebrates in lake Büyük Akgöl was studied in 2009, 2012 and 2014. In 2009, the macroinvertebrate fauna consisted of Gastropoda (53.4%), Bivalvia (26.8%), Oligochaeta (12.6%), Chironomidae (5.9%) and other taxonomic groups (Trichoptera, Ceratopogonidae, Ephemeroptera, Odonata, Chaoboridae, and Hirudinea) (1.04%). After three years, Bivalvia and Oligochaeta increased (38.2% and 15.3%, respectively), whereas the other groups (in particular, Gastropoda and Chironomidae) were found to decrease (41.4% and 4.5%, respectively). For the study period, the relative abundance of D. polymorpha increased from 19.6% (2009) to 34.8% (2014). The species has occupied various benthic habitats of lake Büyük Akgöl and continued to spread during the study period.