Hyporheic fauna from interstitial of the Some River basin (Transylvania, northwestern Romania)

Biodiversity in hyporheic habitats (interstitial water habitats in river bank sediments) has been studied on Some ul Cald (Warm Some ) and Some ul Rece (Cold Some ) River (north-western Romania, Transylvania), from March to October 2004. pH and electrical conductivity were measured monthly at each site, and animals were collected with the Karaman-Chappuis method and by filtering water through a hand-net. The relative abundance of the best-represented hyporheic invertebrates (oligochaetes and insect larvae) was higher in Some ul Cald interstitial habitats than in Some ul Rece. The focus was directed to the role of water mites (Acari, Hydrachnidia), cyclopoid copepods (Crustacea, Copepoda, Cyclopoida) and oligochaetes (Annelida, Oligochaeta) in hyporheic communities. Nine water mites and five cyclopoid species were identified in five sampling sites of the two rivers. Their higher diversity was recorded in two stations on the Some ul Cald River. The cyclopoid copepod Diacyclops disjunctus (Thallwitz, 1927) is a new record for Romania. As for oligochaetes, 17 species were identified and their higher diversity was recorded on Some ul Rece River. Canonical Correspondence Analysis (CCA) shows that presence of some water mites and cyclopoid species can be associated with measured physicochemical parameters (pH, electrical conductivity). Principal Component Analysis (PCA) shows similarities between stations and the dominant taxa in some samples.