Investigations on the zooplankton distribution and composition of Işıklı Lake (Çivril-Denizli/Türkiye), with a trophic status assessment

Abstract

In this study, the zooplankton distribution and composition of Işıklı Lake, located in the Inner West Anatolia region of Türkiye, were examined monthly between 2003-2005. Zooplankton samples were collected with Hydro-Bios plankton net (55 µm) at the surface and fixed in formaldehyde (4 %). Physiological parameters such as surface water temperature, pH, dissolved oxygen, and conductivity were also measured. Also, the frequency index (F %) and the Brachionus / Trichocerca (QB/T) were determined to assess the trophic composition of Lake Işıklı. A total of 49 species have been identified. Rotifera (55 %), Cladocera (27 %) and Copepoda (18%) were represented by the species. The maximum species was found in May 2004 (21 species), while the minimum was found in October 2003 (5 species). Asplanchna priodonta, Keratella cochlearis, Keratella tecta, Polyarthra dolichoptera, Synchaeta pectinata, Bosmina longirostris and Chydorus sphaericus are common species in the lake. The water temperature varied between 3.9-24.6 °C; pH ranged from 8.1 to 8.8; the electrical conductivity ranged from 341 µS/cm to 434 µS/cm; the dissolved oxygen values changed from 5.8 mg/L to 11.1 mg/L. According to the frequency index (F %), the most dominant species are B. longirostris (74 %), K. cochlearis (62 %), A. priodonta (54 %), and C. sphaericus (51 %). A total of 20 species are reported for the first time from the region. Newly reported species from the lake were: the rotifers, A. priodonta, Brachionus angularis, Brachionus calyciflorus, Colurella colurus, Keratella quadrata, Lecane clostrocerca, Lecane ludwigi, Lecane luna, Lecane lunaris, Lecane ohioensis, Lecane quadridentata, Lecane sp., Mytilina mucronata, Notholca acuminata, Notholca squamula, Trichotria tetractis, the cladocerans Acroperus harpae, Daphnia cucullata, and the copepods Eucyclops macrurus and Megacyclops gigas. Considering the Brachionus / Trichocerca (QB/T) ratio according to the Sládeček (1983) index, the lake showed mesotrophic features.