Study on composition and abundance of zooplankton assemblages in Egirdir Lake (Isparta, Turkey)

To determine the composition and abundance of zooplankton assemblages in Egirdir Lake-Turkey, monthly surveys were conducted from January to December 2010 at four stations. A total of 65 major zooplankton species were identified. Rotifera was the most abundant taxon dominated mainly by the species Polyarthra dolichoptera and Keratella cochlearis. Rotifers were recorded at the maximum abundance of 5.609 individuals/L in October at the fourth station, and their highest mean abundance was 783 +/- 1358 individuals/L at the third station. There was a highly significant difference (p<0.001) that October was differentiated from other sampling months with the highest rotifera and zooplanktonic abundance. Although the mean total zooplankton abundance at four stations was changed between 357 +/- 429 and 841 +/- 1375 individuals/L, no significant difference was recorded amongst sampling statitons in view point of abundance variation (p>0.05). The zooplankton abundance comprised: Rotifera = 89.62 %; Cladocera = 7.78 % and; Copepoda = 2.60 %. Newly reported species from the lake were: the rotifers Conochilus dossuarius, Euchlanis dilatata, Trichotria tetractis, Trichocerca bicristata, Trichocerca capucina, Trichocerca cylindrica, Lecane stenroosi and Lepadella patella, and the cladocerans Biapertura affinis, Coronatella rectangula, Alona qaudrangularis, Alona guttata, Alonella excisa, Alonella nana, Disparalona rostrata, IIyocryptus sordidus, Acroperus harpae, Monospilus dispar and Camptocercus uncinatus. The annual mean concentration of chlorophyll-a was 3.0 +/- 0.2 mg/m(3). According to the Carlson's trophic state index, Egirdir Lake is mesotrophic-eutrophic. A Brachionus: Trichocerca quotient value of 1.25 was calculated, clearly indicating that the lake is mesotrophic. Zooplankton composition data were analyzed using Shannon's diversity index and ranged from 0.90-1.77.