The zooplankton composition in two reservoirs in the north-west bulgaria in relation to dreissena spp. Occurrence

Abstract

The qualitative and quantitave parameters of the zooplankton in the reservoirs Ogosta and Poletkovtsi (North-West Bulgaria) were compared. The influence of the reservoir ecotone zones and the impact of Dreissena spp. distribution on the zooplankton composition were studied. Totally 75 zooplankton components were recorded in the reservoirs. The species Testudinella emarginula was newly recorded for the Rotifera fauna of Bulgaria. Most frequent and dominant components were copepodites and nauplii of Copepoda in both reservoirs, as well as copepods and cladocerans in the Ogosta and rotifers in the Poletkovtsi Reservoir. The zooplankton abundance and biomass in the Poletkovtsi were much higher than the Ogosta. © 2009 Taylor and Francis Group, LLC.