Effects of physicochemical factors and Chlorophyll a on diel changes in vertical distribution of zooplankton in a eutrophic reservoir (Tahtalı Reservoir, NW Turkey)

Abstract

Despite recent worldwide increase, artificial water bodies have received little attention for spatial and temporal distribution of their zooplankton communities. Aim of the present study was to reveal diel variations in vertical distribution of zooplankton in water column of a eutrophic reservoir and to detect which environmental and biological factors affect this distribution. All physicochemical and biological (Chlorophyll a and zooplankton species) variables showed a similar pattern, generally a decrease from the surface to depths of 4.5–6.0 m and a rise from this point to the deepest part of the vertical water column. In total, 15 zooplankton taxa were determined being Copepoda the most abundant taxa, followed by Cladocera, and Rotifera. Water temperature, turbidity and suspended load concentration were the most influential factors for the vertical migration of Cyclopoids and Cladocerans whereas the distribution of Rotifers, and Copepod nauplii were related to nutrients, and food concentrations represented by chlorophyll a. Diel changes and depth had significant impact on the abundance of studied zooplankton community in the reservoir. Result of the study revealed variable distribution patterns of zooplankton under effect of different environmental factors in an unpredictable reservoir.