Zooplankton abundance in the lower Sakarya River Basin (Turkey): Impact of environmental variables

In the present study the community structure and diversity of zooplankton were investigated seasonally in the polluted water of the lower Sakarya River Basin during February 2008-January 2009. The environmental variables measured were river flow, water temperature, conductivity, dissolved oxygen, pH, suspended particulate matter, chlorophyll a and nutrients (NO2-N, NO3-N, SiO2, PO4-P, TP). Determined environmental parameters were at the suitable intervals for habitat choice of identified zooplankton species. Thirty-two zooplankton taxa were determined , which were mostly indicators of eutrophic water of the study area. Rotifera was the most abundant group (96.4%), followed by Copepoda (2.7%) and Cladocera (1.0%). The dominant taxa were Brachionus budapestinensis Daday, Keratella cochlearis (Gosse), Polyarthra vulgaris (Carlin), Synchaeta oblonga Ehrenberg and Trichocerca ruttneri Donner from Rotifera, Copepod nauplii from Copepoda and Bosmina longirostris (Müller) from Cladocera. Depending on the station, zooplankton abundance and environmental parameters showed seasonal variation. Generally, higher zooplankton abundance and higher temperature resulted in a higher zooplankton diversity index. Statistical analyses indicated that rotifers and total zooplankton were highly associated with environmental parameters, especially water temperature and nutrients. Degree of pollution determines the quality as well as the quantity of plankton in the study area. Consequently, waste waters should be controlled, and pollution must be prevented to conserve biodiversity of zooplankton fauna and in consequence food web of the study area. All zooplankton species identified were the first records for the study area