Impact of Water Quality Pertubation on the Zooplankton Community of Orashi River, South- South, Nigeria

Abstract

Zooplankton abundance and diversity in any water body is a function of its (water) quality status. Accordingly, the zooplankton community of Orashi River was studied over a six- month period (February -July, 2016) in relation to water quality perturbation. Five sampling stations were established, and standard method was deployed in the collection and analysis of sub- surface water samples for physico-chemical parameters as well as zooplankton identification and enumeration. Numerical estimation of zooplankton was done under microscope using Sedge-Wick Rafter counting chamber. Mean concentrations of the physico-chemical parameters vary across the stations and similar to previous study within the Niger Delta. A total of 27 species of zooplankton belonging to 4 classes were identified and 91 individuals enumerated in this study. The dominant class was Protozoa with 50 individuals (54.94%), followed by Copepoda with 16 individuals (17.58%), Rotifera with 13 individuals (14.29%) was next and finally Cladocera 12 individuals (13.19%). Percentage total occurrence of zooplankton across sampling stations was high in stations 4, 5 and 1 with 31, 27 and 23 individuals respectively, while that of 2 and 3 are low with only 7 and 3 individuals respectively. Only indivduals of class protozoa were observed in all 5 sampling stations, copepod and cladocera were not observed in station 2 and in station 3 rotifera and cladocera were not recorded. Similarly, protozoa was the dominant class in all stations except station 3 where copepod was encountered more, indicating that zooplankton of class protozoa are more favoured to survive in the current environmental condition of the Orashi River. It is therefore concluded that the spatial fluctuations of zooplankton class and species abundance is a response to the variations in the concentration of physicochemical variables of the study area.