Assessment of water quality and plankton of effluent receiving lower Awba stream and reservoir, Ibadan, Nigeria

Abstract

Water quality and Plankton diversity of effluents receiving lower Awba Stream and reservoir were assessed at four stations; three along the stream and one at the reservoir. Significant spatial variation was observed in dissolved oxygen (DO], Biological Oxygen Demand (BOD), Ammonium Nitrogen (N-NH3, N-NH4), Alkalinity and total Hardness (P<0.05) among the physiochemical parameters of the study stations. A posteriori test showed the sewage rich effluents receiving station 2 to account for significant difference in DO, BOD, N-NH3, N-NH4, and Alkalinity. The station had least DO level (1.33mg/l± 0.58) and highest BOD (204.0mg/l ± 23.14), NH3 (3.80mg/l±0.35),NH4 [4.10±0.35] and Alkalinity [139.17mg/l±4.10]. A posteriori test also revealed that station 3 which receives effluents from chemical laboratory was the cause of significant difference in total hardness. The station had highest total hardness (136.83mg/l±34.15). Station 4 which was at the reservoir and devoid of effluent discharge had the most diversed Phytoplankton and zooplankton. Mehinic Diversity Index (MDI) and Simpson diversity Index, (SDI) values at the station for Phytoplankton were 0.30 and 0.81 while those of zooplankton were 0.66 and 0.88. Station 3 had least diversed phytoplankton, MDI and SDI diversity values for zooplankton; MDI: 0.32; SDI 0.51. This indicates undesirable effects of effluents discharge on physicochemical properties and plankton diversity of the receiving water body.

Keywords: Water quality parameters, phytoplankton, zooplankton, effluents, species diversity.

AJAZEB Vol. 6 2004: pp. 81-85