The Effect Of Textile Mill Effluent On Two Brachish Fauna Species (Oreochromis Niloticus And Palaemonetes Africanus) In Ibeshe River Lagos State

Abstract

Acute toxicity of textile mill effluent to two brackish fauna species, Oreochromis niloticus (finfish) and Paleamonetes africanus. (Shrimp) fingerlings were assessed in a static renewable bioassay for 96h to determine median lethal concentrations (LC50). Seven different graded concentrations were prepared as 0.5, 1.0, 2.0, 4.0, 6.0, 8.0 and 2, 4, 6, 8, 10, 12mg L-1 for Oreochromis niloticus and Paleamonetes africanus fingerlings, respectively. However, a control experiment (0mgL-1) was set up accordingly. The 96h (LC50) value computed on logarithm were 1.21 and 5.11mgL-1 for Oreochromis niloticus and Paleamonetes africanus fingerlings, respectively. The median LC50 were 24, 48, 72 and 96h for 4.83, 2.01, 1.38 and 1.20 mgL-1 on Oreochromis niloticus fingerlings, exposed to different concentration textile mill effluent. However, median LC50 were 24, 48, 72 and 96h for 9.02, 7.82, 6.76, and 5.09 mgL-1 on Paleamonetes africanus fingerlings, exposed to different concentrations of textile mill effluent. The fingerlings of tilapia and shrimps exposed to various concentration of effluent showed uncoordinated behaviour, increase in their movements, ventilation, spiral swimming, sideway swimming, effort to swallow air from the surface for the tilapia fingerlings while shrimp fingerlings showed backward swimming and static swimming for few minutes. Mortality was recorded early in Oreochromis niloticus fingerlings at 0.5mgL-1 during a 24h exposure to the textile mill effluent while for the Paleamonetes africanus, mortality was recorded at 6mg L-1 for 24h exposure to the textile mill effluent physico-chemical assessment of the textile mill effluent were given as: Total Suspended Solids TSS (400-mgL-1) Biological Oxygen Demand BOD (362.6-397.1 mgL-1, Detergent (40.2-49.9 mgL-1) Alkalinity (575-1225 mgL-1), Oil and grease 28.3-31.2 mgL-1), Dissolved Oxygen DO (3.30-3.90 mgL-1). These were higher than the FEPA limit for effluent discharge. However, physico chemical analysis revealed low, species diversity of aquatic fauna in Ibeshe River. This suggests that effluent discharge into the river is hig7hly toxic to brackish water fauna species. Keywords: Toxicity, effluent, Oreochromis niloticus, Paleamonetes africanus, physico-chemical parameters. JOAFSS Vol. 4 (1) 2006: pp. 194-203