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The water qualities of three rivers (Asu, Ebonyi and Cross) were evaluated for these physicochemical parameters: transparency, flow rate, depth, temperature, conductivity, total dissolved solid (TDS), pH, dissolved oxygen (DO), phosphate (PO4-) and nitrate (NO3-) for 12 months (August 2014-July 2015). The results showed variations in the water quality parameters among the rivers. Temperature, conductivity and TDS were highest in Asu River with mean values of 30.23 0 C, 88 µS/cm and 42.58 mg/L, respectively. The mean values of pH varied from 7.0 to 6.56 with the highest value (7.0) recorded in Ebonyi River and the lowest value (6.56) recorded in Mid-cross River. The mean value of DO was highest (5.8 m/Ll) in Mid-cross River and lowest (4.9 mg/L) in Asu River. The lowest mean values of transparency, flow rate and depth were recorded in Asu River, the highest (0.5 m) mean value of transparency was recorded in Mid-cross River while the highest mean value (1.48 m) of Flow rate was recorded in Ebonyi River. Variations in the mean value of nutrient in the water showed that PO4-(0.28 mg/L) and N03-(0.40 mg/L) were the highest in Asu River. The lowest PO4 was recorded in Ebonyi River (0.17 mg/L) while the lowest NO3 value was recorded in the Mid-Cross River. Variations in Temperature, DO, Flow rate and PO4 were not significantly different (P > 0.05) while conductivity, TDS and transparency were significantly different (P < 0.05). The results of most water parameters recorded are within the recommended limits of set standards for rivers.

Cypermethrin and dimethoate are pesticides frequently used in agriculture to eliminate pests. Contemporaneity of these and other pesticides in commercial preparations and several aquatic ecosystems is well known, though poorly studied. This study aims to evaluate the effect of sublethal concentrations of combinations of cypermethrin and dimethoate on juvenile catfish, Clarias gariepinus, given that the pesticides concomitantly occur in the floodplains were the fish breed. Behavioral, hematological and histopathological changes in juvenile fish exposed to sublethal concentrations were monitored for 96 hours. Pesticide exposed fish exhibited abnormal behaviors such as erratic swimming, frequent air gulping, sudden jerk movement and rapid opercula movement and these were more pronounced in higher concentrations. Significant reductions in erythrocytes (0.83-20.94%), hemoglobin (4.12-29.23%) and PVC (7.14-28.57%) and increase in leucocytes (4.84-9.32%) were observed (p<0.05). Mean corpuscular hemoglobin concentration (MCHC), mean corpuscular hemoglobin (MCH) and mean cell volume (MCV) reduced significantly in the exposed groups compared to the control. Infiltration of inflammatory cells, distortion of cell architecture, hemorrhage and necrosis were the observed histopathological damages in the heart, brain, gill, liver, kidney and fin of exposed fish. These pathological damages were more severe than previously reported for either chemical. Therefore, the use of these chemicals in agriculture should be regulated, especially near fish breeding sites.

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The bottom-up and top-down interactions of the abiotic and biotic components of Iyieke Lake were studied for eleven months covering a pre-flood, flood and post-flood periods. During the study, some water quality parameters were measured while plankton samples were collected for identification in the laboratory using standard method. The results of the water quality parameters measured showed that water temperature was highest (35.00R”C) in February. pH (7.10) and transparency (0.98 m) were highest in August. Highest TDS (28.0 mg/L) and conductivity (56.00 μS/cm) were recorded in March (pre-flood period) while dissolved oxygen level was lowest (4.00 mg/L) in the pre-flood period (February and March). Nitrate (0.18 mg/L) was highest in August (flood period) and phosphate (0.25 mg/L) at the two extreme periods (pre-flood and post flood). The depth of the lake was highest (3.2 m) in August which was the period of inundation. The phytoplankton (Bacillariophyta, Chlorophyta, Cyanobacteria) and zooplankton (Rotifera, Cladocera, Copepoda) of the lake were made of three divisions and taxa each, respectively. Bacillariophyta dominated among the phytoplankton while Rotifera was the most abundant among the zooplankton. The study revealed that nutrients and zooplankton grazing were the major factors that affected phytoplankton abundance and biomass during the study. Keywords: Flood; phytoplankton; Iyieke; water quality; zooplankton