ABSTRACT

The Study on the limnological survey of Aham Umuoke River in Obowu Local Government Area of Imo State was carried out from June to August 2013 to determine the physicochemical and plankton characteristics of the river. Water sample was collected twice every month and taken to optimum analytical research laboratory for analysis. Temperature, pH, dissolved oxygen, biological oxygen demand transparency, total hardness, total alkalinity, nitrate and phosphate as well as phytoplankton and zoo plankton were analysed. The result showed that dissolve oxygen has the highest mean value in August (5.79±0.35 mg/1) while June (4.88±0.05mg/l.) and July (5.05±0.13mg/l were significantly the same. Biochemical oxygen demand mean value (6.55±0.24mg/l, 7.06±0.26mlg/l) and 7.48±0.178mg/l for June, July and August respectively were observed to be significantly different from each other with August as the highest and June as the lowest. The pH values were observed to be significantly different from each other with August (7.15±O.O23) as the highest and June (6.82±0.024) as the lowest. Transparency mean value in July (34.19±1.14cm) was observed to be significantly higher and statistically different from June (31.20±1.13cm) and August (31.67±1.65cm). Alkalinity mean value in August (81.44±1.44mg/l) was observed to be significantly higher and statistically different from June (78.56±0.92mg/l) and July (79.16±0.50mg/l). Nitrate was observed to be highest in August (4.70±0.950mg/l)and lowest in June (3.23±0.65mg/l). The mean value of phosphate range between 2.62±0.11 mg/1 in June, 2.87±0.11mg.l in July and 3.35±0.18mg/l in August with August having the highest mean value and June having the lowest mean value. The mean value of total hardness was significantly higher in August (29.05±0.059mg/l) and lower in June (23.823±0.98mg/l). The highest temperature range was observed in June (26.83 ± 0.76°C) while July (24.33±I.22°C) and August (24.17 ± 1.50°C) were statistically the same. The phytoplankton identified during the study period were Euglena, Anabaena, Volvox, Spyrogyra and Chlorella. Euglena was observed to be significantly the same throughout the study period and was the highest abundant with the total value of 34.5. Anabaena composition was highest in August (4.00 ± 0.00pm) while June (4.00 ± 1.4pm) and July (7.00 ± 0.00pm) are statistically the same. The mean values of Volvox ranged between 3.00 ± 0.00pm in June, 6.00 ± 0.00pm in July and 3.00 ± 0.00pm in August .the mean value of Spyrogyra was significantly higher and statistically the same in June (9.00 ± 1.41pm) and August (3.50 ± 2.12pm) while July (2.50 ± 0.71pm) was lower. Anabena, Volvox and Spyrogyra has an equal number of 15. Chlorella was statistically the same in June (2.500 ± 0.71pm) and August (2.500 ± 0.71pm) and different from July (2.00 ± 0.00pm). The zooplankton identified were Rotifera, Daphnia, Brachionus, Diatomas and Cyclops. Rotifera was observed to be statistically the same throughout the study period and was the most abundant with the total number of 31. Daphnia abundance was observed to be highest in August (5.500 ± 3.54pm) while June (3.00 ± 1.42pm) and July(8.00±1.42pm)were statistically the same. Brachionus abundance recorded 3.500±0.707pm in June, 3.500± 2.12pm in July and 2.50±071pm in August with August being statistically higher and June lower. Brachionus was the least abundant with a total value of 9.5. Diatomas was observed to the statistically the same and significantly higher in June (4.50±2.12pm) and August (3.00±1.41pm) while July (5.00±0.17pm) was different. Cyclops abundance was highest in August (3.500±0.17pm) while June (3.50±2.12pm) and July (9.00±2.83pm) were statistically the same. These study shows that August Recorded the highest number of organism found in Aham River. This is because in August the water parameters studied were in the level recommended as good for Aquatic life.