STUDY ON WATER QUALITY PARAMETERS AND BENTHIC FAUNA DIVERSITY OF OTAMIRI RIVER IN OWERRI, IMO STATE, NIGERIA.
The study on the physic-chemical parameters and benthic fauna diversity of Otamiri River, Nigeria was carried out from June to December 2015. Water and benthic organisms samples were collected monthly from three sampling stations along the stream. Dissolved oxygen bottles of 1000 ml were used to collect water samples which were fixed with wrinkle’s reagent at the sampling stations. Eckman grab, scoop net, hook and line, cast net, traps and dugout canoe with paddle were used to collect the benthic macro fauna for six months (June-August and October to December). The results of the study yielded 229 benthic organisms belonging to 15 species and 14 families. In relation to stations, Station 3 had more species and higher abundance of benthic organisms than other sampled stations. In Station 1, only six species of benthic organisms were recorded while Station 2 had 11 species and Station 3, 13 species of benthic organisms. Majority of the sampled benthic organisms were localized and restricted to one sampled station which was Station 3. The abundance of benthic organisms in Otamiri River was dependent on season. More benthic organisms were recorded in dry season than in rainy season. The diversity indices yielded high diversity in Station 3 than the other two studied stations. More species dominated with high diversity index in dry seasorn than in wet season in all the sampled stations. Mean values of surface water temperature 26.67±0.63 0C, depth 1.96±0.48 m, COD 25.11±0.24 mg/L, BOD 5.47±0.04 mg/L, DO 5.91±0.19 mg/L, Alkalinity 10.66±0.21 mg/L, pH 6.73±0.16, TDS 315.2±48.5 mg/L, Hardness 0.64±0.08 mg/L, Turbidity 4.52±0.16 NTU and TSS 8.68±0.75 mg/L were recorded. There were fluctuations between the physico-chemical parameters caused by anthropogenic activities, stress to the aquatic life and pollution. Shannon wieners diversity index H = 2.24 was higher in Station 2, while Simpson’s dominance index D= 8.5 was also high at Station 2. Temperature, Depth, BOD and TSS correlated positively and favoured the abundance and of Synodontis spp. Temperature, BOD, Turbidity and TSS were also positively correlated and favoured the abundance of C. nigrodigitatus and C. armatum. Negative correlation was recorded in P. serratus in all parameters and in all seasons and stations C. nigrodigitatus was the most abundant species recorded in the present study (32.65%) while the least abundance species was P. serratus (1.25%) and both were found only in Station 3. The pH, BOD, TDS, hardness, turbidity, DO, BOD, COD and temperature ranges fall within WHO recommendations. Government should make laws restricting dredging and sand mine activities in the sampled area.