Spatial and temporal variations of physicochemical variables in a small pristine stream in Niger Delta, Nigeria. (Special Issue: The future of fisheries in a changing global climate.)

摘要

Spatial and temporal variations of physicochemical variables of Onu-Iyi-Ukwu stream were studied for 12 months from March 2005 to February 2006. Three sampling stations were established along the main stream channel from source to mouth. Spatial variation in physicochemical parameters indicated that total alkalinity, total hardness, conductivity and nitrate-nitrogen (NO₃) recorded their highest values at the upper reaches (with values 14.0 mg L-1, 88.09 mg L-1, 17.00 micro S cm-1 and 0.60 mg L-1, respectively). Dissolved Oxygen (DO) and pH had their maximum values of 8.20 and 6.94 mg L-1 at the middle reaches. Turbidity, Biochemical Oxygen Demand (BOD), temperature and phosphate-phosphorus (PO₄) increased steadily from source to mouth. The observed seasonal variation indicated that wet season values were higher for all the parameters except temperature, turbidity, phosphate-phosphorus (PO₄) and total alkalinity although the values were not statistically significant at p>0.05. The correlation coefficient (R) showed no significant relationships at p<0.05 between physicochemical parameters except DO and BOD with correlation values of 0.75 and -0.54, respectively.