Spatial and Temporal Fluctuations of Physico- Chemical Parameters, Nutrients and Primary Productivity of Gbalegbe River, Delta State, Nigeria

Abstract

Inland waters are very unstable ecosystems. They are affected by anthropogenic and natural activities. Consistent monitoring of the physico – chemical, nutrients and primary production parameters in surface water in Nigeria is vital to the management of the aquatic environment. However, information on the fluctuation patterns of physico – chemical parameters, nutrients and primary productivity of Gbalegbe River is limited. Therefore, the fluctuation dynamics of physico – chemical parameters, nutrients and primary productivity of Gbalegbe River, Delta State, Nigeria were investigated. Gbalegbe River (12.5 km) was spatially stratified into eight zones (S1, S2, S3, S4, S5, S6, S7, and S8) based on proximity to key anthropogenic activities. In each station, three sampling points were randomly selected. Temporal stratification covered wet (March - October) and dry (November – February) seasons. Water samples were collected from each station forth – nightly for 24 months following standard methods. Water samples were analysed for Dissolved Oxygen (DO, mg/L), Temperature (oC), Nitrate (Nitrate, mg/L – N), Sulphate (SO42-, mg/L), Magnesium (Mg, mg/L) and Gross Primary Production (GPP, gC/m2/d) using standard procedures. Data were analysed by using descriptive statistics and ANOVA at α0.05. The highest (4.52±0.56) and least (3.13±0.67) DO were obtained in S1 and S2, respectively. Temperature ranged from 24.28±5.84 to 28.45±2.06 in S3 and S2; Nitrate (1.07±0.03, 1.76±0.21) in S6 and S2, respectively. Temperature values were 27.55±1.60, 26.94±1.97; DO (5.75±0.73, 4.00±0.66) and Nitrate (1.05±0.64, 0.98±0.43) in dry and wet seasons, respectively. Sulphate ranged from 0.80±0.26 to 1.63±0.26 in S2 and S8; Mg (63.30±6.30, 67.51±4.95) in S7 and S1, while GPP values were 10.05±0.09 and 25.75±0.83 in S1 and S2, respectively. Seasonally, Sulphate ranged from 0.97±0.06 to 1.24±0.33; Mg (63.13±20.73, 65.94±6.01) and GPP (20.19±4.91, 35.34±6.37) in wet and dry seasons, respectively. The patterns of physico – chemical parameters, nutrients and primary productivity of Gbalegbe River are fairly unstable with DO, thus its rich fisheries resources could be threatened. Keywords: Inland water, Gbalegbe River, Fisheries resources, Anthropogenic activities.