Primary Productivity of Owalla Reservoir, Osun State, Southwest, Nigeria
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Date
2017
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New York Science Journal
Abstract
This study investigated primary productivity of Owalla Reservoir, Osun State, Nigeria. This was with a view to providing relevant information on the primary productivity of the reservoir. Sampling period covered rainy and dry seasons. Seven Sampling stations were selected on the reservoir for this study (designated 1, 2, 2 3, 4, 5, 6 and 7). At Stations 1 and 3, only surface water samples were collected for primary productivity while water samples were collected from three levels of water column (surface, mid-depth and close to the bottom) of the reservoir at other stations (Stations 2, 4, 5, 6, and 7). Primary productivity was determined using Oxygen Method. The data obtained were subjected to appropriate statistical analysis. The gross primary productivity of Owalla Reservoir during the study period ranged from 17.28 to 126.72 KCal/M3/day. The respiration of Owalla Reservoir during the study period ranged from 1.73 to 103.68 KCal/M3/day while the net primary productivity of Owalla Reservoir during the study period was in the range of 4.90 - 45.22 KCal/M3/day. Net productivity accounted for 34.7% of the Gross Productivity. Respiration accounted for 65.3% of the Gross Productivity. The mean value of the net productivity of the reservoir decreased vertically from surface to the bottom. The mean respiration decreased towards the dam site while the vertical variation generally showed decrease vertically from the surface level to the bottom of the reservoir (P≤0.05). Gross primary productivity decreased down the reservoir column from the surface to the bottom and there was very highly significant difference (P≤0.001) in mean value at the three vertical depths. The reservoir can be classified as oligotrophic based on its primary productivity level. However, the lake should be subjected to regular proper monitoring