Water quality and planktonic community of Owalla Reservoir, Osun State, Southwest Nigeria
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Date
2022
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Acta Limnologica Brasiliensia
Abstract
Aim: Owalla Reservoir, one of the largest and oldest man-made lakes in Osun State
supplies potable water to many towns in the state including the state capital, Osogbo. Active fshing
activities also takes place in the lake. Inspite of the importance of the reservoir, information on the
planktonic community and physico-chemical water quality are scarce. Terefore, this study investigated
the water quality and plankton composition of Owalla Reservoir, Osun State, Nigeria, from October
2012 to November 2013 with a view to providing baseline information on limnology of the reservoir.
Methods: Seven sampling stations (designated Stations 1-7) were established as representatives of the
zones and regions of the reservoir and sampling was conducted quarterly. At Stations 1 and 3, only
surface water samples were collected while water samples were collected from the surface, mid-depth
and close to the bottom at other stations. Samples for total plankton and physico-chemical water
quality were analyzed using standard methods. Results: Te result of the study showed that mean
dissolved oxygen (P<0.001), biochemical oxygen demand, conductivity, pH (P<0.001), and alkalinity
were higher at the surface of the reservoir. As regards seasonal variation, alkalinity, biochemical oxygen
demand had the higher mean values during the rainy season. Also, acidity, dissolved oxygen, and
pH showed signifcantly (P<0.001) higher values during the rainy season. One hundred and thirtyseven (137) taxa of phytoplankton and 39 taxa of zooplankton were recorded from the reservoir. Te
horizontal pattern of variation showed an increase in the mean abundance of most of phytoplankton
groups from inflow to the dam area while vertical variation showed a decrease in mean abundance
from surface to the bottom of the reservoir. Most of the phytoplankton and zooplankton taxa were
more abundant during the dry season than in the rainy season. Conclusions: Te study concluded
that all the monitored physico-chemical water quality parameters were within the guide level range as
of the World Health Organisation (WHO) for drinking water, Owalla Reservoir is qualitatively rich
in both phytoplankton and zooplankton and the reservoir can support a viable aquatic community
and sustainable fshery production
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Citation
Omoboye, H.Y. et al. Water quality and planktonic community of Owalla Reservoir, Osun State, Southwest Nigeria. Acta Limnologica Brasiliensia, 2022, vol. 34, e11