TITLE:
The Limnology of Ohana Lake, a Potential Manmade Aquaculture System in Nigeria
AUTHORS:
Paul O. Ajah
KEYWORDS:
Limnology; Aquaculture; Productivity; Pollution; Fishery; Benthos
JOURNAL NAME:
Open Journal of Applied Sciences,
Vol.3 No.2,
June
20,
2013
ABSTRACT: The concentrations of heavy metals (Fe > Zn > Cu > Pb > Ag) in
bottom sediments and fish gills in Ohana Lake, were found to be significantly
high and far exceeded FEPA and WHO environmental standards for water quality by
1.5 to 18 times, respectively. Six classes of each of phytoplankton and
zooplankton with a total of 35 phytoplankton taxa comprising 46 species i.e. 35(46) and 22(28) faunal were
observed. The class Chlorophyceae dominated the phytoplankton community with
18(22) followed by Cyanobacteria 6(10). The aquatic fauna was dominated by the
Rotifera 8(11), followed by the Copepoda 6(9). The benthic flora community
consisted of five classes of phytoplankton made up of 28(36). The class
Bacillariophyceae 11(15) dominated the group followed by Chlorophyceae 10(11).
Benthic fauna were made up of seven classes of 13(13). The dominant class
Nemata 4(4) was followed closely by Protozoa 2(3). Ohana Lake
is fast turning to a eutrophic ecosystem with accompanied algal bloom due to
very high nutrient contents. The equitability or evenness indices (J) for both
phytoplankton and zooplankton were lowly indicating generally low species
diversities as well as predominantly unstable ecosystem. The aquacultural
implications of these parameters are discussed.