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Articles by N.U. Benson
Total Records ( 3 ) for N.U. Benson
  N.U. Benson , M.U. Etesin , J.P. Essien , I.U. Umoren and M.A. Umoh
  Fishes are important bioindicators of the integrity of aquatic ecosystems and were used to evaluate the status of heavy metal pollution in an oil impacted aquatic ecosystem (Imo River) located within the Niger Delta region of Nigeria. The concentrations of Cd, Cr, Cu, Fe, Pb, Mg, Mn, Ni and Zn were determined using inductively coupled plasma spectrometer (Optima 3000-Perkin Elmer). The metal concentrations in liver and muscle tissues of Ethmalosa fimbriata (bonga fish), Chrysichthyes nigrodigitatus (catfish), Lutiana ava (pink snapper), Stellifer lancelatus (croaker) and Tilapia guineensis (Tilapia) were consistently higher in the livers than in the muscle tissues of all the five fishes. Magnesium concentration was anomalously higher in the muscle tissue than liver of C. nigrodigitatus, E. fimbriata and L. ava but not in S. lancelatus and T. guineensis. Muscle-liver ratios (MLRs) of the respective heavy metals ranged between 0.089 (CuM:CuL) and 1.299 (MgM:MgL) for C. nigrodigitatus, 0.186 (CrM:CrL) and 1.401 (MgM:MgL) for E. fimbriata, 0.194 (CuM:CuL) and 1.498 (MgM:MgL) for L. ava, 0.131 (CuM:CuL) and 0.646 (NiM:NiL) for S. lancelatus, 0.009 (CuM:CuL) and 0.916 (MgM:MgL) for T. guineensis. Interestingly, copper indicated least MLR in almost all the investigated fishes except in E. fimbriata. Magnesium showed the highest MLR in all fish species except in S. lancelatus. On the other hand, the cadmium/zinc ratios were higher in the muscle tissues than livers of all the fishes analyzed except in E. fimbriata. The threshold contamination value for human dietary risk was however, not exceeded.
  J.P. Essien , S.P. Antai and N.U. Benson
  In this investigation the extent to which sediment salinity gradients can be used to predict the sensitivity of microbial populations in mangrove ecosystem was investigated. The microbial groups monitored were heterotrophic bacteria, coliform bacteria, actinomycetes, fungi and yeasts. Pearson`s Product-Moment Correlation (r) analyses were done on Log10 - transformed estimates of population densities. The values obtained from the intertidal (epipellic) and subtidal (benthic) sediments were less than the critical value of 0.707 (n = 8, p = 0.05). This indicates that salinity was less closely related to the microbial population densities. A positive but insignificant relationship was found for fungi (r = 0.03) in intertidal sediment. The total heterotrophic bacteria (r = -0.69), coliforms (r = - 0.54), actinomycetes (r = -0.43) and yeasts (r = - 0.56) were negatively affected by salinity in epipellic sediment. But in the benthic sediment, total heterotrophic bacteria (r = 0.55) and unexpectedly, the fungi (r = 0.58) and actinomycetes (r = 0.29) exhibited positive but insignificant correlations while coliform and yeast counts in the benthic sediments were negatively influenced by salinity. However the coefficient of determinations (R2) revealed that total heterotrophic bacteria (48.06%) and yeasts (31.18%) were more extensively distributed in the intertidal sediments than coliforms (29.38%), actinomycetes (18.68%) and fungi (0.09%). In contrast, the fungi (33.48%) demonstrated a wider distribution in benthic sediment. This may be ascribed to their existence, mostly as dormant, but culturable spores in the anoxic bottom sediment. The weak relationship exhibited by coliforms further confirms their usefulness as indicator of faecal contamination in estuarine ecosystem.
  J.P. Essien , S.P. Antai and N.U. Benson
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