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Studies were carried out on the trace metal contamination of Sarotherodon melanotheron from Alaro stream in Ibadan, Nigeria. Fish were collected between January and December 2003 (Dry and rainy season).Muscle, liver, bone, gills, gut and fins were analyzed for arsenic (As), cadmium (Cd) and lead (Pb) using the inductively coupled plasma-mass spectrometer (ICP-MS).Quality assurance of the results was ensured through the use of bovine liver from the National Institute of Standards and Technology (NIST) as a standard reference material. The range of As, Cd and Pb in the fish organs was 0.000-0.154ppm, 0.000-0.302ppm and 0.00-4.03ppm respectively. Mean concentration of As in all the organs exceeded World Health Organization (WHO) standard while that of Cd concentration in the muscle, gut and fins were below and the liver and gills exceeded it. For Pb, apart from the fins (0.48ppm), all the other organs exceeded the WHO recommended limit standard. The study shows that Alaro stream is polluted and fish (S.melanotheron) caught from it is unfit for human consumption due to public health consequences.

The trace metal levels in the tissues of two popular leafy vegetables Amaranthus caudatus and Corchrus olithorus widely consumed in Nigeria were assessed from a cultivated floodplain receiving effluents from diverse factories in Ibadan. Although the leaves are primarily consumed, the stems are usually used as a feed for farm animals while the roots are disposed by burning when dry or by composting. The objective of this work was to evaluate the level of trace elements in the tissues of these vegetables at harvest time when they become available to the human ecosystem for exposure to the accumulated trace metals, especially the leaves which are cooked and eaten as soup. The results of the mean trace metal levels in the analyses show that the leaves of A. caudatus had the highest bioconcentration in the following order Ba>Mn>Zn>Cu>Pb>Cr>Co>Ni>Cd>U>Sb, stems: Ba>Zn>Mn>Cu>Cr>Pb>Ni>Co>Cd>U>Sb, and roots: Mn>Ba>Zn>Cu>Cr>Pb>Ni>Co>U>Cd>Sb. In C. olithorus, the order was Mn>Ba>Zn>Cu>Pb>Cr>Co>Ni>Cd>Sb>U in the leaves, Mn>Zn>Ba>Pb>Cr>Cu>Co>Ni>U>Cd>Sb in the roots, and Mn>Zn>Ba>Cu>Cr>Pb>Co>Ni>Cd>U>Sb in the stems. The final result of the vegetable samples showed that the trace metal concentration was in the range of Cr (0.8-58.7), Mn (35.0-9,495.9), Co (0.3-33.6), Cu (2.3-60.3), Zn (16.0-538.2), Cd (0.000-40.53), Sb (0.000-0.037), Ba (13.0-1,175.6), Pb (0.9-39.7), and U (0.0-2.2). The bioconcentration factors (BF) for the transfer of trace metals from soil to the tissues showed a higher ease of bioaccumulation when compared to previous studies. The element with the highest BF in the study was Ba (6.45) in the leaves while the least was Co (0.09) in the roots of A. caudatus. The level of bioconcentration of trace metals in the leaves in most of the samples exceeds the recommended levels given by the World Health Organization (WHO) and Federal Environmental Protection Agency (FEPA), Nigeria and therefore constitutes a potential public health risk to the populace who consume these vegetables cultivated in effluent-impacted floodplains.

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Studies were carried out on the distribution and abundance of plankton in Awba stream and reservoir, University of Ibadan over a period of four months between November 2011 and February 2012. Studies were carried out at four selected stations comprising station 1 as the entry point of the stream into the University, which also served as the control, station 2 receiving sewage, station 3 downstream along the stream and at a point along Awba Reservoir serving as station 4. 1 ml aliquot of each plankton sample from the study stations were examined under a binocular microscope while identification of the plankton was carried out using standard textbooks. The results of the phytoplankton indicated the absence of Microcystis flos-aquae, Agmenellum and Oscillatoria limnetica in station 1 while members of the family bacillariophyceae appeared at all stations. All species of chlorophyceae family except Spirogyra were peculiarly absent at station 2. Other phytoplankton representatives at this point (station 2) included Microcystis, Anabaena, Oscillatoria and Melosira. Paramecium was the only zooplankton group that was absent in station 1 but the only species presented in station 2. This station also revealed the lowest diversity indices and very low or no Jaccards coefficient of similarity with the other stations. The overall differences observed in the abundance, species richness, Margalef and Shannon-Wiener indices of diversity of plankton in the study reveal self purification or recovery downstream from the effluent discharge.