The quality of major rivers (Oluwa, Owena, Ogbese and Ose) along the highways in Ondo state, Nigeria
were investigated using water, surface sediment and African catfish, Clarias gariepinus, as
environmental indicators. Results from the study revealed that some of the water quality constituents
exceeded the World Health Organization (WHO) standards for drinking water and water meant for other
recreational uses. Of the four metals (Cd, Cu, Pb and Zn) determined, only Cd was recorded at toxic
level in both water and sediment based on WHO and sediment quality guidelines respectively. Elevated
concentrations of some pollutants detected in surface sediments and water are attributable to run-off
from agricultural site and commercial activities. The pH, EC, TDS and PO4
3- of the water displayed
significant positive correlation with Pb (p = 0.05) and Zn (p = 0.01) while Cl- equally showed correlation
with all the metals. The index of geoaccumulation (Igeo) seems to be a more objective tool for assessing
contamination. Highest and least microbial load were (439 × 106 cfu/100 ml) and least (259 × 106 cfu/100
ml) respectively. In the fish, the highest and least bioaccumulation factors (BAF) were recorded for Pb
and Cu respectively. The bioaccumulated heavy metals in the tissues of C. gariepinus were above the
acceptable limits stipulated by international codes of practice, implying critical pollution in the biota.
Key words: Anthropogenic input, heavy metals, seasonal changes, sediment, pollution.