Productivity and sustainability of water are usually known by the physicochemical properties of water quality. Due to indiscriminate release of wastes, physico-chemical characteristics of water do changes and this could cause hazard effect to flora and fauna of the aquatic ecosystem. Naturally, waters contain some impurities such as metals whose nature and amount vary with source. Some trace metals like copper, zinc, cobalt, iron, and manganese are essential nutrients to plants at very low concentrations.

However, high concentrations of these metals are potential toxins to many biological systems. Reports have shown that high level of pollution with heavy metals result from terrigenous activities, atmospheric precipitation, industrial discharge or domestic sewage and non-point source run-off . The hazard of an environmental chemical is a function of its environmental persistence, toxicity, and bio-accumulative potential. Hence, heavy metals are considered hazardous due to its persistence, bioaccumulation, and toxicity features.

In many developing countries, improper management of domestic waste, burning of fossil fuels, industrial wastes, agricultural run-off and mining of metals have created a potential source of pollution in the aquatic environment of many countries including Nigeria. Some recent research findings have shown that there is continual pollution of Nigerian waters as attested to by high accumulation of toxic metals in fishes caught in them .As a result, it becomes imperative to carry out periodic assessment of aquatic ecosystems in Nigeria. 
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Lucy Morgan
Editorial Coordinator
Journal of Ecology and Toxicology
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