Mercury Concentrations in Water, Sediment, and Biota from Lake Victoria, East Africa

Abstract

Lake Victoria, East Africa, is the site of the world's most productive freshwater fishery. Mercury in muscle tissue of the 2+ and 3+ year old Nile perch ( Lates niloticus), presently the largest constituent of the fishery, was 90 to 250 ng /g wet weight. This is similar to the range of mercury in fish muscle reported for the commercial fish of the Laurentian Great Lakes (140 to 320 ng/g). The average total mercury in the water column (7.5 ng Hg/L; n = 14) was at the upper range normally defined for uncontaminated water (< 10 ng Hg/L). The average mercury concentration in the solid phase of the top 10 cm of sediments was 220 ng Hg/g close to that found in the surface sediments of the Laurentian Great Lakes. Methylmercury measured in the surface water near a variety of wetland vegetation was low with the possible exception of water collected near the roots of the water hyacinth, Eichhornia crassipes. Although the levels of mercury in fish are within the accepted guidelines of the FAO/WHO, the people living in the vicinity of the lake are likely to consume a greater quantity of fish than those living some distance away from the lake. It is important to educate the consumers of the fish from Lake Victoria about any potential risks and to monitor the fish mercury levels.