Ecotoxicity of mercury contaminated sediment collected from Mabubi river (Geita district, Tanzania) to the early life stages Of African catfish (clarias gariepinus)
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Date
2009
Journal Title
Journal ISSN
Volume Title
Publisher
Elsevier
Abstract
The quality of Hg contaminated sediments in artisanal gold mining areas of Tanzania
have to date only been assessed through bulk chemical analysis. However, measurement of
contaminant levels alone has a limited ability to predict adverse effects on living resources. In this
study we investigated the possible effects of Hg contaminated sediments from the river Mabubi
which drains the artisanal gold mine on the hatching success, larval survival and growth of the
African catfish (Clarias gariepinus). The tested species is a resident fish whose demersal behaviour
keeps it in frequent contact with the sediment. Sediments collected downstream of the mine decreased
survival and impaired growth of Clarias gariepinus but did not affect its hatching success. These
effects were observed up to six kilometres downstream of the mining activity. The calculated 5 d-
LC 50 value (larval survival) was 1.75 μg/g Hg dw (95% CL of 0.72 – 2.53), the 5d-NOEC for hatching
was >2.3 μg/g Hg dw and that for larval survival and growth was 0.23 μg/g Hg dw. In conclusion,
chemistry and ecotoxicity results from this study suggest that sediments collected downstream of
the mine adversely affect catfish and probably other fauna and as such present a considerable local
environmental risk.
Description
Journal Article
Keywords
Artisanal gold mine, Clarias gariepinus, Mercury, Sediment