Mouthpart deformities in Chironomidae (Diptera) as indicators of heavy metal pollution in northern Lake Victoria, Uganda

Due to the absence of appropriate and sensitive tools for monitoring heavy metal pollution in northern Lake Victoria (Uganda), this study investigated mouthpart deformities in chironomid larvae (Diptera) in relation to concentrations of lead, copper, cadmium and zinc in lake sediments, and to dissolved oxygen, pH and conductivity. The variables at two rural reference sites in Hannington Bay and two urban-industrial test sites in Napoleon Gulf and Fielding Bay near Jinja were compared. Of the total number of chironomids examined from the two urban-industrial sites, 4.7% and 3.7% (respectively) were deformed. No deformed chironomids were found at the two reference sites. Chironomid mouthpart deformities correlated with concentrations of copper and zinc among the listed metals, but with none of the physical variables. The presence of deformities in chironomid larvae was a sufficiently sensitive proxy measurement to indicate the presence of low concentrations of heavy metals. The higher incidences of mouthpart deformities observed in the larvae of Chironomus sp. II could make them potential bioindicator organisms for heavy metal pollution.