METAL CONCENTRATIONS IN CHIRONOMIDS IN RELATION TO THE GEOCHEMICAL CHARACTERISTICS OF SURFICIAL SEDIMENTS

Concentrations of Fe, Mn, Al, Zn, Cu, and Cd were determined in Chironomidae (Diptera) sampled from three locations in six lakes ranging in pH from 5.0 to 6.5. Results of a two-way ANOVA with sample location and lake as the two co-factors showed that, in general, chironomid larvae metal concentrations were lake and sample site dependent (P < 0.05). To determine if differences in chironomid larval metal concentrations among the six lakes could be related to the geochemistry of the sediments, specifically concentrations of: organic matter, reducible Fe (Fe oxides), easily reducible Mn (Mn oxides) and metal (Fe, Mn, Al, Zn, Cu and Cd) associated with either the easily reducible, reducible and alkaline extract (organic) components of the sediment, a partial correlation analysis was employed. Chironomid Mn, Al, and Fe concentrations correlated positively with total sediment Mn, Al, and Fe concentrations, respectively, and negatively with organic matter; chironomid Zn and Cu concentrations correlated positively with an easily reducible measure of sediment Zn and Cu concentrations and negatively with sediment concentrations of reducible Fe. No combination of sediment geochemical variables significantly correlated with chironomid Cd concentrations. These results support the hypothesized action of reducible Fe (Fe oxides) modifying Zn and Cu accumulation by chironomids. In contrast, sediment organic matter rather than reducible Fe modifies Mn, Al, and Fe accumulation in chironomids.