Many relationships of bioaccumulation of metals have been derived in the past, but verification in the field is often lacking. In the present study, the authors collected field data on bioaccumulation in caged Daphnia magna and Gammarus roeseli in 12 different contaminated brooks. Besides generating a comprehensive data set on bioaccumulation for these species, the authors also checked whether the bioavailability at the biotic ligand is useful to explain differences in observed bioaccumulation. Increasing bioaccumulation of Mn, Cd, Co, and Ni was observed, which leveled off at higher concentrations. Whole-body concentrations of Ca, Na, Mg, K, Fe, Cu, Se, and Zn were independent of exposure concentrations. Univariate and multivariate regressions were performed to examine the relationships between accumulated metals and dissolved metal concentrations (C(w) ), fractional occupancy of the biotic ligand (f(BL) ), species weight, and other undefined species traits. Significant relations between body weight and bioaccumulation were found for Na, Fe, Mn, Cd, Co, and Zn; smaller organisms accumulated larger amounts of these elements. Reduced body weight was accompanied by elevated concentrations of Co, Cu, and Fe in D. magna and elevated concentrations of Mn in G. roeseli, indicating toxicity. Although significant relations were found between bioaccumulation and f(BL) for Mn and Co, C(w) was a better predictor of bioaccumulation.
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