Arch. Environ. Contam. Toxicol. 27, 186-194 (1994) ARCHIVES OF: Environmental Contamination a n d Toxicology © 1994 Springer-Verlag New York Inc. Metal Concentrations in Chironomids in Relation to Peatland Geochemistry L. Bendell-Young 1, J. Chouinard 2, F. R. Pick 3 Department of Biological Sciences, Simon Fraser University, Burnaby, British Columbia, V5A 1S6, Canada 2 Department of Indian and Northern Affairs, Hull, Quebec, K1A 0H4, Canada 3 Department of Biology, University of Ottawa, Ottawa, KIN 6N5, Canada Received: 18 October 1993/Revised: 19 February 1994 Abstract. Concentrations of Zn, Cu, A1, Fe, and Mn were determined in Chironomidae (Diptera) larvae sampled from three sites within eight peatlands, located in south-central On- tario, Canada. The eight peatlands displayed a range in pH and alkalinity and were classified abiotically (i.e., chemically, hy- drologically) and biotically (i.e., dominant vegetation present) as mineral-poor, moderately poor, or as mineral-rich fen. Sur- face peats of mineral-poor fens were distinct from those of moderately poor and mineral-rich fens; mineral-poor fens con- tained higher concentrations of organic matter with low concen- trations of easily reducible Mn vs. the moderately poor and mineral rich fens. A one-way nested ANOVA indicated that chironomid metal concentrations were peatland dependent (P < 0.05). To determine if differences in chironomid metal concen- trations among the peatlands could be related to peat geochem- istry, an R a MAX procedure using peat geochemistry as the independent variable and chironomid metal concentrations as the dependent variable was applied. Peat geochemistry was defined as concentrations of peat organic matter, reducible Fe (Fe oxides), reducible Mn (Mn oxides) and easily reducible metal (where metal = Zn, Cu, A1, Mn and Fe), and reducible metal and organically bound metal. Chironomids from mineral- rich peatlands, i.e., peatlands low in organic matter with high concentrations of reducible Mn and Fe or easily extractable metal contained greater concentrations of Zn, Mn, and Fe vs. chironomids sampled from mineral poor peatlands, i.e., peat- lands with high concentrations of peat organic matter and low concentrations of reducible Mn or easily extractable metal. In contrast, Cu concentrations were greatest in larvae sampled from mineral-poor vs. mineral-rich peatlands. Aluminum lar- vae concentrations were independent of peat geochemistry. We suggest that bioavailability of metals such as Zn, Fe, and Mn will be greater to invertebrates inhabiting mineral rich vs. min- eral poor fens, whereas greater chironomid Cu concentrations will be found in chironomids sampled from mineral poor fens. Differences in metal availability to invertebrates among peat- land types has important implications when comparing the im- Correspondence to: L. Bendell-Young pact of contaminant transfer to higher trophic levels among different types of peatlands. The anthropogenic perturbation of trace metal cycles has re- suited in increased emissions of many metals into aquatic envi- ronments (Forstner and Wittman 1981). To be able to predict the impact these contaminants are having on the receiving envi- ronment, it is important to develop an understanding of the factors that control the speciation and hence the bioavailability of these contaminants to aquatic organisms. Although the be- havior of trace metals in lake sediments and estuaries in relation to metal bioavailability recently has received attention (e.g., Luoma and Davies 1983; Campbell et al., 1988; Bendell- Young and Harvey 1992a; Tessier et al. 1993), few studies have addressed the geochemistry of metals within wetland peats as it relates to metal availability. The lack of research on metal availability in wetlands is surprising since wetlands are an important part of the Canadian landscape and cover a total of 12.76 × 105 km 2 (Gorham et al. 1984). Twenty-three percent of this area is located in Ontario (National Wetlands Working Group, NWWG 1988). Wetlands are prime nesting and breeding grounds for a variety of avian species which depend on the abundance of invertebrates within the wetlands for food. It is important that an understanding is developed of the factors which control the geochemical behav- ior and hence bioavailability of metals to benthic invertebrates within these systems. Recent studies of Albers and Camardese (1993a, 1993b) have suggested that metal concentrations in wetland inverte- brates are independent of wetland water chemistry (pH, metal concentrations) as well as experimentally induced changes to wetland surface pool pH. However, for benthic invertebrates, which live and feed directly on surface sediments, the influence of peat geochemistry may outweigh the possible influence of water column chemistry on metal availability to these benthic invertebrates. For example, in freshwater lakes, invertebrate metal concentrations have been found to be related to the geochemical characteristics of the sediments. Tessier et al. (1984) noted that invertebrate metal burdens correlated with a