Modelling cadmium accumulation by benthic invertebrates in situ: The relative contributions of sediment and overlying water reservoirs to organism cadmium concentrations

Abstract

An in situ experiment was designed (1) to determine the relative importance of Cd in the sediment versus Cd in the overlying water for its accumulation in benthic animals and (2) to test in situ the acid volatile sulfide (AVS) model. Sediments of a low-Cd shield lake were artificially contaminated with various amounts of Cd and placed at a littoral site in open plastic containers in the lake bottom for 11 months to allow colonization by indigenous lake bcnthos. Gradients in sedimentary and interstitial water Cd concentrations were, thus, created in situ, although Cd concentrations in the overlying water remained low. Accumulation of Cd by benthic invertebrates was significantly and linearly correlated with sediment Cd concentrations across treatment levels for most taxa. The magnitude of the response to the sediment Cd gradient was taxon specific and consistent with differences in animal ecology. Despite the high Cd contamination levels attained in the experiment, the population densities of most taxa appear to have been unaffected by the presence of Cd. We used the results from the experimental containers to predict the sources of Cd for benthic animals in the environs. For almost all of the taxa studied, individuals living in the lowCd sediments outside the experimental containers accumulated their Cd almost exclusively from the overlying water; only the burrowing, sediment-feeding taxa Chironomus stuegeri and members of the Tubificidae obtained substantial Cd from the sediment. Cadmium activities in the pore waters of the containers were in agreement with the AVS model, but the Cd concentrations found in the benlhic organisms did not. Our results from this shield lake suggest that predictions of Cd concentrations in most benthic animals would be more accurate if they were based on water column rather than on sedimentary Cd concentrations.Metals associated with sediments pose a potential threat to benthic organisms and from there to upper trophic levels. Before expensive remedial actions are undertaken, the extent to which benthic animals accumulate sedimentary metals, the biological effects of these contaminants, and the effects of various remedial actions on both water quality and organisms need to be determined. To accomplish these tasks, environmental agencies need reliable predictive tools; however, the majority of the tools currently available are unsatisfactory (Luoma 1995). Our ability to predict the biological consequences of metal-contaminated sediments would be improved by the development of reliable models relating metal bioaccumulation or toxicity to metal concentrations in the environment of benthic organisms. For general application, such models should be based on solid scientific grounds, i.e., they should have a theoretical rather than a I Present address:

Exchange rates of cadmium between a burrowing mayfly and its surroundings in nature

“…These results are consistent with those reported for H. limbata colonizing Cd-amended sediments in open containers on a lake bottom, where nymph Cd concentrations reached a plateau after ϳ18 d (Warren et al 1998). The results of laboratory experiments also suggest that rapid Cd exchange rates are typical for aquatic insects.…”

Bioaccumulation of metals in aquatic insects of streams located in areas with sugar cane cultivation

“…32,35 Although predator species can accumulate high concentrations of metals, our results point that, depending on the sediments contamination, the collector organisms as Chironomus larvae, because of their close association with the sediments (benthic organisms) and functional feeding group, accumulate higher concentrations of metals than other groups of aquatic insects. The results also suggest that, with low sediment contamination, as occurred in the S3 stream, predator species accumulate metals in high concentrations, probably by food ingestion, composed of different aquatic organisms.…”

Influence of reactive sulfide (AVS) and supplementary food on Ag, Cd and Zn bioaccumulation in the marine polychaete Neanthes arenaceodentata

“…The geochemical nature of the metal-sediment association and the relative distribution of metals between porewater and sediments could have considerable influence on the eventual fate and bioavailabililty of metals to aquatic organisms (Luoma & Bryan 1982, Di Toro et al 1990, Lee & Luoma 1998. Transfer of metals from sediments to benthic organisms may also be affected by biological attributes of animals such as feeding behaviors, life habits, reproductive cycles, growth, and size (Cain & Luoma 1990, Arifin & Bendall-Young 1997, Warren et al 1998, B. G. Lee et al 2000a) Studies (e.g., Morse et al 1987, Di Toro et al 1990 have recognized reactive sulfides (AVS, acid volatile sulfide) in sediments as a major factor controlling porewater metal chemistry. The AVS consists largely of amorphous iron sulfides and is typically extracted with cold weak acid (1 N HCl).…”