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(474) Effect of sediment particle size on metal bioavailability and toxicity in the midge, Chironomus tentans.
Walski, Kristina*,1, Shafer, Sarah1, Clements, William1, Ranville, James2, 1 Colrado State University, Fort Collins, CO, USA2 Colorado School of Mines, Golden, CO, USA
ABSTRACT- Metal contamination in sediments is a major problem in many aquatic systems. Factors such as organic matter and small sediment particle size can cause metals to adsorbed to sediment particles. It is poorly understood as to how these factors might alter the bioavailability of sediment-associated metals. To investigate the influence of particle size on Zn bioavailability to Chironomus tentans, organisms were exposed to size fractioned sediment (<53, 53-212, >212 m) from a contaminated site (North Fork of Clear Creek) and a reference site (Cache la Poudre River). Organisms were able to regulate Zn when exposed to contaminated sediments of all size fractions. Zn sediment concentrations were higher in the smallest size fraction (<53 m, 868 mg Zn/kg) compared to other size fractions (53-212 m, 257 mg Zn/kg and >212 m, 148 mg Zn/kg), but body burdens of Zn were not significantly different over all sediment sizes. Growth was reduced by 80% as compared to reference sediment in the smallest size fraction (<53 m). In larger size fractions growth was less affected (56% reduction in 53-212 m, and 36% reduction in >212 m). This suggested that Zn associated with smaller sediment particles is more bioavailable due to a dietary route of exposure. This research reinforces the importance of both the dietary and aqueous route of exposure when assessing metal toxicity and bioavailability in aquatic environments.
Key words: sediment, bioavailability, metals, particle size
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