Article ID | Journal | Published Year | Pages | File Type |
---|---|---|---|---|
9478375 | Aquatic Toxicology | 2005 | 12 Pages |
Abstract
The presence of sediment particles in the gut indicated that Daphnia magna used in whole-sediment bioassays ingest sediment. If gut contents are not removed prior to whole-body tissue-burden analysis, then the bioavailability of any sediment-associated contaminants (e.g. metals) can be overestimated. Gut clearing patterns were determined for D. magna after exposure to both clean and metal-contaminated (Cu and Zn) field-collected sediments. D. magna exposed to reference sediment had fuller guts than those exposed to metal-contaminated sediment (95% versus 60% full). Neither reference- nor metal-exposed D. magna could clear their gut completely of sediment particles when held in clean water for 24 h. When Daphnia were transferred to clean water after exposure to metal-contaminated sediment, there was no significant decrease in gut-fullness (P > 0.05) even after 48 h of purging. By comparison, animals transferred to water containing 5 Ã 105 cells of algae (Pseudokircheriella subcapita) after exposure to contaminated sediment showed a significant drop in gut fullness from 56% immediately after exposure to 17% after 4 h of gut-clearance. Although gut fullness did not change significantly beyond 2 h of purging, data were much less variable after 8 h of gut-clearance than after 2 h or 4 h. The depuration of Cu was well described with a two-compartment first-order kinetic model (r2 = 0.78, P < 0.0001) indicating that D. magna exposed to metal-contaminated sediment have one pool of Cu that is quickly depurated (0.2 hâ1), and one that has been incorporated into the tissues (âª0.00001 hâ1). Assuming tissue background of 48 μg/g, an exposed animal which has not been depurated or which has been purged with water alone would yield whole-body tissue Cu concentrations that are 5.6- and 4-fold higher, respectively, than that purged with algae + water (8 h). We recommend that D. magna used to estimate metal bioavailability from sediment be gut-cleared in the presence of algae for 8 h prior to determination of whole-body metal concentrations.
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Agricultural and Biological Sciences
Aquatic Science
Authors
P.L. Gillis, P. Chow-Fraser, J.F. Ranville, P.E. Ross, C.M. Wood,