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(326) Differential uptake of a sediment-bound organic compound in four aquatic macroinvertebrates: potential mechanisms. Gaskell, Paul1, Maltby, Lorraine1, Marshall, Stuart2, 1 2 ABSTRACT- Exposures of Gammarus pulex, Asellus aquaticus, Lumbriculus variegatus and larval Chironomus riparius to artificial sediment dosed with distearyl-dimethylammonium chloride (DODMAC) resulted in apparent uptake of this extremely lipophilic compound. The measured body loadings in gut-purged individuals differed between species such that C. riparius>G. pulex=A. aquaticus>L. variegatus. Here we investigate four possible mechanisms for these inter-specific differences: selective feeding, differential gut retention time, organism lipid content and metabolic ability. DODMAC preferentially associates with small particles within bulk sediment therefore selective feeding on these particles will result in greater uptake. Lipophilic compounds may also preferentially associate with the organic fraction of sediment. Both particle size and loss on ignition values for faecal pellets of each species were used to compare the quality of ingested material. Uptake may also be enhanced by increased gut retention times. Therefore gut retention times were established for each study species and related to ranked tissue loading. Organism lipid content was measured for each species since, for lipophilic compounds, this potentially limits maximal tissue loading. Potential for reduction of DODMAC tissue loadings via metabolism was investigated using HPLC of organism tissue extracts to test for the presence of metabolites. These four mechanisms are evaluated with respect to the previously observed tissue loadings in each species. Key words: Bioavailability |
