Bioconcentration, metabolism and spatial distribution of 14C-labelled laurate in the freshwater amphipod Hyalella Azteca

Regulatory assessment of the bioaccumulation from water is commonly based on bioconcentration factors (BCF) derived from fish flow-through tests. Such experiments require many laboratory animals and are time-consuming and costly. An alternative test set-up for organic, neutral compounds using the amphipod Hyalella azteca was recently suggested, resulting in BCF values, which show a strong correlation with fish BCF data. In the present study, the bioconcentration potential of the ionic compound laurate was elucidated in H. Azteca. The sodium salt of 1-14C laurate was applied to H. azteca in a flow-through and a semi-static approach. Due to rapid biodegradation, a semi-static approach with frequent media replacements was required to ensure stable media concentration. Laurate was also rapidly metabolised by H. azteca. A large proportion of the total radioactivity measured in the amphipod tissue was not extractable suggesting that mineralised laurate was accumulated in the calcified exoskeleton of H. azteca. This was confirmed in a further study using carbonate [14C]. A lipid normalised (5.0 %) Hyalella BCF of 8.9 was calculated for laurate, measured as free fatty acids. The results of the bioconcentration studies with H. azteca confirm the low bioaccumulation potential of the test item previously observed in fish. However, more organic ionic compounds with various properties need to be tested to assess whether a general correlation between fish and Hyalella BCF data exists.