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(M/EH120) The gastro-intestinal solubilization of particle-associated methylmercury in channel catfish and atlantic sturgeon. Leaner, J1, Mason, R1, 1 ABSTRACT- Particle-bound metals are subjected to a solubilization process during its passage through the digestive systems of organisms, and as such become bioavailable to the organism. The intestinal solubilization of sediment-associated metals, as a measure of the bioavailability of the metal to the organism, is an avenue that has been explored only recently, and mainly in invertebrates. In our study, we focus on the mechanisms involved in the release of, and subsequent bioavailability of methylmercury (CH3Hg(II)) that is bound to sediment or food particles. Stomach and intestinal fluid samples collected from two benthic feeders, viz. channel catfish, Ictalurus punctatus, and atlantic sturgeon, Acipenser oxyrhynchus, were incubated, in vitro, with CH3Hg(II)-spiked food or sediment. The experiment was performed in two stages, (i) incubation of the stomach fluid collected from each species with spiked food or sediment for 0.5 and 3h, after which (ii) the intestinal fluid from each species was added and allowed to incubate for a further 2h. Aliquots of each sample were removed at different stages of the experiment, centrifuged, and the supernatents and pellets were analyzed for CH3Hg(II)content. Our results for the stomach fluid incubations show that in sturgeon, the percent CH3Hg(II) solubilized decreased over time, while in catfish no significant differences in CH3Hg(II)solubilization was detected. However, the percent CH3Hg(II) solubilized in catfish and sturgeon increased after addition of the intestinal fluid, and resulted in a 4% and 16%, respectively, solubilization of CH3Hg(II) from the spiked sediment. The role of the digestive system in the release of CH3Hg(II) from spiked sediment or food will be further elucidated. Key words: methylmercury, fish, in vitro solubilization, bioavailability |
