PATHWAYS OF SILVER UPTAKE AND TROPHIC TRANSFER IN ESTUARINE ORGANISMS

An estuarine invertebrate (the grass shrimp, Palaemonetes pugio) rapidly incorporated silver dissolved in brackish water in proportion to its concentration, but did not incorporate significant quantities of silver from either a planktonic (Artemia sp.) or a detrital (Victorella sp.) food source containing elevated silver contents. Silver was also readily taken up and incorporated by the centric diatom, Thalassiosira weissflogii. Once incorporated, silver remained tightly bound to the cell membrane, even after cells were disrupted by sonication, leached at low pH (2.0), or treated with digestive enzymes. Thus, the acts of feeding and digestion by invertebrates are not likely to dislodge silver from biotic particles and food-borne transfer of silver within aquatic food chains is unlikely to occur. Geochemical controls over dissolved silver speciation and bioavailability are much more important in determining silver incorporation.