Influence of oligomeric silicic and humic acids on aluminum accumulation in a freshwater grazing invertebrate

This study examined the influence of oligomeric silicic acid and humic acid on aluminum in the water column and its accumulation in the freshwater snail Lymnaea staynalis. Forty-eight hours after addition of Al (500 mug L-1), 83\% of the metal was lost from the water column. This loss was reduced by oligomeric silica (20 mg L-1) and by humic acid (10 mg L-1). Aluminum accumulated in the digestive gland and, to a lesser extent, in the remaining soft tissues, and this accumulation was reduced by oligomeric silica. In the presence of humic acid, Al accumulation in the digestive gland was unaffected, though less was accumulated in the remaining tissues. Snails accumulated Si preferentially in the digestive gland and this accumulation was increased in the presence of added Al. Thus, both oligomeric silica and humic acid influence Al bioavailability and Si is upregulated in the digestive bland in the presence of Al. (C) 2002 Elsevier Science (USA). All rights reserved.