EXPERIMENTAL-STUDY OF INTERACTIONS BETWEEN 5 TRACE-ELEMENTS CU, AG, SE, ZN, AND HG TOWARD THEIR BIOACCUMULATION BY FISH (BRACHYDANIO-RERIO)FROM THE DIRECT ROUTE

Actions and interactions between five elements-copper, zinc, silver, s elenium, and methyl mercury-toward their bioaccumulation in fish (Brac hydanio rerio) were studied after 12 days exposure, via the direct con tamination route. The experimental approach was based on a centered co mposite factorial design; 43 different contamination conditions were s tudied simultaneously, with five concentration levels in the water for each element. Contaminated media were cyclically renewed (48 hr renew al cycle), in order to control the fish exposure conditions. Data trea tment was essentially based on the multiple regression technique, appl ied successively to the complete factorial design (2(5) = 32 condition s) and to the centered composite design (43 conditions). Results show a complex set of actions and interactions between the elements. The mo st striking result is a marked interaction between silver and methyl m ercury: when Ag is present in the water jointly with MeHg, it exerts a negative action on Hg bioaccumulation in the fish, at the whole organ ism level, Bioaccumulation of silver is also significantly influenced by the presence of Zn, Cu, and Se in the mater, the action of these th ree elements producing an increase in the amounts of Ag in the organis ms. This study corresponds to an exploratory phase in order to reveal interaction effects on the bioaccumulation processes by fish and then to set up more in-depth analysis to increase progressively the underst anding of the ecotoxicological mechanisms involved. (C) 1995 Academic Press, Inc.