TOXICITY AND BIOACCUMULATION OF SELENIUM TO A 3-TROPHIC LEVEL FOOD-CHAIN

Three species, Chlorella vulgaris, Brachionus calyciflorus, and Pimeph ales promelas, were exposed to selenate for 25 d in a three-trophic le vel test system. The organisms were linked in a continuous how-through system in separate vessels, with each organism feeding on the trophic level below it. These organisms were continually exposed for 25 d to 0, 110.3, 207.7, and 396.1 mu g/L total recoverable selenium (Se) from selenate in natural creek water supplemented with nutrients to sustai n algal growth. In an initial algal screening rest, growth rates were reduced at 81.7 and 1,053.7 mu g/L, with no effect at 8.5 mu g/L. In t he trophic test, algal populations showed evidence of reduced growth r ates at 207.7 and 386.1 mu g/L, but not at 110.3 mu g/L. Rotifer popul ation standing crop (measured as dry weight) was significantly reduced at 207.7 and 396.1 mu g/L by day 4, and declined to below detection b y day 7 at these treatments. Fathead minnow growth was impaired after 7 d at the 207.7 and 396.1 mu g/L levels, with 100% mortality by day 1 6. A reduction in rotifers and fish biomass was also apparent at the 1 10.3 mu g/L level after day 20. The amount of Se in whole organisms wa s measured throughout the experiment. Bioconcentration factors were fo und to be dependent on the species, treatment level, and length of exp osure period, and they ranged between 100 and 1,000.