TA4 Metals in the Environment: Dietary Concerns in Aquatic Systems
Room 16A/B, Level 4
8:00 AM - 12:00 PM, Tuesday, 11 November 2003
Chair: Adams, Bill ,
Co-chair: Meyer, Joe ,
(195) Toxicity of dietborne and waterborne copper and silver to Ceriodaphnia dubia.
Kolts, J.1, Boese, C.1, Meyer, J.1, 1 University of Wyoming, Laramie, WY, USA
ABSTRACT- Current aquatic life criteria for metals in the United States are based on toxicity of waterborne metals. However, recent chronic studies have demonstrated that dietborne metals can also be toxic. To test for indirect and direct effects of food, we examined (1) acute toxicity of waterborne Cu and Ag to a cladoceran (Ceriodaphnia dubia) in the presence of food, as well as (2) reproductive impacts of dietborne Cu and Ag. In acute tests in which we either added no food (according to U.S. EPA acute toxicity testing guidelines) or fed the cladocerans a mixture of YCT (yeast-Cerophyll-trout chow) slurry and an alga (Selenastrum capricornutum; according to U.S. EPA chronic toxicity testing guidelines), the 48-h LC50 of dissolved Cu to C. dubia was 9.5x higher in the presence of the food than in its absence, suggesting an important interaction with dissolved components in the food. However, the 48-h LC50 of dissolved Ag to C. dubia was only 1.4x higher in the presence of food than in its absence. In chronic tests in which C. dubia were fed metal-contaminated algae and non-contaminated YCT for the entire 3-brood test, Cu (≤16 
mol Cu/g dw algae, grown in ≤0.8 M Cu) and Ag (≤2 mol Ag/g dw algae, grown in ≤0.08 M Ag) did not significantly decrease reproduction. Similarly, in chronic tests in which C. dubia were fed only metal-contaminated algae (same concentrations as before) for an initial 4-h period, transferred to fresh water, and then fed uncontaminated algae and YCT for the duration of the 3-brood test, reproduction did not decrease in C. dubia fed Cu-contaminated algae but sometimes decreased in C. dubia fed algae that contained intermediate concentrations of Ag. The highest Ag and Cu concentrations in which the algae were cultured for these tests were chosen because they cause about 50% decreases in algal growth rates, making it difficult to grow enough algae at higher concentrations.
Key words: Copper, Ceriodaphnia dubia, Dietborne metals, Silver