Toxicity of silver, zinc, copper, and nickel to the copepod Acartia tonsa exposed via a phytoplankton diet

Toxicity tests were conducted with the marine copepod Acartia tonsa to assess the effects of dietary metal exposure. The diatom Thalassiosira pseudonana was cultured with Ag, Zn, Cu, or Ni and used as diets for adult A. tonsa over a 7-d exposure, and copepod survival and reproduction were measured throughout the exposure period. For all metals, reproduction was the most sensitive endpoint, with 20% effect concentrations (EC₂₀s) corresponding to exposures of T. pseudonana to 0.64, 0.3, 1.2, and 2.4 μg/L for Ag, Zn, Cu, and Ni, respectively. The corresponding metal concentrations in the algae added to copepod test solutions (EC₂₀s) were 5.44, 0.55, 22.3, and 15.3 μg/g for Ag, Zn, Cu, and Ni, respectively. None of the applied metal concentrations influenced algal growth. The results of this study have potential implications for water quality criteria considering that the estimated EC₂₀S fall below the current criteria of 3, 86, 3, and 8.3 μg/L for Ag, Zn, Cu, and Ni, respectively.