Effects of Calcium and Magnesium Ions on Acute Copper Toxicity to Glochidia and Early Juveniles of the Chinese Pond Mussel Anodonta woodiana

We evaluated the effects of calcium (Ca²⁺) and magnesium (Mg²⁺) ions on copper (Cu) toxicity to glochidia and newly-transformed juvenile mussels (age 1–2 days) of the Chinese pond mussel (Anodonta woodiana). Acute Cu toxicity tests were performed with glochidia for 24 h and juveniles for 96 h with measured Ca²⁺ concentrations of 1.1, 14, 26, 51, and 99 mg L⁻¹, or measured Mg²⁺ concentrations of 2.6, 11, 21, and 39 mg L⁻¹. The Ca²⁺ and Mg²⁺ cations provided no statistically significant protection against Cu toxicity to glochidia or juveniles. The 24-h EC₅₀ value for glochidia was 82 μg L⁻¹ Cu, and contrastly, 96-h EC₅₀ value for newly-transformed juvenile mussels was as low as 12 μg L⁻¹ Cu, implying that the juveniles of A. woodiana are more vulnerable to Cu contamination at concentrations close to currently-accepted levels.