Responses of polychaete Hydroides elegans life stages to copper stress

Two experiments were performed to examine the sensitivity of Hydroides elegans to copper stress. The first experiment tested the development of 4 distinct early stages in copper solutions from 10 to 250 μg l^-1. Copper significantly reduced survivorship of the newly released oocyte and trochophore stages at concentrations ≥10 μg l^-1, and of the 2-cell and blastula stages at ≥25 μg l^-1. The EC₅₀ values were 47, 50, 71 and 29 μg Cu l^-1 for the newly released oocytes, 2-cell embryos, blastulae and trochophores, respectively. After 2 h into the bioassay, where Isochrysis galbana was used as food for the trochophores, algal sorption resulted in a reduction in copper concentration from 32 % in the 10 μg l^-1 treatment to 6 % in the 250 μg l^-1 treatment. Duration of development did not significantly differ among the treatments, except in the oocyte to 2-cell stage where higher copper concentration resulted in longer developmental time. In the second experiment, adult H. elegans were exposed to copper concentrations from 125 to 4000 μg l^-1 for 48 h. Significant mortality occurred only at copper concentrations ≥500 μg l^-1. This study thus shows that the embryogenesis and larval development of H. elegans are sensitive to copper stress, and that algal sorption can substantially reduce soluble copper concentration and may affect the larval toxicity result.