Effects of salinity on copper accumulation in the common killifish (Fundulus heteroclitus)

Results of laboratory and field studies have demonstrated that salinity influences the accumulation of copper. The present study is, to our knowledge, the first to examine the effect of salinity on copper accumulation in a teleost fish across a comprehensive range of salinity from freshwater to seawater. This was done in an effort to identify potential target tissues and differences in chemical interactions across salinities that will aid in the development of a seawater biotic ligand model (BLM) for copper. Killifish (Fundulus heteroclitus) were acclimated to five salinities (0, 5, 11, 22, and 28 ppt) and exposed to three copper concentrations (0 [nominal], 30, and 150 microg L(-1), yielding 15 treatment groups. Fish from each group were sampled for tissue copper analysis at 0, 4, 12, and 30 d postexposure. Whole-body and liver accumulations were highest at lower salinities. The liver accounted for 57 to 86% of the whole-body copper even though it accounted for less than 4% of the body mass. Similarly, the gill accumulated more copper at lower salinities, whereas the intestine generally accumulated more copper at higher salinities. Speciation calculations indicate that CuCO3 likely accounts for much of the accumulation, possibly with some contributions from CuOH+ and Cu(OH)2. The free ion, Cu2+, does not appear to be associated with copper accumulation. However, the differences in physiology and in the concentrations of competing cations across salinities suggest that speciation alone cannot explain accumulation. The present findings may have implications for future development of a BLM for saline environments by identifying potential target tissues.