The body ion loss biomarker. 1. Interactions between trace metals and low pH in reconstituted coal mine-polluted water

Net body ion loss of brook charr (Salvelinus fontinalis) was evaluated as a biomarker of the potential toxicity of coal mine-polluted water. Fish were exposed in reconstituted coal mine-polluted water prepared in a continuously flowing system with a mixture of 16 water chemistry variables adjusted to match stream concentrations measured in moderately and severely mine-impacted streams. Changes in net body cation (Na+, K+, and Ca2+) loss rates from the fish were determined. Metal/pH interactions were tested by exposing fish to (1) a mixture of all six potentially toxic metals (Al, Fe, Zn, Mn, Ni, and Cd or Pb), (2) individual metals, (3) no metals (low pH effect), or (4) time control. At severe levels (pH ≈ 3.34) all metal treatments caused a net whole-body sodium loss rate similar to that observed for pH alone. Body potassium rates were essentially unchanged from that of the control; a significant calcium influx observed under control conditions was eliminated by most acid and metal exposures. At less severe pollution levels (pH ≈ 3.95) some metals (Ni2+, Mn2+, and Zn2+) blocked the net loss of body sodium induced by acidity. We conclude that net body sodium loss rate is a sensitive, reproducible, and acute indicator of acid and trace metal pollution and may be a useful biomarker for determining the presence and degree of impact of coal mine-polluted water on fish.