Toxicity of aluminum and hydrogen ions to Daphnia catawba, Holopedium gibberum, Chaoborus punctipennis, and Chironomus anthrocinus from Mirror Lake, New Hampshire

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Abstract
The effect of aluminum on the survival of Daphnia catawba, Holopedium gibberum, Chaoborus punctipennis, and Chironomus anthrocinus was determined. Experiments were conducted in soft water adjusted to pH 6.5 (original), 5.0, 4.5, 4.0, and 3.5, at three concentrations of aluminum (0.02, 0.32, 1.02 mg/L) which cover the range typical of soft-water lakes exposed to acidic precipitation in eastern North America. Our results indicate that D. catawba was the most acid sensitive of the four species tested. It died rapidly below pH 5.0, whereas the others could survive at pHs as low as 4.0 (H. gibberum) and 3.5 (C. punctipennis and C. anthrocinus). None of the invertebrates were particularly sensitive to aluminum. Mortality, attributable to aluminum, occurred only at pH 6.5 for D. catawba at the highest aluminum concentration tested (1.02 mg/L). Most of the aluminum in this treatment was present as a solid-phase aluminum hydroxide complex. Based on our results, these species should be able to tolerate aluminum concentrations in excess of those which now occur in recently acidified oligotrophic lakes. If they are eliminated from acidic environments it is likely to be due to competition for food and (or) prédation pressure rather than direct aluminum toxicity.