Membrane permeability response of lichen Bryoria fuscescens to wet deposited heavy metals and acid rain

Lichen Bryoria fuscescens were treated in the field experiment with heavy metal solutions, containing a mixture of Cu2+ and Ni2+ ions alone or in combination with acidity (H2SO4, pH 3), to study the effects of simulated acid rain and heavy metal deposition on the membrane integrity of lichen. Membrane responses to pollutant treatments were assessed by measurements of the leachate conductivity, the K+ leakage, and the ergosterol concentration. Both Cu and Ni concentrations of lichen were significantly increased by metal treatments. In addition a significant reduction of Ni with acid solution was found. The conductivity of leachate was significantly increased by the acidity but not affected by the metal treatments alone. Increased thallus metal concentrations (>400 μg g−1 Cu, >100 μg g−1 Ni) significantly increased K+ leakage and reduced ergosterol concentration. The results suggest that the differences in the membrane responses are associated with the different sensitivity of algal and fungal partners to the acidity of heavy metal solutions.