Heavy metal uptake by chemically distinct lichens from Aspicilia spp. growing on ultramafic rocks

Accumulation of metals in four crustose lichens with different secondary chemistry growing on serpentinite was studied. Aspicilia cinerea and A. blastidiata contain depsidone norstictic acid, A. goettweigensis contains stictic acid, and A. contorta ssp. hoffmanniana contains aliphatic compound aspicilin. The highest concentrations in lichens compared with serpentinite were found for calcium (Ca; average 11 times, maximum 20 times). Strontium (Sr), Copper (Cu), sodium (Na), zinc (Zn) and chromium (Cr) were 2.8–9 times greater in lichens than in rocks, and other elements such as nickel (Ni), iron (Fe), cobalt (Co), manganese (Mn) and magnesium (Mg) were equal or lower in the thalli than in the substrate. Three species showed little differences in concentrations of the same metals, whereas Aspicilia blastidiata, which is obligate to serpentinite, had statistically higher concentrations of most elements. This implies that the difference in secondary chemistry does not strongly influence accumulation rates of metals in selected species on serpentinite but that lichens have both mechanisms of accumulation and avoidance that may be related to ‘lichen acids’.