Soil algal communities inhabiting zinc and lead mine spoils

Algal communities inhabiting four calamine mine spoils differing in time since cessation of exploitation and loaded with high concentrations of zinc (20,284-61,599 mu g g(-1) soil DW), lead (2,620-3,885 mu g g(-1) DW) and cadmium (104-232 mu g g(-1) DW) were studied. In dump soils of slightly alkaline pH (7.28-7.52) and low nutrient (P-PO43-, N-NH4+, N-NO3-) concentrations, chlorophyll a content ranged from 0.41 to 2.27 mu g g(-1) soil DW. In total, 23 algal species were recorded. Chlorophyta were the dominant taxonomic group (42-55% of all identified species) followed by Cyanobacteria (28-36%) and Heterokontophyta (13-21%). The highest species richness (18) was observed in the oldest dump (120 years old) with natural succession, while in younger dumps it was lower (11-15). Total algal abundance ranged between 5.5 and 19.1 x 10(2) ind. g(-1) soil DW, and values of Margalef's diversity indices (1.59-2.25) were low. These results may suggest that both high concentrations of heavy metals and low nutrient content influenced the algal communities in all the dumps studied. The differences in algal microflora observed between tailing dumps may indicate that habitat quality improved with time and that algae isolated from Zn/Pb-loaded soils may be Zn/Pb-resistant ecotypes of ubiquitous species.