Aquatic hyphomycetes in polluted groundwater habitats of central Germany.

Polluted groundwater wells located in a former copper shale mining district (11 sites; Mansfelder Land, Central Germany) and in meadows of the Mulde and Elbe rivers (2 sites) were assessed for occurrence and species richness of aquatic hyphomycetes. Water temperatures at all sites were relatively low and fluctuated less than in surface waters. Oxygen concentrations were always below saturation, whereas sulfate, nitrate, and phosphate levels reached extremely high values in several of the wells. Relatively high levels of Pb, Mn, and Fe were found in some of the wells, but overall few concentrations of individual metals and metalloids exceeded European guidelines for drinking water. Pollen tube growth inhibition, used to assess cytotoxicity of the water, ranged between 4 and 50%. Between 1 and 10 distinct species of aquatic hyphomycetes colonized sterile Alnus glutinosa leaves exposed at the Mansfelder Land sites; for the meadow sites, 8-20 species were found. Heliscus lugdunensis and Anguillospora sp. were the two most widespread species. Fungal colonization occurred much more slowly than in surface water, as demonstrated by scanning electron microscopy and the release of conidia from recovered leaves. The conidial output from exposed alder leaves ranged from 0.2 to 95 conidia mg (-1) dry mass, corresponding to 10% of the values for contaminated surface waters in the same region. Overall, groundwater appears to be a marginal habitat for aquatic hyphomycetes, but may nevertheless play a vital role as long-term reservoir facilitating rapid recolonization following a collapse in fungal communities in surface waters.