Effects of Cadmium on Aquatic Hyphomycetes

Abstract

Sporulation and growth experiments were carried out to demonstrate the effect of Cd on aquatic hyphomycetes. Oak (Quercus petraea L.) leaves were exposed in a hard-water stream (Luessel, Swiss Jura) and a soft-water stream (Ibach, Black Forest) for 2 mo. In the laboratory, fungal sporulation on the leaves in stream water enriched with Cd (as CdCl2) was studied. A measurable effect was found when the Cd concentration exceeded 0.1 ppm (0.1 mg/l). Concentrations higher than 100 ppm inhibited conidium production completely. This toxic effect of Cd was species dependent and much higher in soft water (water with low concentrations of Cd and Mg) than in hard water. Growth experiments with Alatospora acuminata Ingold, Clavariopsis aquatica De Wildeman, Flagellospora curvula Ingold, Heliscus lugdunensis Saccardo and Therry, and Tetracladium marchalianum De Wildeman showed the same pattern of Cd sensitivity as that seen in the sporulation experiments. Mycelial growth was less sensitive to Cd than was fungal sporulation. High concentrations of competing cations (e.g., Ca and Zn) or potential ligands could reduce Cd toxicity. Ca content seems to be the most important factor responsible for the difference in sensitivity of aquatic hyphomycetes in hard and soft water.