Reproduction of aquatic hyphomycetes at low concentrations of Ca 2+ , Zn 2+ , Cu 2+ , and Cd 2+

Maple leaf disks were conditioned in a stream for three weeks and then aerated for 2 d in distilled water to induce fungal sporulation. The release of aquatic hyphomycete spores increased when the water was supplemented with low concentrations of Ca 2+ (5 µg/L), Zn 2+ (2.5 µg/L), Cu 2+ (0.5 µg/L), or Cd 2+ (0.125 µg/L). Higher supplement concentrations inhibited sporulation. Over the concentration range used, the sporulation response was generally best described by a quadratic regression, suggesting a biphasic or hormetic response. A similar pattern was found with the number of fungal species as the dependent variable. Anguillospora filiformis and Anguillospora longissima were generally least inhibited by metal supplements, and Ca 2+ was the least and Cd 2+ the most toxic metal. Combinations of metals had a more severe effect on fungal sporulation than predicted from addition of the effects of the metals in isolation. The biological significance of the hormetic response is unclear; however, acknowledging it is clearly relevant for establishing guidelines or recommendations in toxicology. Environ. Toxicol. Chem. 2011;30:2868–2873. © 2011 SETAC