Sensitivity differences among five species of aquatic fungi and fungus-like organisms for seven fungicides with various modes of action.

Abstract

Five species of aquatic fungi and fungus-like organisms were used for toxicity assays with seven fungicides to determine the differences in species sensitivity. A microplate toxicity assay with adenosine triphosphate luminescence detection was used as an efficient and economical high-throughput assay. The obtained toxicity data were standardized based on the species sensitivity distribution method. Species sensitivity differed among the fungicides: Rhizophydium brooksianum was most sensitive to hydroxyisoxazole, isoprothiolane, and ferimzone; Chytriomyces hyalinus was most sensitive to tricyclazole; Sporobolomyces roseus was most sensitive to ipconazole; Aphanomyces stellatus was most sensitive to orysastrobin and kasugamycin. Tetracladium setigerum was not the most sensitive species to any of the tested fungicides. The ranges of EC50s to fungal species were lower than to other aquatic organisms (primary producers, invertebrates, and vertebrates) for hydroxyisoxazole, kasugamycin, isoprothiolane, ipconazole, and ferimzone. These results suggest the usefulness of a battery of fungal species to assess the ecological effects of fungicides.