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.