Nutrients and temperature interact with trifloxystrobin on the growth of three aquatic hyphomycete species

Aquatic hyphomycetes (AHs) are a group of fungi central for the decomposition of organic material in aquatic systems. Despite their ecological relevance, ecotoxicological studies involving AHs are fairly scarce. With the aim to better understand AH responses to changes in abiotic factors and increasing levels of contaminants, we explored their sensitivity in a multifactorial approach. Therefore, we assessed the radial growth response of three AH species (Alatospora acuminata, Articulospora tetracladia, and Tetracladium marchalianum) to three temperatures (12, 16, and 20 °C) and nutrient levels (0.0, 0.5, and 1.5% malt extract, w/v) in combination with increasing concentrations of the model fungicide trifloxystrobin (0 to 625 µg/L) over 21 days. The results showed a significant interaction between factors, with temperature being the most significant by potentiating trifloxystrobin toxicity for AH growth. The fungicide affected AH species in the low µg/L range with the lowest effect concentration of 0.1 µg/L for A. tetracladia. Previous study points to a regulatory acceptable concentration of 0.1 µg/L based on the ecotoxicological data of the most sensitive groups reported, which did not include AHs. Particularly in light of the ecological importance of them, their sensitivity to trifloxystrobin shown in our study highlights a fundamental concern when projecting the environmental risk of pesticides that directly affect aquatic fungi.