Abstract
Biodiversity is under pressure worldwide, with amphibians being particularly threatened. Stressors related to human activity, such as chemicals, are contributing to this decline. It remains, however, unclear whether chemicals exhibiting a fungicidal activity could indirectly affect tadpoles that depend on microbially conditioned leaf litter as food source. The indirect effect of fungicides (sum concentration of a fungicide mixture composed of azoxystrobin, carbendazim, cyprodinil, quinoxyfen, and tebuconazole: 100 µg/L) on tadpoles was assessed relative to leaf litter colonized by microbes in absence of fungicides (control) and a worst‐case scenario, that is leached leaf litter without microbial colonization. The quality of leaf litter as food for tadpoles of the European common frog (Rana temporaria) was characterized through neutral lipid fatty acid profiles and microbial sum parameters and verified by sublethal responses in tadpoles (i.e., feeding rate, feces production, growth, and fatty acid composition). Fungicides changed the nutritious quality of leaf litter likely through alterations in leaves’ neutral lipid fatty acid profiles (i.e., changes in some physiologically important highly unsaturated fatty acids reached more than 200%) in combination with a potential adsorption onto leaves during conditioning. These changes were reflected by differences in the development of tadpoles ultimately resulting in an earlier start of metamorphosis. Our data provide a first indication that fungicides potentially affect tadpole development indirectly through bottom‐up effects. This pathway is so far not addressed in fungicide environmental risk assessment and merits further attention.
Highlights
Biodiversity is declining worldwide (Butchart et al, 2010), with amphibians being under a particular strong pressure (e.g., Scheele et al, 2019)
Malathion, an insecticide, induced a complex effect cascade impacting periphyton growth, delaying the development of leopard frog tadpoles (Rana pipiens), and causing mortality when the ecosystem dried out (Relyea & Diecks, 2008). This selection of studies suggests that pesticides with clearly distinct target groups can affect amphibians directly or indirectly during the aquatic part of their life cycle
The impact induced by fungicide exposure on nutritious quality and indirectly on tadpole development was compared to an assumed worst-case scenario, namely leached leaf litter without a microbial biofilm and containing no fungal biomass and bacterial cells as well as low levels of highly unsaturated fatty acids (Hixson et al, 2015)
Summary
Biodiversity is declining worldwide (Butchart et al, 2010), with amphibians being under a particular strong pressure (e.g., Scheele et al, 2019). Malathion, an insecticide, induced a complex effect cascade impacting periphyton growth, delaying the development of leopard frog tadpoles (Rana pipiens), and causing mortality when the ecosystem dried out (Relyea & Diecks, 2008). This selection of studies suggests that pesticides with clearly distinct target groups (i.e., insecticides vs herbicides vs fungicides) can affect amphibians directly or indirectly during the aquatic part of their life cycle. The impact induced by fungicide exposure on nutritious quality and indirectly on tadpole development was compared to an assumed worst-case scenario, namely leached leaf litter without a microbial biofilm and containing no fungal biomass and bacterial cells as well as low levels of highly unsaturated fatty acids (Hixson et al, 2015)
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