Abstract

Waterborne exposure towards fungicides is known to trigger negative effects in aquatic leaf-associated microbial decomposers and leaf-shredding macroinvertebrates. We expected similar effects when these organisms use leaf material from terrestrial plants that were treated with systemic fungicides as a food source since the fungicides may remain within the leaves when entering aquatic systems. To test this hypothesis, we treated black alder (Alnus glutinosa) trees with a tap water control or a systemic fungicide mixture (azoxystrobin, cyprodinil, quinoxyfen, and tebuconazole) at two worst-case application rates. Leaves of these trees were used in an experiment targeting alterations in two functions provided by leaf associated microorganisms, namely the decomposition and conditioning of leaf material. The latter was addressed via the food-choice response of the amphipod shredder Gammarus fossarum. During a second experiment, the potential impact of long-term consumption of leaves from trees treated with systemic fungicides on G. fossarum was assessed. Systemic fungicide treatment altered the resource quality of the leaf material resulting in trends of increased fungal spore production and an altered community composition of leaf-associated fungi. These changes in turn caused a significant preference of Gammarus for microbially conditioned leaves that had received the highest fungicide treatment over control leaves. This higher food quality ultimately resulted in a higher gammarid growth (up to 300% increase) during the long-term feeding assay. Although the underlying mechanisms still need to be addressed, the present study demonstrates a positive indirect response in aquatic organisms due to systemic pesticide application in a terrestrial system. As the effects from the introduction of plant material treated with systemic fungicides strongly differ from those mediated via other pathways (e.g., waterborne exposure), our study provides a novel perspective of fungicide-triggered effects in aquatic detritus-based food webs. (C) 2018 Elsevier Ltd. All rights reserved.

Keywords

Aquatic hyphomycetes; Gammarus fossaruM; Resource quality; Systemic pesticides

Published in

Environmental Pollution
2018, Volume: 241, pages: 549-556
Publisher: ELSEVIER SCI LTD

SLU Authors

• Feckler, Alexander

  • Department of Aquatic Sciences and Assessment, Swedish University of Agricultural Sciences
    

• Bundschuh, Mirco

  • Department of Aquatic Sciences and Assessment, Swedish University of Agricultural Sciences
    
  • University of Koblenz-Landau

Associated SLU-program

SLU Plant Protection Network


UKÄ Subject classification

Environmental Sciences


Publication identifier

DOI: https://doi.org/10.1016/j.envpol.2018.05.069

Permanent link to this page (URI)

https://res.slu.se/id/publ/96237