TEMPURATURE MODULATES THE FITNESS EFFECTS OF A BROAD-SPECTRUM FUNGICIDE IN A ZOOPLANKTON HOST-FUNGAL PATHOGEN SYSTEM

The fungicide azoxystrobin is increasingly used for crop disease management and commonly enters lakes as runoff. Its impacts on disease dynamics in non-target aquatic organisms, however, are understudied, and changing global temperature patterns further complicate our understanding of such impacts. Daphnia dentifera, a planktonic crustacean found in midwestern lakes, is a host for the fungal pathogen, Metschnikowia bicuspidata. We explore how sublethal concentrations of azoxystrobin affect the fitness of this aquatic host and its fungal pathogen at different temperatures. In a series of experiments, D. dentifera were exposed to three azoxystrobin concentrations and Metschnikowia treatments at two temperatures. We found that the effects of these stressors on D. dentifera clonal growth rate, a proxy for host fitness, varied considerably by temperature. We assessed pathogen fitness by quantifying spore production within azoxystrobin-exposed and unexposed hosts, which we found did not vary across azoxystrobin treatments, nor did the viability of spores to infect future hosts. Because we used ecologically relevant concentrations of azoxystrobin and Metschnikowia spores in these assays, we interpret that azoxystrobin runoff can alter D. dentifera population dynamics, and temperature may modulate its effects on host fitness and resulting disease dynamics. As a keystone species in lake systems, understanding the interactions between anthropogenic stressors, disease, and their environment on Daphnia fitness can help us protect lake ecosystems and the important functions they serve.

Presentation Preference: Oral

Primary Presenter: Jeannette Cullum, University of Illinois Urbana-Champaign (jcullum2@illinois.edu)

Authors:

Jeannette Cullum, University of Illinois  (jcullum2@illinois.edu)

Carla Cáceres, University of Illinois  (cecacere@illinois.edu)