This action funds an NSF Postdoctoral Research Fellowship in Biology for FY 2025. The fellowship supports research and training of the fellow that will contribute to biology in innovative ways. Parasites can affect the traits of their hosts. For instance, parasites can change the feeding rate of their host. However, few studies have examined how the impacts of parasites on host traits may extend to influence ecosystem function. Testing when and how impacts of common parasites on their hosts scale up will improve our understanding of ecological patterns across scales. This research will use laboratory and field experiments, focusing on the invertebrate, Daphnia dentifera, and two of its common parasites. Daphnia dentifera is important in lake ecosystems, where it plays a key role consuming algae. This Daphnia-parasite system is well-suited for examining the scaling of parasite impacts on important hosts. Furthermore, the fellow will gain training in additional research areas, develop strong interdisciplinary collaborations, and expand science communication programs. The fellow will measure parasite impacts on traits of multiple Daphnia genotypes during both individual- and population-level experiments. Combining ecological stoichiometry and disease ecology can elucidate how ingestion, assimilation, and release of nutrients change for infected hosts, leading to consequences for primary productivity and nutrient cycling in the ecosystem. Conducting these experiments under dif