The replication rate and harm caused by a parasite can be affected by the nutritional content of its host’s diet. However, the magnitude and direction of these effects vary unpredictably among different hosts and parasites. The goal of this research is to improve our ability to predict how specific parasites will respond to shifts in the nutrient content of their host’s diets. Generating these predictions is important because human activities add nutrients like nitrogen and phosphorus to many ecosystems, directly altering the nutrient content of the diet of animals. Such dietary shifts could favor specific parasites over others. This research will test the hypothesis that the effect of host diet on parasite replication rate is dictated by the flexibility of a parasite’s own nutritional requirements. This project will also improve science education outcomes for students at a local high school. Two high school students will become integral members of the primary research lab for a summer, conducting a small study at the end of their assistantship, and presenting their work to fellow high school students the following year.<br/><br/>The researchers will experimentally manipulate the nutrient content of the diet of an invertebrate host and determine if the relative abundance of carbon, nitrogen, and phosphorus in host diets, hosts, and parasites can help predict outcomes for the parasite and host. To rigorously quantify the nutrient content of microbial parasites, the researchers have adapted an energy dispersive spectroscopy workflow previously used to quantify the nutrient content of free-living microbes. Measurements of multiple single celled parasites within a host will be used to create trait distributions of the nutrient content of parasitic populations within a host. These trait distributions capture within-host variation in parasite nutrient content which will be used to estimate the flexibility of each parasite’s nutritional requirements, and, ultimately, to predict the response of each parasite to shifts in the host’s diet.<br/><br/>This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.