Associate Professor of Mathematics and Statistics Rebecca Everett has been awarded a grant from the National Science Foundation (NSF) to further her research on the effects of food quality on the maturation stages of water fleas (Daphnia Pulex), with a larger goal of better understanding the degree human activities are changing the environment and nutrient cycles.
In addition to Professor Everett, the project, "Collaborative Research: RUI: Structured Population Dynamics Subject to Stoichiometric Constraints," includes mathematicians and biologists from Texas Tech University (lead) and California State University, Northridge. The grant, which totals $400,000 between the three schools, is for three years and will involve students from each school, including two from Haverford. Professor Everett's award falls under NSF's Research at Undergraduate Institutions (RUI) program, which supports faculty "in research that engages them in their professional field(s), builds capacity for research at their home institution, and supports the integration of research and undergraduate education."
"I'm an applied mathematician, specifically a math biologist,’’ says Professor Everett. "So I use mathematical modeling to try to analyze and interpret biological systems. I'm excited about this because I get to work with mathematicians and biologists [to] build math models at the same time as collecting ecological data. I will be mainly contributing to the math modeling part of the work."
As human activities continue to alter environmental balances and nutrient cycles, it is important to understand how these changes can impact the environment. The study has two aims, says Professor Everett, who will enter her sixth year of teaching and research at Haverford this fall. One is a consideration of how the nutrient quality of food sources affect juvenile development and fertility at the individual-level through biological studies. The other is to examine its effect on the Daphnia population level, which will incorporate the math modeling of Professor Everett and her student team.
Daphnia are small crustaceans between 0.2 and 5 mm in length that are native to various aquatic environments. Because they are highly sensitive to various toxins, they are frequently used in studies and labs like this one to determine toxicity.
Typical math models of how populations grow and interact often focus on the amount of food available, but overlook the effects of food quality. Models that do consider food quality, often don't consider how nutrients can affect juvenile consumers differently than adult consumers. This project will design and conduct laboratory experiments in conjunction with developing mathematical models that incorporate age/stage-specific nutritional constraints on growth, time to maturation, and reproduction to get a more complete picture of how nature works.
Says Professor Everett, "The fertilizer we use on the ground causes an increase in nitrogen and phosphorus in the environment, and that can have effects of excess algal growth. We’re changing nutrient levels in the algae by changing phosphorus to carbon ratios and looking at how that affects the Daphnia that eat the algae, both individually as well as on the population level."
Everett’s portion of the award is for $59,845 and runs from now until the end of July 2026. It will allow for two Haverford undergraduates to be involved with her in the math modeling of ordinary and delay differential equations, and to travel to both Texas Tech and UCal-Northridge over two summers to work collaboratively in labs with grad students from those schools. Everett says she hopes to involve students from underrepresented populations in the STEM field, perhaps through the Chesick Scholars Program.
Professor Everett earned her Ph.D. in applied mathematics from Arizona State University. Prior to her arrival at Haverford, she worked as a research assistant professor at the Center for Research in Scientific Computation at North Carolina State University, developing models to help improve personalized health treatment. She has collaborated with a wide range of biologists and health specialists, and has worked on problems that include drug resistance in cancer, immunosuppressant treatment dynamics of renal transplant recipients, and behavior changes in individuals with mild to moderate alcohol use disorder undergoing treatment. She has also been involved in the Pathways TUME Program (Transforming Undergraduate Mathematics Education) that is funded by the NSF.
