MCA: Consequential intraspecific variation in elemental traits in high mountain lake ecosystems

Ecological stoichiometry measures the balance of chemical elements (e.g., carbon, nitrogen, phosphorus) in organisms and their environments to reveal important insights into ecological processes like nutrient limitation and cycling. This project uses ecological stoichiometry to study the evolutionary effects of predation by fish on zooplankton, the tiny animals they eat. Some high mountain lakes have been stocked with trout for fishing while others remain naturally fishless. Trout eat the largest zooplankton which in turn impacts the population of zooplankton by altering the timing and number of young produced. Over time, this can have an evolutionary effect on the chemical balance of zooplankton and the lake environment itself. This project will examine these differences in chemical balance in high mountain lakes with and without trout. The results are important for predicting the impacts of natural and human-induced environmental change. The project will also produce a unit for college students in a large introductory biology course to improve understanding of the effects of chemical balance and changes on the environment. Specifically, this project addresses a knowledge gap by studying intraspecific variation in elemental traits and its effects on ecological processes in lakes. For the first objective, high precision instruments are used to contrast the elemental content between Daphnia populations from lakes with introduced trout, possessing distinct reproductive traits, and Daphnia populations from naturally fishless lakes. By quantifying all detectable biologically essential elements in these two distinct phenotypes, this work will reveal the elemental consequences of life-history traits, which are largely unknown. For the second objective, the mismatch between consumers and their resources (between Daphnia and phytoplankton and between phytoplankton and lake water) will be quantified to assess the effect of trout introductions on the balance of elements between trophic levels. In an experiment, I will also assess how intraspecific variation in elemental recycling by Daphnia differentially alters algal uptake and growth rate. Because all shifts in life-history traits require shifts in elemental requirements, differences between the effects of distinct phenotypes will occur but the magnitude of these differences is unknown. The findings will provide critical insights into the likely consequences of intraspecific variation across levels of biological organization, from organisms to ecosystems. 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.