As part of the Indiana Watershed Initiative, I led a biweekly field monitoring project for three years in which we collected nutrient samples and discharge measurements from agricultural tile drains and stream sites in northwestern Indiana. The goals of this project are to understand both field- and watershed-scale nutrient retention as a result of winter cover crops and the two-stage ditch. This work was recently published in Biogeochemistry.

Previous studies have suggested silicon limitation as a driver of HAB formation, yet few studies quantify the silicon limitation of benthic algae. I used nutrient diffusing substrata to experimentally alter silicon, nitrogen, and phosphorus availability for in-stream algae in each season throughout one year. Preliminary results suggest increased phosphorus and silicon promote algal growth, indicating seasonal phosphorus and silicon co-limitation.

Lake Monroe is the largest reservoir in Indiana and is the source of drinking water for more than 120,000 people in Monroe, Brown, and Lawrence counties. I have worked with the Indiana Clean Lakes Program to collect lake and tributary samples in order to calculate a silicon budget for the Lake Monroe watershed. Calculating a silicon budget for the entire watershed will characterize the temporal and spatial changes occurring in the watershed that lead to changes in export.

The demand for dissolved organic matter (DOM) by microorganisms influences the biogeochemical cycling of inorganic nutrients, but the coupled response in the composition of the DOM and stoichiometry of nutrients has not been documented. Changes in the ambient nutrient stoichiometry that affect diatom production could affect the composition and concentration of DOM in freshwaters. I will characterize the shifts in DOM composition by analyzing the optical properties of samples collected from Lake Monroe; these shifts could indicate processes that influence the uptake and assimilation of nutrients within the reservoir.

As the availability of silicon decreases relative to nitrogen and phosphorus, non-siliceous and often harmful algae are able to outcompete diatoms for the remaining nutrients facilitating harmful algal bloom formation. Working with Jase Hixson, a fellow O'Neill School PhD Candidate, we were able to stimulate a diatom bloom to replace a cyanobacterial bloom in a wastewater lagoon through the addition of dissolved silicon.

Using data from Long Term Ecological Research (LTER) sites that span biomes across the globe, we seek to understand how silicon export changes relative to terrestrial vegetation, river productivity, and climate warming. This will be the first data-driven exploration of how riverine silicon exports will respond to global change. Project details can be found here.