Waiting for the snow to melt…
Beaver dams and the wetlands they create are ubiquitous, landmark features to glaciated river corridors in the West. By building dams and diverting river water into floodplains, beavers fundamentally alter how water flows through a watershed and the biogeochemical processes that occur within the critical zone. Amplified soil weathering conditions, abundant transitional redox boundaries, and heightened aqueous concentrations of iron and dissolved organic matter set the stage for beaver wetlands to be influential bioreactors that can alter downstream water quality. Highly associated with floodplains but marginally understood are colloids; reactive and mobile nanoparticles formed at subsurface redox interfaces, typically rich in iron, organic carbon, and trace metals, and, thus, with the potential to enhance passage of metals and carbon to streams. Unlike hydrologically disconnected floodplains, beaver wetlands are highly engineered systems with substantial advective pathways that allow chemically altered waters, and potentially iron-rich nano-colloids, to be mobilized and transported directly into adjacent streams. My research seeks to understand 1) whether iron-rich colloids are generated in beaver wetlands, 2) whether iron-rich colloids are present in river water downstream of beaver wetlands, 3) how seasonal hydrologic variability influences the abundance and structure of iron within beaver wetlands, and 4) the overall mass loading of iron to rivers from beaver wetlands through surface and subsurface flow paths. Iron particles are widely recognized for their ability to adsorb toxic, redox-sensitive metals from arsenic to uranium, so by focusing on iron this work tracks the water quality implications for harmful trace metals that can be repartitioned within beaver wetlands. In completing this work, I will identify the role beaver wetlands play as an ecosystem control point for river water quality with respect to iron and other affiliated elements and substances.