By Megan Urbanic, Biological Sciences; Jake Beaulieu, US Environmental Protection Agency
Advisor: Michael Booth
Abstract: Greenhouse gas (GHG) emissions from freshwater systems are an important contributor to global carbon emissions, but the factors controlling the rates and forms of carbon released are uncertain. One potential factor is bioturbation, the disturbance of sediment by organisms as they move or feed. Our experiment sought to determine what frequency of bioturbation would result in the largest releases of greenhouse gases and highest ratio of CH4:CO2. This experiment took place in a lab setting using 15 10L fish tanks. Tanks were randomly assigned bioturbation treatment frequencies of either no disturbance, 3d, 7d, 14d, or 21d. GHG diffusion rates were taken using a micro portable GHG analyzer, and GHG ebullitions were measured using inverted funnel gas traps in each tank. Preliminary data was taken for 60 days, and treatments were then implemented for 90 days. The 7d tanks had the highest average cumulative gas volume over the course of treatments, while 3d tanks had the lowest. Disturbances released gasses trapped in the sediment, and more frequent disturbance released less gas per disturbance. The ratio of cumulative CH4:CO2 ebullition was lowest at intermediate disturbance frequencies, however, the greatest overall volume of CH4 and CO2 was released from the 7d tanks.