ASSESSING BIODEGRADATION OF URBAN-DERIVED DISSOLVED ORGANIC CARBON AT THE STREAM-GROUNDWATER INTERFACE

In order to better understand anthropogenic effects on the Kalamazoo River in South Central Michigan from the surrounding urban environment, we carried out experiments on campus-derived dissolved organic carbon (or DOC) in the summer of 2021. Quantitatively measuring how DOC changes over time while exposed to stream-groundwater sediments can help us to understand the fate and transport of biogeochemical solutes within our human-modified environment. The portion of the carbon cycle we are focusing on, inland waters transport, has not received as much attention as compared to the larger sinks and sources (e.g., ocean, terrestrial, etc.) until recent years. Researchers have determined that streams transport and bury a significant amount of carbon that was previously largely unaccounted for in global climate models. Producing an improved understanding of how DOC moves and changes in urban environments will be beneficial to future research on human effects on inland watersheds. In this study, we tested urban-derived DOC and its ability to be broken down over time by organisms within the stream-groundwater interface by simulating this environment in a lab using a batch reactor method. We evaluated the degradation of DOC in the presence of streamwater alone as well as withstream water and sediment, using DOC leachates of various origins, such as pine needles, grass clippings, and storm drain detritus. We simulated stream and stream-groundwater environments using glass amber bottles and were sampled through time to determine the degradation rate of these separate type of DOC. With our data we have produced degradation rates for each DOC source as it relates to the stream, stream-groundwater interface, and control environments. Preliminary evidence indicates that some types of urban-derived DOC are more quickly and thoroughly broken down than others by the organisms within the stream-groundwater environment, and that the stream-groundwater interface is more effective in these biogeochemical reactions.