Carbon Dynamics in Lake Superior

Funding: NASA New Investigator Program 

Dissolved organic matter (DOM) is a critical component of food webs and the global carbon cycle, comprising 80-90% of coastal ocean carbon. Composed of an immensely complicated matrix of organic compounds, from amino acids and neutral sugars to structurally complex molecules such as lignin, DOM is sourced from all facets of an ecosystem and is tightly coupled with seasonal and hydrologic variability in coastal systems, where terrestrial DOM from rivers plays a major role in food web dynamics, carbon and nutrient cycling.

On a global scale, this heterogeneity has fueled a mystery – some studies suggest oceanic DOM is a stable carbon pool that turns over on scales of millenia, while other studies suggest a much shorter residence time, on the order of years to centuries. Tied into this mystery is the fundamental functioning of global ecosystems, from how basic elements like carbon and nitrogen move through the aquatic environment and shape phytoplankton communities that produce half the oxygen we breathe to the functioning of deep sea communities. This project seeks to advance our ability to use satellite observations to observe variability in broad groups of DOM compounds that interact with light, leveraging this spatiotemporal information to begin addressing this scientific mystery that has spanned decades of research progress. In particular, we are focusing on Lake Superior, where colored DOM is the dominant optical constituent and pours into the lake from coffee-colored rivers like the Sturgeon River, shown in the video above. Lake Superior offers a large, isolated aquatic system with a long residence time to explore terrestrial-aquatic coupling and degradation of diverse carbon molecules from satellite sensors, with an eye towards supporting discoveries that will support understanding this carbon mystery.