Sampling beneath the ice
Kyle Zimmer and Leah Domine from the University of St. Thomas, along with Jim Cotner at the University of MN and all of their students are working to understand the modern ecology of these shallow lakes. The research questions being addressed by this team of modern ecologists include the following:
- How does the physical and chemical environment of these lakes (in terms of temperature, pH, oxygen, and nutrient content) change temporally and spatially?
- How do the physical, chemical, and biological environments differ between clear and turbid lakes?
- How do the environments of clear and turbid lakes affect the rate at which organic and inorganic carbon is permanently stored each year?
- On an annual basis, do shallow lakes function as a carbon sink or source in regard to the atmosphere?
- On an annual basis, what is the metabolic balance of these lakes? In other words, does gross primary production equal respiration, or does one exceed the other?
- How do water depth, dissolved oxygen levels, species of primary producers, and abundance of aquatic invertebrate shredders influence decomposition rates of plants and algae in shallow lakes? Could these factors influence overall carbon sequestration rates at the whole-lake scale?
- Distribution of detritivorous fathead minnows is highly variable among Minnesota shallow lakes. How high are consumption and respiration rates of carbon consumed from lake sediments, and could these fish influence carbon sequestration rates?
- This group is also assessing how switching lakes from turbid to clear-water states through biomanipulation influences sediment resuspension, dissolved oxygen dynamics, and carbon cycling and sequestration in a set of experimental lakes.
Will Hobbs, Joy Ramstack Hobbs, and Mark Edlund from the St. Croix Watershed Research Station are working with Kevin Theissen and his students from the University of St. Thomas on the paleoecology of the lakes (how the lakes have changed over time). This group is using biological and geochemical markers in sediment cores to determine how these lakes have changed over the past 150-200 years. Sediment records in shallow lakes hold great potential for understanding the causes and consequences of historical ecological change and ultimately how shallow lakes function in the landscape. This group's work revolves around the following research questions:
- How can multiple biogeochemical proxies be used to disentangle the drivers and impacts of environmental change in shallow lakes?
- How does the function and history of shallow lakes vary across landscapes?
- What physiological and life history traits characterize shallow lake diatom communities?
- How can the sediment record be used to guide management and restoration of shallow lakes?
- How significantly have the dominant sources and rates of burial of organic matter in our study lakes changed over the last two centuries? And how does the timing of these changes correspond to human settlement and influence in west-central MN?
- Are known redox-sensitive elements reliable recorders of redox histories in shallow lakes?
- Can cellulose and calcite be used as a proxy to identify lake state (clear vs turbid) in the sediment record?