Quantifying Carbon Burial in Wetlands

PROJECT OVERVIEW
Shallow lakes are effective carbon sinks and could be used to mitigate carbon dioxide released from use of fossil fuels. Minnesota currently emits over 150 million metric tons of carbon dioxide annually due to fossil fuel use and has a stated goal to stabilize future emissions at 1990 levels. Reaching this goal will require both minimizing sources and maximizing carbon sinks such as shallow lakes. The University of Minnesota will use this appropriation to study how effectively shallow lakes and wetlands in different regions of Minnesota remove and retain carbon dioxide from the atmosphere. Findings will be used to provide guidance on how to manage shallow lakes to maximize carbon sequestration and evaluate the potential for Minnesota shallow lakes and wetlands to have roles on the global carbon trading market.

OVERALL PROJECT OUTCOME AND RESULTS
We examined the potential for shallow lakes to mitigate carbon dioxide release from fossil fuels. The CO2 concentration in the atmosphere is increasing and it is a greenhouse gas that has been strongly connected to climate change on Earth. The state of Minnesota emits over 150 million metric tons of CO2 annually due to fossil fuel burning and a stated goal is to stabilize releases at 1990 levels. Reaching this goal will require both minimizing sources and maximizing sinks such as lakes.

To determine how much CO2 is removed from the atmosphere by shallow lakes, we collected sediment samples from over 100 lakes throughout the state, determined how much organic carbon resides in the sediments and determined the burial rate using a new method that is based on lead isotope dating. Our goals were to identify important variables that facilitate carbon burial and to estimate burial rates for the entire state. We found that shallow lakes bury organic carbon at very high rates compared to other landscape features and that effective burial is facilitated by high rates of productivity that occurs in these systems; anaerobic (no oxygen) conditions, when they occur, particularly in the wintertime under the ice, also facilitate increased carbon burial. Although burial represents a large quantity of carbon, about 6 Tg per year (or 6 million metric tons), the State of Minnesota releases about 150 million metric tons of carbon per year through the burning of fossil fuels.

In addition to the scientific results of our work, this project has helped train 10 undergraduate students from both the University of St. Thomas and University of Minnesota, two graduate students at the University of Minnesota and one post-doctoral fellow for two years.

More information on the results of this project can be found in our final project report.

PROJECT RESULTS USE AND DISSEMINATION
The results from this project have been incorporated into materials for use in the class room at St. Thomas and University of Minnesota. Cotner and Zimmer have used material from this project in lectures they have given locally, nationally and internationally (Sweden, Brazil, Japan). At the recent Ecological Society of America annual meeting, members of our team presented 11 posters and/or oral presentations that were very well received. We also organized a special session on terrestrial-aquatic linkages that had a strong focus on carbon burial. This was an extremely well-attended session at this international meeting. Also, 6 members of our group (Cotner, Zimmer, Hobbs and Ramstack-Hobbs, Herwig, and Hanson) presented results from this project at a Shallow Lakes Workshop that we helped organize in Fergus Falls this past August. This workshop was completely full and was attended by resource managers from throughout the state. Cotner has also been presenting some of this work through informal education talks that he has been giving in the past 18 months to various groups (mostly senior citizens) in the Twin Cities area. He has given approximately 20 presentations that have focused on marine and freshwater resources. Lastly, we have published three papers in the scientific literature based on results from this and a related project funded through the National Science Foundation. We have four other papers that are either currently being reviewed or that will be submitted by June 2014.