CALL FOR PROPOSALS:

ORGANIZERS

  • Harvey Thorleifson, Chair
    Minnesota Geological Survey
  • Carrie Jennings, Vice Chair
    Minnesota Geological Survey
  • David Bush, Technical Program Chair
    University of West Georgia
  • Jim Miller, Field Trip Chair
    University of Minnesota Duluth
  • Curtis M. Hudak, Sponsorship Chair
    Foth Infrastructure & Environment, LLC

 

Paper No. 4
Presentation Time: 9:00 AM

CARBON BURIAL AND ECOLOGICAL REGIME CHANGE IN A MANIPULATED SHALLOW LAKE


HOBBS, Will, St. Croix Watershed Research Station, Science Museum of Minnesota, 16910 152nd St. North, Marine-on-St. Croix, MN 55047, HOBBS, Joy M. Ramstack, St. Croix Watershed Research Station, Science Museum of Minnesota, 16910 152nd St. North, Marine on St. Croix, MN 55047, THEISSEN, Kevin M., Geology, University of St. Thomas, Mail# OWS 153, 2115 Summit Ave, Saint Paul, MN 55105, COTNER, James B., Dept of Ecology, Evolution and Behavior, University of Minnesota, 100 Ecology Building, Saint Paul, MN 55108, DOMINE, Leah M., Biology, University of St. Thomas, 2115 Summit Avenue OWS 390, Saint Paul, MN 55105, EDLUND, Mark B., Saint Croix Watershed Research Station, Science Museum of Minnesota, 16910 152nd St. North, Marine on St. Croix, MN 55047 and ZIMMER, Kyle, Dept. of Biology, University of St. Thomas, Mail # OWS 390, 2115 Summit Avenue, Saint Paul, MN 55105, whobbs@smm.org

Whole-ecosystem manipulations in shallow lakes effectively demonstrate threshold ecological responses, namely a clear water, macrophyte dominated regime and a turbid, phytoplankton dominated regime. Here we show that C burial (total organic carbon mass accumulation rate; TOCMAR) in shallow Lake Christina (Minnesota, USA) is governed more by the long-term trophic state and settlement history of the lake rather than short-term oscillations between clear and turbid regimes. Paleoecological remains of diatoms, along with proxies of primary production (total chlorophyll a and TOCMAR) and trophic state (total phosphorous) from sediment records clearly show a single dramatic shift of the lake in the mid-1950s. During the modern, anthropogenic period of the lake (post-1950), three top-down manipulations (fish kills) induced temporary clear water regimes which allowed for macrophyte growth. While these manipulations induced profound ecological shifts, the temporary regimes yielded insignificant changes in the overall sedimentation and C burial in the lake; instead C burial changed most dramatically following the shift in the 1950s. Preliminary results among multiple shallow lakes in western Minnesota suggest that patterns of TOCMAR are not driven by the prevailing ecological regime. It appears that landscape changes and settlement history have a greater influence on C burial, either through allochthonous contributions of C or changes in nutrient cycling which affect lake primary production.
Meeting Home page GSA Home Page