HISTORICAL CHANGES IN TERRIGENOUS ORGANIC MATTER IMPORTS TO THE LAURENTIAN GREAT LAKES

Lacustrine sediments act as archives that can be used to reconstruct historical changes in the environment. Terrigenous organic matter (OM) that is incorporated into aquatic sediments is relatively stable and provides insights into current and historical conditions of the surrounding watershed. Allochthonous OM imports to the Laurentian Great Lakes (LGLs) are a relatively understudied component of the overall carbon cycle, especially questions surrounding how those carbon inputs have changed over time. As a part of the Great Lakes Sediment Surveillance Program, we have characterized the source of allochthonous OM from a series of sediment cores taken from LGLs Superior, Huron, and Ontario. Sediment cores dating to the early 1800s were collected at three sites in each lake and analyzed for bulk elemental and stable isotope content as well as lignin-phenol biomarkers using cupric oxide oxidation and gas chromatography-mass spectrometry (GCMS). Lignin-phenol proxy ratios in offshore sediment organic matter (SOM) indicate that airborne pollen is a major source of allochthonous SOM in each lake. The effects of urbanization on the watershed and subsequent deforestation were traced as a decrease in pollen input offshore and concomitant “pulses” of soil-derived SOM nearshore. LGLs Huron and Ontario received a larger proportion of their SOM from terrestrial sources than Superior due to differences in watershed to lake surface area and the amount of past human development. These results are the first to show the historical importance of aeolian pollen inputs to multiple LGLs.

Primary Presenter: Jake Zunker, University of Minnesota Duluth (zunke018@d.umn.edu)

Authors:

Jake Zunker, University of Minnesota Duluth, Large Lakes Observatory  (zunke018@d.umn.edu)

Kathryn Schreiner, University of Minnesota Duluth, Large Lakes Observatory  (kschrein@d.umn.edu)

Lily Karg, University of Minnesota Duluth, Large Lakes Observatory  (karg0038@d.umn.edu)

Chan Lan Chun, University of Minnesota Duluth, Natural Resources Research Institute  (chun0157@d.umn.edu)

Euan Reavie, University of Minnesota Duluth, Natural Resources Research Institute  (ereavie@d.umn.edu)

Bridget Ulrich, University of Minnesota Duluth, Natural Resources Research Institute  (ulrichb@d.umn.edu)

Christopher Filstrup, University of Minnesota Duluth, Natural Resources Research Institute  (filstrup@d.umn.edu)