To quantify the environmental history of the White Iron Chain of Lakes (Lake and St. Louis Counties,
Minnesota), five lakes were selected for retrospective analyses. Primary goals were to determine pre-
European settlement conditions and track the timing and extent of anthropogenic impacts and
remediation. Sediment cores were collected from each lake and sediment intervals were dated using
isotopic analyses. Fossil remains, in concord with other stratigraphic indicators (organic and inorganic
materials, sedimentation rates, other biological entities), were used to reconstruct the ~200-year history of
each lake. Pollen analyses allowed for reconstruction of local and regional terrestrial conditions.
Geochemical analyses provided data on historical flux of elemental trace metals to the sediments. Diatom
assemblages were assessed from sediment intervals and inferred trophic conditions in the profiles were
derived using a regional diatom-based model for Minnesota lakes. Eutrophication apparently occurred
following settlement, particularly in White Iron Lake, but reconstructed phosphorus trends indicate more
recent nutrient reductions. Pollen data track the decrease in pine abundance in the region and the rise of
birch. Sedimentary metals largely reflect physical changes in the system, such as a change in sediment
deposition regimes resulting from damming. Recent increases in metals are probably a result of increasing
accumulation of soil and bedrock materials, a trend that is supported by increasing accumulation rates of
overall organic and inorganic material. These recent increases in the last 30-40 years, which include
increased algal deposition in Birch, Farm and Fall lakes, are not well explained at this time, but may be
due to shifting water quality unrelated to phosphorus and possibly hydrological changes.
University of Minnesota Grant Number: 3015 10425 00024017
Reavie, Euan D.
Paleolimnological Reconstructions for the White Iron Chain of Lakes.
University of Minnesota Duluth.
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