Due to potential threats to water quality and fishery health, four lakes in Itasca County (Minnesota) were
selected for retrospective analyses. Primary goals were to determine background conditions and track
probable long-term degradation, timing of impacts and remediation. The lakes range from developed
(Buck, Shallow and Round lakes) to currently undeveloped (Willeys Lake). Sediment cores were
collected from each lake and sediment intervals were dated using isotopic analyses. 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. 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 system. Buck Lake experienced eutrophication and other
anthropogenic impacts, but in recent decades the lake has at least partly remediated. Shallow Lake has
apparently undergone numerous nearshore anthropogenic shifts, but development has not resulted in an
overall increase in nutrient concentrations. Water quality response to early watershed modifications of
Round Lake was limited but eutrophication became a problem in the latter portion of the 20th century due
to historic and recent land use activities. Despite being selected as an “undeveloped” lake, Willeys Lake
showed some subtle impacts due to likely deforestation in the lake’s catchment.
Reavie, Euan D.
Final Report on Sediment Diatom Reconstructions for Four Itasca County Lakes.
University of Minnesota Duluth.
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