To quantify the environmental history of the southern basin of Lake of the Woods (Ontario,
Manitoba and Minnesota), seven core locations 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. Sediments were dated using isotopic analyses and fossil
remains, in concord with other stratigraphic indicators (organic and inorganic materials,
sedimentation rates, other biological entities), were used to reconstruct the ~150-year history of
the lake. 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.
Nutrient reconstructions indicated a period of cultural eutrophication throughout much of the 20th
century. Despite a known reduction in anthropogenic nutrient flux to the lake in recent decades,
there has been no apparent reversal in eutrophication in the pelagic system. Contemporary
observations indicate that blooms of blue-green algae are becoming a greater problem. It appears
that legacy nutrient recycling and other environmental drivers are maintaining the current
condition of pelagic nutrient enrichment. Sedimentary analyses also indicated that physical
changes to the lake resulting from warming may be contributing in small part to the recent
reorganization of algal assemblages.
University of Minnesota Grant Number: 3005 10425 00017805
Reavie, Euan D; Edlund, Mark B; Andresen, Norman A; Engstrom, Daniel R.
Paleolimnology of the Lake of the Woods southern basin.
University of Minnesota Duluth.
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