Browsing by Subject "Nutrient loading"
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Item Completion Report Jessie Lake Paleolimnology Project(University of Minnesota Duluth, 2002) Kingston, JohnJessie Lake is a high-priority lake in terms of the Itasca County Water Plan, recognized as an important resource for multiple-use recreation and for its walleye (Stizostedium vitreum (Mitchill)) fishery in particular. The Jessie Lake Watershed Association has been particularly active in promoting and participating in research to understand and improve the resource. The major concern in the watershed is increasing nutrient loading, according to recent lakewater phosphorous studies. Internal loading is also implicated in keeping the algal growth in the lake at high levels. We are presently using diatoms for paleolimnological interpretations of past baselines, trends, and magnitudes of change in lakewater phosphorous. Jessie Lake has been eutrophic since before European settlement of the area, though phosphorus concentrations were higher in the middle of the 20th century than they are now.Item Completion Report Mille Lacs Lake Paleolimnology Project(University of Minnesota Duluth, 2003) Kingston, JohnMille Lacs Lake is a high-priority lake in terms of its size and premier walleye fishery, and it has a relatively small watershed compared to the size of the lake surface. Expected future increases in development of the lakeshore have prompted a desire to know about water quality baselines for this important lake. This paleolimnological study examines a sediment core collected in late winter of 2002 using radioisotope dating, loss-on-ignition analysis of organic and inorganic sediment components, and diatom analysis as a proxy for nutrient loading. Land use changes in the watershed have caused accelerating soil erosion from 1960 until the present day. Diatom counts show a decline of benthos-dominated assemblages starting by the 1950s, with greater dominance of planktonic species for the last 60 years. This indicates nutrient loading increases and water transparency decreases. The core-top, representing conditions in 2001, shows the highest relative abundance of planktonic diatom species, indicating that nutrient loading is still increasing. Preliminary diatom- based reconstructions of past lakewater total phosphorus concentrations show that nutrient loading in Mille Lacs has increased approximately 30% during the past half century and remains at an historical high level.