Browsing by Author "Kingston, John"

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    Completion Report Jessie Lake Paleolimnology Project
    (University of Minnesota Duluth, 2002) Kingston, John
    Jessie 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.
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    Completion Report Mille Lacs Lake Paleolimnology Project
    (University of Minnesota Duluth, 2003) Kingston, John
    Mille 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.
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    Monitoring Diatom Algae in Northeastern Minnesota
    (University of Minnesota Duluth, 2005) Reavie, Euan D; Kingston, John; Peterson, Morgan; Edlund, Mark B
    Surface sediment samples from 37 Itasca region lakes were appended onto an existing Minnesota lakes diatom calibration set to create a new 145 lake diatom training set with better representation of lakes throughout Minnesota and better reconstruction performance for total phosphorus values above 60 μg/L. Relationships among 15 chemical, physical and spatial (i.e., region) variables and 170 diatom species distributions in the new 145 lake training set were explored using canonical correspondence analysis (CCA), a multivariate ordination technique. Environmental variables that independently explained a significant portion of variation in species distribution were identified using forward selection. Total phosphorus (TP) was one of the most explanatory variables in the refined calibration set, including pH, lake depth, color, chloride, Secchi depth, conductivity, mean lake depth, lake area, and ANC. Weighted averaging partial least squares regression and calibration was identified as the appropriate method for model evaluations. A transfer function for inferring TP was generated from three versions of the lake calibration set: 1) the full 145-lake calibration set; 2) a reduced, 129-lake set where lakes with pH ≥ 9.0 removed to better represent conditions in the Itasca region; and 3) a further-reduced model that eliminated five lakes with poor diatom-inferred (DI) total phosphorus concentrations. The 124-lake calibration set produced a total phosphorus transfer function covering a gradient spanning lakes from 5-364 μg/L TP, and strong predictive ability for TP (r2 = 0.87, r2 jack = 0.77, RMSEP = 0.210 log(μg/L+1)). The transfer function was applied to estimate historical epilimnetic total phosphorus from subfossil diatom assemblages in a sediment core recovered from Jessie Lake, Itasca region. Pre-settlement conditions in Jessie Lake were inferred to be eutrophic, with a temporary augmentation in nutrient load between ~1950 and ~1980.