Browsing by Subject "limnology"

Now showing 1 - 7 of 7
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    Accumulation of recalcitrant dissolved organic matter in aerobic aquatic systems
    (2021-02-09) Cotner, James; Anderson, NJ; Osburn, Christopher; cotne002@umn.edu; Cotner, James; Cotner Lab
    An oxygenated atmosphere led to many changes to life on Earth but it also provided a negative feedback to organic matter accumulation over billions of years by increasing decomposition rates. Nonetheless, dissolved organic carbon (DOC) is a huge carbon pool (>750 Pg) and it can accumulate to high concentrations (20-100 mg C L-1) in some freshwater aquatic systems, yet it is not clear why. Here, we examine DOC in several arctic lakes with varying concentrations and identify processes that alter its composition to make it recalcitrant to further degradation processes. Aging of DOC (from radiocarbon Δ14C ratios) corresponded with changes in its concentration, degradation rates, δ13C-DOC isotope ratios and optical quality, all suggesting that photochemical and microbial degradation processes contributed to decreased DOC reactivity over time. The degradation of young DOC was strongly stimulated by inorganic phosphorus, but older DOC was not, suggesting an important role for nutrients in regulating organic carbon degradation rates and pool sizes. Photochemical processing coupled with decreased habitat and microbial diversity in hydrologically isolated systems may enable recalcitrant DOC to accumulate with important implications for the Earth's carbon and oxygen cycles.
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    Complete Data and Analysis for: Niche models differentiate potential impacts of two aquatic invasive plant species on native macrophytes
    (2021-01-22) Verhoeven, Michael R.; Glisson, Wesley J.; Larkin, Daniel J.; michael.verhoeven.mrv@gmail.com; Verhoeven, Michael R; Minnesota Aquatic Invasive Species Research Center (MAISRC)
    The goal of our study was to elucidate the mechanisms by which two invasive aquatic plant species (Myriophyllum spicatum and Potamogeton crispus) interact with native plant communities in lakes in Minnesota, USA. We used an observational dataset of aquatic plant occurrences—and associated light availability, depth, and temperature—to construct probabilistic models of the ecological niches of 34 aquatic plant species. We then compared shared-ness of these niches between the two invasive aquatic plants and 32 native species to infer the degree of direct competitive interaction. This repository contains the complete dataset as a comma-separated-value file and Program R code necessary to replicate the data prep, exploration, analysis, and visualizations presented in the manuscript.
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    Digitization of Minnesota and Wisconsin bathymetric maps resulting in hypsographic data
    (2020-09-09) Rounds, Christopher I; Hansen, Gretchen JA; Vitense, Kelsey; Van Pelt, Amanda; round060@umn.edu; Rounds, Christopher; University of Minnesota Fisheries Ecosystem Ecology Lab
    The data set includes hypsographic data (area-at-depth) for over 750 Minnesota and Wisconsin lakes throughout the states. The majority of these lakes (650+) did not have publicly available hypsography. The hypsography was derived by digitizing bathymetric DNR maps using ImageJ. One hundred Minnesota lakes were selected that had DNR hypsographic data (in the form of a DEM) available and a comparison between the hypsographic data derived from DEMs and ImageJ was completed. These results, as well as code and hypsographic data is all available. The purpose of this work was to release broad scale lake area-at-depth data for limnological and aquatic biology studies.
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    Eagle Lake Pollution Control Project
    (Water Resources Research Center, University of Minnesota, 1976-08) Abbott, Robinson S.; Grohs, Roy J.; Holt, Robert F.; Latterell, Joseph J.; Nord, Bruce A.; Straw, Thomas E.; Timmons, Donald R.
    This report describes the cooperative efforts that a lake community and several governmental agencies undertook to alleviate increasing cultural eutrophication in Eagle Lake, Kandiyohi County, Minnesota. Two non-point nutrient sources were identified: agricultural runoff and domestic sewage. A lake-encircling collection line now diverts the sewage to a treatment plant. Earthen dams with soil absorption fields have been tested as a means of removing nutrients from part of the watershed runoff. Coincident with initiation of these anti-pollution measures, a comprehensive research project was initiated. Detailed studies of the chemical, physical, and biological conditions in the lake were conducted before the sewage system was completed. Water and nutrient budget estimates have been made. Eagle Lake can be classified as moderately eutrophic. Socio-economic surveys of lakeshore residents, other watershed residents, and non-resident ice fishing users resulted in a base line data profile of recreation use of Eagle Lake and of attitudes toward the lake and toward the anticipated improvements. Hopefully these data will suggest a model of community action. These benchmark studies, while of intrinsic interest, will reach their ultimate utility as a reference for comparison with conditions in the watershed after the pollution control measures have been in operation. Such further studies are anticipated.
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    Eagle Lake Pollution Control Project: Assessment of Lake Improvement
    (Water Resources Research Center, University of Minnesota, 1979-06) Latterell, Joseph J.; Abbott, Robinson S.; Straw, Thomas E.; Van Alstine, James B.; Myette, Charles F.
    In this study of the response of Eagle Lake, Kandiyohi County, MN, to the removal of septic effluent, detailed studies of the biological, chemical, sedimentological, hydrological and physical conditions in the lake were conducted. Comparisons of the data collected in this fifth year study were made with benchmark data. An annual hydrologic budget for Eagle Lake was prepared for the 1978 water year. Results show that the amount of water that flowed through Eagle Lake in the 1978 water year was 6,719 acre-feet. Inflow to the lake comprised 45 percent surface water, 22 percent groundwater, and 33 percent precipitation. Water out of the system comprised 72 percent surface water, less than 1 percent groundwater, 25 percent evaporation, and slightly greater than 2 percent net change in lake storage. Several observations give evidence of an improvement in the quality of Eagle Lake waters after the installation of a peripheral sewage collection line. One such observation is the decrease in total nutrient loads of nitrogen and phosphorus at the spring turnover 1978. However, increases in the phytoplankton biomass and the shifts in the most abundant species with the Blue-Green algae assuming dominance do no t indicate an improvement in water quality. The interpretation of our observations has been compiled by the increased nutrient load of the surface water inlets, especially that which resulted from unseasonably heavy rains flushing large quantities of nutrient rich and biologically active waters stored behind a beaver dam during weeks 24 to 28, 1978.
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    Particle Tracking in Lake Superior using FVCOM with focus on Apostle Islands
    (2021-08) Weber, Grace
    This study explores the movement of simulated neutrally buoyant drifters in far western Lake Superior. It was motivated by a desire to understand the transport and fate of microplastic particles originating near the region’s population centers and their potential impact on the Apostle Islands National Lakeshore. Particle movements were determined using the Finite Volume Coastal Ocean Model (FVCOM) configuration developed by the Large Lakes Observatory at the University of Minnesota Duluth. When exploring vertically averaged monthly output for the years 2015 and 2018, particles (which could include microplastic particles or suspended sediments) were modeled as passive drifters and advected using model output during each month. Exploring month- long and three month-long model runs showed that drifters originating in the St. Louis and Nemadji estuaries move predominantly towards the Apostle Islands. Drifters are also predicted to be more prevalent on the northern side of the Apostle islands. Drifters were also observed to travel faster in the late summer months, with more drifters entering and staying in the Apostle Islands during those months as well. The drifter tracks suggest that if a microplastic or other neutrally-buoyant particle is deposited inside of the estuary, assuming no large wind events, it will most likely end up in the Apostle Islands within 3 months, especially during the late summer months. The results of this analysis will help researchers to better understand the source, transport and fate of microplastics in Lake Superior. Part of this research was intended to aid in further understanding microplastic sampling research done in the Apostle Islands during June through December of 2015 (Whitmire et al 2017), and May and August of 2018 (Minor et al 2020).
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    Upper Midwest lakes are supersaturated with N2
    (2020-06-22) Loeks-Johnson, Brianna M; Cotner, James B; cotne002@umn.edu; Cotner, James B
    Little is known about the exchange of gaseous nitrogen (N2) with the atmosphere in freshwater systems. Although the exchange of N2, driven by excess or deficiencies relative to saturation values, has little relevance to the atmospheric N2 pool due to its large size, it does play an important role in freshwater and marine nitrogen (N) cycling. N-fixation converts N2 to ammonia, which can be used by microbes and phytoplankton, while denitrification/anammox effectively removes it by converting oxidized, inorganic N to N2. We examined N2 saturation to infer net biological nitrogen processes in 34 lakes across 5° latitude and of varying in trophic status, mixing regime, and bathymetry. Here, we report that nearly all lakes examined in the upper Midwest (USA) were supersaturated with N2 (>85% of samples, n = 248), suggesting lakes are continuously releasing nitrogen to the atmosphere. The traditional paradigm is that freshwaters compensate for N-limitation through N-fixation, but these results indicate that lakes in this region arewere constantly losing N to the atmosphere via denitrification and/or anammox, suggesting that terrestrial N inputs are needed to balance the internal N cycle.