Browsing by Subject "Eutrophication"

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Climatic and anthropogenic influences on aquatic ecosystems in the valley of the Great Lakes, Mongolia.
(2008-12) Shinneman, Avery Lynn Cook
Climate warming and major land use changes have profoundly affected the Mongolian landscape in the past several decades. As in many arid and semi-arid regions, water resources are critically important for ecological, social, and economic viability. In Mongolia, traditional semi-nomadic pastoralism contributes substantially to the national economy as well as to individual subsistence and depends on limited freshwater resources to provide for grazing herds and human needs. Yet, because of substantial variability across this immense region, its remoteness, and recent political transitions, little work has been done to monitor water quality or to set baseline standards against which to measure future changes. Compounding the problem is a lack of well-resolved paleo-ecological and paleo-climatological work. These data are necessary to provide a foundation for understanding the natural variability in the aquatic systems of the region, especially with recent changes in climate and land use. This work is a contribution to developing these records by first, developing diatom-based inference models for total phosphorus and salinity, and second, applying the models to investigate lacustrine sediment records of past changes. The diatom-based inference models were based on a survey of the water chemistry, physical characteristics, and diatom flora of 64 lakes in western Mongolia. The region had a diverse diatom flora with over 300 species, nearly 100 of which had not been previously reported from Mongolia, from lakes ranging from fresh to hypersaline. The many isolated lake basins provided unique ecosystems where multiple unique communities, novel species distributions, and new and endemic flora were found. Three of these new species are described here in a careful examination of the genus Cyclotella in western Mongolia. Canonical correspondence analysis (CCA) was used to identify four variables (specific conductivity, total phosphorus, bicarbonate, and lake morphology) that were significantly related to the distribution of diatoms; predictive models were developed for specific conductivity and total phosphorus using weighted averaging regression and calibration methods. The application of these models to dated lake sediment cores, along with interpretations of other geochemical and sediment characteristics, was then used to develop records of variability in lake salinity and nutrient flux. The interpretation of diatom and sedimentary records demonstrated increases in nutrient fluxes to the lakes related to climate warming and major changes in land-use over the last 20 years. Diatom-inferred lake salinity was correlated with changes in temperature over the past 2000 years, as inferred from tree-ring records, demonstrating a positive relationship between increased warming and increased lake salinity in recent geologic history. Changes in warm-season temperature, as inferred from tree-rings, in the most recent decades were less-well correlated with inferred changes in salinity than over most of the 2000 year record. However, instrumental records of winter temperature were well correlated with recent shifts in inferred salinity, perhaps suggesting recent changes in climate that are unique from those over the past several thousand years.
Duluth Area Lakes Water Quality Assessment: Caribou, Grand, and Pike Lakes - 1999; Pike Lake Fall Overturn Studies - 1996-1998
(University of Minnesota Duluth, 2001) Anderson, Jesse; Heiskary, Steven; Axler, Richard P; Henneck, Jerald
Minnesota is divided into seven regions, referred to as ecoregions, as defined by soils, land surface form, natural vegetation and current land use. Since land use affects water quality, it has proven helpful to divide the state into regions where land use and water resources are similar. Data gathered from representative, minimally-impacted (reference) lakes within each ecoregion serve as a basis for comparing the water quality and characteristics of other lakes. Caribou, Grand, and Pike Lakes are located on the northern edge of the Duluth Metropolitan Area (Figure 1) in the Northern Lakes and Forests Ecoregion (Figure 2). Caribou Lake has an area of 569 acres (230 hectares), and a maximum depth of 21 feet (6.4 meters). The majority of the lake is less than 10 feet deep, and is dominated by emergent and submergent aquatic vegetation. Grand Lake has an area of 1742 acres (705 ha). Baby Grand Lake flows into Little Grand, which flows into Grand Lake. Similar to Caribou, much of Grand Lake (~ 95%) is less than 10 feet (3 m) deep, and vegetation dominates the shoreline and near-shore areas. Pike Lake has an area of 508 acres (206 ha), and is much deeper. The maximum depth is 60 feet (~18 m), and most of the lake is between 20-50 feet deep (6-15 m). These lakes all have relatively developed shorelines and are likely to experience increased development pressure in the next decade. They have also experienced some degree of water quality problems in the past. Efforts are underway to improve wastewater treatment on two of these lakes. Construction of a sanitary sewer was recently (1999) begun around Pike Lake, and a constructed wetland wastewater treatment system servicing a cluster of nine (9) lakeshore homes was installed at Grand Lake in late 1995. The present study was conducted because local units of government desired additional water quality information on these Duluth area lakes for planning purposes. The Pike Lake Association also desired some follow-up work for comparison to a previous MPCA study (Bauman 1994), and to better define current lake water quality prior to the installation of a sanitary sewer in the basin.
Effects of Aquaculture on Mine Pit Lakes near Chisolm, MN: Restoration of Twin City-South pit lake by fallowing and status of Fraser pit lake
(University of Minnesota Duluth, 1995) Axler, Richard P; Yokom, Shane; Tikkanen, Craig A; Henneck, Jerald; McDonald, Michael E
Net-pen salmonid aquaculture was carried out from 1988 to 1993 in the Twin City-South mine pit lake on the Mesabi Iron Range in northeastern Minnesota. A water quality controversy enveloped the aquaculture operation from its inception in 1988. In 1992 the Minnesota Pollution Control Agency mandated that all intensive aquaculture operations in the Twin City - South mine pit lake be terminated by July 1993 and that restoration to baseline (i.e. preaquaculture) conditions be demonstrated within three years. This "fallowing" has led to a rapid recovery to near baseline water quality conditions and an oligomesotrophic, i.e. unproductive, status. Water column improvement in regard to phosphorus and hypolimnetic oxygen concentrations has been particularly rapid. Although baseline conditions were not well defined for TC-S, the P budget for the lake in September and November 1994 was typical of reference pit lakes in the area. Oxygen concentrations in near-bottom water remained above 5 mg02/L in November 1994 even without artificial mixing or aeration during the 1994 growing season. Algal growth was low in 1993, as expected due to artificial mixing, and remained low in 1994 without any artificial mixing. Ammonium has been naturally converted to nitrate which is decreasing faster than expected and at a rate similar to its increase during intensive aquaculture. More rapid reductions in water column phosphorus and nitrogen might have been accomplished during the first summer by allowing the lower hypolimnion to become anoxic in order to promote denitrification and minimize sediment resuspension. The natural burial of sedimented aquaculture wastes due to high ambient rates of erosion of inorganic sediment from the basin walls has effectively minimized sediment nutrient transport to the overlying water column. Fallowing for several years appears to be an effective method for lake restoration of these pit lakes. Our data, and our analysis of the NPDES monitoring data, has shown no change in the water quality of Chisholm's drinking water source, the Fraser pit lake, attributable to aquaculture impacts. This, and no apparent change in the water quality of two nearby pit lakes, Grant and Ironworld in recent years, suggests little or no significant off-site migration of aquaculturally impacted water.
Factors contributing to cyanobacteria blooms in Upper Saint Croix Lake, WI
(2012-12) Pevan, Thomas William
Upper Saint Croix Lake is a small, shallow, eutrophic lake that has experienced anthropogenic eutrophication. Nutrients, and in particular phosphorus availability, have long been recognized as a factor influencing the water quality of lakes. If phosphorus is excessive, cyanobacteria are often favored, leading to significant negative implications for the overall water quality and biodiversity of the lake, recreational enjoyment, and human and animal health. Nutrient concentrations, environmental factors, and phytoplankton efficiency were assessed to determine the role of seasonality and associated factors in the development of cyanobacteria blooms, and to examine the influence of year to year variability on the seasonal dynamics of the phytoplankton community. Light measurements, water temperature, and water samples were collected during the summers of 2008 (only year with a significant cyanobacteria bloom), 2009, and 2010, along with some winter sampling in 2010. Chemical analyses included chlorophyll a, particulate phosphorus, soluble reactive phosphorus, total and total dissolved phosphorus, total and total dissolved nitrogen, ammonia, nitrate, and soluble reactive silica in addition to active fluorometry (Phyto-PAM and Fluoroprobe). Results indicate that cyanobacteria in Upper Saint Croix Lake are controlled ultimately by phosphorus, and to a lesser degree, nitrogen and water temperature. Phosphorus concentrations, are in turn, controlled by environmental factors (precipitation, outflow, and inflow) that manipulate the dilution and flushing rate of the phosphorus present in the lake.
Identification and Characterization of Phosphorus Composition in Lake Superior and St. Louis River Estuary Sediments Using Phosphorus Nuclear Magnetic Resonance Spectroscopy
(2017-12) Schoechert, Hannah
Phosphorus has been a contaminant of concern for many freshwater lakes for decades. Excessive bioavailable phosphorus often leads to the eutrophication of a particular body of water. Information on the specific chemical composition of phosphorus in sediment is fundamental to understanding its bioavailability and eutrophication potential to a lake ecosystem. A single-step sodium hydroxide-ethylenediaminetetraacetic acid (NaOH-EDTA) extraction and a phosphorus nuclear magnetic resonance (31P NMR) spectroscopy protocol were developed and subsequently performed on St. Louis River Estuary (SLRE) and Chequamegon Bay (CB) sediment samples. Results show the presence of phosphorus-containing compounds comparable to other oligotrophic waterbodies, and compounds typically detected in sediment samples from eutrophic lakes were not detected in any sample. For the CB samples, as the water depth increased, so did the number of peaks identified. Similarly, as the number of peaks increased, there was an increase in relative abundance of different phosphorus. For the SLRE samples, it was observed that the phosphorus composition in the sediment mirrored the phosphorus sediment composition from the Chequamegon Bay samples, suggesting there are similar hydrological conditions between the two sites.
Limnological Assessment of Mine Pit Lakes for Aquaculture Use
(University of Minnesota Duluth, 1992) Axler, Richard P; Larsen, Christen; Tikkanen, Craig A; McDonald, Michael E; Host, George E
This study addresses water quality issues associated with current and future uses of mine pit lakes for intensive aquaculture. In current net pen aquaculture operations (Minnesota Aquafarms, Inc.), metabolic wastes and uneaten food are dispersed into the lakewater. Intensive aquaculture at Twin City-South and Sherman increased levels of phosphorus (P) and nitrogen (N) and reduced dissolved oxygen (DO) in the water column, and increased the deposition of organic matter to the bottom relative to their previous conditions and to unused mine pit lakes. Numerous trophic status indices suggest that TC-S and Sherman have shifted (or are shifting) from an oligotrophic state to a more eutrophic one. However, due to MAPs intensive aeration, and circulation, conditions necessary for algal blooms (typical of eutrophication) have been infrequent, due to light limitation from vertical mixing. Blooms of scum-forming bluegreen algae have never been observed.
Limnological Re-Sampling of Chisolm Area Mine Pit Lakes with Reference to Former Aquaculture Impacts
(University of Minnesota Duluth, 2000) Axler, Richard P; Henneck, Jerald
Limnological surveys were conducted on two mine pit lakes (Twin City-South and Sherman) used for intensive netpen salmonid aquaculture over the period 1988-1995 and an adjacent pit lake (Fraser) used for drinking water by Chisholm, Minnesota. A water quality controversy had enveloped the aquaculture operation from its inception in 1988 to its bankruptcy in 1995. All intensive aquaculture operations in the Twin City-South pitlake were terminated in mid-1993 as mandated by the Minnesota Pollution Control Agency (MPCA) in order to determine if water quality could be returned to baseline values within three years (a condition of continued operation in the Sherman pit lake). The MPCA mandated that restoration to baseline (i.e. pre-aquaculture) conditions be demonstrated within three years. This "fallowing" led to a rapid recovery to near baseline water quality conditions and an oligomesotrophic, i.e. unproductive, status. Algal growth was low in 1993, due to light - limitation from artificial mixing, but remained low in 1994 without any management due to renewed P-limitation. Water column improvement in regard to phosphorus and hypolimnetic oxygen concentrations was particularly rapid. Although baseline conditions were not well defined for TC-S, the P budget for the lake after 18 months was typical of reference pit lakes in the area and oxygen concentrations in near-bottom water remained above 5 mg02/L without artificial mixing or aeration during the next growing season. Waste product ammonium was naturally nitrified to nitrate which decreased at a rate faster than expected, and similar to its increase during intensive aquaculture. More rapid reductions in water column phosphorus and nitrogen might have been accomplished during the first, summer by allowing the lower hypolimnion to become anoxic in order to promote denitrification and minimize sediment resuspension. Unfortunately these were precluded by the regulatory standards. The natural burial of sedimented aquaculture wastes due to high ambient rates of erosion of inorganic sediment from the basin walls effectively minimized sediment nutrient transport to the overlying water column and sediment oxygen demand.
Paleolimnology of the Lake of the Woods southern basin
(University of Minnesota Duluth, 2015) Reavie, Euan D; Edlund, Mark B; Andresen, Norman A; Engstrom, Daniel R
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.
Regional, Watershed, and Site-Specific Environmental Influences on Fish Assemblage Structure and Function in Western Lake Superior Tributaries
(2005) Brazner, John; Tanner, Danny K; Detenbeck, Naomi E; Batterman, Sharon L; Stark, Stacey L; Jagger, Leslie A; Snarski, Virginia M
This report assesses the impact of human activities and forest fragmentation on fish communities in the western Lake Superior basin. Human-induced activities noted in the report included temperature changes, siltation, erosion, forest cover and forest manipulation, and invasive species. Specific results are reproduced below. “The relative importance of regional, watershed, and in-stream environmental factors on fish assemblage structure and function was investigated in western Lake Superior tributaries. We selected 48 second- and third-order watersheds from two hydrogeomorphic regions to examine fish assemblage response to differences in forest fragmentation, watershed storage, and a number of other watershed, riparian, and in-stream habitat conditions. Although a variety of regional, fragmentation, and storage-related factors had significant influences on the fish assemblages, water temperature appeared to be the single most important environmental factor. We found lower water temperatures and trout–sculpin assemblages at lower fragmentation sites and higher temperatures and minnow–sucker–darter assemblages as storage increased. Factors related to riparian shading and flow separated brook trout streams from brown trout (Salmo trutta) – rainbow trout (Oncorhynchus mykiss) streams. Functionally, fish assemblages at lower fragmentation sites were dominated by cold-water fishes that had low silt tolerance and preferred moderate current speeds, while fishes with higher silt tolerances, warmer temperature preferences, and weaker sustained swimming capabilities were most common at higher storage sites. Our results suggest that site-specific environmental conditions are highly dependent on regional- and watershed-scale characters and that a combination of these factors operates in concert to influence the structure and function of stream fish assemblages. Key points: This study was completed within 160 km of Duluth, Minnesota, in the Northern Lakes and Forests Ecoregion and within two ecological units, the North Shore Highlands (north shore streams) and the Lake Superior Clay Plain (south shore streams)which provided excellent contrast in hydrogeomorphic types. Functionally, south shore fishes tended to be silt-dwelling, trophic generalists with slow current preferences and a tendency towards nest-guarding spawning behavior. North shore fishes tended to be single-bout spawners with fast current preferences. From a management perspective, our results suggest that both timber management and wetland restoration or degradation decisions will need to be considered by resource managers when fish community health is a concern. For example, increasing percentages of mature forest cover should allow for salmonid–sculpin assemblages to become more prevalent in streams with the potential for cool or cold waters. Similarly, increased wetland cover should allow for a greater predominance of healthy warmwater fish assemblages assuming that other landscape features are not too badly degraded. By understanding the species structure and functional character of an assemblage and its relationship to landscape features, managers should be able to make at least a rough assessment of watershed condition. Lacking fish data, it might be easier to simply characterize forest cover and storage as a first step in identifying which watersheds likely contain streams that are degraded. Our results suggest that although in-stream habitat rehabilitation should continue to be used an important tool to improve biological conditions in streams, restoration efforts will have greater success if the potential interactions with landscape conditions are factored into the decision-making process. In some situations, manipulation of forest cover or watershed storage may have a greater impact on fish assemblage integrity than in-stream habitat improvements.”
A Survey of Water Quality in USDA Agricultural Ponds within Blue Earth County, South Central Minnesota.
(University of Minnesota, Water Resources Research Center, 1984-03) Ruotsinoja, Shawn P.

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