Browsing by Subject "Phosphorus"
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Item Agronomic and Environmental Management of Phosphorus(St. Paul, MN: University of Minnesota Extension Service, 1998) Rehm, George; Lamb, John; Schmitt, Michael; Randall, Gyles; Busman, LowellItem Assessing the Effectiveness of Biomass Harvesting at Reducing Phosphorus Loss in Wetland Mesocosms (UROP)(2021-01) Gregersen, LucyThis undergraduate research project assessed how phosphorus levels in student-designed mesocosms in Saint Paul have changed in the span of two years since experimentation on the effectiveness of biomass harvesting. Throughout 2017 and 2018, each mesocosm tank was maintained regularly with 3.75 gallons of water containing 0.06mg/L of phosphorus, and plants were harvested seasonally to assess how much phosphorus can be removed by each species. Soil and plant samples taken in summer and fall of 2020 indicate that soil phosphorus levels increased without fertilizer application and plant harvesting, and phosphorus contained in the plant matter decreased.Item Biogeochemistry of southwestern Lake Superior and watershed, 2017-2021(2023-09-28) Sterner, Robert W.; Lafrancois, Brenda M; stern007@d.umn.edu; Sterner, Robert W.; Large Lakes Observatory, University of MinnesotaBetween 2017 and 2021, 1368 water samples were collected from Lake Superior and its watershed in the region generally between Duluth-Superior and Ashland, WI. Parameters include forms of carbon, nitrogen, and phosphorus, along with total suspended solids, chlorophyll, and phycocyanin.Item Comparing Phosphorus Uptake of Three Plant Types in Wetland Mesocosms(2018-05) Dereskos, Nitsa JWetlands are a type of ecosystem that are saturated with water and contain characteristic vegetation types. They perform many ecosystem services, including water storage and filtration of nutrients, such as phosphorous. Phosphorous is often a limiting factor for plant growth, and frequently present in agricultural surface water runoff, as it is used in fertilizer to grow crops. Excess nutrients in water bodies harm the broader aquatic ecosystem, causing eutrophication and poorly oxygenated water. Wetlands can assist with removing phosphorous from the environment by storing it within the vegetation. The purpose of this study is to compare phosphorous uptake in wetland mesocosms among three species of plants, characterized by growth type: a cold season grass, Canada blue-joint grass (Calamagrostis canadensis); a warm season grass, prairie cordgrass (Spartina pectinata); and a sedge, tussock sedge (Carex stricta). The plants have been grown in mesocosms, and have been dried in an oven to determine their dry weights before their phosphorous content is determined. The results of this research can be applied to the design of treatment wetlands, improving water quality downstream by removing excess nutrients from the water.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 Consumer nutrient stoichiometry : patterns, homeostasis, and links with fitness.(2010-10) Hood II, James MichaelThe linkages between food webs and nutrient cycles are heterogeneous and often influenced by human activities. Ecological stoichiometry provides one framework for understanding and predicting these linkages. Yet, as it has been extended underlying assumptions are often not evaluated. This dissertation shows that examination of implicit and explicit assumptions reveals unknown mechanisms, interactions, and linkages. For instance, theory assumes that invertebrate stoichiometry does not vary with diet stoichiometry (i.e., strict homeostasis), even though many invertebrates are not strictly homeostatic. Chapters one and two examine the role of stoichiometric homeostasis in shaping the fitness of Daphnia species. Chapter one shows that the long-‐term phosphorus (P) use efficiency of stoichiometrically flexible Daphnia species is higher in habitats with temporally variable diets, resulting in higher fitness relative to strictly homeostatic species. Chapter two shows that the P cost of a unit of growth increased with growth rate and structures tradeoffs among growth rate, sensitivity to P limitation, and stoichiometric flexibility. Stoichiometric theory can be extended to novel ecosystems, such as streams, to predict the role of consumers in food web and nutrient cycles. To do To do this, the balance between consumer and diet stoichiometries is a logical starting point. Chapter three examines intra-‐specific variation in consumer-‐resource stoichiometries at a suite of sites within a river network. In contrast to previous work, this chapter describes wide intra-‐ specific variation in consumer stoichiometry, similar in magnitude to the variation among invertebrate taxa. Intra-‐specific variation in nitrogen and phosphorus content was related to both ontogeny and diet. These results suggest that the role of a species in stream nutrient cycles could vary spatially with diet and temporally through ontogeny.Chapter four examines the influence of diet stoichiometry on nutrient release ratios of four stream detritivores. Predictions of nutrient release ratios from bulk diet stoichiometries were misleading for these detritivores, which selectively consumed a nutrient rich portion of the bulk diet. Selective feeding greatly reduced stoichiometric mismatches between these consumers and their diets. Taken together, this dissertation demonstrates that examination of stoichiometric assumptions improves our understanding of consumer-‐resource dynamics, competition, and the role of consumers in nutrient cycles.Item Data for: Internal Loading in Stormwater Ponds as a Phosphorus Source to Downstream Waters(2019-04-15) Taguchi, Vinicius J; Olsen, Tyler A; Natarajan, Poornima; Janke, Benjamin D; Gulliver, John S; Finlay, Jacques C; Stefan, Heinz G; ; taguc006@umn.edu; Taguchi, Vinicius J; University of Minnesota - St. Anthony Falls Laboratory - Stormwater Research GroupStormwater ponds remove phosphorus through sedimentation before releasing captured water downstream. Internal loading can impair net phosphorus removal but is understudied in these highly modified systems. Using a combination of methods, we assessed the prevalence and potential causes of sediment phosphorus release in urban ponds. In a three-year, 98-pond dataset, nearly 40% of ponds had median water column total phosphorus concentrations exceeding the 95% confidence interval for runoff values (0.38 mg/L), suggesting widespread internal loading. In a subsequent intensive monitoring study of four ponds, strong stratification prevented spring and summer diurnal mixing, resulting in persistent hypolimnion anoxia (<1 mg/L dissolved oxygen). Incubated sediment cores from seven ponds demonstrated high anoxic phosphorus release. Sediment analysis revealed high labile organic and redox-sensitive phosphorus fractions with release potential at anoxia onset. Our analyses suggest phosphorus accumulated in stormwater ponds is highly sensitive to internal loading, reducing net removal and contributing to downstream eutrophication.Item Decomposition and Production of Dissolved Organic Matter by Aquatic Bacteria(2019-06) Thompson, SethAquatic ecosystems transport large amounts of organic matter from the landscape to the oceans. Along this pathway, heterotrophic bacteria rapidly cycle these compounds by acting as both degraders and producers of organic compounds. Understanding the ultimate fate of the organic matter and predicting how increased organic matter exports from terres-trial ecosystems will impact its delivery to the ocean, requires a better understanding of the factors that influence organic matter degradation and production in freshwater systems. While many scientists have approached this problem by focusing on microbial modifica-tions of carbon (C), much less attention has been paid to other major elements found in or-ganic molecules (namely nitrogen (N) and phosphorus (P)). A more integrated approach that incorporates microbial processing of both C and major macronutrients such as N and P is needed to describe the biogeochemical transformations of organic matter in freshwaters. In this dissertation I examine the degradation and production of dissolved organic matter by heterotrophic bacteria, specifically focusing on dissolved organic phosphorus (DOP). In chapter 1, I quantify the degradation rates and overall bioavailability of DOP across 27 unique aquatic systems and explore important environmental and chemical regu-lators of these rates. Data from these systems show that DOP degradation rates are spatially variable, but are typically as high or higher than rates of degradation for C. Also, the chem-ical composition of organic matter was an important predictor of DOP bioavailability with DOP bioavailability being lowest when DOP was scarce relative to C. This relationship means that DOP is degraded by bacteria in systems that are more likely to experience P lim-itation, suggesting that DOP may be an important source of P to bacteria in these systems. Chapter 1 concludes by documenting the importance of incorporating estimates of organic matter bioavailability into estimates of resource imbalance experienced by aquatic bacteria. Accounting for the bioavailability of organic matter generally reduces the estimates of nutri-ent imbalance experienced by aquatic bacteria compared to estimates using bulk nutrient concentrations. This reduction in imbalance would result in more efficient C cycling by aquatic bacteria, which has important implications for understanding the composition of organic matter exported downstream and ultimately to the ocean. Chapter 2 goes on to explore the production of organic matter by heterotrophic bac-teria. It is well documented in marine systems that bacteria can produce an immensely di-verse set of organic molecules, even when they are only given a single carbon source to start from. However, the factors that control this production and the extent to which bacteria also produce DOP remains unclear. Previous work has shown that bacteria in freshwaters have different stoichiometric strategies for dealing with nutrient imbalance, with some strains of bacteria capable of changing the chemical composition of their cells to more closely match that of their resources. This flexibility in biomass nutrient composition has important implications for the recycling rates of multiple nutrients and therefore likely im-pacts the production of organic molecules by bacteria as well. Using previously isolated bacterial strains that have had their biomass flexibility quantified, I test the impact of these different stoichiometric strategies on the composition of the organic matter the strains pro-duce. In this chapter, I show that bacteria produce measurable amounts of dissolved organic phosphorus, even under strongly phosphorus limited conditions. Overall, bacteria convert-ed ~0.01%-10% of the phosphate in the original media to dissolved organic phosphorus, with the highest conversion efficiencies under carbon limited growth conditions. Interest-ingly, the conversion efficiency was higher under extreme phosphorus limitation than mod-erate phosphorus limitation. This pattern was driven primarily by relatively high conversion efficiencies by bacteria with flexible biomass stoichiometry in the most phosphorus limited conditions demonstrating the importance of physiological responses to nutrient imbalance. This chapter also explores the impact of bacterial biomass flexibility on the optical proper-ties of the organic matter produced by bacteria. I show that biomass flexibility is signifi-cantly and positively related to the specific ultraviolet absorbance at a wavelength of 254 nm, a measure of the aromaticity of the organic matter, when grown under extreme phos-phorus limitation. This suggested that bacteria with more flexible biomass stoichiometry produce more complex carbon molecules under strong phosphorus limitation than less flex-ible strains do. While more work is needed to fully understand how the physiological growth strategies of different microbial taxa impact the production of DOM, this chapter provides some important first insights into this question. In the final chapter, I transition away from research on aquatic ecology into what I consider to be another fundamental aspect of being a scientist: training the next generation of scientific thinkers. Over the last decade, there has been a clear call to shift the instruc-tional methods used for teaching undergraduate biology courses. We now know that active learning approaches to teaching science lead to better science outcomes for students. Fur-thermore, engaging undergraduate science students in undergraduate research experiences has been shown to have a number of important benefits for students such as increased stu-dent engagement, interest in science careers, and understanding of the scientific process. To offer the benefits of research experiences to a broader set of students, many institutions have started offering Course-based Undergraduate Research Experiences (CUREs) in la-boratory classes for students. It is common for these laboratory sections to be primarily fa-cilitated by undergraduate or graduate teaching assistants (TAs) rather than full-time faculty members. For these TAs to efficiently achieve the goals of these CUREs they must under-stand both (a) the philosophical underpinnings of discovery-based inquiry, and (b) strate-gies for facilitating inquiry, based on evidence-based practices, in the teaching laboratory. However, TAs are rarely trained in pedagogy, which likely limits their abilities to effective-ly facilitate inquiry in the laboratory. Chapter 3 is a case study documenting the results of a theoretically grounded professional development pilot program. This pilot program revealed that novice TAs are initially concerned primarily about the logistical aspects of teaching: classroom management, content preparation, grading assignments, etc. These concerns limit their readiness for engaging with the more complex pedagogical concepts of evidence-based instruction or inclusive teaching. This means that TA professional development needs to be designed to parallel the dynamic nature of TA concerns and that programing focused on advanced teaching techniques is only effective after TAs have established a sense of comfort and confidence in their own teaching.Item Design, Synthesis, and Characterization of Novel Photosensitizers for Use in Molecular Machines(2021-08) Bayard, BrandonPhosphorus porphyrin-naphthyl compounds were synthesized and evaluated for future use as an electron acceptor/donor system within a photoactivated molecular shuttle. This evaluation consisted of characterizing the redox and optical properties of the systems, as well as determining the formation constant of the complex formed between the naphthyl group in each compound and a previously reported macrocycle, cyclobis(paraquat-p-phenylene) (CBPQT), with affinity towards various naphthyl derivatives. This data was holistically reviewed and used to evaluate the potential use of phosphorus porphyrin-naphthyl compounds as an electron donor/acceptor system within a molecular shuttle. Furthermore, an informed design for such a molecular shuttle was produced, and steps towards its synthesis were taken. Two other projects in which novel photosensitizers were synthesized and characterized are detailed here. The purpose of these two projects is to extensively identify their optical and redox properties such that they may be used in future systems such as molecular machines or artificial photosynthesis. The first project explores a series of phosphorus tetraphenylporphyrin derivatives in which the phenyl rings of the porphyrins have various amounts of methoxy groups adorning them. The second project explores a novel phosphorus porphyrin/aluminum porphyrin heterodimer. The goal of which is to characterize the interactions of the chromophores when no exciton coupling is observed.Item Ecological stoichiometry of bacterial assemblages(2013-12) Godwin, Casey MichaelAll organisms are faced with a chemical imbalance between their internal environment (cells, tissues, or body) and their external environment. Homeostasis is the ability to maintain an internal state that is different from the external environment and at least some degree of elemental homeostasis is required for metabolism and growth. Homeostasis is related to fitness since the degree of elemental imbalance between an organism's biomass and its resources controls the growth of populations, predicts the outcome of competition, and determines the relative rates of resource consumption, assimilation, and excretion of elements and energy. Since all organisms are composed of molecules that are comprised mainly of a common set of elements (carbon (C), hydrogen, oxygen, nitrogen (N), phosphorus (P), etc.), stoichiometric ratios of these elements in biomass (e.g. C:Pbiomass) and resources (C:Presources) can be used to diagnose the strength of imbalance and to assess the nutritional state of organisms. The strength of elemental homeostasis is variable within and among groups of taxa; some species and groups maintain strong homeostasis, but others adjust their chemical composition in response to their environment. Since ecosystems seldom contain only a single species, assemblages and communities can respond to elemental imbalance both through changes in the relative abundance of species and through simultaneous changes in the elemental content of the component species. The goals of this dissertation are to evaluate the role of resource competition and species shifts in the stoichiometry of assemblages and to understand the ranges of stoichiometric regulation and biomass chemistry within the bacterial assemblages of lakes. In chapter 1, I introduce the conceptual framework of `stoichiometric strategies' to align the gradient of stoichiometric regulation with physiological tradeoffs. Data from previously published studies on planktonic organisms show that the strength of homeostasis in a species is inversely proportional to the ratio of the two elements in its biomass when the denominator element is limiting. Under nutrient limitation, homeostatic species have lower biomass C:N, C:P, and N:P ratios than do species with flexible biomass stoichiometry. I show how a consumer-resource model with tradeoffs related to competitive ability for C and P couples homeostatic regulation to competitive ability. The result is a conceptual model in which assemblages are dominated by homeostatic species under low resource imbalance and by species with flexible stoichiometry when nutrients are strongly limiting. I test the stoichiometric strategies concept in chapter 2 by culturing assemblages of heterotrophic bacteria at a range of resource ratios and examining the strength of homeostasis in the dominant species. I found that low resource C:P ratios could select for homeostatic strains of bacteria and that higher resource C:P ratios yielded assemblages with flexible composition. In chapter 3, I use bacteria isolated from lakes to describe how homeostatic strains and flexible strains respond to imbalance in C and P. The strains exhibited substantial variation in stoichiometric regulation, but strong homeostasis was associated with higher C and P content and flexible stoichiometry was present only in strains with low P content. These experiments support the hypothesis that flexible biomass composition is competitively superior under P limitation. In the final chapter, I seek to characterize the range of cellular P content attainable by heterotrophic bacteria and determine how bacteria minimize their P content in response to P limitation. I show that bacteria can exhibit greater flexibility in P content than was known previously (< 0.01 to 3% of dry mass as P, biomass C:P of 30:1 to > 10,000:1) and that this flexibility is explained by a simultaneous increase in C content (13 to > 70 fmoles cell-1) and decrease in P content (0.62 to < 0.06 fmoles cell-1) under P limitation. These studies highlight the importance of physiological constraints and assemblage-level interactions to understanding the impact of stoichiometry on biogeochemical cycles. Additionally, the results of these experiments show that strains of bacteria differ dramatically in their elemental composition, stoichiometric regulation, and resource demands and that the assumptions of strong homeostasis and high nutrient content are not representative of bacteria in aquatic environments. Although aquatic heterotrophic bacteria serve as a useful system to address these questions, the constraints appear to be fundamental and these results are likely applicable to other groups of organisms.Item The effects of temperature and phosphorus availability on the biomass composition, phosphorus allocation, size and morphology of freshwater bacteria.(2012-07) Phillips, Katherine N.Freshwater bacteria play a key role in the regulation of nutrients in aquatic ecosystems. Bacteria mediate the availability of nutrients tied up in organic molecules and are therefore capable of constraining both primary production and higher trophic levels in aquatic ecosystems. To assess how changes in temperature and phosphorus availability impact three diverse strains of heterotrophic bacteria (Agrobacterium sp., Flavobacterium sp.,and Arthrobacter sp.isolated from Lake Itasca State Park, MN, I investigated 1) the effects of phosphorus availability on bacterial biomass composition, 2) the effects of temperature on bacterial biomass composition and 3) the combined effects of phosphorus availability and temperature on bacterial biomass composition. To assess how phosphorus availability impacts biomass composition in photoautotrophic bacteria Synechocystis sp PCC 6803, the effect of phosphorus availability was investigated. Under phosphorus limitation I observed two distinct strategies adopted by the three heterotrophic strains. Either the cells became large, long and thin or they stayed relatively small and coccoid in shape. Both strategies observed under phosphorus limitation resulted in different patterns of cellular phosphorus allocation. Controlling for growth rate across changing temperatures, I observed that as temperature increased, all three strains decreased their cellular size, and their carbon, phosphorus, and nucleic acid content. However, a pronounced decrease in DNA content was observed in only one strain. The combined impact of increasing temperature and phosphorus limitation resulted in a more dramatic decrease in cellular size and cellular carbon than when phosphorus was not limiting. These findings suggest no one strategy is adopted by heterotrophic bacteria under phosphorus limitation or across changing temperature. Secondly, I observed that changes in phosphorus availability resulted in a much more flexible C:P biomass composition in Synechocystis than changes in nitrogen availability. These findings suggest that less carbon may be in bacterial biomass when cells are nitrogen limited than when cells are phosphorus limited. These results provide insights into the impact that both increasing temperature and phosphorus has on microbial composition and the potential effects of that composition on the microbial loop in aquatic ecosystems.Item Extractability of carbon, nitrogen, and phosphorus in United States grasslands(2015-02) Thompson, Seth K.Tracking how energy flows within and across ecosystems is imperative for understanding interactions among biogeochemical cycles. Aquatic ecosystem metabolism is inextricably linked to the terrestrial landscape, with many lakes getting over 50% of their carbon from terrestrial sources. Nonetheless, there are few large scale measurements of actual carbon export from terrestrial ecosystems. Instead, scientists have relied on a mass balance approach to estimate the quantity of carbon coming into aquatic ecosystems based on estimates of riverine carbon delivery to the ocean. This approach has left many unanswered questions related to the controls on terrestrial organic matter export, both in terms of quantity and quality. Here I used Water Extractable Organic Carbon (WEOC) to estimate potential terrestrial carbon export and to understand the mechanisms controlling these exports. Results from extractions performed at 19 grassland sites across the United States suggested that 1-5% of their total soil carbon was in the water extractable organic carbon pool. In addition, this work suggested that soils selectively retained nitrogen and phosphorus, with less organic nutrient export relative to organic carbon to aquatic ecosystems. These data demonstrated the usefulness of measuring water extractable organic matter (WEOM) on broad spatial scales to gain a better understanding of both the amounts and types of organic matter that are available for export from terrestrial ecosystems.Item Factors contributing to cyanobacteria blooms in Upper Saint Croix Lake, WI(2012-12) Pevan, Thomas WilliamUpper 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.Item Floating Treatment Wetlands in a Northern Climate: Examination of Phosphorus and Nitrogen Removal(2016-05) Deering, EmilyExcess phosphorus is the largest contributor to nutrient impairment in Minnesota waters. Floating treatment wetlands (FTWs) are a novel best management practice (BMP) to reduce excess nutrients in waterbodies. This study examines the nutrient reduction efficiency of floating treatment wetlands in a northern climate under agricultural loading conditions. A field-based, mesocosm study was completed to quantify the removal efficiency of total phosphorus, Orthophosphate-P, Nitrate-N, and Ammonia-N. The FTWs were each planted with wetland plants Juncus effusus, Eleocharis acicularis, and Glyceria canadensis. A system phosphorus budget was prepared to identify phosphorus sources and sinks within the BMP. Floating treatment wetlands had higher total phosphorus reduction efficiencies. Eleocharis acicularis had the fastest growth rate and highest removal efficiency of the three plants studied. Mesocosms with FTWs had statistically significant lower pH and dissolved oxygen concentrations. Further research areas and FTW design improvements are recommended based on findings from this experiment.Item Hydrology, Nutrient Removal, and Cost Effectiveness of Small, Edge-of-Field Tile Drainage Treatment Wetlands(2019-05) Gordon, BradleyConstructing treatment wetlands is a recommended practice for mediating nutrient pollution from non-point sources in the Mississippi River Basin. This research investigated the nitrogen and phosphorus removal effectiveness of a small, edge-of-field, constructed treatment wetland using field, laboratory, and modeling data. In the field, the wetland removed 67% (48-100%) of nitrate discharging from tile drainage but released soil legacy phosphorus from 2013 through 2016. Denitrification in the shallow groundwater and vegetation harvest were the greatest sinks for nitrogen and phosphorus, respectively. In the laboratory, three plant communities from the wetland (a wet prairie forb-dominant mix, a switchgrass and prairie cordgrass-dominant community, and a reed canary grass monoculture) were compared for nitrate removal. The wet prairie mix removed the most nitrate, and it had the lowest dissolved oxygen concentration and greatest ratio of denitrifying bacteria to total bacteria (nosZ:16S rRNA genes) – measured using a quantitative polymerase chain reaction (qPCR) – in its root zone. For the modeling component, the ACPF toolbox, the SWAT model, and a spreadsheet model were used to estimate the mass of nitrate-N removed from tile drainage if more edge-of-field wetlands were constructed in the Elm Creek HUC12 watershed. These smaller wetlands removed more nitrate-N per wetland area than larger wetlands (watersheds > 60 ha) but cost the same per mass removed if the small wetlands were designed to have a high saturated hydraulic conductivity. Results from this study suggest that edge-of-field wetlands can be more effective with a dual treatment of surface flow and shallow groundwater flow for nitrate removal and vegetation harvest for phosphorus removal. However, reed canary grass invasion could potentially decrease the nitrate removal effectiveness. If the wetland soils have a high conductivity, the smaller, edge-of-field designs could be as cost effective as large treatment wetlands but remove less land from agricultural production. This dissertation is composed of three individual chapters that will be published in peer reviewed scientific journals. The first chapter pertains to a field study that observed a small, edge-of-field tile drainage treatment wetland. This chapter will be submitted to Ecological Engineering. In the second chapter, the nitrate removal in three plant communities from the wetland was compared using mesocosms. Total bacteria and denitrifying bacterial populations in the root zones of these communities were also compared using qPCR. The work from this chapter was submitted to the Journal of Environmental Quality and is currently under review. The final chapter will be submitted to Agriculture, Ecosystems & Environment. This chapter compared the effectiveness of small, edge-of-field treatment wetlands with watersheds less than 60 ha to large treatment wetlands with watersheds greater than 60 ha. Multiple models were used to determine the best locations for each wetland in the Elm Creek watershed in southern Minnesota. Conclusions were drawn that small, edge-of-field wetlands are effective nutrient removal practices and can be improved with high saturated hydraulic conductivity, harvested vegetation, and diverse plant communities.Item Influences of management and the environment on phosphorus leaching in corn-soybean systems in Minnesota(2018-08) Leverich, LeannaPhosphorus is an essential nutrient in corn and soybean systems for maximizing yields and profits in Minnesota. The over-application of P fertilizer can lead to the impairment of freshwater ecosystems throughout the Midwest and United States. Excess P in freshwater can ultimately lead to eutrophication and detrimental species population shifts. To help mitigate such pollution here in Minnesota, research was completed to identify the risk of P loss to the environment through leaching. The objectives of this research were to 1) Evaluate the potential for water soluble P loss from top soils (0-15 cm) across a range of initial soil test phosphorus (STP) levels and timings of leaching events after fertilizer application (denoted as “leachtimes”); 2) Determine the effect of soil type, soil properties, initial STP level, various leaching intensities, and P fertilizer source on P leaching losses; 3) Assess the predictability of P loss through leaching using routine soil tests, leaching intensity, soil properties and sorption estimates. Six sites throughout the state of Minnesota under long-term P management were used for this study. Intact soil columns were taken from all sites to identify the risk of P leaching from various Minnesota soils with varying chemical and physical properties. Columns were leached at 10x field capacity to balance for various water holding capacities among sites. The influences of soil test P (STP), soil type, and timing of a leaching event after fertilization were evaluated for effects of P leaching as P leachate concentration, P load, and percent of P fertilizer leached. In addition, a second set of intact columns were collected from three of the six sites for further evaluation of leaching intensity and P fertilizer source on P leaching potential. Leaching intensity was applied at three rates 200, 400, 600 mL to evaluate effects on P leaching. Liquid P fertilizer, dry P fertilizer, manure, and liquid P fertilizer with the addition of AVAIL® were evaluated for influences on P leaching. Results from this study indicated P leaching is a substantial loss pathway with greater losses occurring at higher STP levels. Leachtime also significantly affected P leaching losses, with immediate leach events after fertilizer applications leading to losses up to 33 percent. Volume of the leaching event was found to be the driver of P load, as P concentrations remain consistent with volume applied, and concentrations were not diluted. Phosphorus fertilizer source also significantly impacted P leaching losses, with dry fertilizers leaching significantly more P than liquid or manure sources. Results indicated soil hydrology may be substantially influencing leaching, with preferential pathways leading to greater P leaching losses. Relating P leaching losses to soil test measures was moderately successful; however, relationships were not strong enough to lead to P leaching loss predictions. Relationships were strongest among the environmental soil tests, Water extractable P (WEP) and BioAvailable P (BAP), and the Olsen P (OP) routine soil test. Further research is necessary to fully understand P leaching especially at deeper depths.Item Iron-Enhanced Swale Ditch Checks for Phosphorus Retention(Minnesota Department of Transportation, 2019-07) Natarajan, Poornima; Gulliver, John S; Weiss, Peter TIron-enhanced ditch checks in roadside swales were developed specifically for capturing dissolved phosphorus and dissolved metals from roadway runoff in both urban and agricultural environments. One iron-enhanced ditch check constructed along CR 15 (formerly TH 5) in Stillwater, Minnesota, was monitored during 40 storm events from 2016 to 2018. The iron-enhanced sand filter insert generally captured phosphate, yielding lower phosphate concentrations and mass load reductions that varied between 22% and 50% during several events. However, the cumulative phosphate retention in the filter insert decreased from 42% in 2015 to 30% in 2016, 25% in 2017, and 23% in 2018. The filter insert was not an effective retention device for dissolved copper and zinc. The overall ditch check’s performance, although unexceptional in 2016 and 2017, appeared to improve in 2018. Sampling issues likely contributed to the low performance measured until 2017. The 2018 water sample collection method provided a better estimate of the ditch check’s performance and roughly matched that of the filter insert. Synthetic runoff testing supported the level of treatment achieved during storm events. Phosphate load from the degrading topsoil and the overutilization of the bottom filter media most likely affected overall treatment performance. Design improvements and recommended maintenance actions were developed based on the lessons learned from field monitoring. The iron-enhanced ditch check can improve net phosphate retention through roadside swales, as long as the recommended maintenance actions are performed as scheduled.Item Minnesota Phosphorus Loss: How Soil Loss Is Only Part of the Story and Why Modeling Can Be Improved by Considering Subsurface Phosphorus Loss(2021-05) Reitmeier, HeidiThis study explores 20 years of Minnesota regional phosphorus (P) management data across agricultural landscapes and how these are modeled by the Minnesota Phosphorus Index (MNPI). Nutrient-loading and farm management records from 1999-2019 were compiled across 17 different Minnesota counties representing 5 different state regions, including sites from Discovery Farms of Minnesota, Minnesota Department of Agriculture, Minnesota Agricultural Water Resource Center, and the University of Minnesota. The consolidated data cover two critical watersheds in nutrient management, one flowing north to Canada's Lake Winnipeg, the other flowing south through the Mississippi River ultimately to the Gulf of Mexico. Best management practices are needed for P loss within these watershed basins due to rising concerns about recurrent algal blooms in both watersheds. This study combines historical nutrient-loading data and farm management data to see how soil loss due to erosion impacts P losses and how the MNPI models P-loss risk.Item Momentum - Fall 2011(2011) University of Minnesota: Institute on the EnvironmentItem Monitoring an Iron-Enhanced Sand Filter Trench for the Capture of Phosphate from Stormwater Runoff(2015-09) Erickson, Andrew J.; Gulliver, John S.; Weiss, Peter T.This monitoring project was performed on an iron enhanced sand filtration (IESF) trench in the City of Prior Lake. Water from the pond and IESF trench discharges into a wetland that ultimately drains into Upper Prior Lake. In 2002, Upper Prior Lake was listed on Minnesota’s 303(d) List of Impaired Waters for nutrient/eutrophication biological indicators with aquatic recreation being impaired. Water quality has been reduced due to excessive phosphorus loading. According to the TMDL implementation plan developed for Spring Lake and Upper Prior Lake, the total phosphorus load must be reduced by 83% and 41%, respectively, to meet water quality goals. Overall, for 28 monitored natural rainfall/runoff events from 2013-2015, the IESF trench removed 26% of the phosphate mass load it received, though after non-routine maintenance in August 2014 the performance improved to 45% phosphate mass load reduction. These results indicate the importance of maintenance. A newer installation was previously monitored, and found to retain 71% of the phosphate (Erickson and Gulliver 2010). Most of the overall phosphate load reduction was achieved during larger events that had comparatively high influent phosphate concentrations (32.3 – 125.2 μg/L) and mass loads. Many small events in this investigation with low influent phosphate concentrations (3.8 – 38.4 μg/L) or mass loads exhibited negative removal (i.e., effluent mass load > influent mass load). The high effluent phosphate concentrations are suspected to be caused by the degradation of floating plants (primarily duckweed) that were deposited on the surface of the filter trench. As mentioned above, nonroutine maintenance to remove this material resulted in substantial performance improvement. After this maintenance, positive removal was observed for influent concentrations ranging from 6.3 – 44.1 μg/L. Detailed results, maintenance activities, design and operating & maintenance recommendations, and lessons learned are given within this report.