Browsing by Subject "Nutrients"
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Item 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 ENet-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.Item Extreme Rain Events' Effects on the Biogeochemistry of Lake Superior(2018-08) Cooney, EllenClimate change is expected to profoundly affect the Great Lakes region of North America. An increase in intensity and frequency of rain events is anticipated to deliver more runoff and to increase riverine inputs to Lake Superior’s ecosystem. The effects of these changes on key biogeochemical parameters were analyzed by coupling satellite data, water column sensor profiles, and discrete surface-water sampling after two “500-year” flood events in the Lake Superior basin. This study provides both a spatial and a temporal sense of how plumes interacted within the ecosystem. We also determined the significant differences in water quality parameters for plume versus non-plume waters. These two plumes were important for delivery of nutrients, with variable transport of sediments and colored dissolved organic matter (CDOM) as well. Data from the 2012 storm event showed a significant input of total nitrogen (TN), total phosphorous (TP) and CDOM to the system. In the 2016 storm event, carbon cycling parameters (which were not measured in 2012) including acidity, total inorganic carbon (TIC), and dissolved organic carbon (DOC) were elevated in the plume, along with ammonia. In neither storm event was there a significant difference in chlorophyll a between plume and non-plume waters during our sampling cruises. These two plume events were similar in amount of precipitation, but their effect on the biogeochemistry of Lake Superior varied due to the differences in the watersheds where the rain fell. The studied plume events were dynamic, changing with currents, winds and the settling of suspended sediments.Item Human Influences on Water Quality in Great Lakes Coastal Wetlands(2008) Morrice, John A; Danz, Nick; Regal, Ronald R; Kelly, John R; Niemi, Gerald J; Reavie, Euan; Hollenhorst, Thomas; Axler, Richard P; Trebitz, Annet; Cotter, Anne C; Peterson, Gregory SThis peer-reviewed article discusses water quality and chemistry issues with anthropogenic causes. Geographically, it covers the US coastal region of the Great Lakes. A map in the article suggests that only one sampling point was within Minnesota’s coastal region. The article focuses on water chemistry in coastal wetlands across the Great Lakes, but not specifically for Minnesota. Key points in the abstract are extracted and reproduced below. A better understanding of relationships between human activities and water chemistry is needed to identify and manage sources of anthropogenic stress in Great Lakes coastal wetlands. The objective of the study described in this article was to characterize relationships between water chemistry and multiple classes of human activity (agriculture, population and development, point source pollution, and atmospheric deposition). We also evaluated the influence of geomorphology and biogeographic factors on stressor-water quality relationships. We collected water chemistry data from 98 coastal wetlands distributed along the United States shoreline of the Laurentian Great Lakes and GIS-based stressor data from the associated drainage basin to examine stressor-water quality relationships. The sampling captured broad ranges (1.5–2 orders of magnitude) in total phosphorus (TP), total nitrogen (TN), dissolved inorganic nitrogen (DIN), total suspended solids (TSS), chlorophyll a (Chl a), and chloride; concentrations were strongly correlated with stressor metrics. Hierarchical partitioning and all-subsets regression analyses were used to evaluate the independent influence of different stressor classes on water quality and to identify best predictive models. Results showed that all categories of stress influenced water quality and that the relative influence of different classes of disturbance varied among water quality parameters. Chloride exhibited the strongest relationships with stressors followed in order by TN, Chl a, TP, TSS, and DIN. In general, coarse scale classification of wetlands by morphology (three wetland classes: riverine, protected, open coastal) and biogeography (two eco-provinces: Eastern Broadleaf Forest [EBF] and Laurentian Mixed Forest [LMF]) did not improve predictive models. This study provides strong evidence of the link between water chemistry and human stress in Great Lakes coastal wetlands and can be used to inform management efforts to improve water quality in Great Lakes coastal ecosystems.Item Is fertilization essential for taking care of the next generation of tropical trees?(2022-12) Toro-Gonzalez, LauraRegrowing tropical forest is one of the main challenges of this decade. However, thischallenge goes beyond tree planting at small scales, ensuring that this practice can be scaled up, that the planted trees will grow, that native species will colonize, and that these plantations will become a functional forest is the main goal. Understanding plant-soil interactions in restoration settings can aid accelerate the regeneration process in degraded areas where active restoration initiatives are needed (tree planting or apply nucleation), and it can also help implement more costeffective restoration strategies. Some studies have found that P is the only nutrient limiting plant performance, while other nutrient manipulation studies and meta-analyses suggest that at the ecosystem scale there is colimitation by N, P, and other macronutrients. However, plant species from different functional groups respond in different ways to P availability. N-fixing species for example have higher responses to P addition, while non-N-fixing species have higher responses when the combination of NP is added. Even though, several nutrient manipulation experiments and meta-analysis have tested these hypotheses at the tree level, few studies have extensively evaluated how this costly practice influences seedling growth and survival across the tropics and how variable the cost-effectiveness of this practice is across species. Therefore, the main goal of this research was to determine how nutrient addition impacts the growth and survival of tree seedling species (i.e., Nitrogen (N)-fixing and non-N-fixing species) across the tropics. To do that, I first investigated how tropical dry forest N-fixing and non-N-fixing seedlings growing in shade house conditions in Costa Rica respond to P addition and how P acquisition strategies vary with P addition. I found that N-fixing seedlings had higher responses to P addition compared to non-Nfixers, and that P acquisition strategies were not down-regulated with P addition. Then, I tested this hypothesis at a larger scale where I established a 7-hectare tropical dry forest active restoration project in Southwestern Colombia. There I tested if P or the combination of multi-nutrients (N, P, and potassium) and water had an impact on seedling growth and survival. I also calculated the costeffectiveness of the different management practices implemented after two years of plant establishment. I found that the management strategies implemented did not have an effect on seedling growth and survival, instead the species identity had the highest influence over these two variables. Additionally, the most cost-effective management strategy was the unamended control. Finally, I conducted a meta-analysis to look at how nutrient addition impacts seedling growth and survival in shade-house and field studies across the tropics and explored the responses of N-fixing and non-N-fixing seedlings. This analysis showed that nutrient addition impacts the growth but not the survival of seedlings growing in both field and shade house studies. Additionally, seedlings grown in shade houses had higher responses to nutrient addition than seedlings growing in the field. v The magnitude of the increase in growth in shade houses double the one reported in field studies. Finally, non-N-fixers were more responsive to nutrient addition than N-fixer seedlings in shade houses and field studies. Collectively, these three studies help us to understand how nutrient addition impacts the survival and growth of N-fixing and non-N-fixing seedlings across the tropics and provide insight into when this practice should be implemented in restoration settings.Item Limnological Re-Sampling of Chisolm Area Mine Pit Lakes with Reference to Former Aquaculture Impacts(University of Minnesota Duluth, 2000) Axler, Richard P; Henneck, JeraldLimnological 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.Item Nutritional Value and Benefits of Food Waste as Potential Feed Ingredients in Swine Diets(2019-08) Fung, Chi Fai LeonardThe increasing generation of food waste over the past decades has become a prominent threat to both the society and the environment in terms of food security, wasting limited natural resources and pollution. The objective of this thesis was to quantify the nutritional, economic, and environmental value of food waste derived at multiple sources as swine feed in order to divert these wasted materials into a reusable form to salvage the resources. Chapter 2 explored the different sources of food waste from the generation streams and determined that food waste generated at the upper stream of the food supply chain have greater values than the ones generated at the lower part of the chain. We then evaluated the feeding value of different upper stream food waste- in-vivo such as Fish Waste, Supermarket Waste and Fruit and Vegetable Waste in Chapter 3. The results concluded that supermarket waste has the greatest potential to be utilized as animal feed owing to its high amino acid and energy content. Finally, in Chapter 4 we explored the possible environmental benefits of these food waste sources in which supermarket waste appeared to be most environmentally advantageous when used to replace traditional ingredients such as corn and soybean meal. Overall, it appears that food waste, especially those generated upstream, has great value to be used as animal feed considering both nutritionally and environmentally. To conclude, the information discussed in the thesis can help establish the basic knowledge of how food waste can be utilized in farm animals feeding programs and hence, providing confidence to reducing the overall volume of wasted food in the society and increasing the sustainability of our food system.Item Rab GTPase mediated regulation of the autophagic pathway and mTOR signaling in the larval fat body of Drosophila melanogaster(2016-07) Ayala-Navarro, Carlos IAutophagy is a conserved lysosomal dependent pathway employed by cells during stress conditions as an alternative source of nutrients to maintain cellular homeostasis and promote survival. The pathway is negatively regulated by the mechanistic target of rapamycin (mTOR) and induced by depletion of nutrients. Over the last decade input in the form of vesicular traffic from an array of cellular organelles (e.g. Golgi, ER, endocytic pathway and mitochondria) has been shown to be required for the delivery of proteins, enzymes and lipids during progression of the autophagic pathway. However, how these organelles switch from their constitutive roles to supply the autophagic pathway with proteins and lipids upon induction is not fully understood. In addition the extent to which these cellular organelles modulate autophagosomal growth and mTOR-Insulin signaling remains incompletely understood. The main goal of this thesis was to uncover novel traffic regulators of the Rab GTPase family required for starvation-induced autophagy in Drosophila fat body cells and evaluate their role in mTOR signaling regulation. To this end we carried a reverse screen using RNAi to knockdown 30 of the 33 Drosophila Rab GTPases. We show Rab 2, 7 and 14 GTPases are required for the induction and growth of autophagosomes and autolysosomal function. Rab5 is required for autophagic vesicle induction and growth, endocytosis and lysosomal maturation. Lastly, that Rab6 is required for the sorting of lysosomal hydrolases, autolysosome turnover and the regulation of mTOR signaling via regulation of the insulin receptor localization in fat body cells. Altogether we uncovered novel regulators in the vesicular traffic regulator Rab GTPase family required for autophagy and mTOR-Insulin signaling regulation in Drosophila.Item Title: R Code, Data, and Output Supporting: Nutrient Data from U.S. Manure Systems(2024-06-27) Bohl Bormann, Nancy; nancy.bohl.bormann@gmail.com; Bohl Bormann, NancyThis repository contains R code, processed data, and associated outputs supporting the results reported in: Bohl Bormann, 2024. Manure Nutrient Data Compilation and Analysis for Agronomic and Environmental Applications. PhD Dissertation.