Dissertationen: „Biology, Ecology|Engineering, Agricultural|Water Resource Management“

1

Littlejohn, Alex. „Nutrient mitigation capacity of low-grade weirs in agricultural drainage ditches“. Mississippi State University, 2013.

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2

Hartung, Erik Walter. „Aging bioretention cells: Do they still function to improve water quality?“ Kent State University / OhioLINK, 2017. http://rave.ohiolink.edu/etdc/view?acc_num=kent1497480428253195.

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3

Paull, Rachel May. „Evaluating the Role of Biotic and Abiotic Ecosystem Components on the Retention and Removal of Ditch Nutrients in Ditches of Different Construction“. Bowling Green State University / OhioLINK, 2020. http://rave.ohiolink.edu/etdc/view?acc_num=bgsu1594220539737151.

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4

Edwards, David D. „Real Exposure: Field Measurement of Chemical Plumes in Headwater Streams“. Bowling Green State University / OhioLINK, 2014. http://rave.ohiolink.edu/etdc/view?acc_num=bgsu1401289267.

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5

Burnett, Danielle Lee. „Determining the relative influence of mental pollutants in Newport and Laguna beach seawater on the Giant Kelp (Macrocystis pyrifera) populations of Crystal Cove State Park by analysis of sieve sap metals“. Thesis, California State University, Long Beach, 2014. http://pqdtopen.proquest.com/#viewpdf?dispub=1527307.

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6

Dancy, Lynn M. „Targeting Wetland Preservation Areas for Compensatory Mitigation Utilizing a GIS Protocol“. W&M ScholarWorks, 1997. https://scholarworks.wm.edu/etd/1539617730.

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7

Lunsford, Tami L. „Comparison of the Fate of Dissolved Organic Matter in Two Coastal Systems: Hog Island Bay, VA (USA) and Plum Island Sound, MA (USA)“. W&M ScholarWorks, 2002. https://scholarworks.wm.edu/etd/1539617785.

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8

Roggero, Molly Mitchell. „Ecosystem Gas Exchange in Natural and Created Tidal Salt Marshes of Tidewater, Virginia“. W&M ScholarWorks, 2003. https://scholarworks.wm.edu/etd/1539617802.

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9

Hauser, Christian A. „Net Microbial Activity, Vegetation Dynamics, and Ecosystem Function in Created and Natural Palustrine Forested Wetlands in Southeastern Virginia, USA“. W&M ScholarWorks, 2011. https://scholarworks.wm.edu/etd/1539617912.

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10

Kreisel, Sara Elizabeth. „Assessing the Functional Status of Created Wetlands in Eastern Virginia Via a Soil and Vegetative Developmental Trajectory“. W&M ScholarWorks, 2010. https://scholarworks.wm.edu/etd/1539626894.

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11

anderson, Britt-Anne. „Bioremediation of Tributyltin Contaminated Sediment using Spartina alterniflora in a Created Tidal Wetland“. W&M ScholarWorks, 2000. https://scholarworks.wm.edu/etd/1539617751.

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12

Stone, Lindsey Fay. „Practicing Conservation Biology at Back Bay National Wildlife Refuge“. Miami University / OhioLINK, 2014. http://rave.ohiolink.edu/etdc/view?acc_num=miami1389191138.

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13

Caldwell, Timothy J. „Effects of Climate and Water Use on the Ecology of Mountain Lakes and Rivers in the Western United States“. Thesis, University of Nevada, Reno, 2019. http://pqdtopen.proquest.com/#viewpdf?dispub=13424864.

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Climate change and over-use of natural resources impacts ecosystems worldwide. Understanding physical impacts from climate and natural resource use on biological processes at multiple scales of spatial and ecological organization is needed to make useful predictions under global change scenarios. Mountain aquatic ecosystems are of particular concern because they are sensitive to climate change, represent hot spots of biodiversity, and they integrate atmospheric, terrestrial and aquatic processes into biological responses. The objective of this dissertation is to quantify physical impacts and biological responses of climate and water use on mountain aquatic ecosystems in the Western United States. In Chapter 1, I developed a data set of ice break-up dates using remote sensing techniques for mountain lakes across the Sierra and Cascade Mountain Ranges coupled with downscaled climate data to quantify drivers of lake ice phenology. I developed a predictive linear mixed effects model and used and ensemble of 15 global climate models to project changes in lake ice break-up dates through the 21^st century. The results suggest that low snowpack and increased energy fluxes associated with elevated air temperatures drive earlier ice break-up dates. Projections of ice break-up show that ice break-up will be 61 ± 5 days if greenhouse gas emissions are not reduced. In Chapter 2, I analyzed specific ecological responses to earlier ice break-up dates in Castle Lake, California (a natural, sub-alpine lake). I predicted that consumer (Brook Trout; Salvelinus fontinalis) energetics and habitat use would be regulated by either climate driven water temperature or variation in food availability. The data suggest that earlier ice break-up results in a longer duration of surface water temperatures > 15 °C, coupled with decreased and increased food production in the pelagic and littoral zones, respectively. Isotopic and telemetry data showed that consumer resources and habitat use were driven by water temperature and were independent of food availability. In early ice break-up years, consumers grew less because they were thermally excluded from productive littoral zones when water temperatures were warmer for longer periods of time relative to late ice break-up years. In Chapter 3, I demonstrate that decreased streamflow in mountain rivers can reduce abundance and size structure of food supply to drift foraging Rainbow Trout (Onchorhynchus mykiss). In response to changes in streamflow and food availability, trout abandoned their energetically profitable drift foraging strategy and actively searched for prey. The shift in foraging behavior resulted in negative bioenergetic efficiencies in flow impaired sites. Taken collectively this research demonstrates that both predictable and unpredictable consequences of physical change drive biological responses across spatial gradients, ecosystem types, and levels of ecological organization.

14

Balcerzak, Ashlee Marie. „Evaluating Long-term Nutrient Impacts within Agricultural Headwater Streams“. The Ohio State University, 2020. http://rave.ohiolink.edu/etdc/view?acc_num=osu1598021048962491.

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15

D'Ambrosio, Jessica Leigh. „Perspectives on the Geomorphic Evolution and Ecology of Modified Channels and Two-Stage Ditches in the Agriculturally-Dominated Midwestern United States“. The Ohio State University, 2013. http://rave.ohiolink.edu/etdc/view?acc_num=osu1356038774.

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16

Henderson, Mark J. „Movements, Growth, and Mortality of Chesapeake Bay Summer Flounder Based on Multiple Tagging Technologies“. W&M ScholarWorks, 2012. https://scholarworks.wm.edu/etd/1539616692.

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The research projects presented in this dissertation used multiple tagging technologies to examine the movements, growth, and mortality rates of summer flounder tagged and released in Chesapeake Bay. In the first two chapters, I used acoustic, archival, and conventional tags to examine the behavior of summer flounder on different spatial scales. Investigating the movement behavior of individuals on different scales is an important step towards understanding how large-scale distributions of a population are established. Based on the observed behaviors of summer flounder, I hypothesize that the movements of these fish are primarily related to foraging behavior while they are resident in Chesapeake Bay. In the third chapter, I use growth models to investigate hypotheses regarding recreational angler noncompliance with minimum size regulations in Virginia. Angler noncompliance with management regulations can severely degrade the ability of fishery managers to prevent overexploitation of fish populations. Using a growth model fit to recreational angler mark-recapture data, I demonstrate that recreational anglers in Virginia responded to changes in summer flounder management regulations, but considerable levels of noncompliance were detected in years when management agencies drastically increased the minimum size regulations. In the final chapter, I attempt to estimate natural and fishing mortality rates of summer flounder using conventional mark-recapture data collected by an angler tagging program. These mortality rates were estimated using a Barker model, which is a generalization of the Cormack-Jolly-Seber tagging model. Results from this study indicated that sublegal summer flounder experience different emigration or mortality processes than do larger fish. Furthermore, handling and tagging mortality rates of summer flounder were much larger than the recreational discard mortality rate currently used in the stock assessment, implying that the recreational discard mortality rate should be reexamined. The research presented in this dissertation provides information that could be used by management agencies to further understand the behavior of summer flounder, and how to most effectively manage this population.

17

Garrett, Jessica D. „Pervasive Thermal Consequences of Stream-Lake Interactions in Small Rocky Mountain Watersheds, USA“. DigitalCommons@USU, 2010. https://digitalcommons.usu.edu/etd/841.

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Limnologists and stream ecologists acknowledge the fundamental importance of temperature for regulating many ecological, biological, chemical, and physical processes. I investigated how water temperatures were affected by hydrologic linkages between streams and lakes at various positions along surface water networks throughout several headwater basins in the Sawtooth and White Cloud Mountains of Idaho (USA). Temperatures of streams and lakes were measured for up to 27 months in seven 6 – 41 km2 watersheds, with a range of lake influence. When they were ice-free, warming in lakes resulted in dramatically warmer temperatures at lake outflows compared to inflow streams (midsummer average 6.4°C warming, but as much as 12.5°C). Temperatures cooled as water traveled downstream from lakes, as rapidly as 9°C km-1. Longitudinal stream cooling was usually not strong enough, however, to reduce temperatures to baseline conditions. In early spring, lakes had the opposite effect on streams, as they released water from beneath the ice at near 0°C. Early spring stream water warmed as it flowed downstream from lakes, influenced by additional groundwater inflows. In addition to lakes, other watershed characteristics influenced temperatures, though effects differed seasonally. Multiple regression analyses indicated that lake size, distance from nearest upstream lake, and stream shading were most important in explaining stream temperatures, but the relative importance of each variable changed seasonally.

18

Crouch, Ryan T. „Adding value to upground drinking water reservoirs: what makes a good yellow perch (Perca flavescens) fishery?“ Bowling Green State University / OhioLINK, 2011. http://rave.ohiolink.edu/etdc/view?acc_num=bgsu1291841439.

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19

Ginger, Luke J. „ONTOGENETIC CHANGES IN THE STOICHIOMETRY OF BLUEGILL UNDER CONTRASTING LIGHT AND NUTRIENT REGIMES“. Miami University / OhioLINK, 2014. http://rave.ohiolink.edu/etdc/view?acc_num=miami1407430829.

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20

Briones, Maria. „Validating the Accuracy of Neatwork, a Rural Gravity Fed Water Distribution System Design Program, Using Field Data in the Comarca Ngöbe-Bugle, Panama“. Scholar Commons, 2018. https://scholarcommons.usf.edu/etd/7268.

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Despite the sustainable development goals to increase access to improved water there are still 884 million people in the world without access to an improved water source (WHO, 2017). One method to improve access to water in rural, mountainous areas, is through construction of gravity fed water distribution systems. These systems should be designed based upon fundamental principles of hydraulics. One method of doing so in a time efficient manner with minimal engineering knowledge is to utilize a downloadable computer program such as Neatwork, which aids in design of rural, gravity fed water distribution systems and has been used by volunteers in Peace Corps Panama for years. It was the goal of this research to validate the results of the Neatwork program by comparing the flow results produced in the simulation program with flow results measured at tap stands of a rural gravity fed water distribution system in the community of Alto Nube, Comarca Ngöbe Bugle, Panama. The author measured flow under default Neatwork conditions of 40% faucets open in the system (in the field an equivalent of 8 taps) to have an initial basis as to whether the Neatwork program and field conditions yielded corresponding flows. The second objective would be to vary the number of taps open if the default condition did not produce comparable results between the field and the simulation, to pinpoint if under a certain condition of open faucets in the system the two methods would agree. The author did this by measuring flow at varying combinations from 10-100% of the open taps in the system (2-20 taps). Lastly the author observed the flow differences in the Neatwork program against the field flows, when the elevation of water in the water reservoir is set to the Neatwork default, where elevation of water is the tank outlet (at the bottom of the tank) versus when the elevation is established at the overflow at the tank (at the top of the tank) for the case of two taps open. The author used paired t-tests to test for statistical difference between Neatwork and field produced flows. She found that for the default condition of 40% taps open and all other combinations executed between 30-80% taps open, the field and Neatwork flows did not produce statistically similar results and, in fact, had the tendency to overestimate flows. The author also found that the change in water elevation in the storage tank from outlet to overflow increased the flow at the two taps measured by 0.140 l/s and 0.145 l/s and in this case, did not change whether the flows at these taps were within desired range (0.1 -0.3 l/s). Changing the elevation of the water level in the tank in the Neatwork program to correspond to a “full” tank condition is not recommended, as assuming an empty tank will account for seasonal changes or other imperfections in topographical surveying that could reduce available head at each tap. The author also found that the orifice coefficients, θ, of 0.62 and 0.68, did not demonstrate more or less accurate results that coincided with field measurements, but rather showed the tendency of particular faucets to prefer one coefficient over the other, regardless of combination of other taps open in the system. This study demonstrates a consistent overestimation in flow using the computer program Neatwork. Further analysis on comparisons made show that between field and flow results across each individual faucet, variations between Neatwork and the field were a result of variables dependent upon the tap, such as flow reducers or errors in surveying. Flow reducers are installed before taps to distribute flow equally amongst homes over varying distances and elevations and are fabricated using different diameter orifices depending on the location of the tap. While Neatwork allows the user to simulate the effect of these flow reducers on tap flow, it may not account for the imperfect orifices made by the simple methods used in the field to make such flow reducers. The author recommends further investigation to be done on the results of field flow versus Neatwork simulated flow using other methods of flow reducer fabrication which produce varying degrees of accuracy in orifice sizing. The author also recommends executing these field measurements over a greater sample size of faucets and more randomized combination of open/closed taps to verify the results of this research. More work should be done to come up with a practical solution for poor and rural communities to fabricate and/or obtain more precisely sized flow reducers. A full sensitivity analysis of the input variables into the Neatwork program should be performed to understand the sensitivity of varying each input.

21

Thomson, Sean Richard. „Methane Production by a Packed-Bed Anaerobic Digester Fed Dairy Barn Flush Water“. DigitalCommons@CalPoly, 2014. https://digitalcommons.calpoly.edu/theses/1329.

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Packed-bed digesters are an alternative to covered lagoon digesters for methane production and anaerobic treatment of dilute wastewaters such as dairy barn flush water. The physical media of packed-beds retain biofilms, often allowing increased treatment rates. Previous studies have evaluated several types of media for digestion of dilute wastewaters, but cost and media fouling have setback commercial development. A major operational cost has been effluent recirculation pumping. In the present effort, a novel approach to anaerobic digestion of flush dairy water was developed at pilot-scale: broken walnut shells were used as a low-cost packed-bed medium and effluent recirculation was replaced by reciprocation mixing to decrease pumping costs and the risk of media clogging. Three packed-bed digesters containing walnut shells as media were constructed at the on-campus dairy and studied for about six months. Over that time, several organic loading rates (OLRs), measured as both chemical oxygen demand (COD) and volatile solids (VS) were applied to the new packed-bed digesters to allow modeling of methane production. The influence of temperature on methane production was also investigated. Additionally, the study measured solids accumulation in the walnut shell packed-bed as well as the effectiveness and durability of walnut shells as packing media. Finally, a simple economic analysis was developed from the methane model to predict the financial feasibility of packed-bed digesters at flush water dairies under similar OLR conditions. Three methane production models were developed from organic loading: saturation-type (following the form of the Monod equation), power and linear. The models were evaluated in terms of regression analysis and the linearity of experimental to predicted methane production. The best model was then chosen to develop the economic predictions. Economic predictions for packed-bed digesters were calculated as internal rate of return (IRR) using the methane models along with additional input variables. Comparisons of IRRs were made using electric retail rates of $0.10 to $0.20 per kilowatt-hour and capital cost subsidies from zero to 50%. Sludge accumulation in the packed-bed was measured via change in porosity, and walnut shell durability was measured as the change in mass of representative walnut shells over the course of the study. The linear-type model of methane production from volatile solids OLR best represented this data set. Digester temperature was not found to influence methane production in this study, likely due to the small daily average ambient temperature range experienced (14°C to 24°C) and the greater influence of organic loading. Porosity of the walnut shell packed-bed decreased from 0.70 at startup to 0.34±0.06 at the end of the six-month study, indicating considerable media fouling. Sludge accumulated in each digester from zero at startup to 281±46 liters at termination. Walnut shells in the packed-bed lost on average 31.4±6.3% mass during the study period which may be attributed to degradation of more readily bio-degradable cellulose and hemi-cellulose within the walnut shells. Given the predicted methane production and media life, at present, the economic outlook for packed-bed digesters at commercial dairies is quite dependent on utility electrical rates, available subsidies and future improvements to packed-bed digester technology. The predicted IRRs ranged from below 0% (at 0% capital subsidy and $0.10/kWh) up to 25% (at 50% capital subsidy and $0.20/kWh) at large dairies (3000 milking cows). Increases in organic loading were not shown to necessarily increase IRR, particularly at OLRs above 10 g/Lliquid-d (as COD or VS). Ultimately, to better assess the value of packed-bed digesters for flush dairies, additional study is needed on topics such as sludge accumulation prevention, long-term walnut shell degradation, dairy barn flush water mixing, and more detailed economic analysis.

22

Gray, Jonathon B. „Reference Diatom Assemblage Response to Transplantation into a Stream Receiving Treatment for Acid Mine Drainage in Southeastern Ohio“. Ohio University / OhioLINK, 2011. http://rave.ohiolink.edu/etdc/view?acc_num=ohiou1317921115.

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23

Kennedy, Matthew R. „The Role of Microzooplankton and Mesozooplankton Grazing During the Planktothrix-Dominated Cyanobacterial Blooms in Sandusky Bay, Lake Erie“. Bowling Green State University / OhioLINK, 2020. http://rave.ohiolink.edu/etdc/view?acc_num=bgsu1589546747826657.

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24

Naigaga, Irene. „Use of bioindicators and biomarkers to assess aquatic environmental contamination in selected urban wetlands in Uganda“. Thesis, Rhodes University, 2013. http://hdl.handle.net/10962/d1002603.

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Pollution of aquatic resources in Uganda is on the increase and the trends are expected to increase with increase in population size and urbanisation. Assessment and mitigation of the environmental impacts on water quality and biodiversity have now become necessary. The aim of the study was to integrate invertebrate and fish as bioindicators and fish histopathology as a biomarker in the assessment of water quality deterioration in urban wetlands in Uganda. The integration harnesses the advantages and counteracts the shortcomings of each method and thus builds a more robust diagnostic tool that gives a better view of the impacts to the entire ecosystem. Four endpoints which included, physicochemical variables, benthic macroinvertebrate bioindicators, fish bioindicators and fish histopathology biomarkers were compared between varied effluent-impacted wetlands (Murchison Bay in Kampala, and Kirinya, Masese and Winday Bay in Jinja) and a non-impacted reference wetland (Lwanika in Mayuge). Results from the effluent-impacted sites differed from the less impacted reference site. The two sampling locations at Murchison Bay (inshore and offshore) and one sampling location at Kirinya (inshore), that were highly impacted with urban effluent, showed elevated nutrient levels, low pH, dissolved oxygen and secchi depth readings. This corresponded with low invertebrate taxa and fish species diversity and richness; and severe histopathological responses in liver, gonads and gills of O. niloticus. Sensitive taxa such as ephemeroptera and trichoptera were completely absent while pollution tolerant taxa Chironomus sp, Corbicula and Oligochaeta were present. Also notable was the absence of many native haplochromines and presence of mainly Brycinus sadleri, Oreochromis niloticus and leucostictus. The organs manifested high prevalence of severe inflammatory and regressive changes and higher organ indices that fell within the pathological category. These sites were consistently classified as highly polluted under the four endpoints. The reference site was classified as least polluted while Masese and Winday Bay were moderately polluted. Results suggested that the approach of using invertebrate and fish as bioindicators and the fish histopathology as a biomarker, in relation to water quality physicochemical variables was a useful tool in highlighting the spatial differences in environmental quality.

25

Engelhardt, Sebastian. „Water Reclamation from Waste Streams using Aquaporin-Based Membranes in Forward Osmosis“. University of Akron / OhioLINK, 2019. http://rave.ohiolink.edu/etdc/view?acc_num=akron156225263942968.

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26

Wahl, Mark D. „Key Influences on Hydraulic Efficiency in Treatment Wetlands“. The Ohio State University, 2013. http://rave.ohiolink.edu/etdc/view?acc_num=osu1385421888.

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27

Wilson, Gregory B. „Ecosystem-Based Management of the Lake Erie Ecosystem: A Survey-Based Approach to Assessment of Management Needs“. Kent State University / OhioLINK, 2011. http://rave.ohiolink.edu/etdc/view?acc_num=kent1302202900.

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28

Brancho, Jennie. „Review of Regulatory Policies for Copper and Silver Water Quality Criteria“. Kent State University Honors College / OhioLINK, 2017. http://rave.ohiolink.edu/etdc/view?acc_num=ksuhonors1493904025463972.

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29

Mukherjee, Jayanti Ray. „Evaluating Native Wheatgrasses for Restoration of Sagebrush Steppes“. DigitalCommons@USU, 2010. https://digitalcommons.usu.edu/etd/659.

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Pseudoroegneria spicata and Elymus wawawaiensis are two native perennial bunchgrasses of North America's Intermountain West. Frequent drought, past overgrazing practices, subsequent weed invasions, and increased wildfire frequency have combined to severely degrade natural landscapes in the region, leading to a decline in the abundance of native vegetation. Being formerly widespread throughout the region, P. spicata is a favorite for restoration purposes in the Intermountain West. Elymus wawawaiensis, which occupies a more restricted distribution in the Intermountain West, is often used as a restoration surrogate for P. spicata. However, since most restoration sites are outside the native range of E. wawawaiensis and as the use of native plant material may be more desirable than a surrogate, the use of E. wawawaiensis as a restoration plant material has been somewhat controversial. The main goal of my research was to identify plant materials of these species with superior seedling growth, drought tolerance, and defoliation tolerance, traits that may contribute to enhanced ecological function in restored rangeland plant communities. I conducted a growth-chamber study to evaluate morphological and growth-related traits of germinating seedlings of these two species. My study suggested that, while the two bunchgrasses are similar in many ways, they display fundamentally different strategies at the very-young seedling stage. While P. spicata exhibited greater shoot and root biomass to enhance establishment, E. wawawaiensis displayed high specific leaf area (SLA) and specific root length (SRL), two traits commonly associated with faster growth. According to the eco-physiology literature, plants with greater stress tolerance display lesser growth potential. However, my greenhouse study showed that E. wawawaiensis was relatively more drought tolerant than P. spicata, despite higher expression of growth-related traits, e.g., SLA and SRL. While the two species displayed similar water use efficiency when water was abundant, E. wawawaiensis was also more efficient in its water use when drought stress was imposed. In a field study, I found E. wawawaiensis to be twice as defoliation tolerant as P. spicata. This study showed that P. spicata is typically more productive in the absence of defoliation, but E. wawawaiensis was more productive after defoliation due to its superior ability to recover and hence is a better candidate for rangelands that will be grazed. Hence, my study showed that E. wawawaiensis, despite being regarded as a surrogate for P. spicata, exhibits superior seedling establishment, drought tolerance, and defoliation tolerance. Therefore, E. wawawaiensis has advantages as a restoration species for the Intermountain West.

30

Selden, Justin D. „The Effect of Dredging on Fish Communities in Agricultural Streams in Crawford, Sandusky and Seneca Counties of Ohio“. University of Toledo / OhioLINK, 2013. http://rave.ohiolink.edu/etdc/view?acc_num=toledo1372421206.

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31

Maharjan, Renu. „Phytoremediation of Selected Pharmaceuticals by and their Phytotoxicity to Aquatic Plants“. University of Toledo / OhioLINK, 2014. http://rave.ohiolink.edu/etdc/view?acc_num=toledo1396172003.

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32

Siman, Kelly. „Social-Ecological Risk and Vulnerability to Erosion and Flooding Along the Ohio Lake Erie Shoreline“. University of Akron / OhioLINK, 2020. http://rave.ohiolink.edu/etdc/view?acc_num=akron1597092923090799.

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33

Brancho, Jennie. „Effects of Precipitation Patterns on Sediment, Nutrient, and Biofilm Dynamics in an Acid Mine Drainage Stream“. Ohio University / OhioLINK, 2019. http://rave.ohiolink.edu/etdc/view?acc_num=ohiou155439364661881.

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34

Mrdjen, Igor. „Harmful Algal Blooms in Small Lakes: Causes, Health Risks, and Novel Exposure Prevention Strategies“. The Ohio State University, 2018. http://rave.ohiolink.edu/etdc/view?acc_num=osu1531135626251706.

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35

„Denitrification and Greenhouse Gas Dynamics in Lakes Receiving Atmospheric Nitrogen Deposition“. Doctoral diss., 2010. http://hdl.handle.net/2286/R.I.8606.

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abstract: The global transport and deposition of anthropogenic nitrogen (N) to downwind ecosystems are significant and continue to increase. Indeed, atmospheric deposition can be a significant source of N to many watersheds, including those in remote, unpopulated areas. Bacterial denitrification in lake sediments may ameliorate the effects of N loading by converting nitrate (NO3-) to N2 gas. Denitrification also produces nitrous oxide (N2O), a potent greenhouse gas. The ecological effects of atmospheric N inputs in terrestrial ecosystems and the pelagic zone of lakes have been well documented; however, similar research in lake sediments is lacking. This project investigates the effects N of deposition on denitrification and N2O production in lakes. Atmospheric N inputs might alter the availability of NO3- and other key resources to denitrifiers. Such altered resources could influence denitrification, N2O production, and the abundance of denitrifying bacteria in sediments. The research contrasts these responses in lakes at the ends of gradients of N deposition in Colorado and Norway. Rates of denitrification and N2O production were elevated in the sediments of lakes subject to anthropogenic N inputs. There was no evidence, however, that N deposition has altered sediment resources or the abundance of denitrifiers. Further investigation into the dynamics of nitric oxide, N2O, and N2 during denitrification found no difference between deposition regions. Regardless of atmospheric N inputs, sediments from lakes in both Norway and Colorado possess considerable capacity to remove NO3- by denitrification. Catchment-specific properties may influence the denitrifying community more strongly than the rate of atmospheric N loading. In this regard, sediments appear to be insulated from the effects of N deposition compared to the water column. Lastly, surface water N2O concentrations were greater in high-deposition lakes compared to low-deposition lakes. To understand the potential magnitude of deposition-induced N2O production, the greenhouse gas inventory methodology of Intergovernmental Panel on Climate Change was applied to available datasets. Estimated emissions from lakes are 7-371 Gg N y-1, suggesting that lakes could be an important source of N2O.
Dissertation/Thesis
Ph.D. Biology 2010

36

Mattocks, Steven R. „Ecological Consequences of Lost Anadromous Forage Fish in Freshwater Ecosystems“. 2016. https://scholarworks.umass.edu/masters_theses_2/433.

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Beginning in the early 1600s, dam construction in New England obstructed anadromous fish access to spawning grounds during migration. As a result, anadromous forage fish populations have declined, which has impacted freshwater, marine, and terrestrial ecosystems. To determine the impacts of dams on anadromous forage fish and freshwater ecosystems, I used historical and current data to estimate population changes in alewives (Alosa pseudoharengus) from 1600-1900. A significant reduction in spawning habitat occurred in New England as a result of 1,642 dams constructed between 1600 and 1900, resulting in 14.8% and 16.6% lake and stream habitat remaining by 1900, respectively. In eight New England watersheds, this translates to an estimated cumulative annual loss of 30 B juvenile alewives available as freshwater forage and 538 M year 1, 2 and 3 alewives available as marine forage. The cumulative annual lost number of adult return spawners was conservatively 17 M fish, or 3,642 metric tons. Lost marine-derived nutrients from adult return spawners were 11 T phosphorus, 64 T nitrogen, and 410 T carbon. A comparison of predator fish growth and condition in alewife and non-alewife lakes showed that white perch (Morone Americana) and yellow perch (Perca flavescens) have higher condition in early summer in lakes with alewives. Predator growth rates (length-at-age) were significantly higher in early life stages (ages 1 and 2) when alewives were present, but significantly lower in late life stages (ages 3 and older). Results indicate a greater maximum length obtained by mature fish when alewives are absent, and an earlier age and length at maturity when alewives are present. These results indicate significant ecosystem impacts of lost anadromous forage fish, with bottom-up trophic effects across multiple time scales and biological processes. An ecosystem-based management approach should be used by inland and marine aquatic managers, and ecosystem connectivity and trophic interactions should be considered when managing migratory fish and prioritizing restoration goals.

Dissertationen zum Thema „Biology, Ecology|Engineering, Agricultural|Water Resource Management“

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