Master of Science (MS), Bowling Green State University, 2025, Biological Sciences

Cyanobacterial harmful algal blooms (cHABs) in Lake Erie's western basin pose significant risks to humans and wildlife due to toxin contamination and hypoxic conditions following bloom senescence. Anthropogenic nitrogen (N) and phosphorus (P) pollution are well-established drivers of cHABs, warranting the recommendation by the International Joint Commission for a 40% reduction in P-loading into Lake Erie. However, both N and P influence cyanotoxin production. This justifies further research on the efficacy of P-only reductions versus a dual nutrient approach in mitigating cHAB threats. Additionally, the influence of Lake Erie nutrient amendments on the broader prokaryotic community may have implications related to biogeochemical cycling, an understudied but critical aspect of ecosystem functioning that could influence bloom persistence and hypoxia. Using a microcosm setup to manipulate nutrient levels in Lake Erie water samples over 3-day incubation periods in June and August 2022 and 2023, we produced water samples representative of Lake Erie with various dilution scenarios of N and/or P. DNA extracts from vacuum-filtered water samples were used for 16S rRNA gene sequencing and quantification of cyanobacteria and genes involved in cyanobacterial toxin synthesis (i.e., microcystins (mcyE), saxitoxins (sxtA), and cylindrospermopsins (cyrA)). We found that nutrient amendment strategies and dilution levels influenced prokaryotic community composition, inferred functional capacities, and cyanotoxin gene copies, with distinct differences between early and late summer. In June, non-cyanobacterial taxa, particularly Proteobacteria, showed strong responses to nutrient manipulation, with severe dilutions and P-dilutions with supplemented ammonium inducing shifts toward communities primed for anaerobic and fermentative processes linked to hypoxia. In August, nutrient amendments and N-speciation were drivers of community composition, with P-dilutions with supplemented ammonium (open full item for complete abstract)

Committee: Christopher Ward Ph.D. (Committee Chair); Justin Chaffin Ph.D. (Committee Member); George Bullerjahn Ph.D. (Committee Member) Subjects: Biogeochemistry; Bioinformatics; Conservation; Ecology; Freshwater Ecology; Microbiology; Molecular Biology; Toxicology

Doctor of Philosophy, Case Western Reserve University, 2025, Civil Engineering

Excess nitrogen (N) and phosphorus (P) from agricultural activities have caused widespread eutrophication in U.S. water bodies, fueling harmful algal blooms (HABs) that release toxins, deplete oxygen, and harm ecosystems, human health, and economies. This dissertation addresses these challenges through machine learning (ML) models for predicting HABs and nutrient levels, alongside practical methods for P removal and monitoring. First, frequent HABs in Lake Erie highlight the need for accurate forecasting. Using a novel dataset (2002–2019) of chlorophyll-a, nutrient inputs, and meteorological factors, ML models achieved high accuracy in 10-day HAB predictions (e.g., 89.6% for 2-level classification). Feature importance analysis revealed critical drivers, including N loads, solar irradiance, and water levels. Integrating long short-term memory (LSTM) model outputs aided HAB prediction, demonstrating the feasibility of short-term HAB forecasting. Second, agricultural runoff is a major P source, yet cost-effective P removal methods remain limited. This study evaluated industrial iron shavings (IS) as a low-cost adsorbent for P removal, achieving a capacity of 2.5 mg/g after NaCl pretreatment. Column experiments maintained >60% P removal efficiency over 60 days, and NaOH regeneration sustained performance across seven cycles. Induction heating further enhanced P recovery (95.3%) in short time. Surface analyses revealed structural changes in IS, offering insights for optimizing its longevity and efficiency. Third, scalable P monitoring methods are crucial for identifying pollution hotspots. An equipment-free, smartphone-based method was developed to measure P concentrations using RGB color values. The method achieved high accuracy (R² = 0.97) and reliably classified P levels below 0.1 mg P/L, promoting public involvement in eutrophication mitigation. Finally, this work extended ML models from Lake Erie to the contiguous U.S. (CONUS) for riverine N predictions. Incor (open full item for complete abstract)

Committee: Huichun Zhang (Committee Chair); Bridget Hegarty (Committee Member); Yinghui Wu (Committee Member); Xiong Yu (Committee Member); Chad Penn (Committee Member) Subjects: Agriculture; Environmental Engineering; Environmental Science

Master of Science, The Ohio State University, 2024, Food, Agricultural and Biological Engineering

Phosphorous (P) is an essential component of all form of life and plays a vital role for plant growth. Fertilizers contribute significantly to agricultural productivity; however, their excessive or improper use can lead to environmental degradation, including water pollution and soil erosion. The surplus P from agricultural land is usually lost via surface and sub-surface runoff, reaching nearby waterbodies leading to eutrophication. Eutrophication can result in harmful algal blooms (HABs), which pose detrimental effect to aquatic life and serious health risk to humans and animals. Thus, removing P from agricultural runoff is crucial. The adsorption process is simple and efficient technology for removing pollutants from water. Abundantly available low-cost agricultural wastes such as dairy manure, corn stover and eggshell can be hydrothermally carbonized to produce hydrochar for use as adsorbent. Activating hydrochar with metal cation increases its affinity towards anionic pollutants. Hence, the main objective of this study was to produce activated hydrochar via co-hydrothermal carbonization of dairy manure, corn stover and eggshell followed by thermal activation, for use as adsorbent to remove P from agricultural runoff. Dairy manure, corn stover and eggshell were mixed in different ratios and hydrothermally carbonized. The feedstock mixes, with and without hydrothermal carbonization, were activated to produce activated hydrochar and activated feedstock mix, respectively. Hydrochar prepared from different feedstock mixes had low P adsorption capacity, ranging from 0.87 to 62.20 mg/g. The P adsorption performance improved after activation, with adsorption capacities ranging from 5.44 to 171 mg/g for activated feedstock mix and 7.93 to 209 mg/g for activated hydrochar. The activated hydrochar with dairy manure and eggshell at equal proportion performed best, with maximum adsorption capacity of 209 mg P/g and 65.97 mg P/g in batch and column experiment, respectively. (open full item for complete abstract)

Committee: Ajay Shah (Advisor) Subjects: Agriculture; Engineering

Master of Science, University of Toledo, 2023, Geology

Over the past ~ 200 years, land-use changes, such as intensive agriculture and urbanization, have affected primary production in West Lake Okoboji (WLO). Lake productivity refers to the amount of energy converted to organic matter that occurs within a lake ecosystem. Thus, understanding the past productivity of WLO is necessary for reconstructing environmental changes and assessing the impacts of human activities. Here, biogenic silica (BSi) analyses and Si/Ti ratios from X-ray fluorescence (XRF) analysis were used to constrain spatial and temporal trends in the paleoproductivity in WLO. Twelve cores were retrieved from WLO, of which three cores were used to assess paleoproductivity. These three sediment cores (WLO-6, -18 and -16) were collected along a transect that includes two shallow bays and the deeper main basin of the lake. WLO-6 (~35 cm), WLO-18 (~40 cm), and WLO-16 (~35 cm) were retrieved from Millers Bay, the main basin of the lake, and Smiths Bay respectively. 210Pb was used to develop chronologies for the sediment cores using the Constant Rate of Supply (CRS) model. BSi analysis via wet alkaline digestion and meto-sulfite reduction directly quantified biogenic silica, while Si/Ti ratios provided a complementary assessment of paleoproductivity. Results of the analyses showed heterogeneity in BSi flux within and between all core analyzed. The last ~20 years showed large increases within Smiths Bay and the main basin concomitant with intensive agriculture and accelerated by urbanization in the WLO watershed. Mean BSi fluxes from WLO cores are 64.35, 102.57, and 88.38 g m-2 yr-1 for Millers Bay (WLO-6), main basin (WLO-18), and Smiths Bay (WLO-16) respectively. Additionally, our proxy analysis shows higher paleoproductivity in the main basin (core WLO-18) than in Millers (core WLO-6) and Smiths Bays (core WLO-16). Generalized Additive Models (GAMs) of Si/Ti ratios data from cores WLO-6, -18, and -16 determined periods of significant increases or reductio (open full item for complete abstract)

Committee: Trisha Spanbauer (Committee Chair); Timothy Fisher (Committee Member); Allison Stegner (Committee Member) Subjects: Environmental Science; Geology; Paleoecology

Master of Science (MS), Ohio University, 2023, Chemical Engineering (Engineering and Technology)

Recovering nutrients such as nitrogen (N) and phosphorous (P) from wastewater streams offers a promising solution to combat the eutrophication of natural water bodies and reduce operational costs in wastewater treatment plants. This will also introduce a sustainable P resource for agricultural activities and industry. This study utilized an impeller-planar electrochemical setup for P recovery from synthetic municipal digester supernatant, focusing on two main objectives. Firstly, a dimensionless correlation between mass and fluid transport was developed to investigate the effect of flow transfer and physical conditions on the mass transfer. Secondly, a Plackett-Burman design was employed to perform statistical screening analysis on ten variables classified into operational, design, and stream categories. Subsequently, the key variables affecting the P recovery and electrochemical specific energy consumption were introduced.

Committee: John Staser (Advisor) Subjects: Chemical Engineering; Sustainability

Master of Science (MS), Wright State University, 2023, Earth and Environmental Sciences

Grand Lake St. Marys is the largest (52 km2) inland lake in Ohio, USA, and receives high nutrient loadings (90th percentile for total nitrogen (N) and phosphorus (P) concentrations in the USA) from a watershed dominated by agricultural row-crops and livestock production. Eutrophication has led to cyanobacterial harmful algal blooms, dominated by non-N2 fixing Planktothrix, that persist year-round, including in winter months. In summer 2020 and 2021, multiple treatments using P-binding agents within a 3.5 ha swimming enclosure were conducted to remove excess dissolved P from the water column. The objective of this study was to examine pre-and-post treatment biogeochemical and physicochemical conditions in contrast to the surrounding lake, in addition to evaluating anomalous conditions that led to removal of the lake's no-contact advisory for the first time in 12 years. In four out of five treatments across both years, total P and chlorophyll-a (chl-a) values were higher three weeks post-treatment within the treated area, indicating failures of the treatments to reduce biomass long-term. The harsh winter of 2020-2021, along with a dry Spring 2021, led to large, temporary reductions in algal biomass and toxicity and sediment oxygen demand, and allowed for denitrifying bacteria to remove excess N from the water column. However, chl-a levels returned to > 300 µg L-1 by July 2021. This study, along with previous studies regarding failures of treatments using P-binding agents to reduce algal biomass and toxicity long-term, provide further evidence that reducing watershed N and P loads is likely the only long-term solution to mitigating eutrophication and cyanobacteria blooms in GLSM.

Committee: Silvia E. Newell Ph.D. (Advisor); Stephen J. Jacquemin Ph.D. (Committee Member); Mark J. McCarthy Ph.D. (Committee Member) Subjects: Environmental Health; Environmental Science; Environmental Studies; Water Resource Management

Master of Science (MS), Ohio University, 2023, Environmental Studies (Voinovich)

Agricultural nutrient pollution is a significant cause of impairment in American surface waters. Wetland restoration projects in agricultural watersheds can provide an effective sink for excess nutrients and potentially improve downstream water quality. Ohio University has partnered with The Stream and Wetlands Foundation to conduct water quality monitoring during the restoration of Bloody Run Swamp, a wetland in a former agricultural field near Columbus, Ohio. This thesis serves as an analysis of the initial water quality impacts of this restoration project. The restoration of Bloody Run Swamp did not significantly impact total dissolved phosphorus, orthophosphate, TKN, or ammonia concentrations. In contrast, both nitrate/nitrate and total dissolved nitrogen concentration and loads were significantly reduced during construction. This may have been due to the dry weather during construction and the removal of drainage tiles from Bloody Run Swamp. Future water quality monitoring is needed to determine the long-term impacts of this restoration project.

Committee: Natalie Kruse Daniels (Advisor); Gregory Springer (Committee Member); Morgan Vis (Committee Member) Subjects: Agriculture; Aquatic Sciences; Biology; Earth; Ecology; Environmental Engineering; Environmental Management; Environmental Science; Environmental Studies; Geomorphology; Hydrologic Sciences; Hydrology; Limnology; Water Resource Management

Master of Science (MS), Bowling Green State University, 2022, Geology

The Western Lake Erie Basin (WLEB) has been experiencing harmful algal blooms due to increases in dissolved reactive phosphorous (DRP) from agricultural land in the Maumee River watershed. Agricultural best management practices (BMPs) can be useful to mitigate the DRP loads; nevertheless, DRP is not always fully removed by in-field BMPs. Phosphorous (P) removal structures can be filled with phosphorus sorption materials (PSM) such as iron and aluminum oxides and can be placed at the junction of runoff and subsurface drainage to trap DRP from tile drainage. However, dissolved organic matter (DOM) from the agricultural farmland might compete with phosphate ions (PO43-) at the adsorption sites in the media, reducing its lifetime and efficiency. Therefore, laboratory flow-through column experiments were conducted to determine whether DOM is affecting P sorption onto iron enhanced activated alumina media (Alcan). The experiments were informed by field data collected from a regional farm. Alcan (Al/ Fe (hydro) oxides) media was efficient in removing PO43- coming into the filtering system and thereby, flow-through column experiments were able to determine a discrete P removal percentage efficiency of 83.32%, 68.26%, 66.54%, 57.16% and 41.27% by the end of treatment I (5mg L-1 PO43- only), treatment II (5mg L-1 PO43- and 5 mg L-1 DOM), treatment III (5mg L-1 PO43- and 10 mg L-1 DOM), treatment IV (5mg L-1 PO43- and 20 mg L-1 DOM), and treatment V (10mg L-1 PO43- and 20 mg L-1 DOM), respectively. Moreover, from exponential regression analysis of P removal curves for each treatment, it was measured that a total cumulative of 231.45 gm, 92.65 gm, 92.06 gm, 65.998 gm and 91.476 gm of P per kg PSM can be added to treatment I, II, III, IV and V, respectively, until the media gets fully saturated, i.e., concentration of influent PO43- would be equal to the effluent PO43- concentrations. It is evident that DOM is competing with PO43- decreasing PO43- sorption onto the Alcan media. (open full item for complete abstract)

Committee: Angélica Vázquez-Ortega PhD (Committee Chair); Enrique Gomezdelcampo PhD (Committee Member); Margaret (Peg) M. Yacobucci PhD (Committee Member) Subjects: Environmental Geology; Environmental Science; Environmental Studies; Geochemistry; Geology; Soil Sciences

Doctor of Philosophy, The Ohio State University, 2021, Food, Agricultural and Biological Engineering

The return of severe algal blooms to the Western Basin of Lake Erie has refocused efforts to manage nutrients in and around the Great Lakes. An important part of this effort has been extensive water quality modeling in the region, especially in watersheds responsible for excessive nutrient loading to at-risk lake basins. Models can expand the predictive impact of limited monitoring data, and therefore provide a powerful tool for water managers. However, models are limited by numerous shortcomings, including data availability, model structure, and equifinal model solutions. Bringing light to these potential issues in model development and implementation is key in the effective use of and public trust in modeling results. The work presented in this document is comprised of four main objectives aimed at examining model confidence. First (Chapter 2), a Soil and Water Assessment Tool (SWAT) model was developed for the Maumee River watershed at the near-farm-field scale, incorporating the best available data for the region. This new model was compared against previous model iterations using edge-of-field monitoring data. A key improvement in soil P initialization values revealed a potential structural limitation in the model to simulate phosphorus export in surface runoff. Second (Chapter 3), a retrospective analysis of land management changes simulated over the past several decades was completed to examine the influence of individual agricultural management practices on driving discharge and loading trends. While climate played a major role in driving discharge patterns, tillage had a significant impact on nutrient loading. Third (Chapter 4), the presence of equifinality—that many differing parameterizations can produce acceptable models—was examined, along with the potential to reduce equifinality using increased data in calibration. A Latin Hypercube Sampling approach was used to select values for 15 parameters, and then constraints were applied across data types an (open full item for complete abstract)

Committee: Margaret Kalcic (Advisor); Kevin King (Committee Member); Gil Bohrer (Committee Member); Jay Martin (Committee Member) Subjects: Agricultural Engineering; Environmental Engineering; Hydrologic Sciences

Master of Arts, Miami University, 2021, Geography

Agricultural land cover in the U.S. Midwest is a major source of nutrient pollution that has led to severe degradation of stream water quality. Previous studies have shown that land cover, stream morphology, and hydrology can influence stream nutrient concentrations. This study examines the impact of a forested state park on nutrient concentrations within an agriculturally dominated watershed. Water samples were collected biweekly from eight stream sampling sites along four creeks and processed for total nitrogen (TN), nitrate (NO3-), phosphorus (TP), and orthophosphate (PO43-). Hydrology, channel morphology, and remotely sensed vegetation data were also collected and analyzed within the study area. An analysis of covariance test (ANCOVA) and a regression coefficient t-test indicated that the state park significantly reduced NO3-, PO43-, and TP concentrations. The park as a whole did not significantly reduce TN concentrations, however, within one of the four creeks, significant decreases in TN concentrations were detected. Discharge was a significant driving factor for changes in TN, NO3-, and TP concentrations within one study creek and change in PO43- concentrations within an additional study creek. The normalized difference vegetation index (NDVI) was a significant predictor of reductions in TN concentrations within one of four study creeks, and NDVI was globally correlated with reductions in NO3- concentrations. The results of the study suggest that conservation of forested areas within agriculturally dominated watersheds can provide meaningful water quality improvements in the U.S. Midwest.

Committee: Bartosz Grudzinski PhD (Advisor); Thomas Fisher PhD (Committee Member); Jessica McCarty PhD (Committee Member); Michael Vanni PhD (Committee Member) Subjects: Environmental Management; Environmental Science; Geography; Natural Resource Management; Water Resource Management

Master of Science (MS), Wright State University, 2021, Earth and Environmental Sciences

Cyanobacteria are important primary producers, but large cyanobacterial harmful algal blooms (HABs) have many negative ecological and health impacts and are becoming increasingly common. Honeoye Lake (New York, USA) is a shallow, eutrophic lake characterized by increasingly frequent HABs. Nitrogen (N) and phosphorus (P) loads often drive HABs in lakes, and sediment processes can contribute to N removal (e.g., denitrification) or loading (e.g., N fixation, remineralization). Sediment cores and lake water were collected during May–October (2016–2018) at two sites and incubated with no amendments (controls) or 15N stable isotopes to measure sediment nutrient fluxes and N cycling dynamics in Honeoye Lake. Sediments were a strong source of ammonium (NH4+; 200 ± 56 µmol N m-2 hr-1) and soluble reactive P (SRP; 1.60 ± 0.67 µmol P m-2 hr-1). Internal loading of NH4+ was greater than previous estimates of external and internal TN loads. In situ denitrification (mean 17 ± 7 µmol N m-2 hr-1) was the main N removal pathway but was limited by NO3- availability and a lack of nitrification (mean 0.007 ± 0.002 µmol N L-1 hr-1). Potential dissimilatory nitrate reduction to ammonium rates (DNRA; 30 ± 11 µmol N m-2 hr-1) suggested sediments may play an important role in internal loading and recycling of N. Water column NH4+ uptake (mean 0.23 ± 0.02 µmol N L-1 hr-1) rates indicated high NH4+ demand, with only 50% of potential uptake being supplied by regeneration (mean 0.11 ± 0.01 µmol N L-1 hr-1) within the water column, while the other 50% can be accounted for from sediment NH4+ loading. Scaling these rates to the whole lake area suggests internal loads of bioavailable N and P are greater than external loads and promote primary productivity and HABs within Honeoye Lake. Shallow lake sediments can be a significant source of reduced N and SRP, which can be mixed periodically supporting HABs. N loads dominated by chemically reduced forms may limit denitrification and favor non-N-f (open full item for complete abstract)

Committee: Silvia E. Newell Ph.D. (Advisor); Mark J. McCarthy Ph.D. (Committee Member); Roxanne Razavi Ph.D. (Committee Member) Subjects: Aquatic Sciences; Biogeochemistry; Environmental Science; Environmental Studies; Geochemistry; Limnology

Master of Science, University of Toledo, 2021, Biology (Ecology)

Chapter 2: Stratification and hypoxia in the western basin of Lake Erie (WBLE) has been shown to result in phosphorus flux from the underlying sediment, which could provide necessary nutrients for harmful algal bloom (HAB) growth. Studying the duration and frequency of hypoxic events would provide pivotal information for estimations of phosphorus flux from underlying sediments. However, due to the ephemeral nature of hypoxic events in the WBLE, planned weekly vessel-based sampling trips are inadequate for alerting researchers of the onset of hypoxia, making sampling such events difficult. Instead, water quality instruments can be deployed to collect and relay live data to researchers in a much more frequent timeline. In this study, a buoy equipped with a thermistor string and an EXO3 sonde (Yellow Springs Institute) was deployed to monitor for potential stratification and depleting lake bottom oxygen concentrations. This system measured water quality parameters and posted the data online every 20 minutes. Using these data, immediate vessel-based sampling trips to 7 sites were made according to observed hypoxia. Data captured show a hypoxic event occurred in the WBLE during early July 2020 that persisted for several days before being mixed by a storm on July 11, 2020. This hypoxic event coincided with 8 days of stratification. In addition, hypolimnion water warmed to over 23 ℃ while remaining stratified from the overlying waters, which could facilitate higher phosphorus flux from sediments. On average, phosphorus concentrations in the hypolimnion were 1.06 µ/L (~43%) higher than in the epilimnion by the end of the event, suggesting that sediments were releasing phosphorus into the overlying waters. Chapter 3: The western basin of Lake Erie (WBLE) has been experiencing Harmful Algal Blooms (HABs) for over a decade. These blooms have been detrimental to the health of Lake Erie and the safety of drinking water for surrounding communities. Nutrient inputs (namel (open full item for complete abstract)

Committee: Thomas Bridgeman Dr. (Committee Chair); Michael Weintraub Dr. (Committee Member); William Hintz Dr. (Committee Member) Subjects: Ecology; Environmental Science; Limnology

Master of Science, The Ohio State University, 2021, Earth Sciences

Artificial Floating Islands (AFIs) have been used in a number of freshwater systems for remediating pollutants including nutrients (N and P), heavy metals, pharmaceuticals and personal care products, and textile dyes from a wide range of effluent types such as agricultural runoff, domestic wastewater, municipal sewage, urban stormwater runoff, textile wastewater, and mine drainage. AFIs have been documented as an efficient, environment-friendly, and cost-effective method to tackle nutrient pollution. However, although the number of AFI studies has steadily increased over the past two decades, a majority of them were conducted in controlled conditions with short monitor duration while our predictive ability of AFI performance under natural environments, having seasonal-variable physical, chemical, and biological conditions, is still limited. In the present study, we reviewed the evolution and performance of AFI applications for water quality improvement over the past two decades, identified the gaps in current studies relating to field-scale applications of AFIs, and conducted a combination of field and mesocosm experiments to assess the nutrient removal efficiency of AFIs containing two native aquatic plant species, Carex comosa and Eleocharis palustris. Results from our field/mesocosm experiments showed that both species experienced a significant decline in biomass accumulation and plant elongation metrics in late summer, suggesting that seasonality strongly influenced the growth conditions of macrophyte, hence affecting the nutrient removal performance of AFIs. Carex comosa significantly outperformed Eleocharis palustris on biomass accumulation, with average increase in dry biomass of 33.2 ± 18.8 g/plant for shoots and 25.3 ± 11.9 g/plant for roots. This suggests that Carex comosa is a promising candidate for AFI applications aiming at removing nutrients from urban runoff effluents.

Committee: Ozeas Costa (Advisor); James Bauer (Committee Member); Jiyoung Lee (Committee Member); Audrey Sawyer (Committee Member) Subjects: Earth; Environmental Engineering; Environmental Science

Master of Science, The Ohio State University, 2021, Chemical Engineering

Eutrophication is an environmental nuisance which costs goverments billions of US dollars every year. Precious nutrients whose reserves in nature remain limited are lost. In the course of tackling this problem, urban wastewater has become the focus of intensive research. Meanwhile, agricultural runoff which can be traced as a key source of nutrient pollution remains ignored. In this work, we present agricultural runoff as a lucrative opportunity for nutrient recycle. We identify current technologies capable of recycling nutrients with a focus on Phosphorus. Since the efficiency of best management practices at nutrient capture has been a topic of intensive research, we consider ecological solutions alongside technological solutions. We analyze the flow of materials through the system boundary for selected recycle routes. We examine the feasibility of implementing these technologies from a Techno-Economic (financial) as well as Life Cycle (environmental) point of view. Indicators are developed to assess the degree of circularity at different points in the process. We find that although the purely technological option outperforms the other routes in terms of recycle efficiency, the economic and emissions burden associated with it are too high. The purely ecological option appears to be a promising candidate on all accounts.

Committee: Bhavik Bakshi Dr (Advisor); Margaret Kalcic Dr (Committee Member) Subjects: Chemical Engineering

MS, Kent State University, 2021, College of Arts and Sciences / Department of Earth Sciences

The Marcellus Formation is a Devonian age shale play in the Appalachian Basin and is an economical energy resource in the Eastern United States. This formation is known to contain high amounts of total organic carbon (TOC), which is one method used to estimate the possible productivity, and therefore economic feasibility, of drilling a well. More recently, degree of pyritization has been another method utilized in answering this same question. This method has even been referenced as the standard to compare geochemical paleo-redox proxies and is based on the idea that the preservation of organic matter is affected by the degree of bottom-water oxygenation. Oxic environments are less favorable for organic matter preservation, whereas anoxic-euxinic conditions are more conducive of organic matter preservation. However, the degree of pyritization method does not distinguish between anoxic and euxinic conditions and it is based upon the assumption that the sulfur values measured in the lab had exclusively a pyritic source. This leads to the following questions: “Are there environments in which degree of pyritization should not be held as the standard method for comparing geochemical paleo-redox conditions?” and “What method(s) can be used to confirm that the degree of pyritization method should be used for a specific set of samples?” The focus of this research was to compare 34 samples from a Marcellus Shale core taken from a producing well in West Virginia to 50 samples from the modern Sluice Pond in Lynn, Massachusetts. The Marcellus Shale core represents an oil and gas play that has proven to be economical. In this study it acts as the industry standard to which the Sluice Pond is being compared. The primary methods used for this comparison were (1) degree of pyritization and (2) framboidal pyrite size and abundance. These two methods allowed for relationships to be drawn between pyritic iron (Fepyr), acid soluble iron, (Fesol) pyritic sulfur (Spy (open full item for complete abstract)

Committee: Jeremy Williams (Advisor); Joseph Ortiz (Committee Member); David Singer (Committee Member) Subjects: Geology

Master of Science (MS), Wright State University, 2020, Earth and Environmental Sciences

Harmful algal blooms (HABs) impact lakes worldwide and are caused by excess nitrogen (N) and phosphorus (P) loading from watersheds. Climate warming and nutrient loading effects on N cycling were examined in shallow lake mesocosms in Denmark. N loading to some mesocosms ceased in June 2018 and resumed in June 2019. Ammonium (NH4+) uptake, regeneration, and nitrification and nitrate uptake rates were evaluated. High nutrient, ambient temperature mesocosms exhibited the highest NH4+ cycling rates. Before resumption of N loading in high nutrient mesocosms, NH4+ regeneration supported 46 % of potential microbial NH4+ demand, versus 24 % with N loading. Nutrient additions generally had a larger effect on rates than temperature changes; however, community structure (phytoplankton versus macrophytes) was the best predictor of NH4+ dynamics. In eutrophic, shallow lakes, where internal NH4+ regeneration can sustain HABs, as observed in some mesocosms, management strategies should aim to reduce external N and P loads and, if deemed necessary, implement biomanipulation methods to obtain macrophyte-dominated, clear-water states.

Committee: Silvia E. Newell Ph.D. (Advisor); Rebecca Teed Ph.D. (Committee Member); Mark J. McCarthy Ph.D. (Committee Member); Erik Jeppesen Ph.D. (Other) Subjects: Environmental Science

Doctor of Philosophy (PhD), Wright State University, 2020, Environmental Sciences PhD

Eutrophication of aquatic systems can have cascading effects along hydrological continua from watersheds to coasts that result in impaired ecosystem health. In freshwater systems, blooms of toxic, non-nitrogen (N) fixing cyanobacteria (cyanoHABs), such as Microcystis, proliferate due to external loading of chemically reduced forms of N (e.g., ammonium (NH4+) and urea), which promote growth and toxin production. In coastal marine systems, nutrient loading can promote harmful algae blooms and threaten vulnerable, native vegetation, such as seagrasses, which provide valuable ecosystem services but are under threat globally from anthropogenic stressors. This dissertation focuses on NH4+ cycling in the water column of Lake Erie and microbial N transformations in St. Joseph Bay (Florida) sediments by combining biogeochemical rate measurements and molecular analysis of selected functional genes. In Lake Erie, NH4+ regeneration in the water column was an important source of internal N loading and may promote and/or sustain cyanoHAB biomass and toxin production beyond external N loads from the watershed. Despite abundant amoA gene copies (the gene responsible for catalyzing ammonia oxidation) at all stations and sampling times, nitrification rates followed seasonal patterns and were greatest outside of cyanoHABs, indicating that nitrifiers were less competitive than cyanoHABs for available NH4+. Nitrification converts NH4+ to nitrate (NO3-), the substrate for denitrification (microbial NO3- reduction to dinitrogen gas); therefore, suppression of nitrification via competition for NH4+ during cyanoHABs may inhibit natural N removal from these systems. In St. Joseph Bay, coupled nitrification-denitrification was the dominant N loss pathway, but high rates of dissimilatory NO3- reduction to NH4+ (DNRA) were also observed in sediments with seagrass vegetation. These results suggested that some of the external N loading is naturally removed from the system via denitrif (open full item for complete abstract)

Committee: Silvia Newell Ph.D. (Committee Chair); Mark McCarthy Ph.D. (Committee Member); Timothy Davis Ph.D. (Committee Member); Megan Rúa Ph.D. (Committee Member); Chad Hammerschmidt Ph.D. (Committee Member) Subjects: Environmental Science

Doctor of Philosophy, The Ohio State University, 2020, Evolution, Ecology and Organismal Biology

Community structure and ecosystem function are often influenced by both food web interactions (e.g., competition, predation) and environmental factors (e.g., temperature, oxygen availability). Identifying the drivers of food web interactions and their response to environmental change can therefore shed insights into how communities and ecosystems are regulated, which in turn can benefit the management of valued ecosystem services (e.g., fisheries). Food web interactions in north-temperate reservoirs, which are the focal ecosystems of this research, are thought to be driven primarily by a planktivorous fish, gizzard shad (Dorosoma cepedianum), by its ability to regulate the abundance of organisms at both higher and lower trophic levels. This current conceptualization, however, overlooks the potential role of bottom hypoxia, which is typically extensive during of the spring through summer growing season and can shift the spatial distributions of organisms and subsequently competitive and predator-prey interactions. It also overlooks the role of the vertically migrating macroinvertebrate, Chaoborus, which is tolerant of bottom hypoxia, and highly abundant in north-temperate reservoirs. Large populations of Chaoborus have been shown to limit zooplankton availability to other intermediate consumers (e.g., planktivorous fish) in other ecosystems, and thus have the potential to also influence food web interactions and fish recruitment in north-temperate reservoirs. Currently, the effects of both Chaoborus and bottom hypoxia on food web interactions in north-temperate reservoirs are largely unknown. To better understand the factors that influence food web interactions, energy flow through the ecosystem, and the processes that limit sport fish recruitment, my collaborators and I set out to determine how hypoxia and Chaoborus alter food web structure, function, and dynamics in north-temperate reservoirs. Specifically, we sought to answer: 1) Does north-temperate reservoir (open full item for complete abstract)

Committee: Stuart Ludsin PhD (Advisor); Joseph Conroy PhD (Committee Member); James Hood PhD (Committee Member); Elizabeth Marschall PhD (Committee Member); Lauren Pintor PhD (Committee Member) Subjects: Ecology; Freshwater Ecology

Master of Science in Engineering, University of Akron, 2020, Civil Engineering

Excess phosphorous in water ways is known to be a cause of harmful algal blooms. These blooms have caused problems with water aesthetics and recreational use. Water Treatment Residual (WTR) has been shown to have an affinity for phosphorous. Since WTR is a bi-product of the drinking water treatment process it has the potential of being a low-cost alternative to remove excess phosphorous from water ways, potentially preventing harmful algal blooms. A previous study proved there was a beneficial reuse for WTR produced at the Akron Water Treatment plant for binding excess phosphorous. This research thesis looked further into Akron Water Treatment Plants WTR, to see if baking could increase its phosphorous adsorption capacity. Initial 24-hour sorption studies determined optimal baking temperatures of 175°C for Al-WTR (ce = 0.31 mg/L, qe = 117.21) and 150°C for PAC-WTR (ce = 0.20 mg/L, qe = 120.00). Isotherm studies for baked Al-WTR (175°C) and PAC-WTR (150°C) found that there was a net desorption of phosphorous when in distilled background solution. A statistical analysis across all experimental conditions determined that baked PAC-WTR (mean qe 11.00 mg/kg) performed significantly (ρ < 0.05) better than baked Al-WTR (mean qe 8.18 mg/kg). When the specific condition of the isotherm experiments were considered, baked PAC-WTR sorbed more PO4 (mean qe 36.64 mg/kg) (ρ < 0.05) when subjected to raw water at 20°C and static in conditions. Baked Al-WTR was the next best (mean qe 21.42 mg/kg) significantly (ρ < 0.05) in 5°C Static in raw water. Continuous flow column tests were also conducted to find the sorption maximum of the baked WTR, and to compare the adsorption capacity of As-Is WTR versus baked WTR conducted. Baked WTR was found to have an affinity for phosphorous with a sorption capacity of 7.91 mg-P/g-WTR for baked Al-WTR and 16.21 mg-P/kg-WTR. When compared to As-Is WTR, baked PAC WTR was the only material found to have a higher adsorption capacity by (open full item for complete abstract)

Committee: Teresa Cutright PhD (Advisor); Donald Ott PhD (Committee Member); Stephen Duirk PhD (Committee Member) Subjects: Civil Engineering; Engineering; Environmental Engineering; Environmental Science

Master of Science, The Ohio State University, 2018, Evolution, Ecology and Organismal Biology

Climate change and eutrophication alter the structure and function of ecosystems; however, the interactive effects of these two stressors are poorly understood. In particular, we lack understanding of how the quantity and stoichiometry of essential nutrients such as nitrogen (N) and phosphorus (P) shape ecosystem responses to warming. Predicting these responses will require a mechanistic understanding of how nutrient availability shapes autotrophic functional groups, nutrient acquisition, and subsequently controls ecosystem response to warming. Because stream biofilms (a matrix of algae, bacteria, fungi, and detrital matter) represent an important component GPP and therefore control the flux of energy and nutrients through aquatic and global ecosystems, improving predictions of GPP and subsequent ecosystem response to warming will require developing a mechanistic understanding of biofilm response to N and P supply. To evaluate how nutrients mediate the temperature dependence of GPP, we conducted three successive stream-side channel experiments to develop biofilm communities across wide gradients of N concentration (0-14.3 µM), P concentration (0-6.5 µM), N:P ratios (<1-40), and across a stream temperature gradient (7.9ºC - 24.1ºC). We measured a variety of ecosystem response variables, including metabolism (gross primary production, respiration, net ecosystem production), autotroph biomass, N-uptake, N2-fixation, and biofilm community assemblage to identify relationships between N and P availability, N acquisition, biofilm functional groups (i.e., N2-fixers versus non-N2-fixers), and subsequent response of primary production to warming. Overall, temperature had a positive effect on metabolism, and was mediated by N concentration. For example, ecosystem respiration increased 11.5-12.1-fold across our temperature gradient under N-limited conditions, as opposed to a 3.1-5.4-fold increase under N-replete conditions. Biomass showed a similar response, increasing 6.7-3 (open full item for complete abstract)

Committee: James Hood (Advisor); James Bauer (Committee Member); Mazeika Sullivan (Committee Member) Subjects: Biogeochemistry; Ecology; Environmental Science; Freshwater Ecology