Master of Science, The Ohio State University, 2024, Evolution, Ecology and Organismal Biology

A major driver of eutrophication in aquatic ecosystems is phosphorus (P) pollution often derived from upstream agricultural or livestock production. While controlling P loss from these sources is essential, P export to lakes and estuaries may also be influenced by P storage and transformation within lotic ecosystems. At large scales P pools tend to be larger in places with high P inputs (i.e. agriculture and urban settings). However, spatial patterns in P storage in different pools (plants, algae, and sediment) across small watersheds with variable habitats has received little attention, but likely varies considerably with flow regime and stream size. I examined the form, mass, and location of phosphorus stored in an agriculturally dominated small watershed (20 km2) in northwest Ohio, USA. I measured the P stored in sediment, plant, and algae pools in 15 reaches varying in size and flow regime from grassed waterways to a third order stream. Sediment P was greater than 60% of the total benthic P mass in all reaches, suggesting processes determining streambed sediment storage also drive phosphorus storage. Additionally, measurements indicate that streambed sediment acted as a dissolved phosphorus sink across all reaches sampled. However, sediment tended to be saturated with P at downstream reaches, indicating that the role of sediment as a P sink may diminish in downstream reaches. Sites that were dry for some or most of the year contained a large portion of the benthic P located in this stream network, suggesting that wet/dry cycles are important drivers of P cycling in much of the stream network. Thus, the impact of streams on P exports may vary substantially within small watersheds.

Committee: Jim Hood (Advisor); Steve Hovick (Committee Member); Vinayak Shedekar (Committee Member) Subjects: Biogeochemistry; Ecology; Environmental Science

Master of Science, The Ohio State University, 2024, Evolution, Ecology and Organismal Biology

Eutrophication of freshwater ecosystems is a global environmental problem often caused by excess bioavailable phosphorus (P). Thus, it is important to understand the sources and sinks of bioavailable P in a watershed. Previous work suggests that during high flow events, which dominate annual P and sediment loads, exchange of P between dissolved and particulate forms impacts the bioavailability of P exports to recipient ecosystems. Yet, suspended sediment is derived from many sources on the landscape, which can differ in chemical composition and likely, affinity for P sorption. Human activities can impact sediment source so, it is important to understand the connection of composition to sediment source, and how source influences sediment-P (sedP)-dissolved reactive P (DRP) interactions during high flow. To address this, I collected seven distinct sources (four streambank soils, two cropland soils, and streambed sediment) from a Maumee River tributary; the Maumee watershed is the main source of P fueling Lake Erie cyanobacteria blooms. Using source material collected in May, June, and December, I conducted three experiments which examined sedP-DRP interactions in a simulated high flow environment for 120 hours. I also measured aspects of sediment composition including size, P content, and P saturation (Mehlich-III P:Mehlich-III Fe). Cropland, streambank, and streambed sources were distinct in chemical composition and P sorption rate capacity; streambed and streambank sources had low P saturation and high P sorption during the first day of the experiment. In contrast, cropland sources had high P saturation and low P sorption. My results indicate that sediment source influences sedP-DRP interactions during high flow events, suggesting that changes in land management that alter the relative balances of sediment sources, or P saturation, may influence in stream P transformations and bioavailability of P exports to recipient ecosystems.

Committee: James Hood (Advisor); John Lenhart (Committee Member); Casey Pennock (Committee Member); Tanja Williamson (Committee Member) Subjects: Aquatic Sciences; Ecology; Geochemistry

BS, Kent State University, 2024, College of Arts and Sciences / Department of Biological Sciences

Wetlands act as a filter between the terrestrial land and a body of water, regulating the flux of nutrients between these. An overabundance of nutrients, such as phosphate, can lead to a harmful algal bloom (HAB), which is known to deplete oxygen from aquatic ecosystems and produce harmful toxins. The goal of this study was to determine the effect of different vegetation patches on the amount of bioavailable phosphorus, measured as soluble reactive phosphate (SRP), in both the surface water and sediment. We sampled surface water and sediment from Turtle Creek Bay located in Magee Marsh Wildlife Area, Ohio, where we identified four distinct vegetation patches: grasses, hardwoods, Typha spp. (cattail), and submerged aquatic vegetation (SAV). Results of this study showed that the SAV patch exhibited significantly less SRP than the other patches (p<0.05). However, there was no significant difference in SRP concentrations for the rest of the patches. Additionally, we experimentally incubated intact sediment cores sampled from a diagonal transect across Magee Marsh. The cores were incubated with four different SRP concentration treatments based on in situ SRP measurements. We found that at ambient SRP concentrations (4 ug/L), sediments released 455.2 ± 518.3 ug SRP/m2/d into surface waters, but when SRP concentrations in the surface water increased (to 18, 39, and 60 ug SRP/L), sediments removed SRP at increasing rates (-919.9 ± 278.7, -2062.3 ± 1001.61, -7378.5 ± 4267.1 ug SRP/m2/d, respectively).The increasingly negative mean flux rates suggest that these coastal wetland sediments can sequester increasing amounts of SRP as surface water concentrations increase.

Committee: Lauren Kinsman-Costello PhD (Advisor); Mark Kershner PhD (Committee Member); Andrew Scholl PhD (Committee Member); David Costello PhD (Committee Member) Subjects: Biogeochemistry; Biology; Conservation; Ecology; Environmental Science; Freshwater Ecology; Plant Sciences

PHD, Kent State University, 2023, College of Arts and Sciences / Department of Biological Sciences

Climate change is exerting profound and far-reaching impacts on ecosystems worldwide, encompassing both aquatic and terrestrial environments. The evolving precipitation patterns and shifting temperature regimes impact fluctuations in hydrology, resulting in shifts in redox conditions which can impact the availability of nutrients like phosphorus (P). Phosphate, the bioavailable form of P, is only present in small amounts within soils, making the biological demand greater than soil phosphate availability. The majority of soil P is present in non-labile forms including organic P and phosphate sorbed to metal oxides like iron (Fe). Microorganisms must content with geochemical and other abiotic factors to access phosphate from these non-labile sources through the use of various strategies including the secretion of enzymes, the production of phosphate solubilizing acids, as well as indirect mechanisms associated with the reduction of Fe oxides. The primary goal of this dissertation was to advance our understanding of how microorganisms access both labile and non-labile forms of P in the presence of changing hydrologic and redox conditions which impact the speciation of Fe that is present, altering phosphate availability. Specifically, I investigated 1) how phosphate availability changes across a permafrost thaw gradient (palsa, bog, and fen) in the presence of iron oxides, 2) how microorganisms access and mobilize chemically diverse phosphorus sources under contrasting redox conditions, and 3) how changes in hydrology, redox, iron mineralogy, and phosphate availability drive shifts in microbial community composition, specifically iron oxidizers, reducers, and phosphate solubilizers. In our first study assessing microbial phosphate accessibility across a permafrost thaw gradient, we found that near surface redox conditions changed as a function of permafrost thaw which impacted phosphate availability. Reducing conditions in the bog promoted the dissolution of Fe oxides, (open full item for complete abstract)

Committee: Lauren Kinsman-Costello (Advisor); Christie Bahlai (Committee Member); David Costello (Committee Member); Christopher Blackwood (Committee Member); Elizabeth Herndon (Committee Member); Timothy Gallagher (Committee Member) Subjects: Biogeochemistry; Climate Change; Ecology; Geobiology; Geochemistry; Microbiology; Mineralogy; Soil Sciences

PHD, Kent State University, 2022, College of Arts and Sciences / Department of Biological Sciences

Nickel (Ni) is a widespread and persistent contaminant in riverine systems that can impair biological diversity and ecological function. The bioavailability and toxicity of Ni are strongly influenced by its complexation with solid-phase ligands in sediments. Riverine sediments are often vertically stratified with thin oxic layers overlying anoxic horizons, and the distinct physicochemical conditions in these sediment layers modify their Ni binding capacity. In anoxic sediment, reduced sulfur (AVS) is the primary metal ligand, whereas iron (Fe) and manganese (Mn) oxide minerals can be important binding fractions for Ni under oxic conditions. The mixture of competing oxidized and reduced ligands in natural sediments is largely driven by physical conditions and the redox metabolism of the sediment microbial community. However, microbes are concurrently susceptible to the toxic effects of nickel, which can ultimately modify the availability of solid-phase ligands. Current sediment quality criteria consider AVS as the major binding phase for Ni but have not yet incorporated ligands that are present in oxic sediments. The overall objective of this dissertation was to improve our understanding of the role that metal oxides play in regulating Ni bioavailability to benthic organisms in natural sediments. The first study used a field-based approach to evaluate the role of metal oxides on Ni bioavailability to the benthic invertebrate community in riverine sediments exposed to effluent from two mining operations in Thompson, Manitoba, Canada. We found that oxide minerals in natural oxic sediments bind a substantial amount of Ni. Oxic sediment chemistry more strongly represented conditions experienced by benthic invertebrates and the inclusion of oxic solid-phase ligands was critical to refine predictions of Ni bioavailability and its impact on benthic community structure. The second study further investigated the geochemical drivers of Ni sorption to natural sediments across a (open full item for complete abstract)

Committee: David Costello (Advisor); Mark Kershner (Committee Member); Alison Smith (Committee Member); Christopher Blackwood (Committee Member); David Singer (Committee Member) Subjects: Freshwater Ecology

PhD, University of Cincinnati, 2022, Arts and Sciences: Biological Sciences

In this dissertation, I focus on longitudinal connectivity in streams, i.e. the upstream/downstream connections within these ecosystems. Longitudinal connectivity is often a primary driver of stream habitat, water chemistry, and biota because of the inherent nature of water's tendency to flow from upstream to downstream within channel banks. This means that what happens in upstream reaches is likely to influence the downstream ecosystem. Within the framework of longitudinal connectivity, I have focused on how anthropogenic disturbance of stream burial (the containment of streams within culverts) and subsequent restoration influence stream habitat and biota (Ch. 2 and 3) and how signals within streams can be propagated downstream with a focus on anthropogenic influences (Ch. 2) and in-stream nutrient signals (Ch. 4). I have examined these topics in three different studies that include reach-scale studies and work completed at a watershed scale. I have evaluated anthropogenic influences on streams and signal propagation downstream by examining their effects on stream habitat, water chemistry, nutrient limitation, benthic algae, and macroinvertebrates. I have shown that urban stream burial alters stream habitat and biota within the culverts themselves and that urban culverts can represent fundamentally different habitat units than observed elsewhere in my study streams (Ch. 2). Stream burial caused habitat simplification within culverts (buried reaches), and I found no longitudinal variation in most parameters monitored within buried reaches. Specifically, I observed deeper water depths, smaller substrates, decreased amounts of basal resources, and decreased macroinvertebrate density and diversity. I have also shown that the impact of culverts is longitudinally constrained to the culverts themselves. I found that when a buried stream was restored, stream habitat can became more heterogenous (both regarding substrate size and water depth) and that benthic alga (open full item for complete abstract)

Committee: Stephen Matter Ph.D. (Committee Member); Michael Booth Ph.D. (Committee Member); Tammy Newcomer Johnson Ph.D (Committee Member); Ken M. Fritz Ph.D. (Committee Member); Ishi Buffam Ph.D. (Committee Member) Subjects: Ecology

Doctor of Philosophy (PhD), Wright State University, 2021, Environmental Sciences PhD

Attached algae are ubiquitous components of lake benthic habitats wherever sufficient light reaches submerged surfaces. Attached algae interact with heterotrophic bacteria and fungi to form complex biofilms (“periphyton”) that provide a nutritious food source for consumers and influence biogeochemical cycling by regulating redox potential at the sediment-water interface. Despite their ecological importance, there are limited data on the role of periphyton in the Laurentian Great Lakes. I quantified wave exposure and light availability in rocky nearshore habitats in Lake Erie and Lake Huron. Periphyton biomass and productivity in nearshore Lake Erie was very high while algal biomass and productivity in Lake Huron were uniformly low irrespective of depth. Regression modeling demonstrated that wave disturbance and light availability control periphyton biomass and productivity in nearshore areas of the Great Lakes. To better understand how attached algal diversity and abundance vary with depth and substrate, I measured the biomass and composition of sediment algae and periphyton growing on Dreissena across broad depth gradients in Lake Ontario and Lake Erie. Sediment and mussel shell algal biomass were greatest around 20 m and declined with depth. Algal photosynthesis on sediments and mussels declined with depth down to approximately 40 m in both lakes. I found that sediments from both lakes were dominated by benthic diatoms and settled phytoplankton. In contrast, mussel shells harbored diverse filamentous algal assemblages. I analyzed the stable isotope signatures of Dreissena tissue and biofilms collected in Lake Ontario and Lake Erie, discovering enrichment of nitrogen isotopic signatures in both organisms with depth. DNA metabarcoding data from Lake Erie revealed that Dreissena biofilms harbor greater abundances of putative nitrifying and denitrifying bacteria than surrounding sediments, suggesting that Dreissena may be hotspots for nitrogen cycling in the Great Lak (open full item for complete abstract)

Committee: Yvonne Vadeboncoeur Ph.D. (Advisor); Volker Bahn Ph.D. (Committee Member); Soren Brothers Ph.D. (Committee Member); Katie Hossler Ph.D. (Committee Member); Silvia E. Newell Ph.D. (Committee Member) Subjects: Ecology; Environmental Science; Limnology

Master of Science (MS), Bowling Green State University, 2020, Biological Sciences

Agricultural fields in Northwest Ohio and the Maumee River watershed are frequently tile drained and fertilized with phosphate to optimize plant growth. Phosphate is often lost from fields via surface runoff and tile drainage, either with particulate soil matter or as dissolved reactive phosphate. Soil health, aided by enzymes produced by microorganisms and plants, can influence the retention and loss of phosphate. Stable oxygen isotopes may provide a non-invasive way of measuring the biological turnover rate of phosphate in soils over longer time scales than previous methods. The ability of oxygen isotopes in phosphate to measure biological turnover was examined in a study with three fields in the Maumee River watershed from fall 2016-summer 2017. Samples were collected after fall tilling and fertilization, and before and after spring planting and fertilization. Soil nutrients and metal concentrations were analyzed as well as oxygen isotope analysis from soil phosphate, soil pore-water, and tile water. Overall, sites had high nutrient and metal concentrations and low levels of phosphate recycling relative to the overall pool of phosphate, based on oxygen isotope analysis. Soil samples did not reach equilibrium with soil pore-water. The most recycled sample collected, a tile drain sample collected five months after fall fertilization, was still about 80% fertilizer. The results suggest that sources of phosphate can be detected for long periods of time in agricultural fields under specific circumstances and that phosphate ion interactions with metal oxides may help explain the lack of equilibrium observed. Oxygen isotope studies of phosphate in soil could help researchers and field managers better understand the mechanisms behind the effects of various best management practices (BMPs) on nutrient runoff.

Committee: Kevin McCluney Ph.D. (Advisor); Shannon Pelini Ph.D. (Committee Member); Angelica Vázquez-Ortega Ph.D. (Committee Member) Subjects: Agriculture; Biogeochemistry; Ecology; Environmental Science; Soil Sciences

Doctor of Philosophy, The Ohio State University, 2020, Earth Sciences

Upland catchments play an outsized role in the processing and export of water, sediments, nutrients, and organic matter, thus strongly influencing downstream water quality. In Chapter 1, an overview of biogeochemical cycling within upland fluvial sediments is presented, focusing on key regional biogeochemical cycling patterns and solute export processes. Additionally, anthropogenic influences on this environment, such as historical mining activities and climate change, are briefly reviewed in this chapter. Chapter 2 explores the relationship between spatial hydrologic heterogeneity and microbial community assembly and functional potential within the hyporheic zone. The region of groundwater and river water mixing, known as the hyporheic zone, is a hotspot of microbial activity that influences solute export and cycling in rivers. Hyporheic mixing patterns can vary over small spatial scales, leading to heterogeneity in fluid chemistry and microbial community composition and function. Here, we integrate new mass-spectrometry data, metagenomic insights, and ecological models with previous analyses of microbial community composition and dissolved organic matter (DOM) quality to understand spatial relationships between hyporheic flow and microbial community assembly, metabolism, and DOM processing at high-resolution (100 locations) along a 200 m meander of East River, Colorado (USA). Ecological modeling revealed a strong linkage between community assembly patterns and underlying hydrologic and geochemical drivers, including the impact of physical heterogeneity (riverbed grain size) on microbial community structure. Geochemical profiles associated with upwelling groundwater suggest the influence of underlying geology, specifically Mancos-derived solutes, in driving community assembly. Distinct microbial community profiles and functional potential in zones of upwelling groundwater suggest that groundwater chemistry may have a greater influence on biogeochemical cycling wi (open full item for complete abstract)

Committee: Michael Wilkins (Advisor); Steven Lower (Advisor); Audrey Sawyer (Committee Member); Elizabeth Griffith (Committee Member) Subjects: Biogeochemistry; Earth; Ecology; Environmental Geology; Environmental Science; Geobiology; Geochemistry; Geology; Hydrology; Limnology; Microbiology; Mineralogy

MS, Kent State University, 2019, College of Arts and Sciences / Department of Earth Sciences

Wetlands are complex ecosystems with unique biogeochemical and hydrological characteristics. These aspects can be traced to the following biogeochemically distinct domains: sediments, porewater, and surface water. Sulfur can play a critical role in aquatic ecosystems, with potential to influence the biogeochemical cycles of freshwater nutrients and metals. Inorganic sulfur can occur in the natural environment in multiple oxidation states. In the presence of oxygen, reduced sulfur readily oxidizes to form sulfate. Wetland hydrology controls the redox states of sulfur, as well as governing the fates trace metals, major cations, and anions in the wetland ecosystem. By examining wetland hydrology and characterizing the biogeochemistry of different wetland domains (sediment, porewater, and surface water), the export and forms of inorganic sulfur in the wetland can be characterized. The study site for this project was a constructed wetland at the Cleveland Metroparks' Watershed Stewardship Center in Parma, Ohio. The study site had interior zones of differing depths and a dynamic hydrologic regime, which could cause a variation in nutrient residence times and transformations within the wetland. To understand the wetland's hydrology and its relationship to sulfate biogeochemistry, interior water levels, outflow discharge, precipitation, water chemistry, sediment chemistry, and porewater chemistry were monitored from June 2015 to October 2016. High concentrations of sulfate were found in the interior zones (arithmetic mean: 185.7 mg/L) and outflow (arithmetic mean: 228.4 mg/L), while inflow concentrations were variable (ranges across inflows: 9.417-902.2 mg/L). Sulfate concentrations in surface water were found to be the highest in the interior and outflow following an extensive drydown period in Summer 2016. High concentrations of sulfate could also signal that sulfide was present in the wetland, but sulfide was below detection in porewater. However, wetland sediments c (open full item for complete abstract)

Committee: Anne Jefferson (Advisor); Lauren Kinsman-Costello (Advisor); Elizabeth Herndon (Committee Member) Subjects: Biogeochemistry; Environmental Geology; Environmental Management; Environmental Science; Freshwater Ecology; Geology; Hydrologic Sciences; Hydrology; Natural Resource Management; Water Resource Management

BS, Kent State University, 2019, College of Arts and Sciences / Department of Biological Sciences

Road salts, brines, and other de-icers are used to melt snow and ice on roads and sidewalks. The runoff resulting from this process is high in salt ions such as sodium, chloride, calcium, magnesium, and potassium. These ions end up in our waterways, and contribute to the problem of increasing salinity in freshwater ecosystems. In this study, two constructed freshwater wetlands near Kent State University were monitored for one year by measuring specific conductance with in situ conductivity sensors and concentrations of road salt ions in surface water with IC and ICP-OES. This data set allowed us to assess seasonal and temporal trends in road salt runoff, as well as possible mechanisms of salt storage and cycling within the wetlands. We found that the wetlands were a considerable sink for road salt ions over the course of the year. Moreover, the degree to which each wetland retained the ions was not the same. The wetland with continuous flow and comparatively less storage space retained less of the ions than the intermittently flowing, deeper wetland. Additionally, we found that there are cation dynamics in which road salt-derived sodium exchanges with cations sorbed to soils, causing a net release of calcium and magnesium from one of the wetlands. The notable imbalance in the salt budget of these wetlands, despite their differences in flow regime, is symptomatic of unsustainable road salt practices in these and similar watersheds. Should this pattern continue, there could reach a point where the wetlands could no longer store the influx of salt ions each year, resulting in a large release of saline water into downstream freshwater ecosystems. These findings can be used to inform management decisions not only in Kent, Ohio, but also in any city to better balance ecosystem function with public safety.

Committee: Lauren Kinsman-Costello Ph.D. (Advisor); David Costello Ph.D. (Committee Member); Michael Tubergen Ph.D. (Committee Member); Alison Smith Ph.D. (Committee Member) Subjects: Aquatic Sciences; Biogeochemistry; Biology; Chemistry; Environmental Geology; Environmental Science; Freshwater Ecology; Geochemistry

Doctor of Philosophy, The Ohio State University, 2019, Earth Sciences

Magnetospirillum magneticum AMB-1 is a member of a phylogenetically diverse group of bacteria characterized by their ability to biomineralize magnetic minerals known collectively as magnetotactic bacteria (MTB). MTB produce chains of membrane-bound intracellular magnetic nanocrystals, collectively known as magnetosomes. The current scientific consensus is that magnetosomes are used by MTB to orient themselves in vertically stratified water columns in order to achieve optimal oxygen concentrations in a process known as magnetoaerotaxis. Biomineralization of magnetosomes is an energy intensive process which accounts for roughly 33% of the cell's metabolic budget. This high metabolic cost seems to contradict with the amount of time MTB cells spend aligned with external magnetic fields. Due to this apparent discrepancy, I examined the potential role the magnetosome may play in bacterial metabolism. Through analysis of comparative growth on a variety of media compositions both magnetic, wild type and non-magnetic, mutant strains of AMB-1, I discovered that cells grown under stress conditions exhibit an inversion of growth dynamics which indicates some advantage for magnetic cells. Non-magnetic, mutant cells display a direct relationship between external magnetic field strength and growth, indicating magnetic field dependence. I believe that this represents a novel magnetosome-dependant mixotrophic metabolism. Due to the ubiquity of MTB and the diversity of sessile eukaryotes which either produce biogenic magnetite or exhibit magnetosensing, this system may be part of a widespread, previously unknown component of global carbon cycling.

Committee: Steven Lower (Advisor); Brian Lower (Committee Member); Ratnasingham Sooryakumar (Committee Member); Ann Cook (Committee Member) Subjects: Biogeochemistry; Geobiology; Geology; Microbiology; Mineralogy

Doctor of Philosophy, The Ohio State University, 2018, Microbiology

Permafrost contains 30–50% of global soil carbon (C) and is rapidly thawing. While the fate of this C is unknown, it will be shaped in part by microbes and their associated viruses, which modulate microbial activities via mortality and metabolic control. To date, viral research in soils has been outpaced by that in aquatic environments due to the technical challenges of accessing soil viruses, compounded by the dramatic physicochemical heterogeneity in soils. The Stordalen Mire long-term ecological field site in Arctic Sweden encompasses a mosaic of natural permafrost thaw stages, and has been well characterized biogeochemically and microbiologically, making it an ideal site to characterize the soil virosphere and its potential impacts on the C cycle. A viral resuspension protocol was developed to generate quantitatively-amplified dsDNA viromes. The protocol yielded ~108 virus-like particles (VLPs) g-1 of soil across three thaw-stage habitats, and seven resulting viromes yielded 53 vOTUs. Viral-specific bioinformatics methods were used to recover viral populations, define their gene content, connect them to other related viruses (globally) and potential hosts (locally). Only 15% of these vOTUs had genetic similarity to publicly available viruses in the RefSeq database, and ~30% of the genes could be annotated, supporting the concept of soils as reservoirs of substantial undescribed viral genetic diversity. The vOTUs exhibited distinct ecology, with different distributions along the thaw gradient habitats, and a shift from soil-virus-like assemblages in the dry palsas to aquatic-virus-like assemblages in the inundated fen. Seventeen vOTUs were linked to microbial hosts (in silico), implicating viruses in infecting abundant microbial lineages from Acidobacteria, Verrucomicrobia, and Deltaproteobacteria, including those encoding key biogeochemical functions such as organic matter degradation. Thirty auxiliary metabolic genes (AMGs) were identified and suggested virus-m (open full item for complete abstract)

Committee: Virginia Rich (Advisor); Matthew Sullivan (Committee Co-Chair); Kelly Wrighton (Committee Member); Matthew Anderson (Committee Member) Subjects: Biogeochemistry; Climate Change; Ecology; Environmental Science; Microbiology; Soil Sciences; Virology

MS, Kent State University, 2018, College of Arts and Sciences / Department of Biological Sciences

Human alterations to the global nitrogen (N) and phosphorus (P) cycles negatively impact ecosystems and threaten human health. Nutrient runoff from agricultural land use practices degrades water quality by stimulating hypoxia (lack of oxygen) and harmful algal blooms. Wetlands are often relied on by humans to provide multiple ecosystem services at a relatively low cost. The objective of this thesis was to better understand the mechanisms driving N and P cycling in Old Woman Creek estuary (OWCE), an unaltered wetland along the coast of Lake Erie. We assessed the seasonal hydrologic influence on nutrient loading to OWCE, estimated an annual mass balance to determine nutrient removal capabilities, determined spatial heterogeneity of N and P removal mechanisms, investigated the vertical distribution of nutrients in surface waters, and determined the potential for wetland sediments to facilitate N and P release. We used daily water quality and hydrologic measurements to calculate complete annual mass balances for water, N, and P for water years 2016 and 2017. We collected water and sediment samples during June 2016, August 2016, April 2017, and August 2017 to assesses the denitrification potential and P storage and conducted a continuous flow-through experiment. The hydrology and seasonal variation of individual wetlands is important to consider when assessing nutrient removal potential. We found that while on the mass balance scale OWCE retains N and P, spatially there is variation where nutrient retention is occurring based on indicators of N and P removal mechanisms, but variation occurred within similar locations demonstrating duel nutrient removal potential. However, sediments have the potential to release N and P in the water column. Biological activity in the wetland may be an important driver in retaining N and P released from the sediment. Overall, nutrient removal in the wetland is controlled by a combination of loading into the wetland, autotroph activity, mic (open full item for complete abstract)

Committee: Lauren Kinsman-Costello (Advisor); Darron Bade (Committee Member); Christopher Blackwood (Committee Member) Subjects: Biogeochemistry; Environmental Science; Water Resource Management

BS, Kent State University, 2018, College of Arts and Sciences / Department of Biological Sciences

Invertebrate activities at the sediment-water interface can facilitate nutrient retention, release, and transformation by changing the nature of oxygen penetration into anoxic sediments, influencing geochemical and microbial-mediated processes. By reworking sediment and conveying oxygenated surface water into deeper anoxic sediment through burrowing activities, bioturbating invertebrates influence nutrient cycling in wetlands sediments. To test the effects of bioturbators on oxygen introduction and nutrient fluxes, we investigated the impacts of two functionally different bioturbators at a range of four densities using a microcosm study. We measured sediment oxygen penetration depth at small-scale resolution using microelectrode sensors and analyzed surface water nutrients weekly over four weeks. Results indicate increased oxygen penetration in regions of normally anoxic sediment with the presence of each of the two bioturbation modes. In general, we observed negative phosphorus fluxes (i.e., into the sediment) with increasing bioturbator densities, indicating retention in the sediment due to bioturbation activities. These activities caused enough retention of phosphorus to counteract the phosphorus released by bioturbator excretion alone. There was a flux of nitrate into the surface water, likely driven by invertebrate excretion of ammonia followed by an oxidative process such as nitrification. This investigation contributes to the growing understanding of how organisms influence nutrient cycling in wetlands, which are hotspots for biogeochemical processing.

Committee: Lauren Kinsman-Costello (Advisor); Andrea Fitzgibbon (Other); David Costello (Committee Member) Subjects: Biogeochemistry; Ecology; Freshwater Ecology; Geochemistry

MS, Kent State University, 2018, College of Arts and Sciences / Department of Earth Sciences

In urban areas, increased runoff from storm events is a significant concern due to flooding, erosion, ecosystem disturbance, and water quality problems. Phosphorus (P) and nitrogen (N) are key limiting nutrients that lead to eutrophication and harmful algal blooms in Lake Erie and other freshwater systems, and urban landscapes are locally important sources of nutrients to downstream water bodies. Green infrastructure (GI) is one increasingly popular solution being used in urban areas to address the water quantity and quality issues that urban runoff creates. Green roofs and bioretention cells are widely used forms of GI designed to decrease and slow down runoff through evapotranspiration and infiltration. I compared the hydrologic effectiveness of a co-located extensive green roof and two bioretention cells in northeastern Ohio, in order to understand their relative capacities to decrease and slow down stormwater runoff, when subjected to the same weather conditions. I also monitored the green roof to understand its effects on water quality, in terms of P and N. From June 2015 to November 2016, 93 storms from 2.5 to 62 mm, were monitored. To assess the hydrologic performance of each site, I measured rainfall, underdrained outflow, groundwater levels in the bioretention cells, and soil moisture on 1–5 minute intervals. To assess water quality for the green roof, I collected precipitation and samples from the green roof downspout. I measured chloride (Cl-) phosphate (PO43-), total P, nitrate (NO3-), ammonium (NH4+), and total N concentrations using ion chromatography and a colorimetric assay. The bioretention cells performed similarly to each other, despite slightly different designs, and they had superior performance to the green roof. The paved lot bioretention cell showed 77% volumetric and 85% peak flow reduction and the gravel lot bioretention cell showed 78% volumetric and 82% peak flow reduction. The green roof only reduced 59% of its water input and 69% (open full item for complete abstract)

Committee: Anne Jefferson (Advisor); Lauren Kinsman-Costello (Advisor); Elizabeth Herndon (Committee Member) Subjects: Ecology; Environmental Science; Geology; Hydrology; Sustainability; Water Resource Management

Doctor of Philosophy, Miami University, 2017, Ecology, Evolution and Environmental Biology

Chapter 1: Comparing the relative importance of photodegradation and biodegradation for transforming dissolved organic matter quality in three temperate lakes of varying trophic status. In this chapter, I tested the relative importance of photodegradation vs. biodegradation for altering dissolved organic matter (DOM) quality and quantity from three temperate lakes ranging in color and productivity. For all three lakes, photodegradation led to larger decreases in DOM color and molecular weight than biodegradation. In addition, DOM with low prior sunlight exposure responded more to photodegradation than previously sunlight exposed DOM. This chapter is currently in preparation for submission to the Journal of Geophysical Research: Biogeosciences. Chapter 2: Sunlight-driven degradation of terrestrial organic matter exceeds microbial respiration. For Chapter 2, I extended Chapter 1 by more completely exploring how sunlight and microbes control the production of CO2 for terrestrial DOM from the watershed surrounding the same temperate lakes and a sub-tropical lake. Here we show that sunlight led to higher amounts of CO2 production than microbial respiration for terrestrial DOM from the watersheds of the brown-water lakes. However, sunlight-driven reductions in DOM quality were greater than CO2 production for DOM from the watersheds of the oligotrophic and eutrophic lakes. This chapter is in preparation for submission to Biogeochemistry. Chapter 3: The potential of high-frequency profiling to assess vertical and seasonal patterns of phytoplankton dynamics in lakes: an extension of the Plankton Ecology Group (PEG) model Here, I compared nightly profiles of chlorophyll fluorescence (proxy for phytoplankton biomass) from 11 global lakes to test the drivers of seasonal changes in sub-surface phytoplankton layers. High-frequency profiles captured the short-term phytoplankton dynamics better than traditional sampling, and physical drivers including light availability and t (open full item for complete abstract)

Committee: Craig Williamson (Advisor) Subjects: Aquatic Sciences; Biology; Ecology

Doctor of Philosophy, The Ohio State University, 2017, Atmospheric Sciences

One of the largest ecosystem controls in the oceans is the presence of dissolved oxygen. As oxygen levels fall, both micro- and macroorganisms face shrinking habitats and potential mortality. There have been several periods in Earth history where oxygen levels have fallen to anoxic (dissolved O2 concentration < 10 µmol L-1) or hypoxic (< 60 µmol L-1) levels in certain ocean basins or within inland seas and some of these events could potentially be linked to mass extinction events. Several hypotheses exist regarding the depletion of oxygen, the spread of hypoxia-anoxia, and why the low oxygen events occur at certain points in the geologic record, including rapid climate warming, enhanced nutrient inputs, and modifications to the surface biological pump. Unfortunately, there is little agreement on which of these potential hypotheses caused individual events and what might impact the oxygenation of our oceans in the future. This dissertation will test hypotheses related to deep ocean oxygen using the University of Victoria Earth System Climate Model. The first set of experiments feature Late Ordovician winds and paleogeography and test the impacts of atmospheric CO2 and O2, ocean bottom topography, and nutrient loadings on deep ocean oxygen concentrations. The second set of experiments is also within the Late Ordovician, but tests the impacts of remineralization rates, detrital sinking velocities, and ocean surface albedo on ocean oxygenation. The final set of experiments tests the impacts of a warming climate on the oxygenation of near-future oceans, in addition to the impacts of detrital sinking velocities and ocean surface albedo. For the Late Ordovician, the factors most favorable for the spread of anoxia are reduced atmospheric O2, increased loadings of nitrate, and a reduction in ocean surface albedo. Climatic factors (namely, increased CO2) played little role in the spread of anoxia or the depletion of oxygen in these experiments. Similarly, phosphate, enhanc (open full item for complete abstract)

Committee: Alvaro Montenegro (Advisor); Bryan Mark (Committee Member); Michael Melchin (Committee Member); Ellen Mosley-Thompson (Committee Member) Subjects: Atmospheric Sciences; Biogeochemistry; Climate Change; Oceanography; Paleoclimate Science

Master of Science, The Ohio State University, 2017, Earth Sciences

Aeolian processes play an important role in the transport of both geological and biological materials globally, on the biogeochemistry of ecosystems, and in landscape evolution. As the largest ice free area on the Antarctic continent (approximately 4800 km2), the McMurdo Dry Valleys (MDV) are potentially a major source of aeolian material for Antarctica, but information on the spatial and temporal variability of this material is needed to understand its soluble and bulk geochemistry, deposition and source, and hence influence on ecosystem dynamics. 53 samples of aeolian material from Alatna Valley, Victoria Valley, Miers Valley, and Taylor Valley (Taylor Glacier, East Lake Bonney, F6 (Lake Fryxell), and Explorer's Cove) were collected at five heights (5, 10, 20, 50, 100 cm) above the surface seasonally for 2013 through 2015. The sediment was analyzed for soluble solids, total and organic carbon, minerology, and bulk chemistry. Of the soluble component, the major anions varied between Cl- and HCO3-, and the major cation was Na+ for all sites. Soluble N:P ratios in the aeolian material reflect nutrient limitations seen in MDV soils, where younger, coastal soils are N-limited, while older, up valley soils are P-limited. Material from East Lake Bonney was P-limited in the winter samples, but N-limited in the full year samples, suggesting different sources of material based on season. Analysis of soluble salts in aeolian material in Taylor Valley compared to published soil literature demonstrates a primarily down valley transport of materials from Taylor Glacier towards the coast. The bulk chemistry suggests that the aeolian material is highly unweathered (CIA values less than 60 %), but scanning electron microscope images show alteration for some individual sediment grains. The mineralogy was reflective of local rocks, specifically the McMurdo Volcanics, Ferrar Dolerite, Beacon Sandstone and granite, but variations in major oxide percentages and rare earth element signa (open full item for complete abstract)

Committee: W. Berry Lyons PhD. (Advisor); Michael Barton PhD. (Committee Member); Michael Wilkins PhD. (Committee Member) Subjects: Earth; Geochemistry; Geological

Master of Science (MS), Wright State University, 2017, Earth and Environmental Sciences

Mercury (Hg) is a volatile element increasing in concentration in the environment as a result of anthropogenic emissions. Microorganisms can transform mercury into monomethylmercury (MMHg), the form of Hg that bioaccumulates, biomagnifies, and can harm humans and wildlife. Most studies of MMHg bioaccumulation in wildlife have focused on aquatic organisms due to consumption of fish being the primary route of human exposure to MMHg. However, organisms in terrestrial ecosystems also are exposed to MMHg that may impact ecosystem biodiversity, food-web dynamics, and organisms and ecosystem health. I investigated bioaccumulation and maternal transfer of MMHg in spotted salamanders (Ambystoma maculatum) captured from two locations in southern Ohio in 2016. Total length, weight, sex, and whole-body concentrations of MMHg were determined for 159 organisms. Spotted salamanders in southern Ohio bioaccumulated MMHg to concentrations (mean = 93 ± 33 ng/g dry wt.) comparable to those is other salamander species in other locations. MMHg concentrations in spotted salamander carcasses were unrelated to organism size. MMHg was maternally transferred to eggs, but concentrations in eggs were not strongly correlated with concentrations in associated maternal carcasses. MMHg concentrations in the distal 4 cm of tail were positively correlated with concentrations in spotted salamander carcasses, which provides a non-destructive sampling method for future screening and biomonitoring MMHg concentrations in these organisms. Due to their ubiquity, spotted salamanders may be useful bioindicators of MMHg bioaccumulation and cycling in forested ecosystems of southern Ohio, and by extension, other terrestrial ecosystems that they inhabit.

Committee: Chad Hammerschmidt Ph.D. (Advisor); Silvia Newell Ph.D. (Committee Member); Mark McCarthy Ph.D. (Committee Member) Subjects: Biogeochemistry; Environmental Science