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

PHD, Kent State University, 2021, College of Arts and Sciences / Department of Biological Sciences

The overall motivations of this work were to better understand anthropogenic and environmental factors that can both inhibit or destroy, as well as promote biological soil crusts (biocrusts) in the North American southwest. Biocrusts are living mats that occupy the first few millimeters of soils in arid environments around the globe. They contribute to many ecosystem services including soil stabilization and nitrogen fixation. The specific research questions of this dissertation aim to unpack to complexity of these unique, specialized organisms capable of inhancing arid environments. The research here was approached from manuipulative and observational frameworks to increase our understanding of the ecology of biocrusts. Chapter I is an introduction to biocrusts, and the broader ecological concepts covered as part of this dissertation. In Chapter II, I present the research that was completed within the Nutrient Network (NutNet) framework at the Sevilleta, New Mexico. Here we showed that vascular plants respond positively to nutrients and consequently outcompete biocrusts for space. Chapter III represents the potential negative effects that nutrient deposition can have on nitrogen fixation of biocrusts. This study was done at the Jornada Basin Long-Term Ecological Research site in southern New Mexico. We also determined that encroaching shrubs were responsible for contributing more fixed nitrogen to the landscape compared to biocrusts, at least prior to the monsoon season. Chapter IV demonstrates the negative effect that livestock trampling has on the cover and function of biocrusts. We did this study at the Santa Rita Experimental Range in southern Arizona. We found that biocrust cover increased with increasing distance from watering holes within a piosphere framework. Chapter V illustrates the effects of elevation and soil parent material on biocrust cover and enzyme activity. This study was done between Phoenix (low elevation) and Flagstaff (high elevation) (open full item for complete abstract)

Committee: David Ward (Advisor) Subjects: Biogeochemistry; Biology; Ecology; Geology; Plant Biology

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

Land managers across the Appalachian region have been dissatisfied with the progress of native temperate forest regeneration on surface mines reclaimed under Surface Mining Control and Reclamation Act of 1977 (SMCRA) protocols. These sites are commonly colonized by invasive plant species and have inadequate soils. Many of the nearly 50 former surface mines located within Cuyahoga Valley National Park (CVNP), Ohio, underwent reclamation following SMCRA protocols as an effort to restore native forest habitat, but park staff have also found succession to occur at a far slower rate than originally anticipated. While many studies have been conducted on acidic coal mines, reclaimed sites in CVNP were mined for non-coal resources and are alkaline. Here I investigated the plant communities and soil chemistry of reclaimed surface mines in CVNP to determine the implications of SMCRA protocols on the landscape on sites with alkaline soils. First, I analyzed how vegetative communities on reclaimed surface mines at CVNP changed over a 28-year chronosequence with particular regard to woody species and invasive species. Natural succession of sites was occurring slower than park staff anticipated, as the presence of woody species did not increase significantly over time. However, this did not appear to be a result of invasive plant colonization because exotic plant presence decreased over time, pointing toward inadequate soil conditions rather than interactions among the plant community withholding the growth of woody species. Results imply that SMCRA reclamation protocols do not improve site conditions sufficiently to facilitate natural succession as a tool to return native forests to mines within the timeframe envisioned by land managers. Second, I observed the effects of early colonization of woody nitrogen (N) fixing individuals on soil nutrient concentrations and vegetative communities at the mines. I compared an invasive N-fixing species, autumn olive (Elaeagnus umbel (open full item for complete abstract)

Committee: Chris Blackwood Ph.D. (Advisor); David Ward Ph.D. (Committee Member); Oscar Rocha Ph.D. (Committee Member) Subjects: Ecology

Master of Science (MS), Wright State University, 2018, Earth and Environmental Sciences

Lake Erie experiences annual cyanobacterial harmful algal blooms (HABs), comprised mostly of non-nitrogen-fixing Microcystis, due to excess nitrogen (N) and phosphorus (P) inputs (eutrophication). Lake Erie's watershed is mostly agricultural, and fertilizers, manure, and drainage practices contribute to high nutrient loads. This study aimed to clarify the role of Lake Erie sediments in either exacerbating or mitigating conditions that fuel HABs via recycling and/or removal, respectively, of excess N and P. Sediment-water interface N dynamics were evaluated in low HAB (2016, dry) and high HAB (2017, wet spring and early summer) years. Intact sediment cores and overlying water were collected in the western basin of Lake Erie during the ice-free seasons in 2016 and 2017. Cores were incubated in a continuous-flow system with either no isotope addition (unamended control), a 15NO3- tracer, or a 15NH4+ tracer to help distinguish between N sinks (denitrification and anammox), N links (e.g., DNRA), and N sources (N2 fixation). Sediments were a net source of NH4+ (29.4 ± 7.41 μmol N m-2 hr-1) and ortho-phosphate (2.19 ± 0.52 μmol P m-2 hr-1) to the water column across all sampling sites and times. Net N2 fluxes reflected net N2 fixation (i.e., N2 influx) in spring 2016 and 2017, then switched to net denitrification (i.e., N2 efflux), the primary N removal mechanism, later in the season. On average, western basin sediments were a net N sink (-77.6 μmol N m-2 hr-1), suggesting that the sediments perform a valuable ecosystem service. Extrapolated to the entire western basin surface area, and considering Maumee and Detroit River discharges, western basin sediments can remove approximately 28.9 percent of the average annual total N load. However, denitrification rates were lower during the more severe bloom year (2017) than in 2016, suggesting that large blooms, similarly to high N loading, can inhibit the capacity of sediments to perform that ecosystem service. To mitigate HABs (open full item for complete abstract)

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

Master of Sciences, Case Western Reserve University, 2018, Chemical Engineering

The industrial production of ammonia is a vital but energy intensive process. Promising alternatives to the costly Haber-Bosch process include the utilization of the enzyme nitrogenase in protein-engineered electrochemical systems. Preparation of pure molybdenum-dependent nitrogenase from the bacteria Azotobacter vinelandii is reported in this thesis. An attempt to incorporate the CRISPR-Cas9 system in A. vinelandii to streamline the process of genetic modification in A. vinelandii is also reported. Specifically, a technical approach was created to test the suitability of the pCRISPR-pCas9 system in A. vinelandii, and initial results are reported that provide evidence that the plasmid pCRISPR is suitable for replication within A. vinelandii. A curriculum featuring molecular cloning in Escherichia coli was developed for the Widening Opportunities for Women in Science Program, and survey results from this program were analyzed to reveal that it was successful in heightening female high school students' awareness and interest in chemical engineering.

Committee: Julie Renner (Advisor); Harihara Baskaran (Committee Member); Heidi Martin (Committee Member) Subjects: Chemical Engineering

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

Chapter 2 Abstract: Anthropogenic changes in the availability of nutrients in freshwater systems can affect the growth and composition of the cyanobacterial community through changes in biological processes. Limitations on these biological processes are used to develop management plans for reoccurring algal blooms. Nitrogen fixation is a biological process that converts inert dinitrogen gas into biologically available ammonium. In freshwater systems, certain cyanobacteria possess this ability to fix nitrogen, giving them an advantage under nitrogen-poor conditions. Nitrogen fixation and cyanobacterial growth could be limited by phosphorus, but pollution has often created situations where phosphorus is in excess. The process of nitrogen fixation is also dependent on the presence of multiple micronutrients, which are involved either as cofactors or in maintenance of cells. This dependence on micronutrients leads to the question of whether micronutrients could limit nitrogen fixation and cyanobacterial growth when phosphorus is abundant. To investigate the response of nitrogen fixation rates to micronutrient enrichment, I conducted macronutrient (phosphorus) and micronutrient (iron, boron, molybdenum) addition bioassays using water samples collected from 8 field sites in northern Ohio. In 5 of the 8 sites sampled, nitrogen fixation rates were significantly increased by additions of phosphorus. Micronutrient limitation was only observed in 1 of the 8 sites, with the molybdenum addition further increasing rates of nitrogen fixation. If micronutrient limitation on nitrogen fixation rates is absent or rare in northern Ohio, nitrogen fixation may serve as a hinderance in nitrogen control practices for the reduction of cyanobacteria growth within freshwater systems. Chapter 3 Abstract: The ability to detect low rates of nitrogen fixation in freshwater systems may differ depending on the method of analysis used. A traditional technique to measure aquatic nitrogen fixatio (open full item for complete abstract)

Committee: Darren Bade Dr. (Advisor); Mark Kershner Dr. (Committee Member); David Costello Dr. (Committee Member) Subjects: Ecology

Doctor of Philosophy, Miami University, 2015, Ecology, Evolution and Environmental Biology

The goal of my dissertation was to understand how phytoplankton, specifically cyanobacteria respond to the individual and interactive effects of land use change and climate change. Chapter 1: Climate and land use interactively affect lake phytoplankton nutrient limitation status. Climate change models predict more frequent and intense summer droughts and precipitation events, which could modify the rates and ratios at which nitrogen (N) and phosphorus (P) enter lakes. However, watershed land use also determines nutrient run off. I found that phytoplankton in lakes with forested watersheds were consistently N-limited. While, phytoplankton in lakes with agricultural watersheds were typically P-limited, they switched to N-limitation during drought. This interaction suggests that droughts would increase the incidence of N-limitation and likely impair valuable ecosystem services. Chapter 2: Increased light and gizzard shad excretion maintain high phytoplankton biomass in a eutrophic reservoir despite watershed management. Conservation tillage aims to control soil and fertilizer loss from agricultural fields with the added benefit of reducing nutrient run-off into nearby lakes. With a 20 year dataset I found that chlorophyll increased following conservation tillage as a result of decreased light limitation (less sediment) and increased internal nutrient cycling by a dominant detritivorous fish. Chapter 3: Phytoplankton community composition, reservoir morphometry, and nutrient concentrations predict microcystin concentrations. Cyanobacteria toxins are a primary concern of eutrophication management but efforts to predict toxin concentrations have implicated numerous physical and chemical variables. I found that shallow reservoirs with high internal nutrient cycling had elevated toxins, implicating lake morphometry as a driver of water quality. Chapter 4: Abundant nitrogen not nitrogen limitation promotes cyanobacteria and microcystin. The importance of nitroge (open full item for complete abstract)

Committee: Michael Vanni J (Advisor); Maria Gonzalez J (Committee Member); Thomas Crist O (Committee Member); Martin Stevens H (Committee Member); Rachael Morgan-Kiss M (Committee Member) Subjects: Aquatic Sciences; Biogeochemistry; Ecology; Limnology

Master of Science (MS), Wright State University, 2010, Biological Sciences

Herbivorous fish negatively impact algal biomass and promote the growth of cyanobacteria. In nutrient poor conditions that sustain high levels of productivity nitrogen fixing cyanobacteria can supply up to 28% of the available nitrogen (Higgins et al. 2001) We investigated the role of grazing fish in sustaining high levels of productivity in nutrient poor conditions. We used the grazing minnow, Campostoma anomalum, and the acetylene reduction technique in a controlled environment to analyze rates of nitrogen fixation and primary production by the periphyton. Fish grazing reduced algal biomass and promoted the growth of cyanobacteria but had no impact on overall rates of primary production and nitrogen fixation. Previous research on the impact of fish grazing on nitrogen fixation is minimal but contradicts our results, showing a need for future studies (Wilkinson and Sammarco 1983).

Committee: Yvonne Vadeboncoeur PhD (Advisor); Thomas Rooney PhD (Committee Member); John Stireman PhD (Committee Member) Subjects: Biology

Doctor of Philosophy (PhD), Ohio University, 2006, Biological Sciences (Arts and Sciences)

A spontaneous Phaseolus vulgaris mutant was isolated that selectively restricts nodulation. This recessive mutation exhibits a phenotype that has never been seen before with beans and is a perfect tool to study the symbiotic relationship and the associated signaling molecules between legumes and Rhizobia. The goal of this dissertation was to characterize the mutant bean's morphology and nodulation capacity. Rhizobial screening was done to examine how many different strains of Rhizobia were able to nodulate the mutant bean. The bean was examined for phenotypic characteristics and then examined for how the mutation was affecting nodulation. This was done by using green fluorescently labeled bacteria to visualize steps in the nodulation process and by chemical isolation and characterization of the signals involved in forming the symbiosis. This research also examined the overall competitiveness of strains with the ability to nodulate the mutant bean. A final experiment used Tn5 mutagenesis of USDA 2669 to determine if any novel signaling molecules were present in the excluded strain. It was determined that the mutant P. vulgaris had no deleterious phenotypic characteristics and that three strains of Rhizobia, USDA 9017, USDA 9032 and USDA 9041, had the ability to nodulate the mutant. It was also demonstrated that the mutation blocked nodulation before the formation of infection threads and therefore was affecting the plant's perception of the bacterial signal.

Committee: Allan Showalter (Advisor) Subjects: Biology, Molecular

Master of Science, Miami University, 2010, Botany

Members of the genus Nostoc are the most commonly encountered cyanobacterial partners in terrestrial symbiotic systems. The objective of this study was to determine the taxonomic position of the various symbionts within the genus Nostoc, in addition to examining the evolutionary relationships between symbiont and free-living strains within the genus by analyzing the complete sequences of the nitrogen fixation (nif) genes. NifD was sequenced from thirty-two representative strains, and phylogenetically analyzed using the Maximum likelihood and Bayesian criteria. Such analyses indicate at least three well-supported clusters exist within the genus, with moderate bootstrap support for the differentiation between symbiont and free-living strains. Our analysis suggests 2 major patterns for the evolution of symbiosis within the genus Nostoc. The first resulting in the symbiosis with a broad range of plant groups, while the second exclusively leads to a symbiotic relationship with the aquatic water fern, Azolla.

Committee: Susan Barnum PhD (Advisor); Hank Stevens PhD (Committee Member); Nancy Smith-Huerta PhD (Committee Member) Subjects: Biology; Botany; Microbiology

Master of Science, Miami University, 2007, Botany

Nitrogen fixation is randomly dispersed throughout prokaryotic lineages, raising the question of its evolution by vertical descent vs. lateral transfer. In this study, the nitrogen fixation gene, nifD, was examined for cyanobacteria. Nucleotide sequence data of nifD from nitrogen-fixing nonheterocystous and heterocystous cyanobacteria was used to generate a phylogenetic tree. The nifD phylogeny was visually compared to 16s ribosomal DNA phylogenies to elucidate the evolution of nifD within the cyanobacteria. It appears that the inheritance of nifD is through vertical descent for most cyanobacteria, with the exception of a possible lateral transfer in Anabaena variabilis. The phylogeny of nifD also provided additional insight into the evolution of the cyanobacteria, supporting previous suggestions that the heterocystous lineage arose from within the nonheterocystous cyanobacteria. The data further corroborates previous data that the nonheterocystous cyanobacteria subsections and genera are polyphyletic suggesting the need for the possible revision of the current classification.

Committee: Susan Barnum (Advisor) Subjects: