Master of Science in Environmental Science, Cleveland State University, 2024, College of Arts and Sciences

Despite the critical role of organic matter (OM) oxidation in depleting oxygen in the hypolimnetic waters of Lake Erie, uncertainties regarding the sources, quantity, and fate of OM continue to challenge our understanding and management of hypoxia in the lake. This study evaluates the effects of OM oxidation through the analysis of stable carbon isotopes (δ13C) of dissolved inorganic carbon (DIC) and dissolved organic carbon (DOC) in the central and eastern basins of Lake Erie. We disclose DIC contributions from OM oxidation and provide insight into the origins of OM in the hypolimnion. Our results reveal significant declines in δ13CDIC in hypolimnetic waters compared to surface waters, indicative of OM oxidation in the deepest portions of the lake. To further examine this process, we employed the Keeling plot method to estimate the composite isotopic signature of OM respiration (δ13CR). The good agreement between the respired source (-24.4‰) and the signature of the organic material (-24.6‰) support the idea that autochthonous material (internally produced OM) fuels OM oxidation in the central and eastern basins. Additionally, a binary mixing model was utilized to quantify the amount of DIC produced and the respective amount of oxygen required by OM oxidation. We estimate that 11.8 ± 1.6 % of DIC was produced in the central basin and 5.6 ± 1.2% in the eastern basin, which accounts, on average, for 89.3 ± 7.1 % of hypolimnetic oxygen depletion in the central basin and 99.2 ± 17.7 % in the eastern basin. This suggests OM oxidation accounts for most of the hypolimnetic oxygen depletion in the lake, however instances of hypoxia in the central basin may promote other mechanisms of oxygen depletion such as oxidation of CH4, Fe2+, and Mn2+. This study reveals a strong coupling between carbon cycling and oxygen depletion in Lake Erie. Our results underscore the applicability of δ13CDIC as a meaningful tracer to quantify the amount of oxygen-consuming OM in hypolimn (open full item for complete abstract)

Committee: Fasong Yuan (Advisor); Brice Grunert (Committee Member); Julie Wolin (Committee Member) Subjects: Biogeochemistry; Environmental Science; Limnology

Doctor of Philosophy, The Ohio State University, 2012, Geological Sciences

Coral reefs are declining globally due to a combination of direct and indirect human impacts. Much of this decline can be attributed to prolonged exposure to elevated sea surface temperatures which induces coral bleaching – a process whereby corals lose their endosymbionts and/or their endosymbiotic pigments resulting in corals that appear pale or white. Corals have extremely different responses to bleaching events: some corals bleach and die, others bleach and recover, and some do not visibly bleach at all. In the absence of abundant photosynthetically fixed C, corals may rely on one or more of the following strategies to sustain themselves and promote recovery: (1) catabolize stored energy reserves, including lipids, carbohydrates, and/or proteins, (2) reduce respiration rates, (3) decrease skeletal growth, (4) increase heterotrophy or (5) shuffle or change their endosymbiont type(s). Although mounding species of coral have been shown to survive bleaching events in greater abundance than branching species, the underlying mechanism(s) for mounding coral resilience is unknown. Furthermore, controlled bleaching and recovery experiments coupled with detailed carbon budgets that incorporate autotrophy and multiple heterotrophic sources (i.e. zooplankton and dissolved organic carbon) do not exist for Caribbean corals. Therefore, two controlled tank experiments, one in Hawaii and the other in Puerto Morelos, Mexico were conducted to understand the bleaching and recovery responses in the Hawaiian coral Porites lobata and the three Caribbean corals Montastraea faveolata, Porites astreoides, and Porites divaricata. Four major findings were observed: 1) Bleaching resilience in the mounding coral P. lobata is due to it harboring a thermally tolerant endosymbiont type combined with an ability to actively metabolize zooplankton acquired C and utilize DOC as a significant fixed C source, 2) Bleached P. astreoides were capable of meeting greater than 100% of metabolic demand by i (open full item for complete abstract)

Committee: Andrea Grottoli Dr (Advisor); James Bauer Dr (Committee Member); Yo Chin Dr (Committee Member); Ozeas Costa Dr (Committee Member); Meg Daly Dr (Committee Member) Subjects: Biological Oceanography

Doctor of Philosophy, The Ohio State University, 2012, Anthropology

This dissertation uses a well-established tool in anthropology – stable carbon and nitrogen isotope analyses of human bones – to reconstruct past human diet in Poland. Bone collagen and carbonate of 32 animals and 167 human skeletons from North-Central Poland are studied. The sites studied are from Rogowo (2nd c. AD), Kałdus (11th-13th c.) and Gruczno (12th-14th c.)., all inland sites near the Vistula River, along with four isolated skeletons from the Neolithic and the Iron Age. With this sample I investigate two primary predictions: 1) stable isotope ratios increase through time, reflecting an increase in consumption of marine fish concomitant with religious and economic change, and 2) stable isotope signatures from medieval samples are more heterogeneous than those from pre-medieval samples and are related to status (as estimated by grave goods) and sex. Collagen was extracted by demineralizing cleaned, ground bone particles in hydrochloric acid, followed by a soak in sodium hydroxide to separate humic contaminants and lipids. Carbonate was purified from bone by soaking cleaned, powdered bone in bleach to remove the organic components, and then in acetic acid to remove diagenetic carbonates. Diagenesis of bone mineral was assessed through Fourier transform infrared spectroscopy. Stable isotope analyses were conducted at the Stable Isotope Biogeochemistry Laboratory in the School of Earth Sciences, The Ohio State University. Stable nitrogen isotope ratios of animals are higher than those usually reported for Europe, revealing a different isotopic baseline for North-Central Poland that may result from land management strategies such as manuring and/or burning fields. Human samples show evidence for millet consumption, a uniquely Slavic cultigen in Europe that may be useful in studying Slavic migrations. During the Roman Era, diet was terrestrial-based and included millet and some fish. At the onset of the medieval period, more fish were eaten and diet was highly v (open full item for complete abstract)

Committee: Douglas Crews Ph.D. (Committee Chair); Clark Larsen Ph.D. (Committee Member); M. Anne Katzenberg Ph.D. (Committee Member); Paul Sciulli Ph.D. (Committee Member) Subjects: Archaeology; Behaviorial Sciences; Biochemistry; Medieval History; Nutrition; Slavic Studies

Master of Science (MS), Ohio University, 2007, Geological Sciences (Arts and Sciences)

The effects of prehistoric and modern land use may be recorded in cave stalagmites and clastic sediments as variations in d13C, which describes the relative influence of C3 versus C4 plants or biological productivity. Mass spectrometry of organic material in cave sediments display fluctuations in d13Corg representing changes in floral composition/productivity at the time of deposition. I report anomalous stable isotope excursions (d13C) in stalagmites of a West Virginia cave that are temporally associated with Native American presence in the study area. I use regional climate histories, pollen data, and independent climate-driven d13C timelines to identify histories suspected of containing land use signals. Hydrologic and geomorphic responses are represented by changes in sediment characteristics and subtle grain size variations. Residual anomalies represent pre-European land use or undiscovered terrestrial processes operating within the study area. Native American land use appears to be the most attributable force affecting flora and geomorphology of the Buckeye Creek watershed since 4000 B.P.

Committee: Gregory Springer (Advisor) Subjects: Geology

Master of Science (MS), Ohio University, 2006, Geological Sciences (Arts and Sciences)

Streams are vital components of many ecosystems and link many earth and biologic systems. Understanding stream behavior is essential to understanding fluvial effects on ecosystems, however, streams are highly sensitive to climate fluctuations. Stream paleohydrologies provide insight into climate effects and extend modern stream data. Paleohydrologic studies have been successfully employed in arid climates, but rarely humid climates. Stream-derived sediments preserved in caves can potentially provide insight into the paleohydrology of humid climate streams. Two caves along the Greenbrier River, West Virginia contain well-preserved flood deposits, which radiocarbon dating shows ages as old as 4010 yrs, that have been used to create a paleoflood history for the river. Floral composition determined from δ13C values from the deposits demonstrates the response of the watershed and its response to climate change during sediment deposition. These proxies provide a means for understanding paleohydrology and paleoclimate for southeastern West Virginia during the late Holocene.

Committee: Gregory Springer (Advisor) Subjects: Geology