Master of Science (MS), Bowling Green State University, 2005, Biological Sciences

Microorganisms perform important roles in elemental cycling and organic decomposition, which are vital for ecosystems to function. Lake Erie offers a unique opportunity to study microbial communities across a large environmental gradient. Lake Erie consist of three basins and is affected by allochthonous inputs of dissolved organic matter (DOM) that increase to the west. In addition, the Central Basin of Lake Erie is characterized by an area dominated by a Dead Zone, which experiences periodic hypoxic events. To evaluate patterns of microbial diversity, environmental samples from eleven sites were selected for PCR amplification, cloning and sequencing of 16s ribosomal DNA genes from microbial species. Samples included inshore sites from the Western, Central and Eastern Basins as well as from the Dead Zone. Characterization of environmental DNA sequences was performed through sequence database searches and phylogenetic analyses. Biodiversity indices and measures of sequence diversity were obtained. Results from this study demonstrated considerable levels of spatial variability of microbial communities throughout Lake Erie. Characterized species included bacterial groups with diverse metabolic capabilities and key members involved in the cycling of nutrients. The relative preponderance of Gammaproteobacteria in the Western and Central Basins, but not in the Eastern Basin, may reflect the presumably widespread carbon substrate range found in the Western and Central Basins due to the greater number of allochthonous inputs. East and Central Basins showed similarities in species diversity, while the Dead Zone represented the most distinct group. These results are consistent with the idea that microbial community structure may be modulated by DOM inputs and environmental conditions.

Committee: Juan Bouzat (Advisor) Subjects: