Date of Award


Degree Type

Honors College Thesis


Biological Sciences

First Advisor

Kevin Kuehn, Ph.D.


This study was conducted to determine whether or not periphytic algae influence the heterotrophic activity of microbial organisms within decaying plant litter. The study utilized experimental stream mesocosms, which were either exposed to natural sunlight or covered with an opaque cloth to prevent light from entering. Standardized leaf discs of Liriodendron tulipifera (tulip poplar) and Quercus nigra (water oak) were placed in the stream and periodically collected over 43 days. Sample leaf discs were returned to the laboratory for determination of the growth and production rates of litter-associated algae, bacteria, and fungi. Additional leaf litter discs were also collected for determination of litter mass loss, litter nutrient contents, and litter-associated biomass of algae, bacteria and fungi. Due to time constraints and laboratory analytical issues, only a small set of the analysis was performed by the time this thesis was submitted. Hence, only a subset of data is presented. Field manipulation of light in experimental streams had a major impact on litter-associated microbial communities. As expected, algal biomass (chlorophyll a) on decaying litter L. tulipifera and Q. nigra increased significantly (p14C-acetate incorporation) were ~8 fold higher, compared to corresponding litter samples that were incubated under dark conditions. Litter associated fungal biomass showed an opposite effect with ~4 fold higher fungal biomass observed on litter incubated under dark conditions. No significant difference in leaf disc mass was observed between the two treatments. Although this thesis presents just a small portion of the data collected, it does demonstrate that periphytic algae can influence the metabolic activity of heterotrophic fungi. Future efforts will be focused on completing the remaining analyses and determining patterns of litter mass loss rates between treatments.

Available for download on Tuesday, March 02, 2219

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