Date of Award


Degree Type

Honors College Thesis


Biological Sciences

First Advisor

Kevin Kuehn, Ph.D.

Advisor Department

Biological Sciences


Recent evidence has suggested that the presence of light (and in conjuction, periphytic algae) stimulates the growth and production of bacteria on decaying plant litter. However, the current method of measuring bacterial biomass, flow cytometry, drastically underestimates the bacterial biomass levels associated with litter samples. To determine and correct for this underestimation, the present study determined conversion factors using direct counting methods via epifluorescence microscopy. These conversion factors were then applied to flow cytometry counts for seven different studies. The studies analyzed the effects of light and other covarying factors on the bacterial biomass associated with various samples of leaf litter that were submerged in freshwater. In six out of the seven experiments I observed that the presence of light, and in tandem algae, positively affected litter-associated bacterial biomass. However, this relationship was likely complicated by a multitude of other factors, including time of litter decomposition, nutrient availability, temperature, and presence of other organisms, such as detrital consumers (shredders). These findings further advance the understanding of interactions between microbes associated with decaying leaf litter in freshwater environments, particularly between autotrophic periphytic algae and bacteria, and how algal stimulation of bacteria can vary with different environmental parameters.