Honors College Theses

Publication Date



Biology (B.S.B.)

Document Type and Release Option

Thesis (open access)

Faculty Mentor

Dr. Risa Cohen


Bacterial communities persist longer in sediment than in the water because sediments offer beneficial conditions for proliferation and formation of self-sustaining colonies. However, environmental- and human-caused sediment disturbance may resuspend bacteria in the water, thus increasing the potential for harmful bacterial to interact with humans and other organisms. I tested the hypothesis that the level of sediment disturbance affects the abundance and duration of bacterial resuspension in artificial stream microcosms. Three treatments were administered: control (no disturbance), low intensity disturbance, and high intensity disturbance (n=5). Water samples were collected before disturbance treatment (P), and at 0, 6, 24, 48, and 72 hours after treatment. Bacterial abundance in the water was compared using two counting methods – traditional heterotrophic plate counts (HPC) and a new method using flow cytometry which takes less time than HPC. Water quality measurements at each sampling time point included temperature, turbidity, dissolved oxygen (DO), conductivity, and pH. Elevated turbidity immediately following disturbance demonstrated sediment resuspension in the water column, but there was no corresponding difference in bacterial abundance across treatments. Bacterial abundance using HPC was positively correlated with abundance using flow cytometry, suggesting flow cytometry might be useful as a rapid method for measuring bacterial abundance. Abundance using both measures changed over time, likely because high temperatures led to bacterial proliferation in all treatments. Therefore, the effects of sediment disturbance on total bacterial resuspension in the water may be obscured by higher temperatures in warmer seasons, but may influence bacterial abundance following sediment disturbance in cooler temperatures.

Included in

Biology Commons