Determination of iron-reducing bacterial activities in lake sediments.

Author

Alexandra KahnFollow

College

Buchtel College of Arts and Sciences (BCAS)

Date of Last Revision

2023-05-04 00:00:39

Major

Geology - Environmental Science Track

Honors Course

3370:497

Number of Credits

6

Degree Name

Bachelor of Science

Date of Expected Graduation

Spring 2020

Abstract

Algal blooms are growing rampantly in lacustrine systems due to an increase of phosphorus, a nutrient for algae. Phosphorus is being released into the environment causing overpopulation and eutrophication which damages the ecosystem. The availability of phosphorus is affected by the solubility of iron which is regulated through iron reducing and iron oxidizing bacteria. Phosphorus adheres to insoluble Fe(III), which prohibits algae from utilizing it, while phosphorus does not attach to soluble Fe(II) and therefore it remains available to algae. The purpose of this study was to determine how bacteria influence iron solubility and what are the ideal environmental conditions required for the bacteria to metabolize specific redox states of Fe(III)/Fe(II). I conducted batch experiments over a 30 day period in which the oxygen conditions varied as well as the live and sterile incubation sets. I measured the total and dissolved Fe(II) concentrations. My study revealed that iron-reducing bacteria do in fact aid in the increase of soluble Fe(II) under anoxic conditions. In oxic environments, no Fe(II) oxidation occurred. As for the total iron, all environmental conditions stayed within a small range and decreased, then increased when there was a rise in Fe(II) in anoxic conditions and decrease of Fe(II) in oxic conditions. The result indicates that total iron decreased at the beginning of bacterial metabolism of iron, and then increased when metabolism was fully active. Furthermore, the pH indicated some correlations; when iron was metabolized by iron reducing bacteria, there was a removal of H⁺ ions, hence pH increased in anoxic conditions when there was an increase in Fe(II). There were issues found in this study between the live and dead batch sets; there were no variations between the two sets which could be due to improper sterilization or residual bacteria in the sterile batch sets. This work may help improve the understanding of how bacteria control the iron solubility in lacustrine environments by identifying where iron reduction takes place. Additionally, this work may aid future studies in determining how changing iron solubility affects phosphorus levels, and if oxygenating benthic sediments can decrease the flux of limiting nutrients.

Research Sponsor

Dr. John M. Senko

First Reader

Dr. Caleb W. Holyoke

Second Reader

Dr. John F. Beltz

Honors Faculty Advisor

Dr. John A. Peck

Recommended Citation

Kahn, Alexandra, "Determination of iron-reducing bacterial activities in lake sediments." (2020). Williams Honors College, Honors Research Projects. 1060.
https://ideaexchange.uakron.edu/honors_research_projects/1060