Date Created: July 24, 2002


The Effects of Water on the Rate of Nitrate Fixation by Heterotrophic Bacteria

 For our environmental research project, we chose to test how the levels of nitrate nitrogen produced by the heterotrophic bacteria in the soil are affected by the amount of water available to the bacteria. 

After completing biota surveys during the first half of our E.S.S.R.E. internship, we preformed t-tests to compare the data from the three different sites that we had surveyed. While comparing data, we noticed that although there are fewer bacteria in site 4 than in site 3, the bacteria in site 4 are converting nitrite nitrogen to nitrate nitrogen at a much faster rate, resulting in higher nitrate levels in site 4 when compared to site 3. After observing this pattern, we compared the physical characteristics of the two sites in an attempt to determine why the bacteria from site 4 fix nitrogen at a significantly faster rate than the bacteria in site 3. Upon examination of the two sites, we found that the sites differed physically in areas such as amount of sunlight that reaches the each site, species of dominant vascular plants and availability of water. We decided to investigate whether or not the difference in water availability between the sites is causing the difference in the rate the bacteria can fix nitrogen. We then hypothesized that heterotrophic bacteria can convert nitrite to nitrate faster when water is abundant, resulting in the higher nitrate levels we observed in the wet environment in site 4 when compared to the dry environment in site 3. 

 We spent the second half of the internship collecting soil samples from the two sites, some of which had been manipulated by the addition of water to compensate for the lack there of in site 3, and testing the soil samples for levels of nitrate nitrogen and heterotrophic bacteria.  This website contains more details and information on our experiment including an in depth procedure, our suggestions on how to improve the experiment if you should wish to perform it, as well as several external links related to our experiment.  If you are left with any questions or comments, please feel free to contact us at the address provided. 




  Sample Data and Explanations


 Trouble-Shooting Suggestions

 External Links

 Bibliography and Acknowledgements

This research project was performed by Laura Campochiaro, Jenna Rogers, Anna Sick and Mariel Torres, in association with the Environmental Science Summer Research Experience for Young Women at Roland Park Country School in Baltimore Maryland. If you have questions about our site, please contact David Brock, the program director, at Brockda@RPCS.ORG.