The Affect of Cellular Respiration on pH levels in Lake Michigan and Silver Lake

Rebecca Romleski

Julie Dropp

Abstract

We tested the pH in the waters of Silver Lake and Lake Michigan. We took samples from 10 different sites at each lake and recorded the pH values from each location. Because plants take CO₂ out of the environment, we hypothesized that a lake with more plant life, therefore increased level of cellular respiration, will have a higher amount of CO₂ in the environment, consequently having lower pH level and making it more acidic (Carru et al., 1999). We found that the pH values between the two are significantly different (p-value= 4.81x10^-4).

Keywords: pH, lake, acidic, neutral, basic, cellular respiration

Introduction

pH is determined by measuring the amount of hydrogen ions in a chemical solution. The amount of hydrogen ions is then compared to the pH scale. The pH scale ranges from 0 to 14; 0-6 is considered acidic, 7 is considered neutral, and 8-14 is considered basic (Wurts & DurBorow 1992). The measurement of ions can be affected in a number of ways. One way is through cellular respiration. Cellular respiration is when plants and animals use sugar and oxygen as energy in the form of ATP. Oxygen is produced by plants during photosynthesis while carbon dioxide is taken in by plants to begin photosynthesis. When an environment, such as soil or water, has carbon dioxide in it, the pH level of that environment is usually of a lower pH (between 0 and 6) causing the environment to be more acidic (Wurts & DurBorow 1992). The by-product of O₂ during photosynthesis reacts with water to form carbonic acid, which will lower the pH of the water. Because of this, we hypothesized that a lake with more plant life, therefore increased level of carbonic acid, will have a lower pH.

In a large body of water, such as a lake, the pH can vary. When the water is shallower, the plant life on the bottom has access to more sunlight. Since sunlight is a reactant in the process of photosynthesis it can be said that the plant life in these areas of the lake can do a greater amount of cellular respiration (Anten & Hirose, 2001). We hypothesized that the pH levels of Lake Michigan would be of a lesser pH (more basic) than the pH levels of Silver Lake because there is more cellular respiration taking place in Lake Michigan due to the difference in size. Also, since Silver Lake is surrounded by homes, Lake Michigan is less affected by the pollutants and inhabitance of the city on its shores; the lack of city interference will allow the plant life in Lake Michigan to flourish and allow more cellular respiration to take place.

Materials and Methods

On Saturday September 29th, 2012 we collected water from 10 different easily accessible sites off shore at Silver Lake (Wautoma, Wisconsin), greater than 16m apart and placed the test water into 10 separate sterile urine specimen cups. We then completed a pH test on the water samples using a pH meter (Xplorer GLX by Pasco). Later in the same day, we completed the same process with 10 different easily accessible sites of shore at Lake Michigan (Milwaukee, Wisconsin), with the same separation requirements of 16m apart. We completed the same pH test on the water samples from Lake Michigan as those from Silver Lake. After recording our data, we placed our data in an Excel© and analyzed it using a 2-tailed, type 1 T-test on Excel© for Windows 2007©.

Results

We found that there was a significant difference between the pH level at Silver Lake and the pH level at Lake Michigan (p-value was 4.81x10^-4). The mean for Lake Michigan was 5.61, with a standard deviation of 1.14. The mean for Silver Lake was 8.32, with a standard deviation of 0.168.

Fig 1. Mean(+/- S.D.) of pH in Silver Lake and Lake Michigan.

Discussion

After completing our data analysis we found that the data did support our hypothesis that the pH levels of Lake Michigan would be of a lesser pH (more acidic) and Silver Lake would be of a greater pH (more basic). The difference between the two locations was significantly different (p= 4.81x10^-4). One limitation to our experiment was that the samples were taken from Silver Lake in the morning and Lake Michigan later in the afternoon. This could have affected the amount of sunlight each area got, ultimately affecting the level of cellular respiration and the pH level.

After this experiment we were interested in comparing different pH levels in different depths of water. Therefore, if we were to do this experiment again we would complete the experiment with the opportunity to retrieve water samples in deeper parts of the body of water. This could give us different pH readings than the offshore readings we did retrieve.

References

Anten, N.P.R. and Hirose, T. (2001). Limitations on photosynthesis of competing individuals in stands and the consequences for canopy structure. Oecologia. 129(2) 186-196. Retrieved from http://www.jstor.org/stable/4223073

Carru, A.M., Chesterikoff, A., Garban, B., Jairy, A. and Ollivon, D. (1999). The role of phytoplankton in pollutant transfer process in rivers: example of river marne (france). Biogeochemistry. 44(1) 1-27. Retrieved from http://www.jstor.org/stable/1469649

Wurts, W., & DurBorow, R. (1992). Interactions of ph, carbon dioxide, alkalinity and hardness in fish ponds. Southern Regional Aquaculture Center, 464(1-4)