Lake Michigan pH compared to pH of Milwaukee’s ponds
We tested whether pH of Lake Michigan was more acidic than the pH of eight different ponds in Milwaukee, Wisconsin. We measured the pH of the water at eight locations in Lake Michigan and in eight different ponds around the Milwaukee area. We found that the pH in Lake Michigan is more acidic pH than ponds in Milwaukee area (P = 0.001).
Keywords: pH, acid, base, respiration, photosynthesis
Measuring pH determines if something is acidic, basic, or neutral by measuring how many hydrogen ions are present in a solution. If a solution is determined to be acidic, it means that it has a high number of protons or hydrogen ions in it. If a solution is determined to be basic, this means the solution has a low hydrogen ion concentration. The pH scale is a range from 0 to 14. While 7 is considered neutral, anything below 7 is considered acidic, and above 7 is considered basic. The recommended pH range for an ideal aquatic environment is 6.5 to 9.0 (Wurts & DurBorow, 1992).
Imbalances can happen in pH levels, and they have negative effects on the environment. One of the factors that can effect pH is cellular respiration. Cellular respiration occurs when plants and animals convert sugar and oxygen to energy in the form of ATP. Oxygen is produced by plants by photosynthesis. The product of this process is water and carbon dioxide. The carbon dioxide reacts with water, and this produces carbonic acid. Carbonic acid is acidic; it lowers pH levels; making the water more acidic (Wurts & DurBorow, 1992).
Sudden changes in pH levels can be fatal to the fish population, and pH can also be a determining factor to which fish can survive in a particular environment. An increase in pH increases toxicity levels of ammonia, therefore having an effect on survival rates (Wurts & DurBorow, 1992). Not only acidic environment affects fish activity, but alkaline environment affects the fish behavior as well. If fish live in an alkaline environment, their ability to excrete ammonia will decrease, and their ammonia levels in the body will increase. Ammonia is toxic to the body, and if it stays, it will alter the normal physiological mechanisms. It could affect their ability to swim, and muscle function. Some kind of fish such as perch, are able to live in an alkaline environment with a pH as high as 10, but they die if exposed to a pH level of 11 (Dawn et al., 2005).
Throughout the day, the pH differs depending on respiration and photosynthesis. After sunset, photosynthesis stops, but respiration continues (Wurts & DurBorow, 1992).In ponds where there is a lot of fish, more carbon dioxide is being produced due to cellular respiration; pH will decrease, causing the water to become more acidic. Fish cannot live where pH is too low, and therefore, respiratory acidosis will occur because of the high levels of carbon dioxide in their bodies. They will have to make up for this by raising their bicarbonate levels and decreasing phosphate levels by getting rid of them (Marten et al., 2006).
In this research my partner and I decided to measure the difference between the pH of Lake Michigan in comparison to the pH of ponds in the Milwaukee area. We hypothesized that lakes will have a pH that’s more acidic than ponds, because there are more plants found in lakes, and therefore, more cellular respiration is happening.
The collection of data started on October 15th, 2011, and ended on November 1st, 2011, during the hours of 1100-2500. We measured the pH at eight different ponds and at eight locations on the lakeshore. The first pond we went to was the pond at Jackson Park (3500 W Forest Home Ave). We had pH strips with us, obtained from the Alverno College laboratory located at 3400 S. 43rd St. We picked a location at the pond where water was within our reach. We then put one of the pH papers in the water and took it out. After 30 seconds, we compared the color to the pH comparison sheet on the pH strip package. We recorded the results in our notebook, and repeated this procedure for 7 more ponds. We chose ponds that were in the Milwaukee area, including Jackson park, Wilson Park (4001 S. 20th St.), Humboldt Park (3000 S. Howell Ave), Whitnall Park (9480 Watertown Plank Road), to a pond very close to Grant park on lake drive (100 Hawthorne Avenue), a pond in Grant park (100 Hawthorne Avenue), Pulaski park (2677 South 16th Street), and McCarty Park (2567 S. 79 St.). This was done on different days, and at different times of the day. For the lake locations, the first location of the lake that we tested was near lake drive and Layton avenue. We obtained the pH reading using the same procedure as that used for the ponds. We then had to drive 1 km away (about a half a mile) from that location to get a second reading, and we decided to drive north of the original location. We stopped where we had access to water and took our readings. This was done for another 7 locations after we drove north of the first location. The distance was controlled to 1 km by watching the car mileage. After we were done, we entered our results into Microsoft word Excel® 2010, and did a t- test that was two tailed, and type two.
There was a significant difference between the pH of lakes and ponds (fig. 1, p = 0.001). The Lake Michigan tests showed a pH that was (Mean = 5.25, S.D. = 1.03) more acidic than the pH of Milwaukee’s ponds (Mean= 7.12, S.D. = 0.83).
Fig1. pH of 8 locations on Lake Michigan compared to pH of 8 Milwaukee ponds
There was a significant difference in our data, and our hypothesis was supported. More plants are found in the lake and are therefore doing more of cellular respiration making the lake more acidic. Most of the readings were taken in the morning when pH levels are high due to the cellular respiration that happened at night. Other readings were taken in the middle of the day where photosynthesis was taking place. The times were inconsistent, because it was hard us both to be available at the same time. This was one of the limitations for our project. Also the distance between the locations on the lakeshores weren’t exactly the same, because we were not always able to reach the water at exactly one kilometer. The temperature on the different days varied also, and some days were sunny while others were somewhat cloudy. This could have affected the carbon dioxide levels. If we were to re- do the experiment, we will make sure to take the pH at the same time every day, and if possible on the same day. This might provide us with more accurate results. We also use a more accurate method to test for pH, because sometimes we had a difficult time deciding what to record for the pH based on the color. To extend on the experiment, we will test more locations, and follow the same specific criteria for each location that we will come up with.
Dawn, S., Lucas, M., Wilson, R. (2005). The effect of high pH on ion balance, nitrogen excretion and behavior in fresh water fish from an eutrophic lake : A laboratory and field study. Aquatic Toxicology, 73(1), 31-43. doi: 10.1016/j.aquatox.2004.12.013
Martens, L., Witten, P., Fivelstad, S., Huysseune, A., & Saevareid, B. (2006). Impacts of high water carbon dioxide levels on Atlantic smolts : Effects on fish performance, vertebrae composition and structure. Aquaculture, 261(1), 80-88. doi: 10.1016/j/aquaculture.2006.06.031
Wurts, W., & DurBorow, R. (1992). Interactions of ph, carbon dioxide, alkalinity and hardness in fish ponds. Southern Regional Aquaculture Center, 464, 1-4