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Effect of pH on Dissolved Oxygen and Nymphaeaceae Decay

Student(s):Gavriella Persing
Grade Level:Secondary School (grades 9-12, ages 14-18)
GLOBE Teacher:Emily Cloud
Report Type(s):International Virtual Science Symposium Report, Standard Research Report
Protocols:Dissolved Oxygen, pH
Presentation Video: View Video
Presentation Poster: View Document
Optional Badges:
Date Submitted:03/11/2021
GLOBE Water Testing measures several different characteristics of water which can determine its ability to be used for purposes such as drinking. One of these characteristics is dissolved oxygen. The pH of water can influence how effective the rate of photosynthesis and respiration are, as each process has an ideal pH based on the organism performing it. Five water samples and lily pads (Nymphaeaceae) were gathered, and each sample was modified to a certain pH level: 3, 4, 5 (original), 6, and 7. The samples were monitored over the course of 10 days, measuring dissolved oxygen levels of each sample as well as its lily pad diameter. The highest dissolved oxygen level was pH 5 (6.868 ppm), then pH 6 (4.848 ppm), then pH 7 (4.040 ppm), then pH 4 (1.616), and lastly pH 3 (0.0 ppm). Increases in dissolved oxygen could also potentially be due to photosynthesis of microorganisms living in the samples. Additionally, any mold that may have grown in the samples over time could have lowered the dissolved oxygen levels because of its own metabolic processes. The total percent change in lily pad diameter was 3.49 for pH 7, 2.36 for pH 6, 1.01 for pH 5, 0 for pH 4, and -2.14 for pH 3. Tonicity differences may have led to osmosis in the lily pads, contributing to growth. Additionally, different pH levels could have been ideal conditions for photosynthesis, increasing lily pad size.


1 Comment

Really nice report. You have nailed one of the most important aspects of presenting a research project - you described your process in such a way that another researcher can take it and reproduce the research. Well done! 

You might consider connecting the project to a broader context as well. It would help to understand the reason behind doing this research and whether it could have any implications for something (local community, global community, or in your project perhaps simply 'how to best grow lily pads' or 'how to improve water quality using lily pads' - things like that). 

I also had one question. Is there any correlation between the dissolved oxygen levels and temperature of the water samples?

Overall a very strong and thoroughly described report. And great job on doing both a poster and a video!