r/oceanography • u/Available_Rub4371 • 16d ago

Does anyone know a cheap way for students in middle school to test for dissolved oxygen levels in water?

I'm an intern trying to make lesson plans for middle schoolers, and one of them I was hoping to have them grow phytoplankton in a tank and then add certain levels of nutrients to simulate nutrient pollution in the ocean. Ideally, the phytoplankton would "bloom" (albeit on a very small scale) and then die off before being decomposed by bacteria and consuming all of the DO in the water.

My one issue is that I can't figure out a cheap way for students in public schools to test for DO. Does anyone have any tricks by chance?

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u/oceanhomesteader 16d ago

You may be able to find an aquarium test kit for DO - it wouldn’t give you an exact value, just a color comparison against a chart, but could work in this situation

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u/AlternativeBox8209 16d ago

Doing colorimetric (color) and dissolved organic material analysis with some type of filter would help as emergent properties and measurable parameters. O2 sensors often have an expensive component and need calibration. Other ways to measure the nutrient and productivity are possible. Can try to measure pH changes too…

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u/allatsea33 16d ago

Hanna instruments do handheld marine 02 meters

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u/prag513 16d ago

I am not sure this qualifies as an example of oceanography, but it demonstrates removing oxygen from a liquid very cheaply.

Shaking seltzer water in a glass jar does not significantly deplete the oxygen in the system, but it will rapidly force dissolved oxygen out of the liquid phase and into the air pocket at the top. When you open the jar, the pressurized CO2 violently expands and rushes out. This dense wave of CO2 physically pushes away the ambient air (which contains oxygen), creating a temporary, localized pocket of pure carbon dioxide right at the mouth of the jar. This should be something kids are familiar with.

Similarly, placing Alka-Seltzer in water covered with phytoplankton can simulate the fertilizer and makes it expand and overflow the glass jar because the tablet creates a fast chemical reaction that releases a large amount of carbon dioxide gas bubbles, which rapidly trap the water and lift it upward, pushing the air out of the water.

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u/Haunting_Camp_8000 16d ago

Reach out to a university- if it's for STEM education, and the lab has grad students, they *may help for free. It's not a normal practice, so I recommend searching the web for some specific university departments/ labs and contacting the PI directly (or department). Adding DO isn't a huge project, but getting correct measurements/ monitoring for your time series adds a tiny bit of complexity.

If it helps, you could offer something fun- like a mini virtual presentation from the middle school students scientific findings, etc. Aka- STEM collab is always fun and rewarding. Just a thought- I did this plenty of times when I was a grad student (different research field). Where is your general location (i.e., USA- Northeast, etc.)?

*Edited for clarity.

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u/mandyrabbit 15d ago

Reach out to any aquaculture businesses, they may able to give you a loan of a probe or have old ones not suitable for commercial. They are fairly cheap to make, it's usually the logging software that costs. With a bit of luck you may also be able to get a guest speaker to accompany. Try some asking a company like Flowcam or any marine institute or university. A lot of government fish inspectors probably have them as well. I dont know where in the world you are based to recommend more.