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Stream Water testing

Postby HopePressler1 » Sun Dec 08, 2019 8:17 am

My 7 year old daughter is testing water along various places along a stream near our house. She wants to compare the different samples to see if there are different amounts of organisms in different parts of the stream. She took some initial samples and expected to see microscopic organisms. However, there were no microscopic organisms present in any of the initial samples. This seemed very strange to me.

Do you have any idea why there would be no organisms present? I was wondering if there was some sort of mistake in how she collected the water or some other variable that I am unaware of that would result in no organisms being preset.

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Re: Stream Water testing

Postby LilGreenFrog » Thu Dec 12, 2019 2:30 pm

Hi Hope, this is a fun project idea, but might be harder than it sounds. How much magnification are you using to view the samples? Many of the micro organisms present in stream water are too small, too fast, or too see-through to be viewed with a home microscope.
My next thought for you would be to look at samples of stream mud (or scrape off the bottom of a few submerged rocks) from various locations. You may have better luck finding macro-scale inhabitants, and the mud will make them move a bit slower.

If you have been using a microscope, I'd suggest shifting to a dissecting scope; it's lit from above and has a much larger area of view. It will also be essential to viewing mud inhabitants. If you/your school doesn't have one, the middle or high school in your area might, and any local college should definitely have one.

Hope this helps! I remember trying to do this in college, and seeing basically nothing. Even knowing there was a flat worm in there (other people saw it), I could never catch it with the view finder. Please let us know if this works out, and hopefully some ecologists will chime in as well.
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Re: Stream Water testing

Postby MS15 » Mon Dec 23, 2019 6:13 pm

It's a great idea to test the water quality of a stream as it runs its course and goes further away from source. LilGreenFrog has already given you some great advice. I would like to add the following points:

1. Make sure the the home microscope you are using is capable of visualizing the world of microscopic organisms that live in water (in terms of magnification). This is your control experiment - can you see them where they definitely should be present? Maybe try to use a drop of 'unclean' water (say from a puddle or a stagnant lake or even water with some soil in it after allowing the soil to settle) and check if you can spot the microorganisms there. If you can, then it would confirm that your microscope is alright but your sampling method for steam water may need to be modified.

2. If you suspect the microscope to be the issue after testing the above, it's best that you find a dissecting microscope or a good quality compound microscope as suggested. If you have access to a phase contrast microscope, that will be best as organisms that live in water tend to be transparent and hence difficult to spot with a regular compound microscope. A phase contrast microscope will increase the contrast of an organism from its background and enhance its visibility. Alternatively, you could add a very very small amount of a dye called crystal violet or gentian violet to your sample. This will stain some of the microorganisms and make them non-transparent and easy to view. But this may be complicated as the amount of the dye will matter and its difficult to get right without being able to remove excess dye from the water. I would recommend this as only a very worst case approach.

3. If you suspect that the microscope setup is fine but sampling is a problem, then maybe talk to a local ecologist. The suggestion of rocks/mud is very good- you should definitely try that. You may have to sample deeper down into the water rather than just the surface. Also keep in mind that an unpolluted flowing stream is likely to have very good quality water and fewer microscopic organisms (it's cleaner so fewer nutrients for them, plus the motion sweeps them away and doesn't allow accumulation) than stagnant water which is home to bacteria, algae, and protists among others.

If your daughter is interested in the history of science, definitely introduce her to the 17th century Dutch scientist called Antonie van Leeuwenhoek who made beautiful hand drawn illustrations of small transparent organisms that he found in water - the first reports of its kind.

Hope this helps and please reach out again if you have more questions.

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Re: Stream Water testing

Postby MadelineB » Sun Jan 26, 2020 3:47 pm

Hello HopePressler,

I've merged this question with the thread from your previous posts on this topic. Keeping these posts together helps the experts who have been helping see that you and your daughter have follow-up questions.

Thank you,

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Re: Stream Water testing

Postby HopePressler1 » Sun Jan 26, 2020 4:00 pm

I see the different posts have been put together. These are different topics. The first one was about microscopic life and the second is about characteristics of the water. I don’t want the two topics to be confused.

Thank you,

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Re: Stream Water testing

Postby AmyCowen » Mon Jan 27, 2020 8:19 am

Hi Hope - Your other student's water science project question can now be found here: viewtopic.php?f=24&t=21072 (You may need to edit the post to change the title.)

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Re: Stream Water testing

Postby cnoonan180 » Mon Apr 06, 2020 10:20 pm


A resource you may want to contact is a scientist or biologist from a nature park or preserve as these professionals are very knowledgeable about the water quality in the parks (Water quality is related to microorganisms as some chemical compounds in water can indicate more of a presence of microorganisms since some compounds serve as nutrients that microorganisms feed on, while other compounds are waste products that microorganisms have excreted similar to how plants excrete oxygen into the air while performing photosynthesis to make food. Microorganisms function in a similar way, but with different compounds.). Also, these facilities normally have records of the water quality in terms of nutrient and microbe content over the years, which if you were to take samples from a nature park, these records could serve as a guide for the types microorganisms you should be finding in the water. In my experience, professionals at nature parks do allow students to take water samples, just make sure to always ask permission first by a simple phone call or email.

Since you are taking samples from stream water which is most likely moving water, this may be a reason you are not finding any microorganisms because for example, bacteria tend to thrive in stagnant or standing water. So, the source of your water may be the problem. Always be careful when you are around or handling stagnant water, should you choose to sample it.

Additionally if you have not already, you may want to try a process called “staining” with your samples which involves adding a type of dye onto a slide where you expect microorganisms such as bacteria to be. The dye will bond to the microorganisms making it easy to see their shape and thus identify the microbes. It is extremely difficult to identify microorganisms such as bacteria without using this technique. The procedure is explained in more detail here:

https://www.sciencebuddies.org/science- ... cteria.pdf

Something else you may want to try is sampling the soil from the bottom of the stream water if it is shallow enough to reach. This is because water is less likely to move when it is contained in mud or heavier sediments that have been filtered out of the moving water above, and an abundance of microbes is generally more prominent in stagnant water, or water with little to no motion.

Hope this helps and good luck with the project!

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