6e02d72e10204c7fa9ec8b734f3bf3fe
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### Measuring amount of algae in water

I am currently working on my 8th grade science fair project on What Effect Does Detergent Have on Algae? To do this, I am growing algae cultures. Thing is, I need to begin with the same amount of algae each time I start growing a culture, and I need to measure how much algae is in the culture after several days. I am unsure how I should accurately measure the amount of algae. Please help.

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### Re: Measuring amount of algae in water

Hello!
For the project, given its technical limitations, you can utilize the turbidity of the medium in which your algae is growing.

1 - Initially you need to cultivate a standard sample from which the aliquots will be withdrawn. The tube with the initial culture must reach a turgid state.
2 - This tube will be stirred until homogeneous.
3 - With the homogenous solution, you should withdraw, with the help of a syringe, a standard amount (1 ml for example) to cultivate in other tubes. So you will have a medium accuracy on the amount of algae you are pulling out of the starter tube.

To increase the relevance and accuracy of your results, make at least 5 culture tubes for each condition (with detergent and without detergent). For final measurements, you can use the turgidity of culture tubes to infer the amount of algae in each tube (more turgid = more algae and less turgid = less algae).

I hope I have helped.

6e02d72e10204c7fa9ec8b734f3bf3fe
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### Re: Measuring amount of algae in water

Thank you, this really helped. However, I am not completely sure what a turgid state looks like. What is the turgidity of a culture? Also, I was planning to grow my algae in culture tubes under a plant growth lamp. About what size of tubes should I use. For my culture, I plan on adding water, brewer’s yeast, and sugar. Would I need to add anything else like plant food, and where should I get the water. Is distilled water ok?

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### Re: Measuring amount of algae in water

This link presents an image with different stages of algae growth. The turgidity of culture increases with algae growth over time. The more algae there is in the tube, the greener (more turgid) it gets.
You can use tubes of different capacities. I recommend using tubes with about 100 ml, because the bigger the tube the more solution there will be in it and thus the more time it will take to reach the turbidity.

https://cdn.shopify.com/s/files/1/1057/ ... 1511098440

6e02d72e10204c7fa9ec8b734f3bf3fe
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### Re: Measuring amount of algae in water

if I just look at the turgidity of the cultures , how will I record my results? Also, I am probably going to use 2 or 3 types of detergents, and with different quantities. Will looking at the turdigity be enough to compare all my results, and I want to start with the same amount of algae each time I grow a culture. I can’t do all of this at the same time, and by the time I start my second batch of algae cultures, the starting culture would have already grown.

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### Re: Measuring amount of algae in water

To record the results, take photos of the tubes at the same time of growth (for example, taking pictures of all 24 hours after cultivation). For each condition (different type and amount of detergent) you need at least 3 culture tubes (called replicates of the same condition). Each step needs to be done at the same time. For example, after the first culture, which will be used to recultivate in the other tubes with the different conditions, you need to take 1 ml of that homogenized initial culture and pass to the tubes to be cultured under the conditions. This needs to be done sequentially to ensure the same growth time for all conditions. This is an approximate method, you will not be able to get exactly the same amount of algae in every 1 ml of standard culture. So having at least 3 replicates for each condition will lessen the error caused by this methodology. If you want to reduce the number of tubes cultivated, decrease the number of detergents used or the different amounts of detergents.

6e02d72e10204c7fa9ec8b734f3bf3fe
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### Re: Measuring amount of algae in water

Thank you so much. Happy holidays! I probably won’t have enough flasks and plant growth lights to carry out the entire experiment at once, so I would need to split it up into 2 or 3 parts. By the time I come around for the second batch of algae cultures, the starting culture would have already grown. Is there a way I can start with approximately the same amount of algae the whole way through? Also should I do 2 detergents each with 3 different quantities or 3 detergents each with 2 different quantities?

ashleywbae
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### Re: Measuring amount of algae in water

Hello!

I would recommend sticking to one variable to focus on for your project. Rather than testing both amount and type of detergent, I would use the same amount of different types of detergent. This will make your results clearer and easier to interpret.