Science Buddies: "Ask an Expert"

Hello,
I am doing a variation of the science buddies experiment: Too much of a good thing? Study the effects of fertilizers on algal growth. How can I collect a quantitative measurement of algae in water? Can I simply drain the algae and measure the mass of it on a scale in a container or should I measure it dry?? I really dont want to use any high tech lab devices for this step.... The Make it Your Own section said: to obtain quantitative measurements of the algae growth, consider the methods in this Science Buddies science fair project: Moss is Boss: Using Plants to Determine Direction. Im not really sure how this method will work. Please give advice ASAP.

sciencealgaelover123 wrote:Hello,
I am doing a variation of the science buddies experiment: Too much of a good thing? Study the effects of fertilizers on algal growth. How can I collect a quantitative measurement of algae in water? Can I simply drain the algae and measure the mass of it on a scale in a container or should I measure it dry?? I really dont want to use any high tech lab devices for this step.... The Make it Your Own section said: to obtain quantitative measurements of the algae growth, consider the methods in this Science Buddies science fair project: Moss is Boss: Using Plants to Determine Direction. Im not really sure how this method will work. Please give advice ASAP.

Hey sciencealgaelover123 (awesome name),

When ScienceBuddies specifies to use the method in "Moss is Boss: Using Plants to Determine Direction", I believe that they're asking you to take a square section of the algae-filled body of water (that you keep consistent), draw small squares within the section (basically covering that section in this: http://cdn.tidyforms.com/Download/html/ ... er/bg1.png), seeing how many squares the algae covers, and then calculating the percentage.

My advice is to take a picture of any specific area of the algae-filled body of water you're trying to measure, cover the picture with a square section of paper that has 100 small square inside (10x10 cm, perhaps), and just see how many squares the algae covers (perhaps it covers 65% of the 10x10cm). Then you could then say that this particular fertilizer (or dilution of fertilizer) caused this % of algae to grow.

Hope this helped (and made sense)! If you have any more concerns/questions, please ask away!

-JSK

Thanks for the advice! Ill try it out!
In this experiment, it also says to perform a dilution series. I can follow all the steps correctly but I am really confused about how a dilution series really works . I have researched many resources but they were not all at a beginner level for me to understand. I know that I will perform dilutions to test a range of fertilizer concentrations but I am still not sure what 1X (which will be the cup that will have 400ml of pond water in it) means for example. Could you explain what it means and a little summary of what the dilutions in the experiment are really about? This would help alot.
Thanks!

Hi,

Since the purpose of this experiment is to determine the effects of different fertilizer concentrations on algae growth, you have to use dilutions to create different concentrations of fertilizer.

The 2X dilution series means that every time you dilute the solution, the concentration of fertilizer is cut in half. The 1X solution means that it's the most concentrated solution you're using.

In the dilution procedure, each cup initially has the same amount of pond water and no fertilizer. For example, take the dilution to 0.5X. Before you begin the dilution series, there is only 200 mL of pond water in the cup, and no fertilizer. Then, you add 200 mL of the 1X fertilizer solution to the 200 mL of pond water. Since you're adding 200 mL of solution with fertilizer to 200 mL of water without fertilizer, you divide the concentration in half. When you repeat the same process for the other cups, you end up with each cup having half the concentration of fertilizer from the previous cup.

Hope this helped,
Allison

Okay, this makes more sense now.
Thanks Alison!

To make things clear, I have to collect pond water with three containers and the fourth is the 10X fertilizer solution with distilled water...Right? I will be using this for all of my trials if I'm correct. As well, in the procedure it says to repeat the procedure two more times. Should I perform all three trials all at once or should I perform each, one at a time? I feel that this will change the other two samples since maybe the algae will start growing in these containers and I need to collect the pond water at the same time since this is one of my constants. Do you have any advice?

Hi,
I collected my pond water samples and they didn't seem to have any algae in it. I decided to start growing the algae from the pond water and observing how the different concentrations of fertilizer make it grow faster, affect its growth etc.. and then I will measure the algae using the method from Moss is Boss experiment. Is it possible to grow algae from normal pond water?

Hi,

The purpose of performing several trials is to make sure that your results are consistent and about the same each time you repeat the experiment. So, for each trial, you should go out and collect new pond water each time, and you're only collecting 2 liters of pond water at once. Since you collect new pond water for each experiment, the amount of algae in the water when you first start each new trial will be about the same.

When you first start your experiment, the water may not look like it has algae in it, since individual pond algae organisms are just single cells. These cells are too small to see when they're individuals. However, once the algae starts to grow, it clumps together into larger blobs, which you can see. By the end of 10 days, there should be algae growing in your cups.

Hope this helped,
Allison

Thank you! I do now see some clumps of algae at the bottom of my cups

Hi JSK and science buddies staff,
When you said to take of square sample of the algae-filled body of water which I am going to measure, should I take a square container to put the algae in? I was growing my algae in circular shaped cups so therefore I would find it difficult to take a picture. What do you recommend? I find this a great way to measure algae and thanks for all the support!

sciencealgaelover123 wrote:Hi JSK and science buddies staff,
When you said to take of square sample of the algae-filled body of water which I am going to measure, should I take a square container to put the algae in? I was growing my algae in circular shaped cups so therefore I would find it difficult to take a picture. What do you recommend? I find this a great way to measure algae and thanks for all the support!

Hi sciencealgaelover123,

Moving the algae-filled water to a square container sounds like a good idea, as that would allow you to then divide the container surface into smaller squares for you to easily calculate the % of algae in the water! (Remember that when you're calculating %, you need to keep the area of the square in mind!)

Hope this helped,

JSK

Its been hard for me to find a container that is exactly 10x10cm though i do have one that is 9x9cm but im not sure how to calculate the percentage from that... Could I take a picture of the algae in a larger container, moving the algae present so it all fits inside the picture, then print with transparent graph paper on top and finally cut the picture so that it is 10x10cm(not cutting out any algae) and then finding the percentage?

Hi sciencealgaelover123,

Instead of using the method you described, you can still easily find the percentage from a 9x9 cm container. To find the percentage, just divide the amount covered by the total area. Below, I've included the formula for finding percent covered.

Percent covered = Number of squares covered/Total squares x 100%

For example, if you made 81 small squares in the container (since 9 times 9 is 81), and counted that 18 squares were filled with algae, the percent would be: 18/81 x 100% = 22%.

You could also just draw 100 squares in the 9x9 cm area (the side length of each square would be a little under 1 cm), and use the same method JSK described.

Hope this helped, and let us know if you have any more questions!
Allison