Algae and Pollution

How does pollution affect algae?  Try this algae and pollution experiment to find out.

Before you begin this experiment get the scientific method worksheet and use this process to set up your experiment.

Collect four or more jars and add pond water to each jar to the same level. If you can actually see some larger patches of algae to scoop up, it will sure help the process to be quicker.

  1. Let it sit in a sunny spot for a week to get growing.
  2. Put some or all of these additives into the jars, one per jar:
  • 1 T. laundry detergent with phosphates
  • 1 T. laundry detergent without phosphates
  • 1 T. multi purpose fertilizer
  • ½ c. multi purpose fertilizer (use the same fertilizer as above)
  • 1 T. vinegar (to create an acidic environment)
  • ½ c. vinegar
  • one or two control jars to which nothing is added

Be sure to properly label the jars then set them in a place with warmth and sunlight for 1-2 more weeks and observe the growth.

You can observe the different amounts of growth by eye or if you want to be really accurate, strain out and weigh the algae to check the differences.

Which conditions created greater algae growth? Which created less? What does this tell you about the effect of things like fertilizer and detergent pollution? Acid rain? What affect does rampant algae growth have on a pond or a lake environment? What does too little algae growth mean for a pond or lake environment? Do you think all types of algae would respond the same way to pollutants that your variety did?

Additional Layers

  • Scientists and entrepreneurs are looking at using certain types of algae to produce bio-fuels.  Research more about this.
  • How does a city sewage system work?  How might pollutants leak from your home into ponds and lakes in your area form the city sewage?  What if you live in the suburbs or country and have a septic tank?  How can pollutants affect the area then?
  • By the end of the experiment the algae had been sitting in the jar for a couple of weeks at least.  How is the environment of the jar different from the environment in a pond?  Do you think that affected your experiment?
  • What role does algae play in the ecosystem of a pond?
  • Did you go into the experiment with expectations of what would happen?  Real scientists do too.  It’s called a hypothesis.  Good scientists don’t let their hypothesis get in the way of the truth though.  If their experiment proves them wrong they’ll change their minds.


    1. Yes, algae will survive if it is in sunlight, at least for the few days or weeks required for the experiment. Also, the details of the experiment are purposely left up to the child. Part of this lesson is learning to think independently and creatively as opposed to following a recipe.

  1. Hi there! I’m doing a research project on How pollution affects algae, and I was hoping if you could possible elaborate more on how pollution effects algae and it’s environment. Great experiment by the way!

    1. Hi Diana, there is tons of research about how algae growth is an indicator of pollution. Here is one article to get you started: There are many kinds of algae and many kinds and amounts of pollution, so the specifics will vary, but in general, as algae has specific growing requirements, you can observe how algae growth is either rampant or stunted by what is present within the water it is growing in. We recommend that you look up several scholarly journals that detail ecological experiments dealing with pollution’s effect on algae growth. This is a topic that is easy to find. Best of luck on your project.

    1. Just read the labels. They will say if they have phosphates. If they do not have phosphates they are usually labeled “phosphate free”. In some places phosphates are illegal (Washington State is one I know of) in laundry detergent, so you won’t find them on grocery shelves.

    2. If you’re still on the topic, I did a lot of looking for detergent with phosphates and I found that phosphates have been banned from detergent because they promote algae growth. This ban caused literally every company to remove phosphates from dish soap, detergent, hand soap, and basically any soap you can find. Luckily, if I did my research correctly, you can just buy trisodium phosphate (TSP) which is marketed as a “heavy duty” all purpose cleaner from home depot for about $7.

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