Science Buddies: "Ask an Expert"

Brainstorming a topic for a research project, and I wanted to identify the effect of sediment, specifically dirt, on the growth of algae in water. The topic is mainly meant to mirror the effect of riverbed erosion on bodies of water.

However, i’m struggling to figure out a way to measure the algae, without having access to expensive tools.

One of the best options would be to use a secchi stick, which determines growth based on visibility of the algae solution.

But because i’m going to be putting in dirt along with the algae, that clouds up the solution and renders the secchi stick useless.

Are there any alternatives to the secchi stick? And if not, how so should I modify my project?

Hi,

This sounds like an intriguing project, but also challenging. I will try to help, but first off, I need to know what you plan to grow the algae in. Also, 'dirt' is not a very specific term. What will you add to take the place of silt from a river?

Is your hypothesis that silt will block some of the sunlight so that the algae grows slower? The methods I am familiar with for measuring algae growth all depend on measuring the optical density (OD) of the growth medium--the more algae, the higher the OD. But any such measurement would be affected by silt in the water.

Algae produce oxygen by photosynthesis, so you could grow the algae in a bottle with a rubber stopper and a tube running through it so that you could collect the gas and measure its volume. The more algae, the more gas produced.

Send me a reply with more details about your experimental setup, and we can talk about how to do it.

Sybee