Question

If we add carbon dioxide to green algae in a tank of saltwater, how will the plant react and will the pH/acidity levels change?

Variables

There are two variables. The independent variable is the amount of carbon dioxide. This is because we decide how much carbon to release into the water and how often we do so. The dependent variable is the pH level. The acidity or pH in the water is dependent on how much carbon dioxide absorbs into the water. 

Hypothesis

If we add carbon dioxide to the water, the pH level will decrease and the water will become more acidic. If the water becomes more acidic, the plant will photosynthesize, but eventually die from living in an overly acidic environment. 

Materials

We used a large variety of materials. These materials include:

-Water

-Aquarium salt

-Pebbles

-Popsicle sticks

-Green algae

-Carbon dioxide tank

-2 1 liter beakers

-Refugia mud

-Sand

-Salinity meter

-pH meter

-Scale

-Tweezers

Procedure

Step 1 - Add 33 g of aquarium salt to each liter of water

Step 2 - Place refugia mud in beakers and take out large pieces of rock

Step 3 - Pour about 1 inch of salt water into each beaker

Step 4 - Use a popsicle stick to distribute the water evenly

Step 5 - Scatter an even amount of pebbles on surface

Step 6 - Fill beakers up halfway with salt water

Step 7 - Plant the plants in both tanks

Step 8 - Finish filling up beakers with salt water

Step 9 - Start process of adding CO2

Step 10 - Take pictures, notes, and check pH level after every addition

Schedule for Adding CO2

5/11 - 1 second burst of carbon

5/12 - 1 second burst of carbon

5/15 - 2 second burst of carbon

5/16 - 2 second burst of carbon

5/17 - 4 second burst of carbon

5/18 - 4 second burst of carbon

5/19 - 4 second burst of carbon

Data

Starting pH of control beaker = 7.1

Starting pH of carbon beaker = 7.2

Day One:

Post Carbon = 6.3

Visual Changes: None

Day Two:

Post Carbon = 6.8

Visual Changes: None

Day Three:

Before Carbon = 7.12

Post Carbon = 7.1

Updated Control = 6.9

Visual Changes: Piece of plant came off, state of plant is not very different

Day Four:

Before Carbon = 7.4

Post Carbon = 6.9

Updated Control = 7.1

Visual Changes: Plant doesn't look as healthy, starting to get a little brown and crispy

Day Five - Part 1:

Post Carbon = 6.4

Updated Control = 7.0

Visual Changes: Plants are getting a bit darker and crispy 

Day Five - Part 2:

Before Carbon = 6.4

Post Carbon = 6.2

Updated Control = 7.0

Day Six:

Before Carbon = 6.8

Post Carbon = 6.4

Updated Control = 7.1

Visual Changes: none

Day Six - Part 2:

Post Carbon 1 hour later: 6.4

Updated Control = 7.2

Day Seven:

Before Carbon = 7.3

Post Carbon = 6.6

Updated Control = 7.3

Error Analysis:

Looking back on our project, there are a few changes we would make if we were to do this experiment again to ensure it is as accurate as possible. First, we would test the pH of both tanks before and after carbon everyday. We had done this occasionally, but a few times we did not test the pH level before carbon. This made our results less accurate because there was some missing information. Second, we would research and find a very specific way to measure the carbon. The way we did our experiment was by measuring the carbon in bursts. This is not the most exact way and therefore, our results could be more accurate.

Conclusion

 In conclusion, our project was successful. We were able to conduct an experiment in which we created a realistic environment for green algae and added carbon. The results partly proved our hypothesis but also positively surprised us.  Now we have a better idea of how we can help stop carbon pollution and keep marine life healthy.