This investigation was conducted to answer the question, how does the pH level of water affect the rate of photosynthesis in Egeria densa? To carry out this investigation, a pH meter was used to measure the initial pH of the water in three beakers, and then different amounts of lime water and elemental sulfur were added to each beaker to adjust the pH of the water. Egeria densa was then added to each beaker, and the volume of oxygen released was monitored for an hour. Analysis of the data concluded that Egeria Densa has a wide tolerance for pH levels ranging from 6.5 to 10, with the optimum at pH 8. This research is important, as it can be used in the manufacturing of fertilisers, and is relevant to globalisation, sustainability and economics. As a student I'm from a farming community, and so I am interested in pursuing this research question further to see if the results are replicable in natural settings.

Independent Variable: pH of the water. 

• It is measured in pH units. 

• The apparatus used to measure the pH of the water is a pH meter. 

• The main problem in measuring/changing the pH is that the pH meter needs to be calibrated to ensure accuracy of the readings. 

• The range of values that can be expected in this experiment for the independent variable is between 6.5 and 8.5, as this is the range of the pH of the water that the Egeria densa can survive in. 

Dependent Variable: Rate of photosynthesis. 

• It is measured in ml of oxygen released per minute. 

• The apparatus used to measure the rate of photosynthesis is an inverted measuring cylinder in water. 

• The main problem in measuring this variable is that the measuring cylinder needs to be positioned correctly so that it is able to measure the volume of oxygen released accurately. 

Control Variables 

• The amount of light available to the Egeria densa. To keep the amount of light available to the Egeria densa constant, the experiment should be conducted in a room with the same light intensity throughout the experiment

• The temperature of the water. To keep the temperature of the water constant, the experiment should be done in a room with a constant temperature and the water should be stirred regularly during the experiment

• The amount of Egeria densa in the water. To keep the amount of Egeria densa in the water constant, the same amount of Egeria densa should be added to each container

• The amount of lime water added to the water. To keep the amount of lime water added to the water constant, the same amount of lime water should be added to each container.

1. Begin by calibrating the pH meter.

2. Fill six beakers with the same amount of water and label them. 

3. Measure the initial pH of the water in each beaker using the pH meter. 

4. Add different amounts of lime water and elemental sulfur to each beaker to adjust the pH of the water in each beaker. 

5. Add the same amount of Egeria densa to each beaker. 

6. Place an inverted measuring cylinder in each beaker and record the initial volume of oxygen in each beaker. 

7. Place the beakers in an area with the same light intensity. 

8. Stir the water in each beaker every 10 minutes and record the volume of oxygen released. 

9. Monitor the volume of oxygen in each beaker for an hour. 

10. Calculate the rate of photosynthesis for each beaker by dividing the total volume of oxygen released by the time taken.

Limitations

1. The pH of the beakers may not be accurately measured due to the limited accuracy of the pH meter.

2. The light intensity in the area may not be the same for all beakers, as not all beakers may be exposed to the same amount of light.

3. The stirring of the water in the beakers may not be consistent, as the beakers may be stirred with different amounts of force.

Effect on Results

1. If the accuracy of the pH meter is limited, then the results will not accurately reflect the pH of the water in each beaker and the data collected may not be reliable.

2. If the light intensity is not the same for each beaker, then the rate of photosynthesis in each beaker will not be consistent and the data collected will be affected.

3. If the stirring of the water in the beakers is not consistent, then the data collected will be affected as the oxygen released in each beaker will not be evenly distributed.

Possible Improvements

1. Use a more accurate pH meter to measure the pH of the water in each beaker.

2. Place the beakers in an area with controlled light intensity.

3. Use a stirrer to stir the water in each beaker at a constant speed.

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