Lesson 3

Determining the Effects of a pH Change on the Hatching and Development of Brine Shrimp Eggs

Objectives:
Students will be able to:

Determine if brine shrimp eggs hatch and develop more readily in an environment which has an acid or a basic pH.
Evaluate the pH level which is optimal for the hatching and development of brine

Note: Safety goggles and aprons should be worn at all times during this lab activity.

Materials:
brine shrimp egg culture
Salt water
1% NaOH
1% HCl
five test tubes
pH paper, pH meter or LaMotte pH test kit
beaker or test tube rack to hold test tubes
hand lens or dissecting microscope
Petri dishes

Procedure:
Working with a partner:
1. Place a dropper of brine shrimp culture in a petri dish. Using a hand lens or a dissecting
microscope, observe the culture and describe the characteristics of a healthy brine shrimp
culture.

2. Label five test tubes # 1-5. Fill each test tube half full with salt water.
3. Find the pH of the salt water in one of the test tubes.
4. Adjust the pH of the salt water in test tubes # 1-4 by adding 1% NaOH or 1% HCL dropwise until the pH of the solutions correspond to the following:

Test tube #1 pH 12 1% NaOH
Test tube #2 pH 8 1% NaOH
Test tube #3 pH 4 1% HCl
Test tube #4 pH 1 1% HCl
Test tube # 5 Control-do not change the pH

5. Test the pH with pH paper after adding each drop of the solutions to the test tubes. Continue adding the appropriate solution dropwise until the necessary pH has been reached.
6. When the appropriate pH has been reached, add one drop of brine shrimp culture to each test tube.
7. Place the five test tubes in a test tube rack or a beaker and place in an area where they will be undisturbed for a 24 hour period.
8. Based on your knowledge of pH and aquatic ecosystems, hypothesize how the cultures will change over a 24 hour period.

Hypothesis:

9. After a 24 hour period, pour the contents of each test tube into a petri dish and observe with a hand lens or dissecting microscope.
10. Record your observations in the data table.

Data Table:

After the observations are complete, answer the following questions.

Conclusions:
1. Does the data collected support your hypothesis? Why or why not?

2. Based on your observations, what is the optimal pH for the hatching and development of brine shrimp?

3. Based on your observations, what would happen to organisms in an aquatic ecosystem if the pH increased or decreased?

4. How would this affect the aquatic ecosystem as a whole? (Consider other organisms such as macroinvertebrates and fish)

5. Research how aquatic organisms change in number and kind as an aquatic ecosystem
become acidified. Write a short paragraph explaining the effects on an ecosystem as the
water becomes more acidic.

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e-mail the author ©1998 April J. Cleveland for Science Junction, NC State University. All rights reserved. page design by Lisa Leonor Grable and April J. Cleveland URL: http://www.ncsu.edu/sciencejunction/depot/experiments/water/lessons/pH/pHlesson3.htm Last Modified: 6/8/98 | Data Depot | Science Junction | NC State University |