Acid Rain on the Survival Rate of Daphnia at Various pH Levels

Researched by Michelle M.
2003-04

PURPOSE
 

The 1st purpose of this experiment was to determine the effect of acid rain exposure time on the survival rate of daphnia.

The 2nd purpose of this experiment was to determine the effect of different pH levels on the survival rate of daphnia.

I became interested in this idea when we studied acid rain last year and went on a field trip in which I learned that the burning of coal is one way that acid rain forms.  

The information gained from this experiment will benefit power plant and factory owners because they will be aware of the effect of the chemicals that they are emitting into the air has on daphnia. It will also benefit automobile makers, so they can make automobiles that don’t harm the environment as much. It will affect all people, because a lower survival rate in daphnia would disrupt the food chain.

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HYPOTHESIS
 

My first hypothesis was that the survival rate of the daphnia would decrease as exposure time to acid rain was increased.

My second hypothesis was that the survival rate of the daphnia would decrease as the pH levels got more acidic.

I based both of my hypotheses on an article in World Book Encyclopedia that stated, “Acid rain harms thousands of lakes, rivers, and streams worldwide, killing fish and other wildlife. ”

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EXPERIMENT DESIGN

The constants in this study were:

  •  Amount of acid
  •  Number of daphnia in each group
  •  Temperature of water
  •  Type of water 
  •  Type of container 
  •  Shape of container 
  •  Size of container
  •  Testing procedures
  •  Amount of testing time
  •  Time of day
  •  Species of daphnia
  •  Amount of light
  •  Temperature of air
  •  Type of acid 
  •  Temperature of acid
  •  Location of testing


The manipulated variable was the daphnias’ exposure time to the acid rain.

The responding variable was the survival rate of the daphnia.  

To measure the responding variable I counted the surviving daphnia by viewing their heartbeat with a jeweler’s loupe.

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MATERIALS

QUANTITY ITEM DESCRIPTION
1 Jeweler’s loupe
8 Divided petri dishes
128 Daphnia
20 ml. 4. 5 pH Solution
20 ml. 5. 5 pH Solution
20 ml. 6. 5 pH Solution
20 ml. 7. 5 pH Solution (water)
1 Eyedropper
1 Graduated cylinder

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PROCEDURES

  I. Setting Up
1) Label each side of two petri dishes, “pH 7. 5. ” This is your control group.
2) Label each side of two more petri dishes, “pH 6. 5. ”
3) Label each side of two petri dishes, “pH 5. 5. ”
4) Label each side of the last two petri dishes, “pH 4. 5. ”
5) Add 8 daphnia to each petri dish by using an eyedropper.  

II. Conducting the Experiment
1) Pour 5 ml of the 7. 5 PH solution into each side of the two petri dishes labeled, “pH 7. 5. ”
2) Using a jeweler’s loupe, check the daphnia’s heartbeat. Count the number of living daphnia and record that number on your data sheet.
3) Pour 5 ml of the 6. 5 PH solution into each side of the two petri dishes labeled, “pH 6. 5” using a graduated cylinder.  
4) Repeat step 2.
5) Pour 5 ml of the 5. 5 PH solution into each side of the two petri dishes labeled, “pH 5. 5” using a graduated cylinder.  
6) Repeat step 2.
7) Pour 5 ml of the 4. 5 PH solution into each side of the two petri dishes labeled, “pH 5. 0” using a graduated cylinder.
8) Repeat step 2.
9) Wait 15 minutes.
10) Repeat step 2 for each petri dish.
11) Repeat steps 9 and 10 until it has been an hour since the first time you checked.
12) Wait an hour and repeat steps 9 and 10.
13) Wait two more hours.
14) Repeat steps 9 and 10.
15) Wait 4 more hours.
16) Repeat steps 9 and 10.

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RESULTS

The first original purpose of this experiment was to determine the effect of acid rain exposure time on the survival rate of daphnia.

The second original purpose of this experiment was to determine the effect of different levels of pH on the survival rate of daphnia.

The results of the experiment were that the survival rate of the daphnia decreased as the exposure time increased, but only in the group that was the most acidic. The 7. 5, 6. 5, and 5. 5 acids did not decrease the survival rate of the daphnia exposed to them. After the total 8 hours, out of eight, the average number of surviving daphnia in the 7. 5 (control) group was 8, 8 in the 6. 5 group, 8 in the 5. 5 group, and 6 in the 4. 5 group.  

See my data table and graph.

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CONCLUSION

My first hypothesis was that the daphnia survival rate would decrease as exposure time to acid rain increased.

My second hypothesis was that the survival rate would decrease as the pH levels got more acidic.

The results indicate that these hypotheses should be accepted. After one hour, one of the daphnia was dead and more died as time passed. More of the daphnia died in the pH 4. 5 group, which was the most acidic.

Because of the results of this experiment, I wonder if other pollutants such as antifreeze or oil would affect daphnia. Also, I wonder if the temperature of the liquid would affect the results.

If I were to conduct this project again I would use more daphnia and check the number of surviving daphnia over 24 hours instead of eight.

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RESEARCH REPORT

Introduction

Daphnia and other micro-organisms are important to the environment. They are a part of the food chain and are the food of many fish. When the survival rate of daphnia decreases, the fish that eat them may die as well. Acid rain is one of the causes of this.

Acid Rain

Acid rain is precipitation with a pH less than 5. 6. It can come in many different forms, such as rain, snow, sleet, hail, mist, dew, fog, frost, or dry precipitation.

Acid rain is measured on the pH scale. PH is used to measure acidity and alkinity. The pH scale ranges from 0 to 14. The higher the number, the more alkaline and less acidic it is. The lower the number, the more acidic and less alkaline it is. Seven being neutral, anything below seven is considered acidic and anything above seven is alkaline.

Acid rain is formed when sulfur dioxide and nitrogen oxide are emitted into the air. These chemicals mix with the water vapor in the air and become nitric acid and sulfuric acid. Winds carry it far from its source. This falls in precipitation. Sulfur and nitrogen oxides are emitted into the air by smokestacks, automobiles, volcanoes, smoke, forest fires, and the burning of fossil fuels such as coal, oil, and gasoline.

Actions are being taken to prevent acid rain from forming. “Scrubbers” are being put in some smokestacks. Some scientists believe that limestone will neutralize acid in water. Other ways of preventing acid rain is to use natural gas, use alternative energy sources, and conserve energy. It is also believed that adding lime to water will reduce acid. Alkaline neutralizes acid. “Buffers” can prevent lakes and streams from becoming acidic.

Acid rain harms the environment. It harms plants, animals, stone, metal, paint, soil, limestone, and water as well as water life. Healthy lakes usually have a pH between 6 and 8. If the pH is below 5. 0, most water life will die.

Daphnia

Daphnia (also called water fleas) are small crustaceans. They are used in many experiments and as fish food. They can usually be found in freshwater ponds, lakes, or rivers. Daphnia usually eat algae, bacteria, and protozoa.

There are two main types of daphnia. They are daphnia magna and daphnia pulex. Daphnia pulex are smaller than daphnia magna. Daphnia pulex males are usually 1. 5 mm long and the females are usually 2. 5 to 3. 5 mm long. Daphnia magna males are usually about 2 mm long and the females are usually about 3 to 5 mm long.

The average life span of daphnia pulex at 20*Celsius is about 50 days. The average life span of daphnia magna at 20* Celsius is about 56 days and about 40 days at 25* Celsius.

Daphnia reproduce very quickly. There is a new brood every two to three days. There are two types of eggs- “summer eggs” and “winter eggs. ” Winter eggs can lie dormant, have thicker shells, and lots of yolk. Summer eggs have thinner shells and less yolk. Sometimes there may be no males during the summer. Males may be hatched during the summer if conditions are unfavorable.  

Daphnia are less than 0. 3 millimeters long. Daphnia have a transparent shell (carapace), an oval shaped heart, a C-shaped intestine, five pairs of legs, a pointed head, leaf-shaped legs, and are pill-shaped. Their two second antennae are used to swim. The nickname “water flea” comes from their jerky swimming movement. The heart is visible and can be seen beating with a microscope. The males are smaller than the females. The head is not inside the carapace. The young look like adults, except without antennae or a carapace.

Summary

Daphnia are an important part of the environment. If many are killed by acid rain or other pollutants, it will disrupt the food chain, by starving the fish that eat them.
 


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BIBLIOGRAPHY
 

“Acid Rain,” Compton’s Interactive Encyclopedia, 1995.

Clare, John. “Daphnia Guide,” September 22, 2003. http://www. caudata. org/daphnia/#what1

Edelson, Edward. Clean Air. Chelsea House Publishers. 1992. p. 42-44

Franck, Irene and Brownstone, David. “Acid Rain,” The Green Encyclopedia. 1-3

Gay, Kathlyn. Air Pollution. USA: Franklin Watts. 1991. p. 26-32

Hart, John. “Acid Rain,” Microsoft ENCARTA Encyclopedia Deluxe 2001.

Likens, Gene E. "Acid Rain,” World Book Encyclopedia, 2002.

McLaughlin, P. A. “Water Flea,” World Book Encyclopedia, 2002. 134

Meyer, B. “Sulfuric Acid,” World Book Encyclopedia, 1999. 967, 968

Miller, Cristina G. and Berry, Louise A. Air Alert: Rescuing the Earth’s Atmosphere. New York, New York: Atheneum Books for Young Adults. 1996. 28-32

Orlans, Barbara F. Animal Care from Protozoa to Small Mammals. Canada: Addison-Wesley Publishing Company. 1997. p. 95, 96

Rose, Emily Jane. “Acid Rain,” World Book Encyclopedia, 1999. 26, 27
 


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ACKNOWLEDGEMENTS

I would like to thank the following people for helping make my project possible:

  •  My parents for helping me with my experiment and always making sure I do my best
  •  Mr. Newkirk for teaching me how to do a science project, helping me with my procedures, and providing materials for my experiment
  •  Mrs. Helms for helping me with my science project

 
 

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