The Effect of Salinity on the Survival Rate of  Daphnia pulex
Researched by Lacey T. 2000-01	PURPOSE  HYPOTHESIS  EXPERIMENT DESIGN  MATERIALS  PROCEDURES  RESULTS  CONCLUSION  RESEARCH REPORT  BIBLIOGRAPHY  ACKNOWLEDGEMENTS ABOUT THE AUTHOR

The purpose of this experiment was to determine the effect of salinity on the survival rate of daphnia.

I became interested in this idea because daphnia and other micro-animals are fed on by many creatures. Today, many rivers continue to become more and more salty due to irrigation and pollution. This made me wonder if micro organisms will continue to survive.

The information gained from this experiment will benefit people who depend on fish for food or employment. Micro organisms are important in the food chain for fish.

My hypothesis was that as salinity increases, the survival rate of the daphnia would decrease over a period of 24 hours.

I base my hypothesis on The World Book Encyclopedia article, "Water Flea" written by P. A. McLaughlin, which states "Daphnia live mostly in fresh water ponds and lakes," So it seems they are normally found in low salinity levels.

The constants in this study were:

•  Amount of liquid daphnia are in
• Temperature of liquid
• Temperature of lab 
•  Type and number of daphnia 
•  Size of experimental container
•  Source of liquid
• Time daphnia are in salty conditions

The manipulated variable was the amount of salt added to the water.

The responding variable was the number of living daphnia.

To measure the responding variable I looked at the daphnia under a jeweler’s loupe and determined the survival rate for each group by counting the number of daphnia with a visible heartbeat.

1. Gather materials
2. Label  Cups and petri dishes A-F
3. Combine 1 cup water with 6 tbsp. of salt in measuring cup
4. Microwave 30 seconds
5. Stir well 
6. Repeat  steps 4-5 four times
7. Add one cup of water to the mixture and stir until most of the salt is dissolved
8. Measure 200 ml and pour in Cup A
9. Take 100ml of mixture A and move to cup B
10. Add 100ml water to cup B so it is equal to 200ml of water
11. Repeat steps 5-6 except use appropriate cups and stop with cup E.
12. Fill cup F with 200ml; make sure that each cup has sat for 45 minutes before starting experiment.
13. Apply 20 daphnia to each Petri Dish; 5 in each divided section
14.  Pour 40ml of mixture A into petri dish A(10ml per section)
15. Let sit in different salinity levels for 24 hours
16.  Observe in dish with  jeweler’s loupe
17.  Determine either living or deceased by checking to see if there are signs of life 
18. Record data
19. Repeat for trial 2

The original purpose of this experiment was to determine the maximum amount of salinity possible that daphnia ‘s survival rate would not decrease. 

The results of the experiment were that as salinity levels increased, the survival rates decreased at a rapid rate.

See the table and graphs.

My hypothesis was that as salinity increases, the survival rate of the daphnia would decrease.

The results indicate that this hypothesis should be accepted.

Because of the results of this experiment, I wonder if I tried different types of salt, if it would change the outcome of this experiment. I also wonder if I were to put more daphnia in container if that would change the results or if I would have started out with all young daphnia and raised them myself until they were at a mature age for the experiment.

My findings should be useful to many ocean employees or people who are involved with the industry, because seeing as how industry is indeed the biggest consumer of water, when the water is to salty even for animals that live within it, what will become of the industry? Most likely, at that point, it will be extremely hard to farm and produce the needed products of the world. When it becomes to salty to even grow crops, and then we must face the fate of cows and other livestock who’ve relied on industry for food.

If I were to conduct this project again I would not only test different amounts of salt, I would test different types to see if that would make any difference based on ingredients included in the product. I would try putting more daphnia in an experimental group so that not only would I see if the population being less would make a difference, but I would also see if the culture being more heavily populated would make a difference. I would most definitely run more trials and look for different sources of daphnia. By collecting daphnia from different areas, it would help to show my results accurate for daphnia worldwide.
 

RESEARCH REPORT INTRODUCTION  Daphnia are a very important part of the food chain. Daphnia are eaten by fish, which are caught, cleaned, sold, and eaten as well.      DAPHNIA PULEX   Daphnia are small mostly freshwater crustaceans. Some people know them as a "water flea". They move in short jerky motions, this is how they got their nickname. There are different types of daphniidae all over the world. The two types that are the most varied and the biggest food source for young and adult freshwater fish are moina and daphnia. Moina are the species of daphniidae used in culture the most often. Daphnia produce a brood of eggs every 2 to 3 days. Some say that within 60 days, 13 billion eggs are produced. The freshwater daphnia feed mostly on Bacillus coli, Euglena, chilomonas, and smaller green alge. The daphnia predators include fish, hydra, tadpoles, and larva salamanders. There are many different experimental studies that can be performed with these crustaceans.  Such experiments can be done in areas that include physiological, macological, and biochemical. There are different types of daphnia such as magna and pulex.  The sizes vary with daphniidae species. Moina, when newly hatched, are slightly bigger than baby brine shrimp, and twice the size of an adult rotifer. Newly hatched daphnia are twice the size of Moina.  Daphnia have both reproductive and nonreproductive stages. Groups of daphniidae mainly consist of females that are asexual. This however, is only in most environments. In the best conditions, a female will lay brood of 100 eggs every 3 days. Some females will even brood as many as 25 times in a lifetime, although the average is only about 6. A female will brood at four days of age, and lay 4 to 22 eggs. Under lesser conditions males are produced and sexual reproduction begins. The result is laying resting eggs. It’s triggered by the lack of food, low oxygen supply, high population density, or low temperatures.  The daphnia’s nutritional needs are different depending on age and what they’ve eaten in the past. Adults have higher fat content than that of a juvenile.  A live moina is made up of 95% water, 4% protein, 0.54% fat, 0.67% carbohydrates, and 0.15% ash. Fishfry need the fatty acid composition for survival and growth. Although all daphnia have needs, each species may have different ones. Freshwater daphnia obviously need freshwater, although some daphnia can be found in slightly salty water. Some daphnia have been seen in salinities of up to 4ppt. Salinities of 1.5 to 3 ppt. are common in pond cultures in the orient.  Daphnia are usually able to live in poor water quality and dissolved oxygen levels range from close to zero supersaturation. Survival in oxygen poor environments is possible. It is the ability of the daphnia to synthesize hemoglobin. High temperature and population promote hemoglobin. Daphnia also despise fine air bubbles.  Daphnia can stand limited ranges of pH and ammonia. The pH level can range between 6.5 and 9.5. High ammonia levels mixed with high pH levels result in low reproduction rates. This is the only side effect and doesn’t harm the animals otherwise. This means that measuring the pH and ammonia is not vital.  Daphnia like having a lot of room to roam. They dislike the disturbance of ionic composition in their habitat. With salts like sodium, potassium, magnesium and calcium, it crowds the area of environment. With low concentrations of phosphorus, reproduction is sped up greatly. It is important not to use concentrations higher than 1.0 PPM; it causes harm to the young. Magna have the ability to resist phosphorus and can survive with 5 to 7 PPM.  Nitrogen hasn’t any effect on daphnia, so be sure to treat the water with de-chlor before starting a culture. Amazingly, just by 0.01 PPM copper, the movement will decrease.  The daphnia are really sensitive to metal ions, for instance, copper, zinc, pesticides, detergent, bleaches and dissolved toxins.  If contaminated water are used, such as sea or well water, to start a culture, it won’t be successful and kill the culture. The best source of water to use is filtered stream or lake water. Rain water will work if it is collected in a low pollutant area. Never use distilled water with a culture. Daphnia Magna can live in temperatures varying from 18 degrees Celsius to 22 degrees Celsius or 64 degrees Fahrenheit to 72 degrees Fahrenheit. Moina can survive with temperatures of 24 degrees Celsius to 31 degrees Celsius or 75 degrees Fahrenheit to 88 degrees Fahrenheit. The temperature variance is convenient for temperature changes throughout the year.  Cultures can be maintained anywhere from 2 Liter bottles to 10-gallon tanks.  If a metal tank is used to start a culture, make sure that it’s stainless steel. If a growlite bulb is used it is possible to keep indoors.   To keep the culture healthy and productive, is should be harvested daily. 0.25 or less is the amount of culture that should be harvested daily. This amount varies depending on the quality of the cultures population. There are a few ways to harvest daphnia, including netting them. Drain dead daphnia and feed to the living ones. Daphnia can survive in the refrigerator.     CRUSTACEANS  The crustacean is an invertebrate animal with many legs and a hard outer shell. Crustaceans don’t have any bones and the exoskeleton, which is the hard outer shell, covers and protects the body. Some examples of crustaceans are crabs, crayfishes, lobsters, shrimp, barnacles, waterfleas, and wood lice.  There is a great number of crustacean species spreading up to 42,000. The largest species is the giant spider crab found only in Japan. It can measure up to 12 feet (3.7 meters) long between its claws when outstretched.  Some of the smallest crustaceans, which include copepods, and water fleas, can measure up to only 1/24 of and inch (1 millimeter) long. Crustaceans are mostly found in salt water, but few live in fresh water. Some species live on land such as some types of crabs and wood lice.  Crustaceans are very important to water ecology. In most aquatic habitats small floating organisim which make up phytoplankton, are the main food producers. Many crustaceans eat phytoplankton. Then fish, larger crustaceans and sometimes-even baleen whales consume them. This forms an aquatic food chain from crustaceans to larger animals.  Crustaceans do both good and bad things for people. They provide food and they also can cause damage to a human’s property. A vessel ship could have a decreased speed due to barnacles attaching to the ship. In some tropical regions, crabs can cause harm to crops. WATER  Out of all the water on the earth, 97% is salty. People have discovered that in future water shortages distillation may be the best answer. Table salt is the same salt in ocean water. Water that has less than 0.5 kilograms salt to 100 kilograms of water is safely drinkable by a human. Seawater has about 7 times more salt. If a human drinks only seawater, death will result. It will occur by dehydration of the cells while they are trying to eliminate the salt from the seawater. Seawater also isn’t any use for agriculture or industry because of its unusually high salinity level. It would kill crops and rust machinery.   Many ways of desalting water have been discovered. It won’t solve all of earth’s problems, but may be a start. It will help to solve some and most water shortages near the sea. Earth will continually have water problems, for example, pollution, food control, and water distribution. Earth has many interesting facts about its water-containment’s. There are over one million gallons of water from all over the world. 3 percent of all of the water is fresh; water also has 3 forms that consist of liquid, solid, and gas. Top off these interesting facts, industry is the biggest consumer of water and the planet isn’t expected to use up its supply of water.  SALT .  Minerals that were dissolved in rainwater are what make seawater salty. Within minerals is sodium and chlorine. Then rivers pass down these minerals to the sea. This salt is called "solar salt". In seawater, 2.5% is salt and 1% is other minerals. Along with salt and a few other minerals, there are compounds of calcium, potassium, and magnesium. Minerals separate from seawater at different rates. Salt is one of the later minerals to separate. Once the water is completely done passing through, most of the salt is 95% to 98% sodium chloride. SUMMARY  As irrigation and pollution continue to change our earth, sometimes failure to notice what is happening to the creatures being affected by it occurs. If water continues to become salty can damage and even wipe out an important species of the aquatic and even land food chain. Daphnia have a low tolerance of high salinity levels and they are a huge part of the food chain. Without them, many species would be wiped out and closer to extinction. Each person should do his or her best to help prevent this possibly fatal result.

BIBLIOGRAPHY Research Orlans, Barbara F. Animal Care from Protozoa to Small Mammals. California: Menlo Park, 1977. Pp. 95-99 McLaughlin, P.A. "Water Flea", World Book Encyclopedia.1999. Vol. 21. Pp. 134 Dean, Walter, E. Jr. "Salt", World Book Encyclopedia. 1998. Vol. 17 pp. 72-73 Keinath, Thomas M. "Water", World Book Encyclopedia. 1999. Vol. 21 pp.127, 117,124. Schumann, Kia, Daphnia FAQ-Prototype, http://freshaquarium.about.com/pets/freshaquarium/gi/dynamic/offsite.htm?site=http%3A%2F%2Fwww.ee.pdx.edu%2F%7Edavidr%2Fdiscus%2Farticles%2Fdaphnia.html, 11-14-2000 Images Picture#1 of daphnia http://ebiomedia.com/gall/classics/Daphnia/daphnia_behave.html Picture#2 of daphnia http://www.cladocera.ca/taxonomy/daphnia/display.htm

I would like to thank the following people for their help and contributions to my science project. I feel that without their help and support, my project wouldn't be the same. First I would like to thank my parents, Jame and Kelly, for their support and advice. They help me when I was so frustrated and they inspired me greatly. 
I would like to thank Mr. Francis Sweeney, the director of the King County Environmental labs in Seattle. Without his help and generosity, my project would never have been possible without his donations of daphnia. 
I also want to thank my friends Tiera G., Vanessa W. , Heather K., Nichole A.,  Carly C., and all of my other pals. They helped me calm down and finish my project at good quality. 
To all of you who helped me, I would just like to thank you for everything that you've done for me. Thank you. 

Menu of 2000-2001 Science Projects

Back to the Selah Homepage