Population Density of Brine Shrimp (Juliana Capra)

Research Question and Hypothesis

Research question: How does salinity affect the growth rate of brine shrimp?

Hypothesis: The percentage of dissolved salt will affect the number of brine shrimp in every square millimeter.

Standards

Experimental Design

There are four 200 mL beakers filled with distilled water and salt. The percentage of salt diluted in each beaker is different. The concentration of dissolved salt is adjusted to 0%, 2.5%, 5.5%, and 7.5%. The amount of solute was determined from information found online from a collection of Brine Shrimp growing websites.

Independent variable

What is the independent variable?

• The percentage of salt dissolved in distilled water.

How will you measure the independent variable?

• Calculate the molarity or salinity level; measure the amount of salt and mix with the distilled water.

Dependent variables

What is the dependent variable(s)?

• The number of brine shrimp in every square millimeter of salt water.

How will you measure the dependent variable(s)?

• I will count how many shrimp are found in one square millimeter (graph paper mounted to the back of the beaker) and multiply the population size of one square millimeter by the number of squares in a beaker.

Series

Study the population density of brine shrimp hatchlings as a function of time at various salinity levels.

Constants and Controls

What factors are held constant?

• The factors held constant include the water temperature, volume of water, mass of brine shrimp eggs, the mass of food (dry active yeast) fed to the hatchlings, and the amount of light exposure.

What serves as a control?

• The condition in this experiment will be a beaker of water with a salinity level of 0%.

Materials

Provide a complete list of all materials needed and explain where they may be obtained.

• Four 200 mL glass beakers (or clear cups)

• Graph Paper

• Kitchen table salt (Iodized salt)

• Distilled water

• Brine Shrimp Eggs (can be purchased from Science Laboratory Equipment suppliers (such as Flinn Scientific or Carolina), pet and fist stores, or various online retailers. Make sure to find ready to hatch brine shrimp eggs NOT freeze dried eggs or brine shrimp.

  • I have found the most luck so far with the eggs purchased from YourFishStuff (claim to have a 90% hatch rate

• Measuring spoons or balance with weighing paper to measure salt and brine shrimp eggs

• Spoon or stirring rod to mix the salt with the water

• Camera to take photos of shrimp hatchlings

• Calculator

• Clear tape

Procedures

1. Cut a sheet of graph paper into fourths, so that you have enough paper for each beaker. The paper should cover approximately one side or about a third of the beaker. The paper should not cover the entire beaker. This paper will serve as a reference to count the hatchlings. Secure the graph paper to the outside of the beaker with clear tape.

2. Fill each beaker with 200mL of distilled water, the water should be at room temperature (around 75 degrees Fahrenheit or 24 degrees Celsius)

3. Add salt to the appropriate beakers

   1. Beaker 1: add 0 grams of salt. (0% salinity)

   2. Beaker 2: add 5 grams of salt. (2.5% salinity)

   3. Beaker 3: add 10 grams of salt. (5% salinity)

   4. Beaker 4: add 15 grams of salt. (7.5% salinity)

4. Stir each beaker with a clean spoon or stirring rod to dissolve the salt

5. Add 0.25 grams of brine shrimp eggs to each beaker

6. Very gently stir the eggs into the water to mix, making sure to not let eggs stick to the side of the beaker. Note: The eggs will float at the surface at first, leave these eggs alone.

7. Using a camera, take a picture of each beaker on at a time. Do not use the zoom feature on the camera as this will lower the image quality. Take pictures of each beaker at 12 hour intervals over a period of 3 or 4 days (longer if you would like to see the brine shrimp grow and develop)

8. To calculate the population density of your brine shrimp

   1. Using an image processing program (such as Google Photos or iPhoto) open the desired image and zoom in your image

   2. Choose a location on your image and zoom in on one square (using the graph paper as a reference.

   3. Count the number of brine shrimp hatchlings in the square and record the data

   4. Multiply the number from step 3 (density per square millimeter) by the number of squares on the graph paper

   5. Record data (link to a Google Sheet Template)

Sample data and graphs

Link to data set and graphs via Google Sheets

Analysis & Conclusions

Analyze the data and draw conclusions relevant to your research question and hypothesis.

Based on the data collected, overall it is evident that there is a connection to population density and the salinity level. When observing the beakers with the unaided eye one can see that there is a higher density of brine shrimp in the 2.5% and 5% salinity beakers. There are no shrimp hatchlings in the 0% salinity, and there is a lower amount of hatchlings in the 7.5% beaker. As a whole, there are more unhatched eggs in the 5% beaker compared to the 2.5% beaker. However there was a 24 hour period when the 5% beaker had more hatchlings present then the 2.5% beaker.

The data from this first study is inconclusive because more information is needed and the method for counting brine shrimp hatchlings is not necessarily the best means of calculating population data. One possible way to improve would be to find some software or program that is more precise with counting the number of shrimp hatchlings in the beaker.

Photos & Movies

Link to PicasaWeb Album

Link to video of hatchlings swimming via YouTube

References

Concentration and Molarity

• Source 1

• Source 2

Hatching Brine Shrimp Eggs

• Source 1

• Source 2

Brine Shrimp eggs ordered from YourFishStuff