CREATING A SELF-SUSTAINED UNDERWATER ECOSYSTEM

 

Jennifer L. Luebke-Wheeler and Elizabeth A. Rute

Department of Biology, Ecology (BI 341), Alverno College,

Milwaukee, Wisconsin 53234 USA

 

Abstract. By enclosing a specific amount of available resources inside a glass jar, a self-sustained ecosystem can be created. Theoretically, this can be accomplished in an underwater setting by a specific balance of oxygen, carbon dioxide, caleurpa, phytoplankton, shrimp, water, sunlight, and temperature. We attempted to create a self-sustained ecosystem by using these resources and manipulating the amount of light and shrimp we had. Since our self-sustained ecosystemís did not produce the expected results, it was determined that more research and testing on other variables such as, pH, microorganisms, nutrients (nitrogen and potassium) and the type of shrimp may produce the desired results.

Key Words: phytoplankton, algae, self-sustained ecosystem, and brine shrimp

 

INTRODUCTION

An ecosystem can be described as a balance of plants, animals, energy, and their physical interactions in a defined space. This defined space can be any size, from the entire globe, to a small pond. Being able to create an ecosystem, in vitro, can be challenging but rewarding.

Theoretically, a portable, underwater, self-sustained ecosystem, can be created by adding a specific balance of oxygen, carbon dioxide , caleurpa (algae), phytoplankton, Artemia selena (brine shrimp), water, sunlight, and temperature in an enclosed container. Phytoplanktons are single-celled organisms that live in salt water. (Russel-Hunter, 1979)

The brine shrimp, which are filter feeders, produce CO2 and eat the phyotoplankton. (Lutz, 1937) The caleurpa consume the CO2 and, in turn, produce O2 that the shrimp use. The gravel added to the contained ecosystem allows some of the microorganisms that might be living on the caleurpa and the phytoplankton to hide from the shrimp so that there is a good balance of food for the shrimp and enough to continue reproduction. The temperature of this system needs to remain consistent because the brine shrimp are temperature sensitive.

We hypothesized that by providing the basic resources necessary for an ecosystem such as O2, CO2, and organic matter we will be able to determine the amount of animal life needed to sustain a self-contained ecosystem without replacement of resources externally.

We determined that animal life is not the only factor that contributes to the success of an ecosystem but that other organic factors such as minerals (phosphorus, silica, and nitrogen) and chemical factors like pH may also contribute.

MATERIALS AND METHODS

We began by taking 6: 500ml glass jars with rubber stoppers, to be used for the enclosure of our ecosystem, and filling them with 100ml of gravel. 400ml of phytoplankton in seawater were then added to the jars and approximately 5.5g of caleurpa. Each jar was labeled and the A. selena was finally added in the corresponding amounts: 0, 5, 10, 15, 20, and 25 of each. These jars were placed along the window ledge in direct sunlight (DS).

One additional jar was made with twenty shrimp and the same amount of other materials. This jar was placed farther back in the room getting only indirect sunlight (IS). The time, date, temperature of the room, and some observations were recorded over two weeks. Results are in the Table of Observations and Recordings.

When we completed all of our observations, we took each of the ecosystems apart and tested for pH and dissolved O2 content using a kit by LaMotte Co., Model EDO, Kit #7414 and a pH meter. Results are in Table: Dissolved O2 and pH.

RESULTS

Table: Observations and Recordings

Time

Date

Temp

(° C)

Observations

9:30am

(DS)

102199

23

All systems look good and the shrimp look healthy (0,5,10,15,20,25)

12.:30pm

(DS)

102599

24

The algae atrophied and all the shrimp are dead

12:45pm

(IS)

102599

24.5

New system created (20 shrimp)

4:00pm

(IS)

102799

24

Shrimp look healthy, algae looks thinner and not as green

5:00pm

(IS)

110299

5:00

All but 3/20 shrimp died and the ones alive look extremely red

2:00pm (IS)

110499

24

3 alive, very red

11:00am (IS)

110999

23.5

1 alive, very red

4:00pm (IS)

111599

23

All dead

You can see from the table that the shrimp in the direct sunlight died after 3 days. Whereas the shrimp kept in indirect sunlight, some were still alive after 6 days.

Table: Dissolved O2 and pH

Sample ( # of shrimp)

Dissolved O2 (ppm)

pH

0 (DS)

6

7.7

5 (DS)

8

7.9

10 (DS)

10

8.1

15 (DS)

8

8.0

20 (DS)

6

8.1

25 (DS)

8

7.8

20 (IS)

6

6.8

 

 

DISCUSSION

One reason our shrimp died after a few days in direct sunlight is because UV light waves enter the glass bottle and some of the waves get trapped in there, heating up the inside of the bottle, changing the temperature of the ecosystem. Since brine shrimp and the caleurpa are temperature sensitive, this explains why the caleurpa atrophied and the shrimp died (Vanni, 1987). But there are still questions as to why the shrimp continued to die even during indirect sunlight and a constant temperature. We noticed that the phytoplankton settled to the bottom of the glass jar so the shrimp may have had trouble getting at it.

Brine shrimp are filter feeders, so one modification of our experiment is to take the brine shrimp out of the water and look under the microscope to see if they are eating the phytoplankton. In addition we can lower the amount of gravel added to each jar so that some of the phytoplankton can hide but make it easier for the shrimp to get at it.

We also observed that the shrimp became extremely red before dying. This occurs because of an increase in haemoglobin production. The brine shrimp produce more haemoglobin when O2 levels in the surrounding water are low. The dissolved O2 amounts in the water were low in every ecosystem. Measures would need to be taken to increase the amount of O2 that is available for the shrimp. Preliminary testing of the dissolved O2 content needs to be done previous to the experiment and after in order to get a better picture of the amount of dissolved O2 that is being used.

More experimental data needs to be collected on the nutrient levels present in our ecosystem. Also, nitrogen and potassium levels should be tested in order to detect minute amounts. More preliminary data needs to be gathered if a self-sustained ecosystem is going to be a reality.

LITERATURE CITED

Vanni, M. J. 1987. Effects of nutrients and zooplankton size on the structure of a phytoplankton community. Ecology, 68(3), pp.624-635.

Lutz, F.E. Welch, P.S. Galtif, P.F. Needham, J.G. 1937. Culture Methods for Invertebrate Animals. Dover Publications, Corp. New York.

Russell-Hunter, W.D. 1979. Life of Invertebrates. Macmallin Publishing Co Inc. New York.

 

REFERENCES

  1. Ecosphere Associates Inc. 1997-1999. Ecospheres, Enclosed Systems. October 31, 1999. http://www.eco-sphere.com/index.html

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Data Sheet

Author:

Jennifer Luebke-Wheeler

Dates of experiments:

October 21, 1999-November 24, 1999

Independent variables:

  1. Quantity of phytoplankton
  2. Magnets
  3. Gravel quantity
  4. Pressure
  5. Light
  6. Temperature
  7. Amount of algae

Controls:

  1. Ecosystem with no invertebrate life (brine shrimp)
  2. Ecosystem with no plant life or inert supplies

Method of data collection:

  1. Up to November 2, the data was collected as observation, see data in

Table: Observations and Recordings below. Dissolved O2 content and pH was collected using "Dissolved O2 Testing Kit, by LaMotte Co., Model EDO, Kit #7414. See Table: Dissolved O2 and pH

 

 

 

 

 

 

 

 

 

 

 

 

 

Table: Observations and Recordings

Time

Date

Temp

(° C)

Observations

9:30am

(DS)

102199

23

All systems look good and the shrimp look healthy (0,5,10,15,20,25)

12.:30pm

(DS)

102599

24

The algae atrophied and all the shrimp are dead

12:45pm

(IS)

102599

24.5

New system created (20 shrimp)

4:00pm

(IS)

102799

24

Shrimp look healthy, algae looks thinner and not as green

5:00pm

(IS)

110299

5:00

All but 3/20 shrimp died and the ones alive look extremely red

2:00pm (IS)

110499

24

3 alive, very red

11:00am

(IS)

110999

23.5

1 alive, very red

4:00pm (IS)

111599

23

All dead

Table: Dissolved O2 and pH

Sample ( # of shrimp)

Dissolved O2 (ppm)

pH

0 (DS)

6

7.7

5 (DS)

8

7.9

10 (DS)

10

8.1

15 (DS)

8

8.0

20 (DS)

6

8.1

25 (DS)

8

7.8

20 (IS)

6

6.8