Photo Credit: djpmapleferryman / [CC-BY-2.0], via Wikimedia Commons
To develop an understanding of how growth and survival of an organism depends on physical conditions. This is accomplished by designing an artificial environment in which brine shrimp can thrive.
This lesson is the second of a two-part series on brine shrimp. These lessons relate to the idea in the central benchmark that in any particular environment, the growth and survival of organisms depend on the physical conditions.
Animals that live in salt marshes, mangrove swamps, and tidal flats all have built-in adaptations to deal with saltwater and changing levels of salinity. For example, brine shrimp can survive in seawater and brackish water and can be found in salt lakes and brine ponds all over the world. Brine shrimp have no defense against predation, however, so they can best thrive in conditions in which their predators cannot, such as high salinity and temperature.
In Brine Shrimp 1: Hatching Brine Shrimp, students determined the optimum salinity for hatching. In Brine Shrimp 2: Brine Shrimp Survival, students will raise brine shrimp, designing an artificial environment in which they can survive.
Since newly hatched brine shrimp can be grown to full maturity in about three weeks, student investigations in this lesson can be carried out over a period of three weeks or a month, with students returning to record their observations of the brine shrimps' development at regular intervals.
If you haven't done so already (as suggested in the Hatching Brine Shrimp lesson), read Brine Shrimp and Ecology of Great Salt Lake, from the Water Resources of Utah website, for background information on brine shrimp before you begin this lesson.
Determine students' prior experience with brine shrimp or sea monkeys. Remind them that if they did the first lesson of the series, Brine Shrimp 1: Hatching Brine Shrimp, they investigated the optimum salinity for brine shrimp hatching. Now they will take that further and investigate conditions in which brine shrimp can survive.
Have students read these two articles:
After reading these articles, ask students what it tells them about what brine shrimp need. Record and save their responses; they will be revisited at the end of the lesson.
In this part of the lesson, students will raise live brine shrimp, investigating conditions in which they can survive. Students can use the shrimp hatched in the previous lesson, or you can provide each group with a set of shrimp that were all hatched under the same conditions.
Have students work in small groups to develop a question about brine shrimp survival they want to answer. For example, students could investigate questions such as:
- Is the best salinity for hatching also the salinity in which the shrimp are most likely to thrive once hatched?
- What happens if you transfer the hatched shrimp to water of different salinities? Do they survive?
- How drastic of a salinity change can brine shrimp tolerate?
- Does temperature affect the survival of brine shrimp eggs?
- Does acid rain affect the survival of brine shrimp?
In order to better inform their questions and subsequent experimental designs, students could read articles on the Natural History of Mono Lake website. Of particular interest is the Brine Shrimp: Mono Lake's Unique Species page. Advanced students can read about the Chemistry of Mono Lake, at the Chemistry: Strange Water Strange Towers page, for more ideas about designing a habitat for brine shrimp.
In addition, the Brine Shrimp and Ecology of Great Salt Lake has information on how brine shrimp live in the Great Salt Lake and how they are harvested there.
Next, have each group record their experimental design, including the question they wish to explore and the procedure that they will use. Discuss these with the groups, focusing on experimental design issues such as variables. In general, help students be sure these are sound experiments.
When you are sure the students' ideas and procedures are well thought out, instruct them to carry out their experiments, having them keep records of how long their shrimp live, how they move, what they look like, and so on. Have them carry out the experiment as they do others in your class, following the same lab journal/report guidelines, etc. Be sure to discuss the results when all students are finished with the experiments.
Here are some tips for raising brine shrimp:
- One tablespoon [15 ml] of salt mixed with one cup [240 ml] of water is usually a good mixture for hatching the brine shrimp eggs.
- Brine shrimp are sensitive to poor water quality, so be sure to use only spring water or aged tap water.
- Enough tiny algae and bacteria may grow in the containers to feed the brine shrimp. To feed the brine shrimp and keep them alive longer, you may also want to add small amounts of packaged yeast as well. (A pinch of yeast is all you need. Too much yeast can kill the shrimp).
- In low salinity and optimal food levels, fertilized females usually produce free swimming offspring called nauplii at a rate of up to 75 per day. In order to observe this in the classroom, you will need to provide an optimum environment with regards to pH, light, and oxygen. A pH of around 8 is best; a pH less than 5 and greater than 10 will likely kill the brine shrimp. The pH can be increased with baking soda, and lowered with muriatic (hydrochloric) acid. The level of oxygen in the water is very important; with a good oxygen supply, the brine shrimp are a pale pink or yellow, or if they are heavily feeding on microalgae they will look green in color. In this ideal condition, growth and reproduction is rapid, and a self-sustaining supply is possible.
In order to summarize the lesson, review the articles that students read in the Motivation, and revisit the students' recorded responses about what brine shrimp need. What new thoughts do they have as a result of this lesson?
Then assess student understanding by critiquing the experiments. Pay attention to experimental design as well as ideas/conclusions about brine shrimp survival. For example, did students structure and carry out sound experiments? Did they provide evidence to support their conclusions?
A brine shrimp project for high-school students can be found at The Brine Shrimp Project, part of the Science Junction website produced by North Carolina State University.
The Salt Pond Ecosystem is a good resource for further study of the ecology of salt ponds.