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Brine Shrimp & pH

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Juliet Morales

on 17 November 2013

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Transcript of Brine Shrimp & pH

Introduction
Materials and Methods
Results
Discussion
References
Hatching Viability of Brine Shrimp with Respect to Water pH
Franky McMahon, Juliet Morales,
Anthony Velte

Research Question
Background
Hypothesis
Materials
Set-Up & Procedure
Graph
Data Table
Variables and Groups
What effect does pH have on the hatching viability of brine shrimp?
Brine shrimp are small crustaceans that thrive in their ecosystems. Part of the success of this species is their adaptation to produce cysts rather than eggs. If conditions are not ideal, such as with the salinity, oxygen level, and acidity, the cysts can stay dormant until more favorable conditions return. The brine shrimp live in saltwater lakes, such as Great Salt Lake and Mono Lake. Respectively, their pHs are about 9 and 9.8.
Sulfuric Acid
Sodium Hydroxide
Brine Shrimp Eggs
Scissors
Pipette
Paintbrush
5 microscope slides
Stereomicroscope
Double-sided tape
Dechlorinated Water
5 Petri Dishes
Permanent Marker
Stirring Rod
Graduated Cylinder
Scale
5 Beakers
Sodium Chloride
pH Strips
0 Hours:
Prepare and label five beakers of 30-mL salt solutions, using 0.15 grams sodium chloride and dechlorinated water.
Label five petri dishes, 5, 6, 7, 8, and 9.
Prepare a solution with a pH of 5 and one with 6 by slowly adding sulfuric acid to a beaker of salt solution. Check the solution using pH strips until the desired pH is obtained.
Pour into the petri dish labeled 5 and 6, respectively.
Repeat step 3 and 4 with two other beakers and sodium hydroxide to obtain pHs of 8 and 9.
Leave one beaker at a neutral pH of 7. Check the pH to be sure it is, in fact, 7.
Measure and cut 1.5 cm of double-sided tape.
Stick the double-sided tape to a microscope slide.
Lightly touch the paintbrush to the side of the bag containing the brine shrimp eggs. The goal is to collect only approximately 20 eggs on the brush.
Dab the paint brush onto the tape on the microscope slide.
Examine the slide under a stereomicroscope.
Count the number of eggs on the slide and record this number in a table under the label “0 hours”.
Place the microscope slide in the 5 petri dish, tape-side up, and place the lid on the dish.
Follow steps 7-13 for the remaining slides and dishes, until you have prepared five microscope slides of eggs, recorded the numbers in the table, and placed each slide in its appropriate pH solution.
Allow the dishes to sit at room temperature undisturbed for 48 hours.
24 Hours:
Examine each petri dish with a stereomicroscope.
Count the number of swimming brine shrimp. Also, count the number of dead brine shrimp. Record the sum of these numbers in the table under "24 hours."
Count the number of partially hatched. Record this in the table under "24 hours."
Count the number of unhatched eggs and record this in the table under "24 hours."
Repeat steps 1-4 for each of the petri dishes.

48 Hours:
Examine each petri dish with a stereomicroscope.
Count the number of swimming brine shrimp. Also, count the number of dead brine shrimp. Record the sum of these numbers in the table under "48 hours."
Count the number of partially hatched. Record this in the table under "48 hours."
Count the number of unhatched eggs and record this in the table under "48 hours."
Repeat steps 1-4 for each of the petri dishes.
Clean up as advised by instructor.
Independent Variable: Acidity (pH)
Dependent Variable: Hatching Viability

Control Group: pH 7
Acid Groups: pH 5 and 6
Basic Groups: pH 8 and 9
If brine shrimp eggs are placed in solutions of varying acidity (pHs of 5, 6, 7, 8, 9), then the eggs in the basic solutions will have a greater hatching viability than those in the neutral or acidic solutions because the ideal hatching acidity for brine shrimp eggs is around the pHs 8 and 9.
About Mono Lake: Quick facts. (n.d.). Retrieved September 23,
2013, from Mono Lake Committee website: http://www.monolake.org/about/stats
Utah Division of Forestry, Fire & State Lands. (n.d.). Great
Salt Lake. Retrieved from http://www.ffsl.utah.gov/sovlands/greatsaltlake/techteam/presentations/feb07/SALT%20balance.ppt
The results for acidic pH tests, 5 and 6, had no or low hatching viability, respectively 0% and 5.56%. The neutral, control group had a generous hatching viability of 28.57%. The basic tests for pH 8 and 9, those predicted to be the most ideal, had 13.04% and 36.96%, respectively.
The calculation for hatching viability was different in this lab from the salinity lab. Rather than counting the dead with the "partially hatched" group, they were included in the "hatched" group. The lab was to test the hatching viability, not overall viability. Therefore, those that hatched but did not survive afterward would still be considered as hatched.
Those included as "eggs" were simply those in the cyst phase. Those included as "partially hatched" included eggs in the umbrella stage and those with cracked eggs.
All counting of the brine shrimp, whether in the egg, umbrella, or nauplius stage, are subject to error. The acid/base had an effect on the adhesive of the tape that caused the eggs to detach and float to the top of the solution. This made it difficult to count.
All of the water in the petri dishes had a salinity of about 0.5% hatching viability. This was the group with the highest hatching viability in the salinity lab. Although it may have been found to be the best condition for our group in the salinity lab, it may not have been the true best condition.
With consideration to the question "What effect does pH have on the hatching viability of brine shrimp?", the results show that acidity below 7 is not effective as a hatching condition and the acidity equal to or above 7 is ideal. Although there was a decrease in hatching viability from 7 to 8, the general trend is still showing that the higher the pH, for the groups tested, the higher the hatching viability. The results were as expected in the hypothesis.
Interestingly, the control group had a lower hatching viability than the petri dish with the same conditions in the salinity lab (50% hatching viability). If the salinity lab were repeated to observe the precision of the conclusion drawn from that lab, then this pH lab could be repeated with a better controlled salinity variable.
Another important expansion on this lab would be to test pH levels 7 to 14. The data collected cannot conclude that pH level 9 is the absolute most optimal value for the hatching of brine shrimp. Levels above 9 could be better, or they could have a maximum at 9 and decrease from that point. It is important to test this before concluding the best condition.
The pHs were measured using pH strips, which are not the most accurate of measuring tools. Also, acid/base were added to the salt water of the petri dishes with a guess and check method.
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