ENV 121 Ocean Acidification lab fall 2023
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Feb 20, 2024
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Environmental Science
ENV 121
LAB: Ocean Acidification
Name: _Dylan_______________
Introduction:
Global Climate Change encompasses more than just changing temperature. In addition to increases in temperature, we are also experiencing changes in precipitation, more frequent and
intense storms, melting polar ice, sea-level rise, and the decreasing pH of the ocean. The decreasing pH of the ocean is also called ocean acidification
. As we increase the amount of carbon dioxide (CO
2
) in the atmosphere, mainly through the burning of fossil fuels, we also increase the amount of CO
2
in the ocean, because of gas exchange between the ocean and atmosphere. As CO
2
in the ocean increases, the pH of the ocean decreases. pH is a measure of free hydrogen ions (H
+
). When CO
2
dissolves in water it forms carbonic acid (H
2
CO
3
). This is less stable than bicarbonate (HCO
3
-
) so the carbonic acid disassociates to form bicarbonate and a free hydrogen ion, resulting in a lower pH (H
+
+ CO
3
-
). This system is known as the bicarbonate buffering system. A buffer is a weak acid and its conjugate base. Buffering systems minimize the change of pH. The bicarbonate buffering system is one of the systems our body uses to maintain a relatively constant pH. Scientists only started biological studies of ocean acidification in 2003 because prior to that they believed the buffering capacity of the ocean would resist changes to pH.
In the mid-1800s the pH of the ocean was about 8.17. The pH of the ocean as of 2010 was about 8.04. This might not seem like a big change, but because the pH scale is logarithmic, a change of a full unit is actually a ten-fold change, so the decrease from 8.17 to 8.04 represents a 47 % increase in acidity. In addition to increasing the acidity of the ocean, the additional CO
2
also decreases the availability of the carbonate ion (CO
3
2-
) because more of it is bound to hydrogen ions to form bicarbonate. Many organisms combine carbonate ions to calcium ions (Ca
2+
) to form calcium carbonate shells. Less carbonate means that it is harder for these organisms to make their shells and grow. These changes have the potential to not only slow the growth of organisms, but to impact their basic biology, eventually cause their shells to dissolve if the pH drops enough, and could lead to the extinction of many organisms. These consequences have the potential to cascade through the ecosystem as many organisms would be without food or shelter if we lose the organisms that utilize calcium carbonate.
Because cold water can hold more gas than warm water, more CO
2
is able to dissolve in polar regions, making the pH there drop faster. In this lab we will explore the changing pH of the ocean on the growth of sea urchin larvae.
Procedure:
Videos: https://www.youtube.com/watch?v=4QPpDGUuZE4
https://encounteredu.com/steam-activities/dissolving-coral-and-shells-in-vinegar
The two video links above demonstrate experiments we would have done in the lab to visualize how the pH of water can change and the impact that can have on marine organisms.
Please watch the videos and answer the following questions.
What color is the water in the flask initially immediately before the person starts blowing through the straw? The water was pink in tone.
What color does the water turn after the person stops blowing through the straw?
Color fades away to reveal nothing.
What caused the water to change color?
Initial reactions between sodium carbonate and phenolphthalein resulted in a pink color shift. When air was later blown into the pink mixture, the production of carbonic acid changed the color of the liquid to colorless.
What does the chalk represent in the second video?
The chalk represents coral.
What happens to the chalk?
The chalk started to dissolve.
The remainder of the lab is an on-line simulation. Please go to the following website:
https://depts.washington.edu/vurchin/index.php?view=acidocean&part=part0
Part 1: Go through part one and read about ocean acidification and what types of organisms will be impacted. Take time to go through the model “exploring carbon levels and effects” then answer
the following questions:
What is the current level of atmospheric CO
2
? (Use 2010 data) What is the current ocean pH?
The current CO2 concentration is 391. The ocean's pH right now is 8.04.
Under the most optimistic scenario what is the atmospheric CO
2
level and ocean pH in 2090? Under the most pessimistic scenario what is the atmospheric CO
2
level and ocean pH in 2090? Scenario with high probability: CO2 level = 545 Ocean pH = 7.92
Scenario with low confidence: CO2 level = 885 Ocean pH = 7.73
What is the sea urchin’s skeleton made of? Why does this make them a good organism for studying ocean acidification?
Calcite, a calcium carbonate that is rich in magnesium, makes up the sea urchins’ skeleton. Compared to other forms of calcium carbonate, this one dissolve faster.
Write a hypothesis to explain what you think will happen in this lab.
If acidification occurs, then it will reduce the growth of sea urchin populations.
Part 2:
Complete the virtual lab exploring the impact of ocean acidification on sea urchin larvae. Read and follow the instructions carefully. You can’t move on to the next task until you have fully completed the previous task. I suggest keeping the hints on. It will let you know exactly what you need to do to move on to the next task. Answer the questions as you work through the lab:
What are the two different pH treatments you are using? Why?
Since pH 8.1 is the average pH of ocean water right now and pH 7.7 may be the typical pH of sea water towards the end of the century, two distinct pH treatments were applied.
How did you drop the pH of the second treatment?
By adding CO2 into it.
Why do you add algae to the cultures?
To test algae's development at various pH levels, we introduce algae to the cultures.
After 2 days when you examine the pH of your treatments, did the pH change in either treatment? If so, why?
Only the pH of the pH 7.7 jar changed because of the carbon addition. Because the pH in the jars is affected by ambient CO2 level, which now results in a pH of 8.1 after equilibration, the pH
on the pH 8.1 jar did not change.
How many replicates are there of each treatment?
3 replicates of each treatment.
Part 3: Data Collection
Measure each of the three sea urchin larvae from both of the treatments and record your individual measurements and your average.
Treatment_7.7_________
Treatment_8.1__________
1.400
1.520
2.460
2.500
3.480
3.520
Avg.446.7
Avg.513.3
How does your data compare to the complete data set?
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The average for pH 7.7 is 452.0, while pH 8.1 is 535.3 for the entire data set. My value therefore
differs from the data set.
After examining the data read the “so what?” section.
What are the consequences of shorter larval arms for the sea urchin larvae?
The larval arms are used by sea urchin larvae to feed themselves. Shorter arms indicate slower growth and poor feeding.
What could possibly happen to sea urchin populations as a result of this change?
Due to poor growth and predation, fewer sea urchins will reach adulthood, which will lead the population to fall quickly.
What other species could be impacted by these changes to sea urchins?
Sea otters who depend on sea urchins for food would be affected by the decline in number.
Questions:
1. What is ocean acidification and where is it most intense?
Ocean acidification, which is mostly brought on by the absorption of carbon dioxide from the atmosphere, is the prolonged decrease in the pH of the ocean. Ocean acidification is especially harmful to the polar oceans in the Arctic and Antarctic.
2. What are some of the possible consequences of ocean acidification?
Since the amount of carbonate that marine species use to create their shells and skeletons is reduced as a result of ocean acidification. Without their exoskeleton, they will be more likely to be devoured by predators. Additionally, acidification will dissolve their current shell.
3. Why didn't people think ocean acidification would be a problem?
People did not initially consider ocean acidification to be an issue because they believed that the ocean's absorption of CO2 would balance the planet's temperature, even though the amount that the ocean really absorbs is greater, causing the ocean's acidity to decrease.
4. What is causing ocean acidification? What can be done to minimize ocean acidification?
Ocean acidification is brought on by an increase in atmospheric carbon dioxide that the ocean absorbs. Utilizing public transit, consuming less energy, recycling products, and saving water are
all ways that we can cut down on carbon dioxide pollution.
5. Using the Act section of the lab, what are some of the other stressors impacting ocean health?
Numerous stresses, such as acidification, climate change, overfishing, and pollution, pose a threat to the health of the ocean. These problems also include deoxygenation, invasive species, nutrient contamination, and habitat degradation. Consistent efforts for conservation and sustainable practices are required to address these issues.
6. Using the Act section of the lab and thinking about what you know is contributing to ocean acidification, what are things you can personally do to make a difference? (Think about how to counteract the stressors as well as the “me to we” section in the act portion of the lab)
Reduce your carbon footprint, choose sustainable seafood, and use less plastic in order to fight ocean acidification and enhance ocean health. To safeguard marine habitats, educate yourself and others, give to conservation groups, and encourage ethical travel.