TEACHER PAGES
LESSON TWO
Plankton and CO₂
What impact do phytoplankton and zooplankton have on CO₂, DO and pH levels in marine environments?
A Partnership between California Current Ecosystem Long Term Ecological Research (CCE LTER) and Ocean Institute (OI)
Beth Simmons, Education and Outreach Coordinator, CCE LTER, Scripps Institution of Oceanography, Christy Millsap, Teacher, Rancho Bernardo High
School, San Diego, California.
Introduction:
Phytoplankton (plants) and zooplankton (animals) impact the concentrations of dissolved gases like carbon
dioxide (CO₂) and dissolved oxygen (DO) in marine environments. Through the process of photosynthesis,
millions of phytoplankton in the ocean use the reactants carbon dioxide, water, and energy from the sun to
produce sugar (glucose) and oxygen. Living organisms
use the products of photosynthesis (glucose and
pH and Carbon Dioxide
oxygen) to respire and gain energy (ATP). As a result of
The pH scale has values from (0 to 14) with 7 being neutral
respiration, water and carbon dioxide are released as
pH > 7 (alkaline) pH < 7 (acidic)
byproducts. Photosynthesis and respiration remain in
pH of the ocean normally ranges from 8.1 to 8.4 at the surface
equilibrium as long as the populations of plants and
pH is directly influenced by carbon dioxide levels
Animal
Activity: Increases acidity (lower pH values) respiration
animals remain in balance and conditions within the
decreases
O₂ levels and increases CO₂ levels
environment remain stable. A change in the abundance
Plant Activity: Decreases acidity (higher pH values) increases
of organisms or the concentration of dissolved gases like O₂ and decreases CO₂ from the water through photosynthesis
carbon dioxide and oxygen will affect the chemistry in
the ocean. This in turn affects the pH balance of
seawater and impacts many biological processes. If the pH increases, it causes the water to become more
“basic.” In other cases, if the pH decreases, then the water becomes more acidic. A drop of one pH unit
corresponds to a 10-fold increase in the concentration of charged particles in the water, making it more acidic
(Doney, 2006). The pH of seawater ranges from 8.0 to 8.3, meaning that the ocean is naturally somewhat basic.
Changes in water chemistry of ocean ecosystems affects the health and survival of organisms over time.
Target audience: Grade 9-12 Biology, Marine Science, or Environmental Science
Time Frame: Initial set-up and data collection will take one lab period (one hour) and final data collection and
conclusion will be one lab period (one hour). This experiment can be extended up to five days of observations.
Purpose: In this simulation, groups of students will record and observe the impact of plants (Elodea) and animals (brine
shrimp) on carbon dioxide, dissolved oxygen and pH levels in a marine environment. They will review and discuss the
processes of photosynthesis and respiration as vital biological processes and the impacts of changes in the processes on
the health of the phytoplankton and zooplankton over time.
CA standards addressed:
Life Science standards- 1f,1g, 6b , 6d.
Earth Science Standard 7a.
Investigation and Experimentation 1a, 1b, 1c, 1d, 1j, 1k,1m.
National Science Standards:
NS.9-12.1 SCIENCE AS INQUIRY - Abilities necessary to do scientific inquiry investigations and understand scientific inquiry
NS.9-12.6 PERSONAL AND SOCIAL PERSPECTIVES - Environmental quality
NS.9-12.7 HISTORY AND NATURE OF SCIENCE - Nature of scientific knowledge
1
Created by: Beth E. Simmons © 2009 (Revised 2011)
Education & Outreach Coordinator CCE Long Term Ecological Research (LTER)
Disclaimer: May be reproduced for educational purposes; cite appropriately
TEACHER PAGES
LESSON TWO
Materials:

4 sample bottles with lids

Aqueous Carbon Dioxide (CO₂) probe or chemical test kit for
CO₂

Deionized water (DI)

Dissolved Oxygen (DO) probe or chemical test kit for DO

Water bath (large aquarium or container)

pH probe or chemical test kit

Ultraviolet light or other grow light

Elodea sprigs (2 small sprigs per group)

Thermometer or temperature probe

Brine shrimp (2 shrimp per group - if shrimp are small add more
per group)

Heavy duty trash bag (to darken aquarium)

Duct tape
Hypothesis: Brine shrimp (animals) and Elodea (plants) will change the levels of carbon dioxide (CO₂) and dissolved
oxygen (DO) values within the water sample under light and dark environmental conditions which will result in the
alteration of the levels of pH of the water.
Procedure:
1.
Obtain 4 sample bottles-label them as follows:
1-brine shrimp, light
2- Elodea, light
3- brine shrimp, dark
2.
4- Elodea, dark
Fill all four bottles with deionized water to equal volumes.
3. Take initial values for CO₂ , DO, pH and temperature in all four sample bottles and record in data table.
4. Place the brine shrimp in vials one and three, an Elodea sprig in vials two and four, then seal tightly with duct
tape.
5. Carefully place vials one and two in a water bath under a light. (Note: The water bath can be an aquarium
filled with room temperature water).
6. Carefully place vials three and four in a water bath in the dark. The water bath can be an aquarium covered
with a trash bag to maintain a dark environment and filled with room temperature water.
7. Leave all the sample vials for 24 hours. (Note: Create graphs for each of the variables measured ahead of
time. There will be graphs needed for CO₂ versus time, DO versus time, and pH versus time.)
8. In class the next day, remove each sample from the water baths. Remove covers and record CO₂, DO, pH
and temperature values for each sample bottle in your data table. (Note: If you are running the experiment
for five consecutive days, then recap the vials immediately after data are taken. Otherwise, dispose of the
contents properly and clean out all sample bottles.)
2
Created by: Beth E. Simmons © 2009 (Revised 2011)
Education & Outreach Coordinator CCE Long Term Ecological Research (LTER)
Disclaimer: May be reproduced for educational purposes; cite appropriately
DATA TABLE
TEACHER PAGES
Oxygen
+
DAY 2 Values
Glucose
DAY 3 Values
Carbon Dioxide + Water
6H₂O
CO₂
DO
Temperature
pH
CO₂
DO
Temperature
pH
CO₂
DO
Temperature
pH
CO₂
DO
Temperature
pH
DAY 4 Values
Energy
C₆H₁₂O₆ + 6O₂
INITIAL Values
FINAL Values
Elodea (light)
6CO₂ +
Photosynthesis
Brine shrimp (light)
INITIAL Values
DAY 2 Values
DAY 3 Values
DAY 4 Values
FINAL Values
+ Energy
Carbon Dioxide + Water
6CO₂
INITIAL Values
DAY 2 Values
DAY 3 Values
DAY 4 Values
FINAL Values
Elodea (dark)
Oxygen
DAY 2 Values
+
DAY 3 Values
DAY 4 Values
Glucose
6O₂
INITIAL Values
C₆H₁₂O₆ +
Respiration
+
6H₂O + 6ATP
Brine shrimp (dark)
FINAL Values
3
Created by: Beth E. Simmons © 2009 (Revised 2011)
Education & Outreach Coordinator CCE Long Term Ecological Research (LTER)
Disclaimer: May be reproduced for educational purposes; cite appropriately
TEACHER PAGES
LESSON TWO
Plankton and CO₂
What impact do phytoplankton and zooplankton have on CO₂, DO and pH levels in marine environments?
A Partnership between California Current Ecosystem Long Term Ecological Research (CCE LTER) and Ocean Institute (OI)
Beth Simmons, Education and Outreach Coordinator, CCE LTER, Scripps Institution of Oceanography, Christy Millsap, Teacher, Rancho Bernardo High
School, San Diego, California.
Analysis:
1. Create a graph comparing CO₂ concentrations over time and write a brief statement describing your
findings. (Note: If you only completed one 24-hour period of observations, record your initial and final
values over time.)
2. Create a graph comparing DO concentrations over time and write a brief
statement describing your findings.
3. Create a graph comparing the pH values over time and write a brief
statement describing your findings.
Copepod
4. Why were the samples put in both light and dark environments? Explain.
5. Compare what happened to the levels of CO₂ over time in the dark and
light brine shrimp vials and the dark and light Elodea vials.
6. Compare what happened to the levels of DO over time in the dark and light brine shrimp vials and the
dark and light Elodea vials.
7. Compare the DO and CO₂ graphs to the pH graph. Explain your observations.
8. What is the relationship between the brine shrimp and respiration in the vials?
Diatoms
9. What is the relationship between the Elodea and photosynthesis in the vials?
10. What would happen to CO₂ and DO concentrations in the ocean if the number of
phytoplankton (plants) decreased?
11. What would happen to the CO₂ and DO levels in the ocean if the number of animals
increased?
12.
If CO₂ levels became very high, what would happen to pH levels? What impact might this have on plants
and animals living in marine environments?
Conclusion:
Formulate a thoughtful conclusion to this experiment written in paragraph form. The conclusion should consist of
the following:
a. What was the initial hypothesis of this research?
b. Explain any possible errors that may have affected your experimental results.
c. Explain your understanding of the exchange of dissolved gases within the ocean’s realm between plants and animals
and the impact of these exchanges on the pH of the water. Evidence of your understanding should address the implications of
an imbalanced pH in ocean water.
4
Created by: Beth E. Simmons © 2009 (Revised 2011)
Education & Outreach Coordinator CCE Long Term Ecological Research (LTER)
Disclaimer: May be reproduced for educational purposes; cite appropriately
TEACHER PAGES
Possible Student Responses:
Analysis:
1.
2.
3.
4.
The student graph comparing CO₂ values over time should show the following trends:
•
Elodea dark- no change to slight increase in CO2 level (due to lack of light for photosynthesis)
•
Elodea light- large decrease in CO2 level (due to photosynthesis)
•
Brine shrimp dark- increase in CO2 level (due to respiration)
•
Brine shrimp light- increase in CO2 level (due to respiration)
The student graph comparing DO values over time should show the following trends:
•
Elodea dark- no change to slight decrease in DO level (due to lack of light for photosynthesis)
•
Elodea light- large increase in DO level (due to photosynthesis)
•
Brine shrimp dark- decreased DO level (due to respiration)
•
Brine shrimp light- decreased DO level (due to respiration)
The student graph comparing pH values over time should show the following trends::
•
Elodea dark- no change to slight decrease in pH level (due to slightly increasing CO2).
•
Elodea light- increase in pH level (due to decrease in CO2)
•
Brine shrimp dark- decrease in pH level (due to increase in CO2)
•
Brine shrimp light- decrease in pH level (due to increase in CO2)
Why were samples (plants and animals) put in the light and the dark? The samples were placed in the light and the dark
environments to explore the impact of light on the levels of dissolved gases and pH. Light serves as an energy source and it is
necessary for plants to undergo photosynthesis. The plant in the dark was the control in this experiment, showing that
photosynthesis cannot take place without light. Therefore, the plant in the dark should have shown no change. In order for
our experiment to remain valid, the brine shrimp also had to be placed in the same experimental conditions. Students should
have observed very little difference between the two brine shrimp vials since they do not undergo photosynthesis.
5. Compare what happened to the CO2 levels over time in the dark and the light brine shrimp vials and the light and dark
elodea vials. Over the observed time period, the measured CO2 values for both the light and dark brine shrimp vials should
have been similar. Due to animal respiration, the CO2 levels should have increased in the vials as the shrimp gave off CO₂ as
a by-product of respiration, and the rate of it is not impacted very much by light. However, the light and dark plant samples
should have yielded different CO2 values. This is because plants in the light underwent photosynthesis causing a decrease in
CO2 values. Remember that during photosynthesis, plants consume CO2 to make food (glucose). In contrast, the plant
sample in the dark was unable to perform photosynthesis; therefore one would expect only a small increase (if any) in CO₂ as
the plant respires.
5
Created by: Beth E. Simmons © 2009 (Revised 2011)
Education & Outreach Coordinator CCE Long Term Ecological Research (LTER)
Disclaimer: May be reproduced for educational purposes; cite appropriately
TEACHER PAGES
Possible Student Responses Continued...
Analysis:
6.
Compare what happened to the DO levels over time in the dark and light brine shrimp vials and the dark and light Elodea
vials. The Elodea vial placed in the light should have shown increased DO values since photosynthesis occurred. Oxygen is a
by-product of photosynthesis. The Elodea vial placed in the dark lacked light, so photosynthesis did not occur and DO levels
would expect to decrease as respiration occurs. Since brine shrimp do not require light to respire, regardless of whether
they were in light or dark vials the DO levels should have decreased over time.
7.
Compare the DO and CO₂ graphs to the pH graph. Explain your observations. When all three graphs are compared,
CO₂ and pH are inversely related. That means, as CO₂ levels increase, pH levels decrease and as CO₂ levels decrease, pH
levels increase.
8.
What is the relationship between the brine shrimp and the rate of respiration in the vials? The process of respiration
requires oxygen and glucose. This process produces CO₂, water (H₂O) and energy (ATP). Brine shrimp are animals and all
animals perform respiration to give their cells energy for growth and repair.
DO in vials containing the brine shrimp decreased because it was “used up” and CO₂ which should have increased in this
scenario was produced. Note: CO₂ reacts with the water to produce a weak acid which caused the water’s pH to increase.
9.
What is the relationship between the Elodea and the rate of photosynthesis in the vials? The process of photosynthesis
requires CO₂, energy (light), and water to produce oxygen, and glucose. The Elodea in light showed decreased CO₂ levels (it
was “used up”) and increased DO levels (it was “made” as a product). pH values change as a function of CO₂ values. So in
other words, as CO₂ decreases, pH increases because less carbonic acid is produced (fewer free hydrogen ions). The Elodea
in the dark lacked light for photosynthesis, so CO₂ levels should have increased and O₂ levels decreased as respiration
occurred.
10. What would happen to CO₂ and DO levels in the ocean if the number of phytoplankton (plants) decreased? If the
number of plants (photosynthetic organisms) in the ocean decreased, we would expect CO2 levels to increase and DO levels
to decrease- due to the lack of photosynthesis occurring. If this continued we would see animals dying due to a lack of
oxygen.
11. What would happen to the CO₂ and DO levels in the ocean if the number of animals increased? If the number of
animals (organisms performing respiration) were to increase in the ocean, we would see decreasing DO values and increasing
CO₂ values-due to the increase in respiration occurring.
12. If CO₂ levels became very high, what would happen to pH levels? What impact might this have on plants and animals living in marine environments? If the CO₂ levels became very high, pH levels would decrease (become more acidic). There is
an optimal range of pH in the ocean of 7.8-8.4 the average being around 8.0. In lesson 5 we will explore the negative impact that decreasing pH can have on oceanic plants and animals. Students can hypothesize as to what may happen.
Conclusion:
Students should have similar conclusions to this experiment written in paragraph form. Their conclusions should consist of
the following:
a. Their initial hypothesis of the research
b. Any possible errors that may have affected their experimental results
c. Their understanding of the exchange of dissolved gases within the ocean’s realm between plants and animals, and the
impact of these exchanges on the pH of the water. Evidence of their understanding should address the implications of an imbalanced
pH in ocean water.
6
Created by: Beth E. Simmons © 2009 (Revised 2011)
Education & Outreach Coordinator CCE Long Term Ecological Research (LTER)
Disclaimer: May be reproduced for educational purposes; cite appropriately
TEACHER PAGES
Vocabulary:
acidic: a pH value below 7.
ATP: An organic compound that contains large amounts of energy.
phytoplankton: Microscopic algae that live in the water and produce their own food through the process of
photosynthesis. Collectively, phytoplankton are the foundation of the marine food web.
zooplankton: Drifting marine animals either invertebrates or larval fishes. These organisms are grazers, feeding on
phytoplankton or predators, which consume other organisms.
photosynthesis: Chemical process by which plants convert light energy into chemical energy (glucose) 6CO₂ + 6H2O +
light energy → C6H12O6 + 6O2
respiration: Chemical process through which animals convert chemical energy (glucose) into ATP to fuel cells C6H12O6 +
6O2 → 6CO₂ + 6H2O + energy(ATP).
pH: A common measure of how acidic or basic a solution may be.
dissolved oxygen: (DO) oxygen dissolved in water.
carbon dioxide: (CO₂) a chemical molecule composed of two oxygen atoms and one carbon atom; it is essential for
many biochemical and living processes.
glucose: (C₆H₁₂O₆) a sugar that serves as the main source of energy for most living things.
Additional Resources and Notes:
1. Aqueous Dissolved Oxygen and pH probes are available through
a. Pasco scientific- http://www.pasco.com/
2. DO, CO₂, and pH chemical test kits can be obtained through La Motte- http://www.lamotte.com/pages/edu/index.html
3. Test kits, probes and other water sampling supplies can be obtained through Wardshttp://wardsci.com/category.asp_Q_c_E_915_A_Water+Testing+and+Sampling
4. Brine shrimp may be purchased from local fish and aquarium stores or can be hatched. Information and purchasing can be
found at http://www.brineshrimpdirect.com/Hatching-Brine-Shrimp-Cysts-c169.html
5. Doney, Scott (2006) The Dangers of Ocean Acidification , Scientific American, pgs. 58 - 65.
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Created by: Beth E. Simmons © 2009 (Revised 2011)
Education & Outreach Coordinator CCE Long Term Ecological Research (LTER)
Disclaimer: May be reproduced for educational purposes; cite appropriately
TEACHER PAGES
LESSON TWO
Phytoplankton’s Influence?
Extension: Besides acting as the first link in the food chain,
phytoplankton are a very important part of ocean life.
Phytoplankton play a role in acting as transporters of CO₂ from
the atmosphere into the ocean. The direction of exchange
(accumulation versus absorption) depends on how much is in
excess and how much is absorbed by plankton. There is a
constant exchange of CO₂ between the atmosphere and the
oceans. Because of the large size of the ocean, and the
occurrence of phytoplankton everywhere, the ocean is a sink for
atmospheric carbon dioxide. What would happen if
phytoplankton did not bring CO₂ from the atmosphere into the
ocean?
Questions:
a. What might cause phytoplankton abundances to decrease?
Figure 1. Satellite image of chlorophyll a concentrations (which
acts as a proxy for plankton biomass) from October 6, 2002
off the coast of California. Reds indicate high concentrations
and blues indicate low concentrations.
b. If fewer phytoplankton existed, what might happen to
atmospheric carbon dioxide?
c. What would the implications of decreased phytoplankton be for
the ocean ecosystem?
Possible resources:
a. Satellite Images of Marine Phytoplankton Blooms http://geology.com/nasa/marine-phytoplankton.shtml#top
b. Hays, Graeme C., et. al. (2005) Climate Change and Marine Plankton, Trends in Ecology and Evolution, Vol. 20 No.6,
pages 337 - 344.
c. Morello, Lauren (2010) Phytoplankton Population Drops 40 Percent Since 1950, Scientific American, July. http://
www.scientificamerican.com/article.cfm?id=phytoplankton-population
8
Created by: Beth E. Simmons © 2009 (Revised 2011)
Education & Outreach Coordinator CCE Long Term Ecological Research (LTER)
Disclaimer: May be reproduced for educational purposes; cite appropriately