DATA IN THE CLASSROOM: LEVEL 1
How Does Rising CO
2
Impact Ocean pH?
1. Calculating Change Over Time: How much have CO
2
levels in the ocean changed over time? Use the graph to answer
the question.
2. Make a Prediction: Observe the graph showing CO
2
measurements at Mauna Loa Observatory, Hawaii, from 1958 to
2018. Then, predict the likely effect of rising CO
2
on ocean pH by completing the table below.
3. Illustrate Your Prediction: Illustrate your prediction by drawing a black line on the graph below. See instructions.
a. Complete the legend (black will represent ocean pH)
b. Create a pH scale along the y-axis on the right side of the graph. Note: Do NOT make your scale from 0 to 14. Keep it
centered around your prediction.
c. Find the year 1988 on the x-axis. Ocean pH was 8.1 in 1988. Place a black dot at this location on the graph.
d. Starting from the dot, create a line that shows your predicted change in ocean pH from 1988 to current.
In 1988, the pH of the ocean was approximately 8.1. What do you predict
the pH of the ocean is today?
Example student answer:
Prediction of current ocean pH = 7.0
Explain why you made your prediction above. Use evidence from the graph
(hint: explain how changes in atmospheric CO
2
and ocean CO
2
could have
caused pH to change).
Example student answer:
Atmospheric CO
2
increased from about 350
ppm in 1988 to 412 ppm in 2019. Ocean
CO
2
increased from 330 to 390 ppm.
What are the primary chemical reactions that may explain your predictions?
Use chemical equation(s) or words or both.
Equation: CO
2
+ H
2
0 → H
+
+ HC0
3
-
When CO2 combines with seawater, it
forms carbonic acid. The carbonic acid
further breaks down, releasing H+ ions in
the process.
Type your
answer directly
into the box.
How much has CO
2
in the ocean increased since 1988?
To calculate percent change, find the difference between the starting and ending
values, and then divide by the starting value.
Percent (%) change = 389 ppm - 330 ppm
330 ppm
Percent (%) change = 17.8%
Type your
answers directly
into the boxes.
Type your
answers directly
into the box.
Type your y-axis values
directly into each of the
rows in the table.
Prediction: How Rising CO2 Has Changed Ocean pH (Hawaii)
Insert pH
scale here
8.2
8.0
7.8
7.6
7.4
7.2
7.0
6.8
LEGEND:
Red = Atmospheric CO
2
Blue = Ocean CO
2
Black = Ocean pH (predicted)
DATA IN THE CLASSROOM: LEVEL 2
Measuring Changes in pH
1. Predicted vs Actual Change in Ocean pH: After completing the online activities in Level 2, compare your predictions from
Level 1 with the actual changes in ocean pH.
2. Illustrate the Actual Change in Ocean pH: Draw a line on the graph to show the actual change in ocean pH over time.
a. Note: the pH scale along the secondary y-axis is completed for you.
b. Complete the legend (black will represent ocean pH)
c. Draw a black trend line on the map to show the long-term trend in ocean pH over time.
3. Analyzing Short & Long-term Changes in Ocean pH: How much does ocean pH vary over short and long time scales?
What words or numbers complete the sentences? Type the 2 missing words or values below.
My prediction was that pH would …………… [increase or decrease]
by …………… pH units.
Decrease, 1.1
The data show that pH actually …………… [increased or decreased]
by ………...….. pH units.
Decrease, 0.5
Type your
answer directly
into the box.
Draw a line to
represent ocean
pH directly on
the graph
Need help?
Refer to Levels 1
and 2 for ideas.
Measured Change in CO2 and Ocean pH (Hawaii, 1988 - 2017)
LEGEND:
Red = Atmospheric CO
2
Blue = Ocean CO
2
Black = Ocean pH (actual)
CO
2
and pH both change in a predictable pattern
from year to year. Describe the pattern.
Short time scales: pH decreases from May-Sept and increases
from Oct-May
What causes the predictable pattern? In the late spring and summer, algae draw large amounts of CO2
from the water for photosynthesis, causing acidity to increase.
What is ocean acidification?
Define the term in your own words.
Ocean acidification refers to a reduction in the pH of the ocean
over an extended period of time, caused primarily by uptake of
carbon dioxide (CO2) from the atmosphere.
DATA IN THE CLASSROOM: LEVEL 3
Examining Acidification Along the Coast
1. How is acidification different along the coast? Watch the interactive animation & answer the question below.
2. Detecting Acidification Near the Coast: Use the map tool to collect & analyze ocean pH data at two locations, Hawaii
and coastal Washington, between 2010 and 2017. Record below.
3. Construct an Explanation: Is ocean acidification is occurring in Washington, in the same way that it is in Hawaii? Answer
the question using the claim, evidence, reasoning table below.
4. Coastal Acidification: How would you define coastal acidification? Use your answers in Q1-3 to help form a definition, in
your own words.
In addition to the absorption of CO
2
from the
atmosphere, identify and describe TWO processes
that can affect ocean pH closer to shore?
1. Excess input of nutrients from shore (from fertilizers, wastewater,
animal manure and more): stimulate algae growth. This in turn
leads to intense respiration by animals that eat them, and the
respiration drives up the local CO2 concentration in the water.
2. Upwelling: deep waters that ‘rise up’ during upwelling are
naturally enriched with CO2 because respiration processes
dominate in the deep.
Type your
answer directly
into the box.
Type your
answers directly
into the boxes.
Type your
answers directly
into the boxes.
Location Highest pH value Lowest pH value Range
(highest - lowest pH)
Cha Ba (Washington)
8.42 7.92 0.5
WHOTS (Hawaii)
8.10 8.05 0.05
Is ocean acidification is occurring in
Washington, in the same way that it is in
Hawaii?
My Claim:
Along the coast, ocean pH is more variable, with extreme (seasonal) changes
in pH.
Include specific data measurements from
the graphs & from the table in #2 above.
My Evidence:
Between 2010 and 2017, the difference between the highest and lowest pH
values was 0.5 in coastal WA and 0.05 in Hawaii.
Connect the evidence to your claim
My Reasoning:
Along the coast, there is more life. Therefore, photosynthesis and
respiration activities naturally affect pH more in these regions. Nutrients
from human sources can make seasonal changes in pH even more extreme.
My definition for
Coastal Acidification
Coastal acidification refers to the same processes resulting from the absorption of atmospheric
CO2, as well as a number of additional, local-level processes, including the excess input of
nutrients from shore (from fertilizers, wastewater, animal manure and more).
Type your
answers directly
into the box.
DATA IN THE CLASSROOM: LEVEL 4
Acidification’s Impact on Animals
1. Acidification’s Effect on Shell Building Animals: Use the online graphic titled ‘Ocean Acidification–What Does it Mean
for Oysters?’ to answer the question below.
2. How is Acidification Impacting Oysters? Aragonite saturation state (Ω) is a measurement that describes the tendency
for calcium carbonate to form or to dissolve. What is the relationship between aragonite saturation state, CO2 and pH?
3. How is Acidification Impacting Oysters? Complete the table below to show WHEN ocean conditions might negatively
affect the growth and survival of larval Pacific oysters. For each month, write the % of observations that fall below the
threshold (Ω < 1.5 and Ω < 2.0).
Changes in ocean chemistry reduce the ability of some
animals to build their calcium carbonate (CaCO3) shells.
Write the chemical reaction(s) to illustrate this statement.
CO
2
+ H
2
O + CO
3
-
2
→ 2HCO
3
-
Explain the reaction(s) in 1-2 sentences. Carbon dioxide reacts with seawater and carbonate to
form bicarbonate - reducing the amount of carbonate in
seawater available for shell-building organisms.
Type your
answer directly
into the boxes.
Type your
answers directly
into the boxes.
Type your
answers directly
into the box.
What word(s) complete(s) the sentences below?
Write the words that fill in the blanks,
below. Word choices: increases, decreases
When CO2 in the atmosphere increases, ocean CO2 ………....…………..
increases
When ocean CO2 ………..……………..….…….., pH …...……......……………………
Increases; decreases
When pH ………......………………………......., Ω …...……......……………………...……
decreases; decreases
Aragonite saturation
state (Ω)
Jan
(% obs)
Feb
(% obs)
Mar
(% obs)
Apr
(% obs)
May
(% obs)
Jun
(% obs)
Jul
(% obs)
Aug
(% obs)
Sep
(% obs)
Oct
(% obs)
Nov
(% obs)
Dec
(% obs)
Ω < 1.5
lethal conditions
8 5 27 2 1 0 1 0 0 0 1 6
Ω < 2.0
conditions not adequate for growth
78 100 82 13 6 1 5 6 6 13 39 72
DATA IN THE CLASSROOM: LEVEL 4
Acidification’s Impact on Animals
4. Construct an Explanation: Given the current conditions in Washington, will larval oysters have enough aragonite to
grow and build shells? Answer the question using the claim, evidence, reasoning table below.
Type directly
into the boxes.
Given the current conditions in Washington, will
larval oysters have enough aragonite to grow and
build shells?
My Claim: Larval oysters may not have enough aragonite to grow
and build their shells during certain times of the year (from
December through March).
Include specific data measurements from the data
table in #3.
Describe any patterns that you notice, including
seasonal patterns.
My Evidence:
In Washington, observations of aragonite saturation state (Ω) were
below the 2.0 threshold 72% of the time during the month of
December, 78% of the time in January, 100% of the time in February
and 82% of the time during March. During the summer months,
<6% of the observations fell below this threshold.
Connect the evidence to your claim.
Need some help with this section? Consider the
following questions.
In natural systems, oysters reproduce in the summer months.
Will larval oysters be able to build their shells given the
current summertime conditions?
Could larval oysters experience lethal conditions at any point
during the year?
My Reasoning:
Larval Pacific oysters may not enough aragonite, a form of calcium
carbonate, to grow and build their shells when aragonite saturation
state (Ω) is less than 2.0. Ω fell below this threshold between 72 and
100% of the time during Dec-Mar. During these months, larval
oysters may not have enough aragonite to grow. However, because
oysters reproduce in the summer months, larvae will be more
abundant during these months (May-Sept). At these times of the
year, Ω fell below the threshold no more than 6% of the time.
Therefore, growth during their first months of life may not be
affected.
DATA IN THE CLASSROOM: LEVEL 5
Design an Investigation
1. Develop Your Question: Ask a question that can be answered using the data available in Level 5 of the module.
Some sample questions are below.
○ How has water chemistry in the Gulf of Maine been affected by global increases in atmospheric CO2?
○ Does ocean pH in the Gulf of Maine follow the same seasonal pattern as coastal Washington?
○ Do the current conditions in the Gulf of Maine support the growth and survival of the soft-shell clam?
○ In 20, 50 or 100 years, will conditions in the Gulf of Maine be suitable for soft-shelled clams and other shellfish?
2. Collect Data: Identify the data that you need to answer your question. If possible, paste or attach your data maps or
charts to this document.
3. Use the claim, evidence, reasoning format to help answer your question.
Type your
answer directly
into the box.
Type your
answers directly
into the boxes.
Type your
answers directly
into the boxes.
Identify a question of interest
about acidification.
Data Date Map or Graph
Example: Gulf of Maine, Ocean pH 2010 – 2015 graph
Claim: Record a simple statement that answers
your question and is based upon evidence.
Evidence: Include specific data from the the
data maps, graphs or charts you have analyzed.
Reasoning: Connect the evidence to your claim.
