Name: _____________________________________________ Date:_________ period:_____
Unit 2: Ecology and Global Climate Change
Double-Y Practice
Essential Question: How do I rock the next Earned Honors test?
The Intergovernmental Panel on Climate Change collects data on the pH of oceans at the surface and
atmospheric carbon dioxide (the data is presented below). Graph this data on a double-y graph.
 Plot the surface pH on the left side vertical axis.
 Plot atmospheric CO2 on the right side vertical axis.
 Time (years) should be plotted on the horizontal axis.
 Use different colored lines for pH and CO2.
 When setting up the vertical axis scales, set them so that the maximum surface pH and maximum
atmospheric CO2 correspond roughly to the same height. (Remember your scale should take up as
much of the graph as possible!)
Relationship between Surface pH and Atmospheric CO2 in Oceans over time.
Year
Surface pH
2000
2020
2040
2060
2080
2100
8.10
8.00
7.95
7.90
7.8
7.74
Atmospheric CO2
(µatm)
360
400
500
600
750
950
Graph Analysis Question:
1. Does surface pH or ocean water and atmospheric CO2 concentrations appear to be related? Explain.
Directions: Read and annotate the passage below from the Center for Ocean Solutions. Once you are
done, respond to the reflection questions.
The oceans have absorbed almost one-half (approximately 525 billion tons) of human-released CO2
emissions since the Industrial Revolution. Although this has reduced the effect of greenhouse gas emissions
on global warming, it is chemically altering marine ecosystems 100 times faster than it has in the last
650,000 years. In fact, recent studies suggest that the oceans are becoming less able to absorb as much
carbon dioxide as they have in the past, decreasing their ability to buffer against climate change.
By absorbing massive amounts of carbon dioxide, the pH (a measure of acidity) in ocean surface waters has
dropped approximately 30%. Naturally, the oceans are slightly basic, meaning they are slightly above 7 on
the pH scale (7 is neutral, below 7 is acidic, and above 7 is basic). As CO2 dissolves in the ocean, the water
becomes more acidic and the amount of dissolved carbonate available for calcium carbonate shell and
skeleton formation – important to corals, plankton and shellfish – decreases.
Prior to industrialization, the pH of the oceans was on average about 8.2; however, since then, the average
pH has dropped about 0.1 units. While this may seem like a small change, it actually represents a 26
percent increase in water acidity.
As higher levels of CO2 are absorbed into the oceans, fewer carbonate ions (CO32- ) are available for
organisms such as corals, clams, sea urchins and plankton to produce their calcium carbonate (CaCO 3)
shells and skeletons. With increasing ocean acidity, the rates at which reef-building corals produce their
skeletons decreases, and if the carbonate concentration falls too low, the shells may start to dissolve. By
the middle of the century, coral reefs may erode faster than they can be built.
These impacts will have serious consequences for people that depend on the reefs for their livelihoods,
whether from subsistence use or from larger scale tourism, coastal protection and commercial
fisheries. Studies show that the consequences become successively worse as CO2 concentration increases,
and unmanageable for CO2 concentrations above 500 ppm.
A lower pH means it will become harder for some plankton to maintain their protective shells. Plankton,
which are tiny floating plants and animals, form the base of the ocean food chain and produce over half the
oxygen in the air we breathe through photosynthesis. Many types of plankton, for example,
cocoolithophores and foraminifera, form calcium carbonate shells and will be affected by acidification.
A lower pH is not only trouble for corals and plankton, but is likely to affect a wide range of marine
organisms. For instance, it may decrease the survival rates of young fish. Scientists predict that mussel and
oyster calcification could decrease significantly by the end of the 21 st century and crustose coralline algae, a
major component of marine habitats from polar to tropical regions, have calcium carbonate
components. These algae help provide the foundation for the growth of corals and if affected by ocean
acidification, coral reefs may be compromised.
Pteropods, small marine planktonic snails, are another crucial link in the ocean food chain. They are an
important source of food for juvenile North Pacific salmon, giant whales and tiny krill. However, scientists
have determined that under the condition of increasing ocean acidification, pteropod shells will weaken,
thus compromising the health of these organisms. This has the potential to create significant changes in
the biodiversity of the oceans.
Based on future CO2 emission projections, the Intergovernmental Panel on Climate Change predicts that by
2100 the ocean will be 2-2.5 times more acidic than pre-industrial levels. Marine life as we know it, is not
adapted to these conditions. Scientists are working to determine the full extent of the problems associated
with acidification. However, they know that many marine plants and animals are at risk from rapid
acidification. Without effective and efficient action, it will take the oceans thousands of years to reestablish
chemical conditions that resemble those found today.
Reflection Questions:
1. How have oceans helped reduce the effect of greenhouse gas emissions on global warming?
2. What impact does acidic water have on the amount of dissolved carbonate available? What
consequences could this have?
3. What impact could the erosion of coral reefs have on humans? Why?
4.
a. What are the direct consequences a lower pH on plankton?
b. What are the possible consequences this could have on humans? Explain.
5. Based on future carbon dioxide emissions projections, what did the IPCC predict about the ocean’s
acidity by the year 2100?