Lesson Title: Understanding The
Harmful Effects of Ocean Acidification
on Marine Life through simulation
Grade Level: 11-12
Prepared by: Molly Nation
Subject Area(s): Marine Science
Associated with: Chemistry Unit
Time Required: 1 class period (beginning and end of experiment)
Background
For tens of millions of years, Earth's oceans have maintained a relatively stable level
of acidity. It is within this steady environment that the rich and varied web of life in
today's seas arose and flourished. But scientific research done by NOAA (National
Oceanic and Atmospheric Administration) shows that a recent and rapid drop in the
pH of the water near the surface of the ocean could undo this ancient balance, which
can have devastating global consequences.
Since the beginning of the industrial revolution in the early 1800s, fossil fuelpowered machines have driven an unprecedented burst of human industry and
advancement. The unfortunate consequence, however, has been the emission of
billions of tons of carbon dioxide (CO2) and other heat trapping gases into Earth's
atmosphere.
Scientists now know that about half of this anthropogenic, or man-made, CO2 has
been absorbed by the oceans. This has benefited us by slowing the climate change
these emissions would have instigated if they had remained in the atmosphere. The
result of this is that the massive amounts of CO2 that the oceans have already
absorbed has altered the water chemistry, which affects the life cycles of many
marine organisms, particularly those at the lower end of the food chain.
Carbonic Acid
When carbon dioxide dissolves in the oceans, carbonic acid (H2CO3)is formed. This
leads to higher acidity (lower pH), mainly near the surface, which has been proven
to inhibit shell growth in marine animals and is suspected as a cause of reproductive
disorders in some fish.
On the pH scale, which runs from 0 to 14, solutions with low numbers are
considered acidic and those with higher numbers are basic. Seven is neutral. Over
the past 300 million years, the pH of the oceans has been slightly basic, averaging
about 8.2. Today, it is around 8.1, a drop of 0.1. Because pH is a logarithmic scale,
this small numeric change represents a 25% increase in acidity since the beginning
of the industrial revolution in the early 1800s.
Carbon Storehouse
The oceans currently absorb about a third of human-created CO2 emissions, roughly
22 million tons per day. Projections based on these numbers show that by the end of
this century, continued emissions could reduce ocean pH to 7.6, a decrease of 0.5.
Shell-forming animals including corals, oysters, shrimp, lobster, many planktonic
organisms, and even some fish species could be gravely affected.
Equally worrisome is the fact that as the oceans continue to absorb more CO2, their
capacity as a carbon storehouse could diminish. That means more of the carbon
dioxide we emit will remain in the atmosphere, further aggravating global climate
change.
Scientific awareness of ocean acidification is relatively recent, and researchers are
just beginning to study its effects on marine ecosystems. Fossil and other evidence
indicate that for tens of millions of years the Earth's oceans have maintained a
relatively stable level of acidity. It is within this steady environment that the rich
and varied web of life in today's seas has arisen and flourished. However, as the
oceans acidify, marine species will be under increasing pressure to adapt to their
habitat's changing chemistry or become extinct. (Source: National Geographic)
Learning Objectives:
1. Students will be able to define ocean acidification.
2. Students will be able to understand and apply a simulation of the effects of
ocean acidification on marine life.
3. Students will understand why is important to understand the effects of
dissolved CO2 in our oceans.
4. Students will be able to link ocean acidification to its effects on marine life.
5. Students will be able to explain the relationship among the human
production of CO2, ocean acidification, and climate change.
Procedure:
Teacher leads discussion about the effects of Global Climate Change and the addition
of CO2 into our atmosphere and how it can relate to Ocean Acidification. To simulate
the negative effects of lower pH ocean water on marine life the students will create a
simulation using household acids or chemicals available to them in their classrooms.
1. Students should identify normal ocean pH and simulate that pH in their
container. (Test using the pH paper)
2. Place the marine animal shell in the bottom of the 50mL beaker, cover with
20mL of tap water and make observations.
3. Lower the pH of the water in the container (by adding one mL/or 10 drops of
the acidic solution to the container) to simulate ocean acidification.
4. Measure the pH of the water using the pH paper.
5. Make observations about what is happening to the marine life at the bottom
of the container.
6. Continue to lower the pH of the water (by adding 1mL at a time until you
have reached 5mL) and make observations about the effects of the lower pH
on the marine life until the water solution reaches a pH of ~4
Materials:
-Shell Samples (Echinoderms, Coral, Bivalves, Gastropods)
-Acid (Vinegar 0.83M, or 0.1M HCl, etc.)
-50mL Beaker
-dropper or 10mL graduated cylinder
-tap water (20mL)
-scale/balance
-pH Paper (Which can measure an acidic range from 2-6)
Lesson Title: Understanding The
Harmful Effects of Ocean Acidification
on Marine Life through simulation
What factors Influence Ocean Acidification?
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Record your Observations
Initial mass of Calcium Carbonate Material (Shell, coral, etc.) ___________g
pH of the Water in
your Beaker
Observations, what changes happened to the
marine animal when you added the acid and
lowered the pH? Why do you think this
happened?
Final mass of Calcium Carbonate Material (Shell, coral, etc.) ___________g
Conclusions and Data Analysis:
1) How is ocean acidification happening in our oceans?
2) What sorts of negative effects does ocean acidification have on marine animals?
(Specifically those made of Calcium Carbonate)
3) How could climate change factors influence the future of marine life in our
oceans?
4) What future impacts could these changes have on our oceans and ocean life?
5) How did your final and initial weight of your Calcium Carbonate sample change?
What do you think happened to the material and why do you think this happened?
6) What can be done to help slow the process of ocean acidification? How can you
personally influence this change?