Ocean Acidification

Part B: Ocean Acidification - A Risky Shell Game?

Ocean acidification can impact marine organisms in a variety of ways

Scientists are only beginning to do the research on how individual species of organisms might respond to increasing levels of ocean acidity as atmospheric levels of CO₂ continue to rise. How will ocean acidification impact Earth's biodiversity? Will all species respond to ocean acidification in the same way? Will some species adapt and others not? To try and find answers to some of these questions, first watch the video "Demystifying Ocean Acidification and biodiversity." As you watch, take notes on how ocean acidification can affect different types of marine organisms.

If the video does not play, you can watch it here: Demystifying ocean acidification and biodiversity impacts - Global threats to biodiversity - Khan Academy

Next, read how scientists at Woods Hole Oceanographic Institute and Marine Laboratories are trying to answer some of the puzzling questions of ocean acidification's effects on biodiversity.

1. Read the Oceanus article Ocean Acidification: A Risky Shell Game. This article reviews the results of lab investigations on the effects of increasing concentrations of atm CO₂ on several different species of marine organisms.
2. Read carefully paragraphs 4 and 5 to understand how they set up their experimental tanks.
3. Make a 4-column table in your lab notebook with the following headings:
   • name of organism
   • temperate or tropical environment (if available)
   • concentration of atm CO₂ exposure (e.g., 400 ppm, 600 ppm, 900 ppm, 2850 ppm)
   • responses to increased acidity
4. Make sure you read both the main article and the slide show of article images pictured on the upper right. As you read, make note of the names of organisms they tested and how they responded to increasing amounts of atm CO_2. Write this information in your table.
5. Explore the interactive (Learn How Animals Build Their Shells) embedded in the article. This interactive will help you understand the chemical relationship between carbon dioxide, shell-building, H+ ions, and ocean acidification.

Now its your turn to do some research of your own!

In Lab 6A, you learned that the ocean's biological pump sequesters large amounts of carbon dioxide in shell-building organisms that eventually die, sink and become part of deep ocean sediments for very long time scales - thousands to millions of years.

Could ocean acidification inhibit the oceanic biological pump by reducing the ability of shell and skeleton builders to sequester carbon? If so, what might happen to other components of the carbon cycle?

To research answers to these important questions, you will take on the role of a marine biologist studying the effect of ocean acidification on Echinoderms, a group of marine organisms that includes star fish, brittle stars and sea urchins. Echinoderms take calcium carbonate out of the seawater and use it to make their internal and external skeletons. As seen in the video below, the sea floor is teeming with Echinoderms.

For this reason, scientists believe that Echinoderms are a significant contributor to the movement of carbon from the biological pump into sea floor sediments.(M. Librato et.al) For your research, you will be studying the effects of ocean acidification on sea urchins, a specific group of Echinoderms. Dr. Gretchen Hofmann, a marine biologist, is a leading researcher on the effects of ocean acidification on sea urchins.

Preparation

Before you begin your own research, listen to Dr. Hofmann describe her research on sea urchins and ocean acidification.

Review the life cycle of sea urchins and how they build their internal and external skeletons.

• Explore the sea urchin life cycle interactive and see a short video on sea urchin development created by Stanford University and the University of Washington at Virtual Urchin Part One.
• You will arrive at the Title page of "Our Acidifying Ocean".
• Next, click on "Cycles" in the menu at the top. This will take you directly to the life cycles of sea urchins interactive. You can also view a video on sea urchin larval development from the Plankton Chronicles Website or Plankton Chronicles-Vimeo.

Develop an experimental hypothesis to answer the research question:
Does ocean acidification inhibit the ability of sea urchins—a type of Echinoderm—to build their internal and external skeletons?

Virtual Urchin Lab Activity

Sea Urchin eggs collected from off the coast of California will be raised in two different pH environments—a pH of 8.1, which represents ocean pH conditions today, and a pH of 7.7, which is predicted within the next 100 years if CO₂ emissions continue to rise. When the sea urchin larva have reached their juvenile stage, you will measure the length of one of the urchins two internal spines(arms). Next, you will calculate the average arm length for each experimental group of larvae. (or larva from the entire class) Note: Your teacher may have you combine the data from the entire class on a class data table. If so, you will determine your average from this class data.

1. Enter The Virtual Urchin Part Two and click Part 2 at the upper right to begin the experiment.
2. Work in the Virtual Urchin Laboratory until you reach the Graphs: Interpreting Results section in Part 3.
3. Copy the data table, graph your data, and include with your written conclusion. If your teacher has the class combine the data from the entire class on a class data table, then you will base your analysis on the class data table.
4. Write a conclusion:
   • Summarize your experiment.
   • Discuss and interpret the results. Explain how the evidence from the lab supports or refutes your hypothesis.

Optional Extensions

Want to find out more about ocean acidification? Check out these resources:

• Research the latest research! New research on the carbon cycle, climate and the environment is on-going. You can use ScienceDaily and/or Phys.org to research recent research on ocean acidification and marine organisms by using combinations of the following tags: ocean acidification, coral reefs, pteropods, sea urchins, lobsters, coccolithophores or any other marine organism you would like to research. Here is an example:
  Rapidly acidifying waters pose major threat for pteropods in the Southern Ocean ecosystem. Be sure to watch the YouTube video that accompanies the article.
• NOAA PMEL Ocean Acidification
• NOAA Ocean Acidification Program
• Wood's Hole Oceanographic Institute
• Ocean Acidification Could Have Driven Earth's Biggest Mass Extinction
• Explore the predicted effects of increasing ocean acidification on coral reefs using this NOAA simulation. Understanding Ocean Acidification Simulation
• Watch the NOVA video Lethal Seas.
• Watch Acid Test Note: There is a misconception in this video that oceans will become an acid. Oceans will become more acidic as more CO₂ is absorbed, but oceans will not become an acid.