Ocean Acidification

Introduction

In the previous Lab, you learned that oceans currently behave as carbon sinks because they absorb approximately 25-30% of the carbon dioxide put into the atmosphere by human activities. That's a good thing, right? Not necessarily so, as scientists are now discovering. Oceanographers and marine biologists are now seeing a relationship between changes in ocean pH and carbon dioxide dissolved in sea water. Ocean acidity, as measured by pH, has increased by 30% since the industrial revolution and scientists predict pH will continue to change as increasing amounts of carbon dioxide are absorbed by oceans. Because the chemistry of the oceans is important to life, subtle changes in that chemistry may have significant effects on the health of individual species and on entire ecosystems. Corals and other shell-builders such as oysters, lobsters and pteropods may be at risk as ocean ph chemistry becomes more acidic. How will individual species and ecosystems respond as oceans become more acidic?

In Part A, you will carry out a class experiment to test the effects of increased amounts of CO₂ on pH. Then, you will analyze time-series graphs to search for relationships between trends in atmospheric CO₂, dissolved CO₂ in seawater, and changes in ocean pH. In Part B, you will review and analyze the results of research compiled by the Woods Hole Oceanographic Institute on the effect of ocean acidification on a variety of marine organisms. You will then carry out a virtual lab—the Virtual Urchin—to study the effect of a more acidic seawater pH on sea urchin larvae.

After completing this Lab, you should be able to:

• Explain what ocean acidification is and why it is happening.
• Describe ways in which individual species and marine ecosystems might respond to ocean acidification.
• Describe how ocean acidification may impact the ability of oceans to store carbon in deep sea sediments.

Keeping Track of What You Learn

Throughout these labs, you will find three kinds of questions.

• Checking In questions are intended to keep you engaged and focused on key concepts and to allow you to periodically check if the material is making sense. These questions are often accompanied by hints or answers to let you know if you are on the right track.
• Stop and Think questions are intended to help your teacher assess your understanding of the key concepts and skills you should be learning from the lab activities and readings.
• Discuss questions are intended to get you talking with your neighbor. These questions require you to pull some concepts together or apply your knowledge in a new situation.

Your teacher will let you know which answers you should record and turn in.