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These materials are part of a collection of classroom-tested modules and courses developed by InTeGrate. The materials engage students in understanding the earth system as it intertwines with key societal issues. The materials are free and ready to be adapted by undergraduate educators across a range of courses including: general education or majors courses in Earth-focused disciplines such as geoscience or environmental science, social science, engineering, and other sciences, as well as courses for interdisciplinary programs.
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Unit 2: Ocean Acidification

Michelle Kinzel (San Diego Mesa College/Southwestern College)
Astrid Schnetzer (North Carolina State University)
Cara Thompson (Santa Monica College)

These materials have been reviewed for their alignment with the Next Generation Science Standards as detailed below. Visit InTeGrate and the NGSS to learn more.


In this unit, students begin by estimating their carbon footprint. Students plot authentic ocean pCO2 and pH data using Excel and investigate trends. They are introduced to concepts of carbon cycling, carbon dioxide solubility in oceans and ocean carbon system buffers. Student groups are provided with pH and pCO2 data from different oceans and asked to describe the data, compare to other student groups and interpret their findings.

Science and Engineering Practices

Using Mathematics and Computational Thinking: Use digital tools (e.g., computers) to analyze very large data sets for patterns and trends. MS-P5.1:

Cross Cutting Concepts

Patterns: Different patterns may be observed at each of the scales at which a system is studied and can provide evidence for causality in explanations of phenomena HS-C1.1:

Cause and effect: Cause and effect relationships can be suggested and predicted for complex natural and human designed systems by examining what is known about smaller scale mechanisms within the system. HS-C2.2:

Disciplinary Core Ideas

Earth’s Materials and Systems: All Earth processes are the result of energy flowing and matter cycling within and among the planet’s systems. This energy is derived from the sun and Earth’s hot interior. The energy that flows and matter that cycles produce chemical and physical changes in Earth’s materials and living organisms. MS-ESS2.A1:

Chemical Reactions: Substances react chemically in characteristic ways. In a chemical process, the atoms that make up the original substances are regrouped into different molecules, and these new substances have different properties from those of the reactants. MS-PS1.B1:

Performance Expectations

Earth's Systems: Analyze geoscience data to make the claim that one change to Earth's surface can create feedbacks that cause changes to other Earth systems. HS-ESS2-2:

This material was developed and reviewed through the InTeGrate curricular materials development process. This rigorous, structured process includes:

  • team-based development to ensure materials are appropriate across multiple educational settings.
  • multiple iterative reviews and feedback cycles through the course of material development with input to the authoring team from both project editors and an external assessment team.
  • real in-class testing of materials in at least 3 institutions with external review of student assessment data.
  • multiple reviews to ensure the materials meet the InTeGrate materials rubric which codifies best practices in curricular development, student assessment and pedagogic techniques.
  • review by external experts for accuracy of the science content.

This activity was selected for the On the Cutting Edge Exemplary Teaching Collection

Resources in this top level collection a) must have scored Exemplary or Very Good in all five review categories, and must also rate as “Exemplary” in at least three of the five categories. The five categories included in the peer review process are

  • Scientific Accuracy
  • Alignment of Learning Goals, Activities, and Assessments
  • Pedagogic Effectiveness
  • Robustness (usability and dependability of all components)
  • Completeness of the ActivitySheet web page

For more information about the peer review process itself, please see

This page first made public: Nov 22, 2016


Students will be provided with seawater pH and carbon dioxide concentration (pCO2) data spanning as far back as 1850. They will describe trends in pH, pCO2 and atmospheric CO2 concentration, outline why these parameters are related, and predict how changes in these parameters will affect marine biology. Each group of students will be given a different set of data from different regions and asked to compare with other groups to determine if seawater pH change is a global or regional phenomena. This unit will provide students with an understanding of the pH buffering system and an opportunity to interpret real climate data.

Learning Goals

By completing this unit, students will be able to:
  • Describe carbon dioxide dissolution and solubility in the context of the ocean carbon system;
  • Explain how the ocean carbon system buffers the ocean against rapid changes in seawater pH;
  • Interpret real seawater pH and pCO2 data.

This unit directly supports multiple InTeGrate guiding principles and addresses grand challenges by introducing students to how human activities are connected to the overall health of the ocean, providing a global perspective of seawater pH, and encouraging interpretation of real scientific data.

Context for Use

This unit can be used as a stand-alone unit or as part of the Ocean Sustainability Module. It can be used in an introductory oceanography or environmental science course. This unit is designed to be used in a classrooms of six or more students over the course of one 50-minute class period. Most work is completed in-class, but a pre-homework assignment is available.

Description and Teaching Materials

Pre-lecture Homework Assignment 1: Estimating your carbon footprint

So that students can understand their role in ocean acidification, the instructor should assign pre-lecture homework on using a carbon footprint calculator. The Nature Conservancy provides a great calculator that can be used for either individual or family carbon footprint calculations: Below is a set of questions that can be used as a pre-lecture homework assignment. This assignment should also be completed by the instructor so that his/her carbon footprint estimate can be included in the PowerPoint lecture.

Pre-lecture homework 1 files:

Pre-lecture Homework Assignment 2: Plotting seawater data

This pre-lecture homework assignment can be assigned to help students see where to access and learn how to plot real scientific data. The National Oceanic and Atmospheric Administration (NOAA) is a great place to access such data. In the following assignment, students are led through a data base to access data, then asked to plot that data in Excel and identify trends.

Pre-lecture homework 2 files:

Instructor answer keys:


Activity 2.1. What happens to carbon dioxide after it is taken up by the ocean? (25 min total)

In this activity, students will be introduced to the solubility cycle, then use what they learn to complete a solubility cycle flowchart for carbon in the ocean. They will use this flowchart to interpret real-world data provided to them in Activity 2.2.

10 min: Break students up into groups of 2–4 and have students compare their carbon footprints within their group — understanding that their carbon footprint does not just affect the atmosphere will motivate students to understand the ocean carbon cycle. Introduce the carbon cycle and review basics of the solubility cycle using the PowerPoint provided below or your own short lecture. These slides provided cover the basic marine carbon cycle and how dissolved CO2 changes seawater pH.

15 min: Stop on "Solubility Chart Exercise" lecture slide and provide students with solubility cycle charts. Students can practice the steps of CO2 dissociation using by filling in a solubility cycle flowchart individually for ~8 minutes. At the end of 8 minutes, the instructor should direct them to compare with their neighbors (think-pair-share format). Note to students: the word bank contains some terms that will not be used.

Activity 2.2. How has increased carbon dioxide changed ocean chemistry? (25 min total)

In this activity, students will be provided with data sets of pCO2 and pH (one data set also includes atmospheric CO2), asked to describe the relationship between these parameters, determine the implications these data have for the ocean's ability to buffer against pH changes with modern fossil fuel usage, and predict the implications these data have for organisms that precipitate carbonate shells or skeletons. They will use the carbon cycle flowcharts they made in Activity 2.1 to help them interpret the data sets from the Caribbean Sea, Northern Atlantic Ocean, and Pacific Ocean (see data sets below).

5 min: Review slides 11–14. Slides 11–14 are used to transition to Activity 2.2 and show data that students will be working with in this activity.

20 min: Have students split up into groups. Provide each group of students (3–4 in each group) with one seawater pH and pCO2 data set (Caribbean Sea, Northern Atlantic or Pacific) and guided questions (provided below). Each group is asked to describe the data they are provided in terms of what parameters are given, what trends exist, and how the parameters are related. In smaller classes, groups should compare their data set with nearby groups that have a different data set. In larger classes, have groups summarize their findings for the class.

All groups should work through the guided questions using their data set. Question #6 in the guided questions requires groups to communicate with nearby groups that have different data sets — in the case of smaller class sizes, students may need to move around. In the case of larger class sizes, sub-groups will communicate with each other.

Activity 2.1 and 2.2 files:

Instructor answer keys:

Teaching Notes and Tips

To encourage students to internalize the carbon cycle for themselves, Activity 2.1 should be treated as a think-pair-share exercise. Students should begin to work on the solubility chart on their own for at least five minutes, then share their answers with neighboring classmates after they have had a chance to think on their own. During this activity, the instructor should walk around to make clarifications and answer questions regarding the exercise.

While students are working on Activity 2.2, the instructor should walk around the classroom and ask group members to explain out loud to each other the connection between atmospheric carbon dioxide concentration, partial pressure of carbon dioxide in seawater, and pH.


Rubric for pre-homework assignments 1 and 2 and Activities 2.1 and 2.2 Unit 2 rubric (.xls) (Excel 2007 (.xlsx) 43kB Oct25 16) Unit 2 rubric (.pdf) (Acrobat (PDF) 55kB Oct28 16)

Assessments for Activity 2.1 gauge whether students can describe the carbon cycle. Assessments also assess whether students are able to describe and interpret real scientific data regarding modern changes in the marine carbon cycle and describe how the ocean is buffered against rapid changes in seawater pH.

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These materials are part of a collection of classroom-tested modules and courses developed by InTeGrate. The materials engage students in understanding the earth system as it intertwines with key societal issues. The collection is freely available and ready to be adapted by undergraduate educators across a range of courses including: general education or majors courses in Earth-focused disciplines such as geoscience or environmental science, social science, engineering, and other sciences, as well as courses for interdisciplinary programs.
Explore the Collection »