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In this activity, learners explore the factors that tend to resist changes in pH of the ocean and why the ocean is becoming more acidic. This lesson guides inquiry into some properties of the ocean’s carbonate buffer system, and how changes in atmospheric carbon dioxide levels may affect ocean pH and biological organisms that depend upon calcification. This lesson was first created for the 2008 Deepwater Coral Expedition: Reefs, Rigs, and Wrecks, but has been updated in 2009 to include recently published information.

Quick Guide

Preparation Time:
30 to 45 minutes

Learning Time:
1 to 2 hours

Estimated Materials Cost:
Over $20 per group of students

Age Range:
Ages 14 - 18

Resource Types:
Activity, Experiment/Lab Activity, Lesson/Lesson Plan


Materials List (per group of students)

  • Copies of Ocean Acidification Inquiry Guide
  • Copies of Ocean Acidification: A Summary for Policymakers from the Second Symposium on the Ocean in a High-CO2 World (optional)
  • Protective goggles and gloves
  • 100 ml glass beakers
  • 100 ml graduated cylinders
  • 500 ml glass beaker
  • 2 - 1 liter beakers or Erlenmeyer flasks for mixing solutions
  • Glass stirring rods
  • Sodium hydroxide pellets, approximately 50 grams (see Learning Procedure Step 1)
  • Solid citric acid (to neutralize sodium hydroxide spills); approximate 450 grams
  • Distilled water
  • Artificial seawater
  • pH test paper, wide range
  • Dilute acetic acid solution in dropper bottles
  • 0.1 M sodium hydroxide solution in dropper bottles


  • Earth and Space Science
    • Earth Processes
      • Weather and Climate
    • Earth Structure
      • Oceans and Water
      • Atmosphere
  • Life Sciences
    • Diversity of Life
      • Plants
      • Animals
    • Ecology
      • Ecosystems
      • Human Impact
  • Mathematics
    • Algebra
      • Equations and Inequalities
    • Data Analysis and Probability
      • Data Analysis
      • Data Collection
      • Data Representation
    • Reasoning and Proof
    • Representation
  • The Nature of Technology
    • Technology and Society
      • Technology and the Environment
  • Physical Sciences
    • Chemistry
      • Chemical Reactions
      • Acids and Bases
      • Chemistry of Life
      • Solutions
    • Structure and Properties of Matter
      • Elements and Periodic Table
      • Elementary Particles and Nuclear Physics
  • The Nature of Science
    • Science and Society
      • Risks and Benefits
    • The Scientific Process
      • Conducting Investigations
      • Gathering Data
      • Formulating Explanations
      • Communicating Results

Informal Categories

  • Animals
  • Nature and Environment


To use this activity, learners need to:

  • see
  • see color
  • read
  • touch

Learning styles supported:

  • Involves teamwork and communication skills
  • Involves hands-on or lab activities


Includes alignment to state and/or national standards:

Includes assesments for student learning:

This resource is part of:

Access Rights:

  • Free access


  • Office of Ocean Exploration, NOAA


  • All rights reserved, NOAA,