Ocean acidification (OA) refers to the change in ocean chemistry caused by increasing concentrations of anthropogenic carbon dioxide (CO2) in the atmosphere. OA often co-occurs with hypoxia, which are conditions of low dissolved oxygen in marine systems.

OA in the Pacific Northwest


In 2020, the MWEEs by the Sea project held a one-hour webinar for educators focused on the problem of Ocean Acidification (OA). Participants heard from NOAA researchers about the causes and impacts of OA, learned about Oregon's OAH Council, and were presented with an overview of a new OA high school curriculum from Oregon Sea Grant. The session ended with a period of Q&A.


  • Shallin Busch, Ph.D. - NOAA OA Program, Northwest Fisheries Science Center
  • Paul McElhany, Ph.D. - Northwest Fisheries Science Center
  • Charlotte R. Whitefield, Ph.D. - OA Policy Asst. Project Leader, ODFW
  • Tracy Crews - Oregon Sea Grant Marine Education

Watch the Recorded Webinar


Photo: NOAA Ronald H. Brown research ship - Simone Alin (top) and a colleague perform maintenance on a moored ocean buoy [Credit: Bruce Cowden]

Classroom Activities

Data in the Classroom

Data in the Classroom websiteUse NOAA's Data in the Classroom lessons to engage high school students with real-time ocean data. Updated in 2019, the new Data in the Classroom website includes interactive web maps, apps, videos, and high-resolution images.  The curriculum includes five unit topics, teacher guides, student worksheets, and mapping tools so that students can "get data".

The Understanding Ocean & Coastal Acidification unit consists of five lesson levels that help students use NOAA data to understand patterns in ocean pH levels and impacts of OA. Lessons begin with basic graph interpretation and build towards activities that challenge students to ask questions and develop their own data investigations.

Changing Ocean Chemistry

In 2019, Oregon Sea Grant published a new high school curriculum based on OA's causes, impacts, and solutions, based on a comprehensive review of  existing OA lessons available. The resulting curriculum contains the best lessons available and attempts to fill two gaps identified by the research review. The lessons move beyond the typical focus of shell dissolution as an impact, and incorporates activities where students can work on solutions to the OA problem.

Bromothymol Blue Experiments

Bromothymol blue (BTB) is a pH indicator that is often used to detect the effects of carbonic acid in water. After adding a few drops of 4% BTB to otherwise clear water, the liquid will remain blue when the pH is alkaline (near 7.6). If the pH of the water is closer to 6.0, then the liquid will turn yellow. During the transition to or from alkaline and acidic solutions, the water appears as a greenish color. The visual effect of the water changing color is fun and engaging for learners of all ages. 

In the most basic set-up, BTB can be used to demonstrate to students that:

  1. CO2 from the atmosphere can enter water, and
  2. Atmospheric CO2 changes the pH of that water.

More explanation and procedures for demonstration is detailed in the NOAA Ocean Explorer lesson below. In short, after adding a few drops of BTB to a cup of water, one notices the color of the water (blue). After exhaling through a straw into the water, thus bubbling CO2 into the solution, one observes the water color change to yellow.

Extensions and Considerations:

  • As in the NOAA lesson above, compare and contrast seawater and fresh water to launch a discussion about the carbonate buffer system of seawater.
  • Preserve wonder by not revealing what the experiment is about, or even that BTB has anything to do with pH. Instead, let students figure out what is going on as they move through the procedure. At each step, ask "What do you notice? What is going on?" Student observations can lead to discussions about density, human respiration, pH, and ultimately, OA. Read more about using BTB in this way in Salter, et al (2008): Injecting Inquiry into Photosynthesis Investigations
  • Many lessons involving BTB suggest that users wear safety glasses during the experiment. This experiment may not be appropriate for younger students who might suck up liquid into the straw. Therefore, consider using another source of CO2 instead of breathing through a straw (like a soda bubbler), or sharing the experiment as a class demonstration rather than an experiment the students do themselves.
  • Be aware of potential misconceptions. For example, animal respiration is not the cause of ocean acidification. The change in ocean pH is caused by CO2 produced by human burning of fossil fuels.

Well, Well, Well

The Northwest Association of Networked Ocean Observing Systems (NANOOS) created a lesson to help students use the NANOOS Visualization System to understand processes surrounding upwelling and downwelling off the coast of Oregon and Washington. At the end, students are challenged to explore the role of upwelling in ocean acidification and coastal hypoxia.

Field Experiences

Measuring pH and dissolved oxygen


Students can collect their own measurements of pH and dissolved oxygen (DO) in aquatic and marine environments to help characterize water quality in the watershed. Visit the Streamwebs website for water quality tutorials, data sheets, and watersehd investigation curriculum. Students can also upload their data into the platform and visual their results and the findings of other students throughout the state.

Oregon Coast educators can borrow Venier equipment and other field supplies no cost for up to two weeks from any of the Oregon Coast STEM Hub resource trailers. Some trailers have OA Kits from Streamwebs, as well.

Salmon Watch Videos
in 2020, the Oregon Department of Fish and Wildlife began creating videos to take the place of salmon-focused watershed field trips which had been interrupted by the COVID-19 pandemic. In the water quality video, a presenter demonstrates how to measure physical and chemical characteristics of an inland stream (temperature, turbidity, dissolved oxygen, and pH).

Find more resources on the MWEEs by the Sea Water Quality page.

Oyster Farm Tour

How does OA affect shellfish growers? Plan a field experience to an oyster farm to find out how shellfish are raised and harvested, and ask questions to find out how the industry is planning for the future.

Industry Impacts Background

Setting up an Industry Tour (limited during COVID-19)

More OAH Resources

Ocean Acidification and Hypoxia in Oregon


Ocean Acidification and Hypoxia in Washington

Explore Washington Sea Grant webpage dedicated to OA Outreach and Education. Find fact sheets, videos, ideas for simple OA demonstrations, and more!

Oregon Marine Scientist and educator Alliance Lessons

ORSEA Lesson: Oyster Larvae Catastrophe, 2020

The Oregon Marine Scientist and Educator Alliance (ORSEA) lesson Oyster Larvae Catastrophe was created by scientist/teacher teams and piloted in middle school classrooms on the Oregon coast. The project based learning lesson is centered around the driving question "What caused the oyster larvae die off, and what can we do?"




Photo: Wikimedia Commons



ORSEA Lesson: Geometry of Marine Invertebrates, 2020

The Oregon Marine Scientist and Educator Alliance (ORSEA) lesson Geometry of Marine Invertebrates was created by scientist/teacher teams and piloted in a middle school classroom on the Oregon coast. The project based learning lesson is centered around the driving question "How does the surface area to volume ratio affect the ability of marine invertebrates to obtain oxygen?" The answer may help scientists understand how different marine invertebrates respond to hypoxic events.


Photo: Patiria miniata, by MacKenna Hainey

NOAA OA Resources



CSI Webinar: George Waldbusser, December 2020

This Careers in Science Investigations (CSI) webinar from Oregon Sea Grant features George Waldbusser, a biogeochemist at Oregon State University who studies how carbon dioxide is changing the chemistry of the ocean and affecting shellfish, including oysters and pink shrimp. CSI webinars are designed for students in high school, and presenters talk the work they do, how they arrived at their marine science career, and what advice they have for students who may be interested in pursuing a marine science career. Read more * Watch Video



Photo: Oregon Sea Grant

Student Stewardship and Action Projects

Get Involved: High school interns help monitor OA at Redfish Rocks Marine Reserve

Learn more



Battling Climate Change: Ecologist and a network of volunteers monitor ocean pH levels

Read the article