Monitoring - NOAA Ocean Acidification Program

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Research Area
Monitoring & Modeling
Ocean acidification monitoring and modeling are essential to assess ocean conditions and link ocean chemistry to impacts to marine life and the people who depend on healthy ecosystems.
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Monitoring "The Big Four"
Learn about what we measure and why.
pH
When the ocean absorbs carbon dioxide, chemical reactions create hydrogen ions that act like free agents, able to react with other compounds. Two ways we track ocean acidification are through pH and total alkalinity (TA). pH is a measure of how many free hydrogen ions are in the seawater. The more carbon dioxide in the ocean, the more these free agents are created, causing lower pH (more acidic).
pCO2
The partial pressure of CO2 (pCO2) tells us how much carbon dioxide is in seawater. This information helps us understand ocean carbonate chemistry and biological productivity in the region. pCO2 increases when the ocean absorbs more CO2 from the atmosphere with elevated emissions.
TA
Alkalinity is the ocean’s buffering system against increasing acidity. Total alkalinity is a measure of the concentration of buffering molecules like carbonate and bicarbonate in the seawater that can neutralize acid.
DIC
Dissolved inorganic carbon (DIC) tells us how much non-biological carbon is in seawater. Inorganic carbon comes in three main forms that we measure for DIC: carbon dioxide (CO2), bicarbonate (HCO3-), and carbonate (CO32-). Understanding DIC can help us determine the balance of carbonate forms in the ocean and the likelihood of ocean acidification.
NOA-ON: Buoys & Moorings
We currently have 15 OAP-supported buoys in coastal, open-ocean, and coral reef waters and one in the Great Lakes.
There are currently 15 OAP-supported buoys that contribute to NOAA's Ocean Acidification Observing Network (NOA-ON).
Currently, there are several types of floating platforms to which instruments can be added in order to measure various ocean characteristics - buoys or moorings,
wave gliders
, and
saildrones.
Buoys are moored, allowing them to remain stationary and for scientists to get
continuous, real-time measurements
from the same place over time. The time series created from these measurements are key to understanding how ocean chemistry is changing over time.
There are also buoys moored in the open-ocean and near coral reef ecosystems to monitor the changes in the carbonate chemistry in these ecosystems. The
MAPCO2 sensors
on these buoys measure pCO2 every three hours.
Access Buoy Data
Ship Surveys
Ocean acidification rsearch cruises are a way to collect information about a certain ecosystem or area of interest.
Anchors aweigh on ocean acidification research cruises
For decades, scientists have learned about physical, chemical and biological properties of the ocean and coasts by observations made at sea. Measurements taken during research cruises can be used to validate data taken by autonomous instruments. These research cruises serve as anchors to bring together researchers from the region and to serve as high-quality data benchmarks for other ocean monitoring in the area.
Coastal OA Cruises
The CTD
One instrument that is paramount on research cruises is a conductivity, temperature, and depth sensor (CTD). CTDs measure fundamental water properties that are essential in water analysis, namely temperature, salinity, and depth. The sensor often goes in the water on a rosette, which also carries Niskin bottles used to collect water samples from various depths in the water column.
What we can learn from the CTD...
Numerous chemical and biological properties can be measured from water collected in the Niskin bottles. These properties include different parameters of the carbonate system used to assess ocean acidification, but also oxygen, nutrients, phytoplankton and more. This approach has the potential to co-locate several types of chemical, physical and biological information that can be used to elucidate processes and ocean acidification effects.
Ships of Opportunity
Partnering with the Private Sector
Ships of Opportunity (SOPs) or Volunteer Observing Ships (VOSs) are vessels at sea for reasons other than ocean acidification , such as commercial cargo ships or ferries.
The owners of these vessels allow scientific instrumentation that measures ocean acidification parameters to be installed and collect data while the ship is underway. This allows data on ocean chemistry to be collected in many remote areas of the world’s ocean, such as high latitude waters, long distances from land (e.g. mid-basin waters), and places not easily accessible by research cruises. These partnerships have greatly increased the spatial coverage of ocean acidification monitoring world-wide. To learn more, check out the Ships of Opportunity programs established by the
NOAA Pacific Marine Environmental Laboratory
(PMEL) and the
NOAA Atlantic Oceanographic Marine Laboratory
(AOML).
Related Projects
See our funded projects in monitoring.
How ocean acidification affects microbes and plankton in the Gulf of America
PI(s): Emily Osborne. NOAA Atlantic Oceanographic and Meteorological Laboratory
Fiscal Year Funded: 2024, 2025, 2026
Partners:
Atlantic Oceanographic & Meteorological Laboratory (AOML)
Cooperative Institute For Marine And Atmospheric Studies (CIMAS)
This project assesses how ocean acidification impacts microbes and phytoplankton driving the biological carbon pump in the Gulf of America...
Project Summary >
Optimizing the ocean acidification observing system in California
PI(s): Christopher Edwards, University of California, Santa Cruz
Fiscal Year Funded: 2019, 2020, 2021
Partners:
Monterey Bay Aquarium Research Institute (MBARI)
University of California, Santa Cruz
This project specifically investigates how the observing network is contributing to forecasting models using these complex tools to estimate ocean acidification conditions throughout the central California Current System...
Project Summary >
Building capacity for seawater certified reference materials
PI(s): Denis Pierrot, NOAA Atlantic Oceanic and Meteorological Laboratory; Katelyn Schockman, University of Miami/CIMAS
Fiscal Year Funded: 2024, 2025, 2026
Partners:
Atlantic Oceanographic & Meteorological Laboratory (AOML)
University of Miami/CIMAS
This project will build a reference material (RM) production facility at NOAA’s Atlantic Oceanic and Meteorological Laboratory (AOML), with the capability to produce RMs for use by NOAA laboratories and..
Project Summary >
Wave Gliders
The Carbon Wave Glider
Scientists at the NOAA Pacific Marine Environmental Laboratory (
PMEL
) work with engineers at
Liquid Robotics, Inc.
to optimize a
Carbon Wave Glider
This wave glider can navigate via satellite from land. Carbon Wave Gliders can be outfitted with pCO2, pH, oxygen, temperature and salinity sensors. Gliders takes measurements as it moves through the water, expanding the spatial sampling of the area. The glider’s motion is driven by wave energy, and its sensors are powered through solar cells and batteries, when needed.
Coral Reef Monitoring
NOAA’s Coral Reef Conservation Program (
CRCP
) in partnership with OAP engages in a coordinated
and targeted series of field observations, moorings and ecological monitoring efforts in coral reef ecosystems.
The Coral Reef Conservation Program (
CRCP
) documents the dynamics of ocean acidification in coral reef systems and tracks the status and trends in ecosystem response. This effort serves as a subset of a broader CRCP initiative referred to as the National Coral Reef Monitoring
Plan
, which was established to support conservation of the Nation’s coral reef ecosystems.
OAP contributes to this plan through overseeing and coordinating carbonate chemistry monitoring. This monitoring includes a broadly distributed spatial water sampling campaign complemented by a more limited set of moored instruments deployed at a small subset of representative sites in both the Atlantic, Caribbean, and Pacific regions.
Coral reef carbonate chemistry monitoring is implemented by researchers at the NOAA Atlantic Oceanographic & Meteorological Laboratory (
AOML
) and NOAA’s Pacific Islands Fisheries Science Center (
PIFSC
) Coral Reef Ecosystems Division.
Benthic Surveys
Divers conduct benthic surveys to account for coral diversity and assess fish communities.
Calcification Accretion Units
Calcification Accretion Units (CAUs) assess the effects of changes in seawater carbonate chemistry on calcification (growth) and accretion in coral reefs and fleshy algae.
Monitoring Carbonate Chemistry
Carbonate chemistry monitoring determines the status of ocean acidification and its potential impacts on calcifiers like coral reefs and coralline algae.
Benthic Quadrats
Benthic quadrats are a common field tool when assesing coral cover.
CT Scans
Computerized tomography (CT) scans image the internal structure of corals.
Autonomus Reef Monitors
Deployed instruments monitor ocean conditions on reefs continuously.
Figure from: Harvey et al. 2010
Ecosystem Modeling
Experiments on species response suggest that ocean acidification will directly affect a wide variety of organisms from calcifying shellfish and coral to fish and phytoplankton. Ecosystem models can capture the complex effects of ocean acidification on entire ecosystems.
How marine organisms respond to ocean acidification will be influenced by their reaction to chemistry change and their interactions with others species, such as their predators and prey. Scientists use ecosystem models to understand how ocean chemistry may affect entire ecosystems because they account for the complex interactions between organisms. Output from such modeling exercises can inform management of fisheries, protected species, and other important natural resources. Because ecosystem feedbacks are complex, understanding the uncertainty associated with these models is critical to effective management.
From Observations to Forecasts
Turning current observations into forecasts is the key mechanism by which adaptation plans are created.
Forecasting provides insight into a vision of the future by using models that visualize how quickly and where ocean chemistry will be changing in tandem with an understanding of how sensitive marine resources and communities are to these changes.
By making predictions about the future, we can better adapt and prepare for ocean acidification. Coastal forecasts for ocean acidification are currently being developed for the West Coast, Chesapeake Bay, the East Coast, Caribbean and the western Gulf of America (formerly known as Gulf of Mexico).
Ocean acidification hotspots are areas that are particularly vulnerable, either from a biological, economic, or cultural perspective. Identification of these hot spots in coastal waters is a priority for the Coastal Acidification Networks (CANs), fostered by the Ocean Acidification Program around the country.
These networks bring together scientists, decision makers, fishermen and other stakeholders to identify and answer the most important questions about acidification and its effects in the region.
NOAA scientists have played an important role in development of the
J-SCOPE forecast system
, used to create seasonal forecasts for the North Pacific region. These forecasts will allow fisheries managers to predict seasonal outlooks for management decisions. Click on the image to open a lightbox.
Related Publications
See publications from our funded projects for ocean acidification monitoring.
Modeling the spatiotemporal effects of ocean acidification and warming on Atlantic sea scallop growth to guide adaptive fisheries management
Halle M. Berger, Samantha A. Siedlecki, Shannon L. Meseck, Emilien Pousse, Deborah R. Hart, Felipe Soares, Antonie Chute, Catherine M. Matassa
Ecological Modelling
December 13, 2025
Citation:
Halle M. Berger, Samantha A. Siedlecki, Shannon L. Meseck, Emilien Pousse, Deborah R. Hart, Felipe Soares, Antonie Chute, Catherine M. Matassa, Modeling the spatiotemporal effects of ocean acidification and warming on Atlantic sea scallop growth to guide adaptive fisheries management, Ecological Modelling, Volume 513, 2026, 111434, https://doi.org/10.1016/j.ecolmodel.2025.111434.
Read Summary >
Three-dimensional photogrammetry-based monitoring to enhance site-level carbonate budget assessments of coral reefs
John T. Morris, Clinton B. Edwards, Alice Webb, Hannah Barkley, T. Shay Viehman, Ana Palacio-Castro, Michaela Wong, Aliany Ramos-Rosado, Heidi K. Hirsh, Nicole Besemer, Vid Petrovic, Chris T. Perry, Kayelyn R. Simmons, Ian C. Enochs
Limnology and Oceanography: Methods
September 13, 2025
Citation:
Morris, J.T., Edwards, C.B., Webb, A., Barkley, H., Viehman, T.S., Palacio-Castro, A., Wong, M., Ramos-Rosado, A., Hirsh, H.K., Besemer, N., Petrovic, V., Perry, C.T., Simmons, K.R. and Enochs, I.C. (2025), Three-dimensional photogrammetry-based monitoring to enhance site-level carbonate budget assessments of coral reefs. Limnol Oceanogr Methods. https://doi.org/10.1002/lom3.70000
Read Summary >
Mechanisms of Ocean Acidification in Massachusetts Bay: Insights from Modeling and Observations
Lu Wang, Changsheng Chen, Joseph Salisbury,Siqi Li, Robert C. Beardsley, Jackie Motyka
Remote Sensing
July 30, 2025
Citation:
Wang, L., Chen, C., Salisbury, J., Li, S., Beardsley, R. C., & Motyka, J. (2025). Mechanisms of Ocean Acidification in Massachusetts Bay: Insights from Modeling and Observations. Remote Sensing, 17(15), 2651. https://doi.org/10.3390/rs17152651
Read Summary >
Get involved with ocean acidification
The NOAA Ocean Acidification Program exists to meet the ocean acidification research and monitoring needs of the U.S. See how you can get involved to serve your community and participate in cutting-edge research and education and outreach.
Current Funding Opportunities
Bioeconomic modeling to inform Alaska fisheries management
Image credit: Allen Shimada, NOAA NMFS
Bioeconomic models are a multidisciplinary tool that use oceanography, fisheries science and social science to assess socioeconomic impacts. Funded by the Ocean Acidification Program, researchers at the
Alaska Fisheries Science Center
use a bioeconomic model to study the impacts of ocean acidification on Eastern Bering Sea crab, northern rock sole and Alaska cod. The goal is to predict how ocean acidification will affect abundance yields and income generated by the fisheries. This work informs the potential economic impacts of ocean acidification and future decision making and research planning.
More about this work
Effects of ocean acidification and temperature on Alaskan crabs
Image credit: David Csepp, NMFS AKFSC ABL
Long-term declines of red king crab in Bristol Bay, Alaska may be partially attributed to ocean acidification conditions. These impacts may be partially responsible for the fishery closures during the 2021–2022 and 2022–2023 seasons. Researchers found that ocean acidification negatively impacts Alaskan crabs generally by changing physiological processes, decreasing growth, increasing death rates and reducing shell thickness. Funded by the Ocean Acidification Program, scientists at the
Alaska Fisheries Science Center
continue to investigate the responses of early life history stages and study the potential of various Alaska crabs to acclimate to changing conditions. Results will inform models that will use the parameters studied to predict the effects of future ocean acidification on the populations of red king crab in Bristol Bay as well as on the fisheries that depend on them. Fishery managers will better be able to anticipate and manage stocks if changing ocean chemistry affects stock productivity and thus the maximum sustainable yield.
More about this work
Forecasts for Alaska Fisheries
Image credit: Michael Theberge
Understanding seasonal changes in ocean acidification in Alaskan waters and the potential impacts to the multi-billion-dollar fishery sector is a main priority. Through work funded by NOAA’s Ocean Acidification Program, the
Pacific Marine Environmental Laboratory
developed a model capable of depicting past ocean chemistry conditions for the Bering Sea and is now testing the ability of this model to forecast future conditions. This model is being used to develop an ocean acidification indicator provided to fisheries managers in the annual NOAA
Eastern Bering Sea Ecosystem Status Report
ADAPTING TO OCEAN ACIDIFICATION
The NOAA Ocean Acidification Program (OAP) works to prepare society to adapt to the consequences of ocean acidification and conserve marine ecosystems as acidification occurs. Learn more about the
human connections and adaptation strategies
from these efforts.
Adaptation approaches fostered by the OAP include:
FORECASTING
Using models and research to understand the sensitivity of organisms and ecosystems to ocean acidification to make predictions about the future, allowing communities and industries to prepare
MANAGEMENT
Using these models and predictions as tools to facilitate management strategies that will protect marine resources and communities from future changes
TECHNOLOGY DEVELOPMENT
Developing innovative tools to help monitor ocean acidification and mitigate changing ocean chemistry locally
REDUCING OUR CARBON FOOTPRINT
50 more ways to reduce your carbon footprint >
On the Road
Drive fuel-efficient vehicles or choose public transportation. Choose your bike or walk!
Don't sit idle for more than 30 seconds.
Keep your tires properly inflated.
With your Food Choices
Eat local- this helps cut down on production and transport! Reduce your meat and dairy. Compost to avoid food waste ending up in the landfill
With your Food Choices
Make energy-efficient choices for your appliances and lighting. Heat and cool efficiently! Change your air filters and program your thermostat, seal and insulate your home, and support clean energy sources
By Reducing Coastal Acidification
Reduce your use of fertilizers, Improve sewage treatment and run off, and Protect and restore coastal habitats
TAKE ACTION WITH YOUR COMMUNITY
You've taken the first step to learn more about ocean acidification - why not spread this knowledge to your community?
Every community has their unique culture, economy and ecology and what’s at stake from ocean acidification may be different depending on where you live.  As a community member, you can take a larger role in educating the public about ocean acidification. Creating awareness is the first step to taking action.  As communities gain traction, neighboring regions that share marine resources can build larger coalitions to address ocean acidification.  Here are some ideas to get started:
Work with informal educators, such as aquarium outreach programs and local non-profits, to teach the public about ocean acidification. Visit our
Education & Outreach
page to find the newest tools!
Participate in habitat restoration efforts to restore habitats that help mitigate the effects of coastal acidification
Facilitate conversations with local businesses that might be affected by ocean acidification, building a plan for the future.
Partner with local community efforts to mitigate the driver behind ocean acidification  – excess CO2 – such as community supported agriculture, bike & car shares and other public transportation options.
Contact your regional
Coastal Acidification Network (CAN)
to learn how OA is affecting your region and more ideas about how you can get involved in your community
More for
Taking Community Action