Ocean Acidification

What is it?

As carbon dioxide gas is released into the atmosphere and absorbed into the ocean, the gas then dissolves and leads to the formation of carbonic acid. The presence of carbonic acid lowers the concentration of the carbonate ion and pH of the ocean. Lower levels in pH translates to higher acidity levels, thus the term "Ocean Acidification."

H2O + CO2 H2CO3 (carbonic acid)

What are the impacts?

While the impacts of ocean acidification are vast, organisms that rely on the carbonate ion to build their shells such as clams, oysters, urchins, and even coral reefs are at great risk. The decreasing concentrations of the carbonate ion can make maintaining shells more difficult and increasing levels of acidity prove to be corrosive and harmful to such organisms. Another organism that faces the impact of ocean acidification is phytoplankton. Even though these organisms are microscopic, their response to changing levels in pH can have a drastic bottom-up effect on marine ecosystems. Some species of phytoplankton will thrive and others will die out due to competition and available resources. This imbalance of phytoplankton species will influence what higher trophic levels with members such as fish, will be present. This trend will continue up the food web, eventually affecting local fisheries and aquafarms.

Ocean Acidification in the Media

Published in Nature International Journal of Science, a team of scientists from Scripps Institution of Oceanography at University of California San Diego and J. Craig Venter Insitute uncovered how ocean acidification is having detrimental effects on microorganisms like diatoms. Led by Jeffery B McQuaid 2018, he and his team discovered how lower levels in pH decreased the efficiency of a key biological mechanism. The mechanism needed to absorb iron is carbonate dependent, and with decreasing levels of the carbonate ion due to ocean acidification, the more difficult it is for these organisms to obtain the proper amounts of iron needed for overall growth.

Baumann and Smith 2017 over a continuous 15-year study, analyzed the relationship between temperature with fluctuating pH levels, dissolved oxygen, nutrients and measurable levels of chlorophyll present across 16 diverse estuarine environments. What they found was metabolically driven fluctuating levels in pH and dissolved oxygen are a common feature of coastal estuaries, and that mean pH can be estimated by taking measurements of salinity and dissolved oxygen. They also stated with strong empirical data to support, coastal acidification is greater with higher temperatures but chlorophyll and nutrient concentrations had an inverse relationship.

Want to learn more about the chemistry behind ocean acidification? Here is a link to Part One and Part Two of Scripps Institution of Oceanography Professor Andrew Dickson’s "Introduction to CO2 Chemistry in Seawater" lecture on UCTV.

What is SCCOOS doing?

SCCOOS has added ocean acidification monitoring to its ongoing observations of the coastal ocean. Sensors that monitor pH, CO2, and dissolved oxygen have been added to pier stations and gliders. In addition to that, SCCOOS has a burkeolator located at the Carlsbad Aquafarm. This machine was specifically designed to measure fluctuations in marine water chemistry by monitoring pH, salinity, and pCO2. These additions to our monitoring systems will allow for continuous measurements of acidification in the Southern California Bight and will allow for improvements to be made to the models that forecast climate change.

Integrated Ocean Observing System

To better understand ocean acidification and the effects on shellfish, four IOOS Regional Associations have partnered with the shellfish industry to develop more affordable and accurate sensors (ACDC). Five prototypes have been created and deployed at Carlsbad Aquafarms, Hog Island Oyster Company, Whiskey Creek Shellfish Hatchery, Taylor Shellfish, and Alutiiq Pride Shellfish Hatchery.

Underwater Spray Gliders

SCCOOS maintains a network of gliders in the waters off California to monitor climate and ecosystem change. This glider network has been in operation continuously since 2005, with data updates in near real time. Measured variables include pressure, temperature, salinity, currents, and oxygen via integrated dissolved oxygen sensors. The glider data has been used to estimate pH and aragonite saturation, which is important for if the aragonite concentration falls below one, it will lead to the dissolution of shells.


SCCOOS supports nine nearshore stations of the California Cooperative Oceanic Fisheries Investigations (CalCOFI). The CalCOFI group collects samples to characterize the inorganic carbon system at selected locations along its research cruise tracks. Total inorganic carbon and alkalinity are measured which allows for the calculation of pH and pCO2.

California Ocean Acidification and Hypoxia Science Task Force

Formed by scientists from California, Oregon, and Washington, this collaborative effort seeks to provide scientific support to the advisory board of the Ocean Protection Council. Their mission is to aid and inform the OPC in support of continued actions to help protect the California coast from ocean acidification and hypoxia.

Santa Barbara Coastal LTER

The Santa Barbara Coastal Long Term Ecological Research Project (SBC LTER) is a project which aims to monitor and understand the ecology one of the world's most productive types of ecosystems, giant kelp forests. Since its start in April of 2000, the SBC LTER has installed pH sensors and CDTO sensors along the Northern Santa Barbara Channel Islands to carefully monitor acidity, conductivity, temperature, and oxygen levels.


The National Oceanic and Atmospheric Administration (NOAA) Pacific Marine Environmental Laboratory (PMEL) Carbon Program measures ocean carbon levels and ocean acidification with a series pCO2 measurements, from moorings and underway platforms, together with other ancillary measurements such as pH and oxygen levels.


The California Current Acidification Network (C-CAN) is a collaborative effort between the West Coast shellfish industry and scientists to explore what is causing shellfish losses, the role of ocean acidification, and how to adapt to these changes in order to sustain shellfish resources.