A 37-year record from the California Cooperative Oceanic Fisheries Investigations program provides direct evidence of ocean acidification in the Pacific — the oldest such time series in the ocean.
The ocean has absorbed approximately 30% of the carbon dioxide emitted by human activities since the Industrial Revolution. This service has slowed climate change — but at a profound cost to marine chemistry.
A landmark study published in Communications Earth & Environment (Wolfe et al., 2023) presents the first analysis of a 37-year ocean acidification time series from the California Cooperative Oceanic Fisheries Investigations (CalCOFI) program — the oldest such record in the Pacific. The dataset, collected at CalCOFI line 90 station 90 from 1984 to present, shows an unambiguous acidification signal: a decrease in pH of −0.0015 ± 0.0001 per year, in agreement with the global surface ocean trend.
When CO₂ dissolves in seawater, it forms carbonic acid, which dissociates to release hydrogen ions. The result is a measurable drop in ocean pH. Since pre-industrial times, surface ocean pH has fallen from approximately 8.2 to 8.1 — a seemingly small change that represents a 26% increase in acidity due to the logarithmic nature of the pH scale.
The organisms most immediately threatened are those that build shells or skeletons from calcium carbonate: oysters, mussels, sea urchins, corals, and pteropods (tiny free-swimming snails that form the base of many marine food webs). In more acidic water, these structures dissolve faster than they can be built.
NOAA's Ocean Acidification Program (OAP) has documented significant impacts on Alaskan crab fisheries. Long-term declines of red king crab in Bristol Bay may be partially attributed to ocean acidification conditions — impacts that 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 by changing physiological processes, decreasing growth, increasing death rates, and reducing shell thickness.
The economic stakes are enormous. Global shellfish aquaculture is a multi-billion dollar industry. Wild fisheries that depend on pteropods and other calcifiers as prey — including Pacific salmon and Antarctic krill — face cascading disruption. Researchers are calling for urgent investment in ocean alkalinity enhancement and other carbon removal strategies to slow the acidification trajectory before irreversible tipping points are crossed.
Sources & Attribution
This article is based on published research and official reports from credible marine science institutions. Full credit goes to the original authors and organizations listed below.
- 1Wolfe et al. (2023) — A 37-year record of ocean acidification in the Southern California current (Communications Earth & Environment)
Wolfe, W.H., Martz, T.R., Dickson, A.G., Goericke, R., & Ohman, M.D. (2023). A 37-year record of ocean acidification in the Southern California current. Communications Earth and Environment, 4, 406.
- 2NOAA Ocean Acidification Program — Effects of ocean acidification on Alaskan crabs
NOAA Ocean Acidification Program. (2024). A 37-year record of ocean acidification in the Southern California current. NOAA OAP Publications.
- 3NOAA Ocean Acidification Program — Overview & Adaptation
NOAA Ocean Acidification Program. (2024). Understanding and preparing for ocean acidification. National Oceanic and Atmospheric Administration.