Ocean Acidification Disrupting Marine Food Chains
Ocean pH has declined by approximately 0.1 units since the pre-industrial era, representing a 26-30 percent increase in acidity. The ocean absorbs roughly 30 percent of anthropogenic CO2, and pH is projected to decline a further 0.15 to 0.5 units by 2100 depending on emissions. Acidification reduces calcium carbonate availability critical for shell-forming organisms, causes a 74 percent decline in fish egg and larval survival rates, and disrupts predator-prey interactions throughout the marine food web.
Probability
Horizon: 30y
By consensus
High divergence across consensus frameworks
Claims
Ocean pH is projected to decline by an additional 0.15 to 0.5 units by 2100, depending on emissions trajectories, with severe consequences for calcifying organisms.
IPCC AR6 WG1 provides these projections based on multiple Earth system models across SSP scenarios. The chemistry of CO2 dissolution is well-understood and projection uncertainty is dominated by emissions pathway uncertainty.
Coastal indigenous communities dependent on shellfish harvesting are already documenting changes in shell quality and species abundance consistent with acidification impacts.
Acknowledges the chemistry but expects decarbonization plus potential localized alkalinity enhancement technologies to moderate the worst-case projections.
Ocean acidification causes cascading disruption through marine food webs by degrading primary producer food quality and impairing larval development of commercially important species.
Multiple experimental and observational studies document impacts on primary producers, secondary consumers, and trophic transfer efficiency. The food web disruption pathway is well-characterized if precise magnitude remains uncertain.
Marine food webs are complex adaptive systems where disruption of foundational organisms (calcifying plankton, shellfish) produces nonlinear cascading effects through multiple trophic levels.
Indicators
- • Ocean pH declined 0.1 units since pre-industrial era with continued decline
- • Calcification rates declining in corals, mollusks, and planktonic organisms
- • 74 percent decline in fish egg and larval survival rates under acidified conditions
- • Disrupted predator-prey interactions across trophic levels
- • Aragonite saturation state declining toward dissolution thresholds in polar regions
- • Shellfish industry losses already documented in Pacific Northwest
Interactions
Amplified by
Sources
- EPA — Effects of Ocean and Coastal Acidification on Ecosystems (accessed Fri Apr 03 2026 00:00:00 GMT+0000 (Coordinated Universal Time))
- NOAA Fisheries — Understanding Ocean Acidification (accessed Fri Apr 03 2026 00:00:00 GMT+0000 (Coordinated Universal Time))
- Frontiers in Marine Science — Impacts of Ocean Acidification on Marine Food Quality (accessed Fri Apr 03 2026 00:00:00 GMT+0000 (Coordinated Universal Time))
- EEA — Ocean acidification indicator (accessed Fri Apr 03 2026 00:00:00 GMT+0000 (Coordinated Universal Time))
- Science Times — Ocean Acidification Threatens Marine Biology (2025) (accessed Fri Apr 03 2026 00:00:00 GMT+0000 (Coordinated Universal Time))