Ecosystem Responses to Ocean Acidification

Ocean acidification, driven by the uptake of anthropogenic CO₂, lowers seawater pH and reduces carbonate ion availability, undermining calcification in corals, shell-forming molluscs and other keystone taxa. Non-calcifying organisms may transiently benefit from elevated CO₂ through enhanced photosynthesis or growth, yet indirect effects via altered competition, herbivory and trophic interactions often outweigh direct gains. Field studies at natural CO₂ seeps and controlled mesocosm experiments reveal habitat-specific shifts: carbonate-based communities simplify into algal turfs, diatom blooms or soft-bodied assemblages, while functional diversity and redundancy decline. Emerging evidence suggests physiological tipping points near 500 µatm pCO₂, beyond which irreversible regime shifts—such as loss of habitat-forming species and changes in nutrient cycling—become more likely. Such transformations carry profound implications for fisheries, coastal protection and carbon sequestration, underscoring the urgency of integrated management strategies.

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Ecosystem Responses to Ocean Acidification publication trend

The graph below shows the total number of articles in ecosystem responses to ocean acidification across all publications each year (not limited to Nature Index journals).

Technical terms

pCO₂: Partial pressure of carbon dioxide in seawater, a measure of CO₂ concentration affecting pH and carbonate chemistry.

Carbonate saturation state: The availability of carbonate ions needed for calcification; lower values impede shell and skeleton formation.

Trait diversity: The range and relative abundance of functional characteristics (e.g. feeding mode, growth form) within a community.

Functional redundancy: The extent to which different species perform similar ecological roles, buffering ecosystems against species loss.

Physiological tipping point: A threshold in environmental change at which direct organismal responses lead to abrupt ecosystem-level shifts.

References

1. Functional changes across marine habitats due to ocean acidification. Global Change Biology (2024).
2. Are physiological and ecosystem-level tipping points caused by ocean acidification? A critical evaluation. Earth System Dynamics (2024).
3. Living under natural conditions of ocean acidification entails energy expenditure and oxidative stress in a mussel species. Marine Pollution Bulletin (2024).
4. Functional biodiversity loss along natural CO2 gradients. Nature Communications (2018).
5. Ocean acidification drives community shifts towards simplified non-calcified habitats in a subtropical−temperate transition zone. Scientific Reports (2018).