Physiological Responses of Marine Fish to Ocean Acidification

Ocean acidification alters seawater chemistry by increasing dissolved carbon dioxide and lowering pH, imposing challenges on fish homeostasis. To maintain internal pH, marine fish deploy acid–base regulation via ion‐transport mechanisms in gill epithelia, yet this compensation incurs metabolic costs. Elevated CO₂ often modifies resting and maximal oxygen uptake, narrowing the aerobic scope available for growth, reproduction and escape responses. Sensory systems, particularly olfaction and neural circuits mediated by neurotransmitters, can be disrupted, leading to altered behaviour such as impaired predator avoidance and social interactions. Early life stages—eggs and larvae—appear most vulnerable, showing shifts in development, calcification and survival. Otolith chemistry further records environmental changes, affecting navigation and growth estimates. At the molecular level, stress‐response pathways including heat shock proteins and oxidative defences are activated, reflecting a trade‐off between maintenance and performance. Combined with warming, acidification can exacerbate reductions in metabolic efficiency and disrupt trophic dynamics. These physiological responses underpin species‐specific resilience or vulnerability, with far‐reaching implications for fish populations, fisheries management and ecosystem stability worldwide.

Research from Nature Portfolio

Recent studies have adopted meta‐analytical approaches to quantify physiological deviations under acidification, revealing that absolute shifts in traits such as metabolism, survival and calcification occur even at moderate CO₂ levels, exceeding earlier directional estimates. This comprehensive analysis suggests stronger ecosystem impacts than previously recognised. Complementary experimental work on mesopredatory sharks demonstrates that the dual stressors of warming and elevated CO₂ impair olfactory‐mediated foraging, reduce metabolic efficiency and slow growth, indicating that top‐down control by predators may weaken in future oceans.

Physiological Responses of Marine Fish to Ocean Acidification publication trend

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

Technical terms

Aerobic scope: The difference between resting and maximal oxygen consumption, indicating energy available for activity beyond maintenance.

Acid–base regulation: The process by which fish maintain internal pH stability through ion exchange and bicarbonate buffering in gill tissues.

Hypercapnia: Elevated levels of dissolved carbon dioxide in body fluids that, if uncompensated, lead to acid–base disturbances.

Otolith: A calcified structure in the fish inner ear that records chemical and temperature history and assists in balance.

GABAergic pathways: Neural circuits mediated by gamma‐aminobutyric acid, critical for regulating behaviour and sensory processing.

References

1. Hidden impacts of ocean warming and acidification on biological responses of marine animals revealed through meta-analysis. Nature Communications (2024).
2. Ocean acidification and global warming impair shark hunting behaviour and growth. Scientific Reports (2015).
3. Recalibrating the significance of the decline effect in fish ocean acidification research. PLOS Biology (2023).
4. Neuromolecular responses in disrupted mutualistic cleaning interactions under future environmental conditions. BMC Biology (2023).
5. Effects of climate change on growth and otolith thermometry of sand whiting (Sillago ciliata). Geochimica et Cosmochimica Acta (2024).