Carbon Dioxide Effects on Aquatic Ecosystems

Carbon dioxide exerts a multifaceted influence on aquatic environments through its role in carbonate chemistry, physiological stress and ecosystem dynamics. When CO₂ dissolves in water it lowers pH and alters the equilibrium among carbonate species, undermining calcification processes in shell-forming organisms and shifting nutrient availability for phytoplankton. In freshwater and marine habitats alike, elevated CO₂ can exacerbate hypoxia by stimulating respiration in both microbes and metazoans, reducing oxygen solubility and intensifying diurnal fluctuations in dissolved gases. Fish and invertebrates respond to hypercapnia with acid–base disturbances that may impair growth, reproduction and behaviour, while some primary producers adjust photosynthetic rates under variable CO₂ regimes. In engineered systems, such as recirculating aquaculture, CO₂ accumulation affects water quality management and animal welfare, driving innovations in degassing technology and system design. Beyond individual organisms, rising CO₂ contributes to trophic shifts, alters carbon sequestration pathways and interacts with temperature and nutrient stressors. This global phenomenon carries practical implications for fisheries, conservation of coral reefs and the design of sustainable aquaculture, underscoring the urgent need for integrative management strategies that balance carbon fluxes and ecosystem health.

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Carbon Dioxide Effects on Aquatic Ecosystems publication trend

The graph below shows the total number of articles in carbon dioxide effects on aquatic ecosystems across all publications each year (not limited to Nature Index journals).

Technical terms

Hypercapnia: Elevated concentration of dissolved CO₂ in water that leads to respiratory acidosis in aquatic organisms.

Recirculating aquaculture system (RAS): A closed‐loop fish‐rearing system in which water is continuously filtered, treated and reused to maintain quality.

Acid–base regulation: Physiological processes by which organisms maintain internal pH homeostasis despite external CO₂ fluctuations.

pCO₂: Partial pressure of carbon dioxide in water or gas, indicating its availability and impact on acid–base balance.

Metabolic scope: The difference between maximum and standard metabolic rates, reflecting an organism’s capacity for growth, activity and stress response.

References

1. A descriptive study of carbon dioxide production and removal in full-scale RAS for Atlantic Salmon (Salmo salar L.) post-smolt: A comparison of two different measurement methods for CO2. Aquacultural Engineering (2024).
2. Rapid blood acid-base regulation by European sea bass (Dicentrarchus labrax) in response to sudden exposure to high environmental CO2. Journal of Experimental Biology (2022).
3. Acid-base disturbances and effects on oxygen uptake rates in Nile tilapia (Oreochromis niloticus) following acute and prolonged CO2 exposure. Aquaculture (2024).