Physiological Responses of Marine Invertebrates to Ocean Acidification

Ocean acidification, driven by the uptake of anthropogenic CO₂, alters seawater carbonate chemistry and imposes widespread physiological challenges on marine invertebrates. Shell‐forming taxa such as molluscs and echinoderms commonly exhibit reduced calcification rates, net dissolution of existing skeletal structures and compromised growth, as carbonate ion availability declines. Crustaceans often maintain exoskeletal integrity through active acid–base regulation, yet this incurs elevated metabolic costs, shifts in energy allocation and trade‐offs with immune and reproductive functions. Metabolomic and gene‐expression analyses reveal species‐ and population‐specific thresholds beyond which acid–base compensation fails, leading to metabolic down-regulation, oxidative stress and impaired homeostasis. Transposon activation and other epigenetic mechanisms have emerged as contributors to phenotypic plasticity, enabling some populations to “harden” against low-pH conditions. Vulnerability varies with life stage, habitat and thermal context, such that combined acidification and warming can exacerbate mortality, development delays and larval carry-over effects. Understanding these interconnected responses is critical for predicting range shifts, informing sustainable fisheries and guiding aquaculture practices under future ocean conditions.

Research from Nature Portfolio

Recent studies have demonstrated that regional adaptation underpins species‐specific sensitivity to reduced pH. Through integrated analyses of growth, mineralization, physiology and metabolomics, latitudinal populations of a common periwinkle were shown to differ in shell dissolution and metabolic plasticity, predicting shifts in distribution under future acidification scenarios. In another investigation, short‐term reduction in seawater pH led to altered exoskeleton mineral composition in a caridean shrimp, increasing the calcium to magnesium ratio without affecting overall growth, but triggering changes in cuticle structure and transparency with potential consequences for predator avoidance and mechanical defence.

Physiological Responses of Marine Invertebrates to Ocean Acidification publication trend

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

Technical terms

Ocean acidification: Decrease in seawater pH caused by uptake of atmospheric CO₂, altering carbonate chemistry and challenging marine organism homeostasis.

Calcification: Biological process of depositing calcium carbonate to form shells or skeletons, sensitive to changes in carbonate ion availability.

Acid–base regulation: Physiological mechanisms by which organisms maintain internal pH, often involving ion transporters and metabolic adjustments.

Phenotypic plasticity: Ability of an organism to modify physiology or morphology in response to environmental change without genetic alteration.

Hemocyte: Circulating blood cell in invertebrates responsible for immune functions such as phagocytosis and wound healing.

References

1. Narrowed gene functions and enhanced transposon activity are associated with high tolerance to ocean acidification in a juvenile subarctic crustacean. PLOS Climate (2024).
2. Regional adaptation defines sensitivity to future ocean acidification. Nature Communications (2017).
3. Effects of Ocean Acidification on Juvenile Red King Crab (Paralithodes camtschaticus) and Tanner Crab (Chionoecetes bairdi) Growth, Condition, Calcification, and Survival. PLOS ONE (2013).
4. Effects of CO2-induced pH reduction on the exoskeleton structure and biophotonic properties of the shrimp Lysmata californica. Scientific Reports (2015).
5. Ocean Acidification Affects Hemocyte Physiology in the Tanner Crab (Chionoecetes bairdi). PLOS ONE (2016).