Ocean Acidification Effects on Pteropod Ecology

Pteropods, or sea butterflies, are pelagic molluscs whose delicate aragonitic shells render them especially susceptible to declining carbonate saturation. As the ocean absorbs anthropogenic carbon dioxide, pH reductions and shifts in carbonate chemistry threaten pteropod physiology, behaviour and population dynamics. Shell dissolution can impair buoyancy, growth rates and reproductive success, with cascading impacts on food-web structure and biogeochemical cycles. Early life stages exhibit heightened sensitivity, while adult specimens may exhibit variable resilience, influenced by prior exposure and energetic reserves. The loss or weakening of pteropod shells not only compromises their survival but also attenuates the vertical flux of carbonate and organic carbon to the deep ocean, diminishing a key component of the biological carbon pump. Geographic variation in vulnerability has been documented, with polar and subpolar regions facing the most rapid onset of aragonite undersaturation. Emerging research highlights the roles of shell repair mechanisms and the protective function of the periostracum in mediating dissolution, yet the energetic costs of such processes remain poorly quantified. Understanding threshold levels of aragonite saturation and the interaction between acidification and concurrent stressors such as warming and hypoxia is essential for forecasting pteropod responses and informing ecosystem management strategies.

Research from Nature Portfolio

Recent studies have elucidated the limits of pteropod physiological tolerance and resilience. One investigation examined pteropod populations along the California Current, revealing that both the magnitude and duration of prior exposure to corrosive conditions determine subsequent calcification and survival under elevated carbon dioxide. Findings indicated no evidence of acclimatisation capacity beyond current exposure ranges, suggesting that key species are approaching their physiological thresholds. Another study employed high-resolution imaging to uncover extensive shell repair in polar pteropods. Despite localised loss of original shell material due to mechanical damage and dissolution, individuals were able to thicken the inner shell wall, maintaining structural integrity. This repair process, however, is likely to incur substantial metabolic costs, with implications for growth and reproductive output under persistent acidified conditions.

Ocean Acidification Effects on Pteropod Ecology publication trend

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

Technical terms

Ocean acidification (OA): Reduction in seawater pH and carbonate ion concentration due to absorption of atmospheric CO₂.

Aragonite saturation state (Ωar): A dimensionless parameter indicating seawater’s capacity to support aragonitic shell formation; values below one denote corrosive conditions.

Pteropods (Thecosomes): Holoplanktonic gastropods with aragonitic shells, commonly known as sea butterflies.

Periostracum: The organic outermost layer of a mollusc shell that protects underlying mineral layers from dissolution.

Calcification: Biological process of calcium carbonate precipitation to form shells or skeletons in marine organisms.

Meta-analysis: Statistical technique combining results from multiple studies to derive overarching patterns and thresholds.

References

1. The global distribution of pteropods and their contribution to carbonate and carbon biomass in the modern ocean. Earth System Science Data (2012).
2. Systematic Review and Meta-Analysis Toward Synthesis of Thresholds of Ocean Acidification Impacts on Calcifying Pteropods and Interactions With Warming. Frontiers in Marine Science (2019).
3. Exposure history determines pteropod vulnerability to ocean acidification along the US West Coast. Scientific Reports (2017).
4. Imminent ocean acidification in the Arctic projected with the NCAR global coupled carbon cycle-climate model. Biogeosciences (2009).
5. Impact of ocean acidification and elevated temperatures on early juveniles of the polar shelled pteropod Limacina helicina: mortality, shell degradation, and shell growth. Biogeosciences (2011).
6. Energetic Plasticity Underlies a Variable Response to Ocean Acidification in the Pteropod, Limacina helicina antarctica. PLOS ONE (2012).
7. Pteropods counter mechanical damage and dissolution through extensive shell repair. Nature Communications (2018).