Ocean acidification stunts molluscan growth at CO₂ seeps

Area of Science:

• Marine Biology
• Oceanography
• Climate Change Science

Background:

• Ocean acidification poses a significant threat to marine bivalves, particularly impacting their shell calcification processes.
• Volcanic CO2 seeps serve as natural laboratories, providing valuable insights into how marine organisms adapt to future ocean conditions.

Purpose of the Study:

• To investigate the calcification and growth responses of the coastal mussel Septifer bilocularis under elevated pCO2 conditions at natural CO2 seeps.
• To understand the physiological and ecological implications of ocean acidification on bivalve molluscs.

Main Methods:

• Reciprocal transplantation of Septifer bilocularis between reference and elevated pCO2 habitats over two months.
• Analysis of mussel condition index, shell growth, soft tissue stable isotopes (δ13C and δ15N), and shell carbonate chemistry (isotopes and elemental signatures).

Main Results:

• Mussels exposed to elevated pCO2 exhibited decreased condition index and reduced shell growth.
• Physiological changes were linked to altered food sources and modifications in calcifying fluid chemistry.
• Shell growth records confirmed reduced rates under acidified conditions, with smaller shell sizes observed.

Conclusions:

• Ocean acidification at CO2 seeps negatively impacts mussel growth and physiological performance.
• Reduced shell growth may be a survival mechanism for bivalves facing stressful, acidified marine environments.