Morphological adjustments enable sea urchins to sustain calcified structure function under ocean acidification

Area of Science:

• Marine Biology
• Oceanography
• Climate Change Science

Background:

• Ocean acidification poses a threat to marine calcifiers by reducing calcified structure size.
• The functional implications of these size reductions remain unclear.
• Morphological plasticity may allow calcifiers to maintain functionality despite ocean acidification.

Purpose of the Study:

• To investigate the effects of ocean acidification on sea urchin calcified structures.
• To assess if morphological changes impact the mechanical and chemical properties of these structures.
• To determine the adaptive capacity of sea urchins to high-CO2 environments.

Main Methods:

• Studied sea urchins at natural CO2 vents, simulating ocean acidification.
• Analyzed morphological (test thickness, teeth size, spine density) and mechanical properties (resilience, wear resistance, bending strength).
• Examined chemical properties, including ion concentrations (Na/Ca ratios), to understand calcification mechanisms.

Main Results:

• Sea urchin tests were thinner, teeth smaller, and spine density lower at CO2 vents.
• Despite morphological changes, mechanical performance of calcified structures was maintained.
• Evidence suggests sea urchins sustained acid-base balance for calcification via increased Na/Ca ratios.

Conclusions:

• Morphological plasticity allows sea urchins to maintain structural performance under ocean acidification.
• Sea urchins may acclimate or adapt to changing ocean conditions, ensuring population persistence.
• Ecological functions of sea urchins can be sustained in future high-CO2 oceans.