Ocean acidification affects coral growth by reducing skeletal density.

Area of Science:

• Marine Biology
• Climate Change Science
• Coral Reef Ecology

Background:

• Ocean acidification (OA) poses a significant threat to coral reef ecosystems globally.
• Reduced carbonate ion availability due to OA is expected to impair coral skeleton formation.
• Existing research shows inconsistent responses of coral calcification to OA.

Purpose of the Study:

• To investigate the differential impact of OA on coral skeletal extension and densification.
• To develop and validate a numerical model for predicting coral skeletal growth under OA.
• To project the future impact of OA on the skeletal density of Porites corals.

Main Methods:

• Developed a numerical model linking Porites skeletal density to seawater carbonate chemistry.
• Validated the model using skeletal data from six Porites species across five reef sites.
• Projected the effects of 21st-century OA on Porites skeletal density globally.

Main Results:

• Coral skeletal density is directly sensitive to changes in carbonate ion concentration, unlike skeletal extension.
• The numerical model accurately simulates Porites skeletal growth based on environmental conditions.
• Projected declines in Porites skeletal density due to OA range up to 20.3 ± 5.4% globally.

Conclusions:

• Ocean acidification primarily affects coral skeletal density, with implications for reef structural integrity.
• Porites corals are vulnerable to OA, with significant predicted reductions in skeletal density.
• These findings highlight the urgent need for climate change mitigation to protect coral reefs.