Coral calcifying fluid pH dictates response to ocean acidification

Area of Science:

• Marine Biology
• Coral Reef Ecology
• Biogeochemistry

Background:

• Rising atmospheric CO2 causes ocean acidification, a major threat to marine ecosystems.
• Coral calcification, essential for reef building, is impaired by ocean acidification.
• Understanding coral's physiological responses to changing ocean chemistry is crucial for predicting reef futures.

Purpose of the Study:

• To investigate the relationship between spatial variations in coral internal calcifying fluid pH (pHcf) and calcification sensitivity to ocean acidification.
• To determine if pH regulation within coral colonies differs spatially.
• To identify factors influencing coral resilience to ocean acidification.

Main Methods:

• Studied coral colonies (Stylophora pistillata) under varying CO2 conditions.
• Measured spatial variations in internal calcifying fluid pH (pHcf) within coral colonies.
• Assessed calcification rates and their sensitivity to acidification across different coral regions (apical vs. lateral).

Main Results:

• Coral apexes exhibited higher pHcf and lower sensitivity to acidification compared to lateral growth areas.
• Lateral growth regions showed lower pHcf and were more negatively impacted by acidification.
• Spatial heterogeneity in pHcf regulation was observed within individual coral colonies.

Conclusions:

• Spatially variable regulation of internal calcifying fluid pH (pHcf) is critical for coral calcification.
• Differential pHcf control influences coral's sensitivity to ocean acidification.
• Targeted physiological differences within corals dictate their vulnerability to climate change impacts.