Mid-Late Holocene coral calcification dynamics: deciphering climatic and environmental effects

Area of Science:

• Marine Biology
• Paleoclimatology
• Geochemistry

Background:

• Coral reefs worldwide show declining calcification over the past 40 years, linked to climate change and human impact.
• Understanding past natural and human-induced factors on coral calcification is limited.
• Geological records are crucial for deciphering long-term coral calcification trends.

Purpose of the Study:

• Investigate coral calcification parameters in *Porites* corals from the South China Sea.
• Reconstruct calcification changes across Holocene climatic epochs.
• Differentiate the influence of natural variability versus anthropogenic factors on coral growth.

Main Methods:

• Analyzed skeletal density, linear extension, and calcification rates of 82 *Porites* coral specimens.
• Covered growth periods spanning the Holocene Climate Optimum, 4.2 ka BP event, Medieval Climate Anomaly, Little Ice Age, and Current Warm Period.
• Compared calcification data across different climatic and industrial periods.

Main Results:

• Observed a progressive increase in coral skeletal density toward the present.
• Detected variations in linear extension and calcification rates correlating with temperature shifts (warm vs. cold phases).
• Found significantly reduced linear extension and calcification rates during the Current Warm Period, indicating a dominant human impact.

Conclusions:

• Temperature is a primary driver of coral calcification, influenced by volcanic activity and solar radiation.
• Contemporary human activities exert a greater influence on coral calcification than natural variability.
• The findings highlight significant threats to the future of coral reefs under ongoing climate change and anthropogenic pressures.