Coral Microtolls
Why it Matters?
Sea levels in the Indian Ocean are rising faster than the global average, threatening coral reefs and island nations. A new study using coral microatolls from the Maldives shows that sea-level rise began in the late 1950s, much earlier than assumed, with a rise of 30–40 cm over the last 60 years.
What You Should Know?
A coral microatoll is a type of coral colony that grows outward rather than upward.
Its upward growth stops when it reaches the lowest tide level because exposure to air at low tide kills the top surface.
As a result, it forms a flat, disk-like structure resembling a small atoll.
The top surface of a microatoll records the lowest sea level at that place over time.
Growth rings, like tree rings, store information about past sea levels, climate events, and bleaching episodes.
Microatolls can live for decades or even centuries, making them natural archives of long-term sea-level changes.
Scientists use them to reconstruct historical sea-level rise in regions where tide gauge or satellite data are lacking.
Presence in India:
Found mainly in Lakshadweep and Andaman & Nicobar Islands, where fringing reefs and atolls exist.
The Gulf of Mannar (Tamil Nadu) and Gulf of Kachchh (Gujarat) also host reef ecosystems where microatolls may form in shallow reef flats.