Bar Reef Kalpitiya Porites coral corallite growth bands: sclerochronology and paleoclimate proxies?

Colossal Porites boulder corals inhabiting the Bar Reef Marine Sanctuary off Kalpitiya grow by depositing calcium carbonate skeletal layers year after year, functioning as natural marine climate archives. Sclerochronology studies involve extracting core samples from live massive coral colonies using underwater pneumatic drills. X-radiography of thin coral slices reveals alternating high-density and low-density annual bands (analogous to tree rings). High-density bands form during rough monsoon upwelling, while low-density bands form in calm inter-monsoon periods. Stable oxygen isotope ratios (d18O) measured across these bands reconstruct multi-century records of Indian Ocean sea surface temperature and monsoonal freshwater discharge.