Monsoon signature in corals from the northern Indian Ocean

Abstract

The Indian monsoon significantly influences the sea surface conditions in the northern Indian Ocean. Corals growing in shallow waters record such monsoon-induced surface water changes. The record of monsoon signatures in the stable isotopic composition of the Porites coral skeleton from the Lakshadweep Islands, off the coast of Southwestern India, has been investigated. Corals record enhanced rainfall periods on the interannual scale along with seasonal changes in the sea surface temperature (SST) in their stable oxygen isotopic composition (δ18O). Inter-colony variability observed in the δ18O of the Lakshadweep corals was studied to decipher the δ18O-SST relation of the region. The carbon isotopic (δ13C) values for the coral show change during the monsoon period. The observed variations in the coral δ13C values are modulated by other processes, along with its photosynthetic activity. The stable isotopic variation from the Lakshadweep coral demonstrated seasonal and interannual scales variability induced by monsoon activity. Thus, past monsoonal variations can be deciphered from long-term coral records from the Lakshadweep region.