Seasonal variations in the stable oxygen isotopic composition in Porites corals from the northern Gulf of Aqaba, Red Sea

Abstract

An 18-year (1988-2005) stable oxygen isotopic composition (δ18O) of two coral colonies (Porites lutea and P. lobata) from two different sites in the northern end of the Gulf of Aqaba (Red Sea) successfully records the seasonal variability in sea surface temperature (SST). The mean annual SST record from the study sites ranges between 21.18°C to 26.32°C (1988-2005), whereas seawater salinity is close to 40.55 with annual variation less than 0.26 (1997-2005). Coral δ18O records from both corals showed consistent seasonal patterns of variations closely tracking the measured SST, with correlation coefficient (R2) of -0.67 to 0.72 at a monthly time scale. Results showed that the slopes of the δ18O-SST relation from both corals are similar (averaged 0.191‰/°C) and close to those reported earlier for Porites corals from other regions. The seasonal variations of coral δ18O (0.85-0.88‰) reveals 92-95% of the seasonal SST cycle indicating that large majority of the variations in coral δ18O data can be explained by variations in the SST, and only a small fraction (neglected) can be attributed to δ18O variations of seawater. Results from this study also indicates that splicing of isotopic transects in a single colony have no effect on its isotopic composition.