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

An 18-year (1988-2005) stable oxygen isotopic composition (8180) 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 degrees C to 26.32 degrees C (1988-2005), whereas seawater salinity is close to 40.55 with annual variation less than 0.26 (1997-2005). Coral delta O-18 records from both corals showed consistent seasonal patterns of variations closely tracking the measured SST, with correlation coefficient (R-2) of -0.67 to 0.72 at a monthly time scale. Results showed that the slopes of the delta O-18-SST relation from both corals are similar (averaged 0.191 parts per thousand degrees C) and close to those reported earlier for Porites corals from other regions. The seasonal variations of coral delta O-18 (0.85-0.88 parts per thousand) reveals 92-95% of the seasonal SST cycle indicating that large majority of the variations in coral delta O-18 data can be explained by variations in the SST, and only a small fraction (neglected) can be attributed to delta O-18 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.