Ideally, the SSS-δ 18 O sw relationship should be established on a local/regional basis because of variation in the isotopic composition of rainfall and river water (Corrège, 2006). Published values of the slope of the SSS-δ 18 O sw relationship obtained in the tropical Pacific Ocean vary between 0.27 and 0.45 psu (Fairbanks et al., 1997;Morimoto et al., 2002). As an estimate of salinity values, the equation generated by Morimoto et al. (2002) from Palau, when applied to the **data** in this study, yielded a mean value of 34.7 psu for both modern and mid-Holocene δ 18 O sw records. This value corresponds well with the 35.1 psu mean value from the SODA salinity dataset, given that salinities are likely to be lower in the nearshore area of King Reef, and the satellite **data** average a square grid of 0.5° × 0.5°. The annual salinity range of 2.1 psu obtained by applying the Morimoto et al. (2002) equation to the modern δ 18 O sw is higher than the annual salinity range of 1.67 psu indicated by the SODA dataset. The Holocene δ 18 O sw record indicates an annual salinity range of 2.4 psu, suggesting that the annual salinity range was significantly greater in the nearshore GBR at ~ 4700 cal. yr BP.