Oxygen isotope compositions of Porites sp. were measured in order to examine the effect of the 1998 bleaching event on the skeletal record of 6 neighboring colonies from Sesoko Island, Okinawa, Japan. A δ 18Oc-SST dependency of 0.18‰/°C was calculated using a 10 yr record, well within accepted calibrations. The skeleton portion accreted during 1998 exhibited 0.3‰ enrichment in δ18O, which differs from the depleted values expected during abnormally high SST conditions. Growth rate changed significantly during the bleaching event, and its manifestation in skeletal δ18O masked the temperature signal. The δ18O variance among the 6 colonies was noticeably higher during 1998 in comparison with 1997 and 1999. A residual analysis revealed that 75% of the interannual variation of the δ18O record is explained by variation in annual extension rate. The increase in δ18O variance is proposed as a novel indicator for stressful environmental conditions.
- Sea surface temperature
- Stable isotopes