MEPS 314:127-133 (2006)  -  doi:10.3354/meps314127

Impact of the 1998 bleaching event on δ18O records of Okinawa corals

Michael Rosenfeld1,*, Aldo Shemesh1, Ruth Yam1, Kuzohiko Sakai2, Yossi Loya3

1Department of Environmental Sciences and Energy Research, Weizmann Institute of Science, PO Box 26, Rehovot 76100, Israel
2Sesoko Station, Tropical Biosphere Research Center, University of the Ryukyus, Sesoko, Motobu-Cho, Okinawa 905-0227, Japan
3Department of Zoology, George S. Wise Faculty of Life Sciences, Tel Aviv University, Tel Aviv 69978, Israel

ABSTRACT: 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 δ18Oc–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 inter-annual 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.

KEY WORDS: Coral · Stable isotopes · Sea surface temperature · Bleaching

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