HR: 0800h
AN: PP31B-0417    [Abstracts]
TI: Mg/Ca ratio in a coral skeleton as a possible proxy for the skeletal growth rate
AU: * Inoue, M
EM: mayuri-inoue@ori.u-tokyo.ac.jp
AF: Ocean Research Institute, The University of Tokyo, 1-15-1 Minamidai, Nakano-ku, Tokyo, 164-8639, Japan
AU: Suzuki, A
EM: a.suzuki@aist.go.jp
AF: Geological Survey of Japan, National Institute of Advanced Industrial Science and Technology, AIST Tsukuba Central No. 7, 1-1-1 Higashi, Tsukuba, 305-8567, Japan
AU: Hantoro, W S
EM: hantoro@geotek.lipi.go.id
AF: Research & Develoment Centre for Geotechnology Indonesian Institute of Sciences, Jl. Sangkuriang, Bandung, 40135, Indonesia
AU: Kawahata, H
EM: kawahata@ori.u-tokyo.ac.jp
AF: Ocean Research Institute, The University of Tokyo, 1-15-1 Minamidai, Nakano-ku, Tokyo, 164-8639, Japan
AU: Kawahata, H
EM: kawahata@ori.u-tokyo.ac.jp
AF: Graduate School of Frontier Sciences, The University of Tokyo, 1-15-1 Minamidai, Nakano- ku, Tokyo, 164-8639, Japan
AB: Besides Sr/Ca ratio, Mg/Ca ratio in a coral skeleton has been used as a thermometer in the sea surface. Especially, Mg/Ca ratios in corals collected from sub-tropical regions where seasonal variations of sea surface temperature (SST) exceed 3-4u^C show good correlation with SST. However, some other corals exhibit influence of vital effects on its Mg/Ca ratios rather than SST. In order to evaluate the behavior of Mg/Ca ratio in a coral skeleton, we cultured corals (Porites spp.) with different growth rate in the thermostated tanks. As a result, Mg/Ca mainly reflected the growth rate rather than temperature with negligible contribution from different species. Then we measured Mg/Ca along a growth axis of a coral core collected from the Java Sea where SST usually varies less then 2u^C and compared Mg/Ca variation with skeletal density bands. Consequently, variation of Mg/Ca mostly reflected that of density band, high Mg/Ca occurred with high density band, with little impacts of temperature. As the widths of high and low density bands were almost same on this core, calcification would occur more vigorously during the time when high density band was formed. Ultimately, it is suggested that Mg/Ca ratio in a coral skeleton could have a potential as a proxy for the skeletal growth rate or calcification rate. If skeletal growth rate varies together with SST, Mg/Ca of such a coral would apparently reflect SST.
DE: 0419 Biomineralization
DE: 0473 Paleoclimatology and paleoceanography (3344, 4900)
DE: 0793 Biogeochemistry (0412, 0414, 1615, 4805, 4912)
DE: 4916 Corals (4220)
SC: Paleoceanography and Paleoclimatology [PP]
MN: 2007 Fall Meeting