open access

https://hdl.handle.net/2115/56462

High resolution reconstruction of water temperature estimated from oxygen isotopic ratios of a modern Tridacna shell based on freezing microtome sampling technique

日本語

freezing microtome sampling

1998-05-20

日本地球化学会

地球化学

32(2)

87-95

A modern Tridacna (Hippopus hippopus) was collected on September 5,1993 from a coral reef at Ishigaki Island in Ryukyu Archipelago, Japan, in order to investigate the environmental changes recorded in the shell. We adopted freezing microtome technique for high resolution analysis of the oxygen isotope of the shell. A portion of the innner layer, where daily growth lines are observed under a microscope, was cut out vertically from the inner surface. A stick measuring 20x1x2mm was then placed in water and frozen. Using a microtome, 50um interval samples were pealed off the stick in a room maintained at -20℃. We determined the date of the formation of each sample by measuring the distance from the inner surface of the shell and by counting the daily growth lines. The water temperatures estimated from the oxygen isotopic values at 1-2 day intervals agreed very well (correlation coefficient: 0.90) with the observed water temperatures which have a seasonal temperature range between about 20℃ and 32℃. This implies that the Tridacna precipitates its shell in isotopic equilibrium with the surrounding sea water and that the oxygen isotope values are mainly determined by the water temperature.

学術雑誌論文

Version of Record

0386-4073