| Budget Amount *help |
¥3,700,000 (Direct Cost: ¥3,700,000)
Fiscal Year 2005: ¥500,000 (Direct Cost: ¥500,000)
Fiscal Year 2004: ¥800,000 (Direct Cost: ¥800,000)
Fiscal Year 2003: ¥2,400,000 (Direct Cost: ¥2,400,000)
|
|---|
| Research Abstract |
The growth and depositional history of reef-buildings corals provide excellent records of the environment in which they grew. Using living corals collected from Okinawan coral reefs, laboratory experiments were performed to investigate the relationship between coral calcification and aragonite saturation state (Ω) of seawater at 25℃. Calcification rate of a massive coral Porites Iutea cultured in a beaker showed a linear increase with increasing Ω_<aragonite> values (1.08-7.77) of seawater. The increasing trend of calcification rate (c) for Ω is expressed as an equation, c=aΩ+b (a, b : constants). When Ω was larger than 4, the coral samples calcified during nighttime, indicating an evidence of dark calcification. This study strongly suggests that calcification of Porites lutea depends on Ω of ambient seawater. A decrease in saturation state of seawater due to increased pCO_2 may decrease reef-buildings capacity of corals through reducing calcification rate of corals.
The drill core of F
… More
unafuti Atoll, collected by the Royal Society Coral Reef Expedition in 1896-8, has been dated using high-precision ^<14>C and Sr isotope measurements determined by mass spectrometry. The core top is a Holocene reef deposit, reflecting 26.4m of reef growth since 8 ka, and is underlain by Pleistocene reef-lagoonal deposits separated by a series of inferred hiatuses at 26.4 m, 30 m,〜65 m and 〜80 m(〜0.1 Ma,〜0.2 Ma,〜0.3 Ma and 〜0.6 Ma, respectively), reflecting atoll carbonate deposits associated with late Quaternary sea-level changes. In turn, the underlying sequence below 〜80 m comprises an upper section of additional Pleistocene reef-lagoonal deposits, having a high accumulation rate >100 m/Ma, and a heavily dolomitized lower section. Sr isotope data in the lower section provide maximum (oldest) ages for dolomite formation and, depending on the extent of the isotopic memory from precursor CaCO_3, reflect ongoing diagenetic alteration from 〜2.3 Ma (i.e., the oldest dolomite) or in one or more discrete diagenetic events at 〜1 Ma, and possibly at 〜2 Ma. The coral reef sequence reflects interaction between atoll carbonate sedimentation, tectonic subsidence, and eustatic sea-level change. We also performed the chronology of Midway atoll and would like to publish the results. Such deep coring projects are expensive and cores are therefore difficult to obtain for scientific purposes. The sea-level signatures recorded by deep cores in subsiding areas are therefore rare and precious.
These two methods are especially useful for correlations between global warning and sea-level rise. A blending of such information from two very different approaches might clarify eustatic sea-level changes. Less
|
