|
Environmental
effects on the stable carbon and oxygen isotopic
compositions and skeletal density banding pattern of Porites
coral from Khang Khao Island, Thailand
MD. Hossain Sazzad, Anugrah
Ricky Wijaya, Kentaro Tanaka and Shigeru Ohde*
Faculty of Science, University of the Ryukyus, Nishihara,
Okinawa 903-0213, Japan.
*Corresponding author.
E-mail:
sazzadbau@gmail.com. Tel: 81-90-6636-4035.
Accepted 9 July, 2010 |
|
The timing of band formation and linear skeletal growth rate
based on environmental changes were investigated using
alizarin red S (ARS) in Porites lutea coral at Khang
Khao Island, the Gulf of Thailand from November 10, 1999 to
March 15, 2001. The X-radiograph of the vertical section of
the Porites coral skeleton was examined and three
pairs of density bandings including intermediate bandings
were observed in one year, suggesting that additional
factors other than sea surface temperature (SST) were
associated during the process of band formation. We assumed
that variation of salinity variations,
nutrition/sedimentation load and light intensity may control
the process of density band formation which may be
influenced by the river run-off due to heavy rainfall. The
coral skeleton was analyzed and measured from top to a depth
of 47 mm by mass spectrometry and three cyclic changes in
both oxygen and carbon isotopic values which reveal the
abrupt changes of aquatic environment was observed. By using
isotopic compositions, X-radiography and analyzing ARS line,
the average annual growth rate of the Porites coral
was inferred at ~17.91 mm/year. Our results demonstrate that
the density bands of coral and perhaps a useful proxy of
extension rate could also be a potential indicator for
reconstructing the past SSTs in rain-infested areas like the
upper Gulf of Thailand.
Key words:
Oxygen isotopes, carbon isotopes, Porites coral,
density bands, skeletal growth, sea surface temperature,
salinity, Khang Khao, Gulf of Thailand. |
