Basic HTML Version
International Journal of Marine Science 2013, Vol.3, No.36, 285-294
http://ijms.sophiapublisher.com
288
supernatant. Samples were decalcified using 0.05 N
HCl to remove any inorganic carbonate, before rinsing
twice with DDW. After decalcification, samples were
prefrozened and then freeze-dried overnight using an
Eyela freeze-dryer. Eleven zooplankton samples (one
sample of Locality 1, five samples of Locality 2 and
five samples of Locality 3) were disaggregated from
POM samples under a binocular microscope.
Sample weights of 0.80
±
0.05 mg were placed in tin
capsules for isotope measurements. The
δ
13
C and
δ
15
N
values were analyzed in duplicate using a continuous
flow stable isotope ratio mass-spectrometer
(ANCA-mass 20-20, Europe Scientific Instruments,
UK), where glycine and/or citric acid were run as
standards. Measurement errors were within 0.1‰ for
δ
13
C and 0.3‰ for
δ
15
N. Samples were re-analyzed if
the difference between the two sample analyses
exceeded the measurement error.
Data were statistically analyzed using SPSS software.
Analysis of variance (ANOVA) and multivariate
analysis of variance (MANOVA) were conducted with
the following dependent factors:
δ
13
C of coral tissue;
δ
13
C of zooxanthellae;
Δδ
13
C, which indicated the
differences in
δ
13
C between the coral tissue and
zooxanthellae;
δ
15
N of coral tissue;
δ
15
N of
zooxanthellae; and
Δδ
15
N between the coral tissue and
zooxanthellae. Differences in species, seasons,
localities and depths were subjected to a factor
analysis. An alpha of 0.05 was taken to indicate
statistical significance.
3 Results
Coral samples for this study were collected in August
2006 (1
st
dry season), November 2007 (rainy season)
and August 2008 (2
nd
dry season). Average rainfall
during survey were 83.7 mm, 235.8 mm and 141 mm
respectively. In the study area dry season usually falls
between July and September and rainy season occurs
from October to May (Wiryawan et al., 2005).
3.1 Comparison among genera
Table 1 shows the distribution of the carbon content,
nitrogen content, C-N ratios, and the
δ
13
C and
δ
15
N
values of coral tissue and zooxanthellae from the
three branching. The mean carbon content in the
coral tissues, as well as zooxanthellae, from
Porites
was lower than that in
Seriatopora
and
Stylophora,
although these differences were not significant. The
only mean nitrogen content of zooxanthellae from
Seriatopora
and
Stylophora
were significantly higher
than
Porites
. The mean C-N ratio of coral tissues
from
Porites
was higher than those of
Seriatopora
and
Stylophora
, but the differences were not
significant.
Table 1 Mean %C, %N, C/N,
δ
13
C and
δ
15
N values of coral tissues and zooxanthellae for
Porites
,
Seriatopora
and
Stylophora.
P values
are presented for ANOVA results
Coral genera
Porites
(
n=67
)
Seriatopora
(
n=52
)
Stylophora
(
43
)
%C
Coral tissue
35.6±8.6
37.6 ±7.1
37.3 ±8.0
Zooxanthellae
44.5 ±7.1
43.3 ±5.7
45.7 ±7.6
%N
Coral tissue
6.2 ±2.1
8.7 ±2.2
7.8 ±1.9
Zooxanthellae*
7.8 ±1.6
10.0 ±2.5
9.9 ±2.4
C/N
Coral tissue
6.0 ±1.1
4.5 ±1.1
5.0 ±1.2
Zooxanthellae
5.9 ±1.3
4.6 ±1.4
4.6 ±0.9
δ
13
C (‰)
Coral tissue*
-
13.0 ±1.4
-
15.8 ±1.0
-
14.0 ±1.3
Zooxanthellae*
-
13.9 ±1.4
-
16.1 ±1.0
-
14.3 ±1.3
δ
15
N (‰)
Coral tissue
4.7 ±1.1
5.0 ±1.2
4.7 ±0.9
Zooxanthellae
4.5 ±0.8
4.3 ±0.9
4.5 ±1.0
Note: *The mean difference is significant at the 0.05 level
When the
δ
13
C values of corals were examined, it was
found that there were significant differences of coral
tissues and zooxanthellae among genera.
Seriatopora
had lower values of
δ
13
C in both the coral tissue and
zooxanthellae when compared with
Porites
and
Stylophora
.
3.2 Comparison by depth
The mean values
δ
13
C of coral tissues and zooxanthellae
collected from 3 m depth were significantly different
(ANOVA, n=162, p<0.05) compared to those of
samples collected from 10 m. Those collected from 3 m