Basic HTML Version
International Journal of Marine Science 2013, Vol.3, No.36, 285-294
http://ijms.sophiapublisher.com
289
(–13.6
±
1.8‰ and –14.2
±
1.8‰ for coral tissues and
zooxanthellae, respectively) had higher
δ
13
C values
than those from 10 m (–14.3
±
1.5‰ and –14.7
±
1.4‰, respectively). The mean
δ
15
N values of coral
tissues and zooxanthellae from 3 m depth (state values)
were lower than those from 10 m (4.5
±
0.9‰ and
4.1
±
0.7‰, respectively). However, there were no
significant statistical differences in the
δ
15
N values of
samples from –3 m and –10 m.
3.3 Comparison of localities and seasons
Locality 1 was situated in the northern coral area and
it was the closest to the main river route, while
Locality 3 was pure marine water; Localitly 2 was
intermediate. Table 2 shows the mean
δ
13
C values for
coral tissue and zooxanthellae during the 1
st
dry
season, the rainy season, and the 2
nd
dry season. The
δ
13
C values of coral tissue were always higher than
those of zooxanthellae in all seasons. The
δ
15
N values
of coral tissue were higher during the 1
st
and 2
nd
dry
season compared with zooxanthellae. However, during
the rainy season, the
δ
15
N values of coral tissues and
zooxanthellae were very similar, with no significant
differences.
Table 2 Mean
δ
13
C and
δ
15
N values (
±
SD) of coral tissue, zooxanthellae, POM and Zooplankton for the different localities and seasons
δ
13
C (‰)
δ
15
N (‰)
Season
Locality
Coral tissue Zooxanthella POM Zooplankton
Coral tissue Zooxanthellae POM Zooplankton
Locality 1 1st dry season
-
14.2 ±1.7
-
14.9 ±1.9
-
18.0 nd
5.0±0.8
4.2±0.4
5.4
nd
Rainy season
-
14.0 ±2.1
-
14.9 ±1.8
-
19.1
-
19.2
4.5±1.0
4.6±0.7
3.2
4.9
2nd dry season
-
14.9 ±1.8
-
15.8 ±1.1
-
18.7
-
19.5
5.3±0.8
4.7±0.4
5.2
5.9
Locality 2 1st dry season
-
13.5 ±1.7
-
14.3 ±1.6
-
18.5
-
18.8
5.0±0.8
4.4±0.6
5.8
6.4
Rainy season
-
13.3 ±1.8
-
14.2 ±1.2
-
18.0
-
19.5
4.0±1.1
4.4±0.7
4.0
5.3
2nd dry season
-
14.3 ±2.0
-
14.8 ±1.6
-
19.9
-
19.5
5.8±0.9
5.3±0.9
5.5
5.8
Locality 3 1st dry season
-
14.1 ±1.6
-
14.3 ±1.4
-
19.9
-
19.8
4.4±0.9
3.9±1.0
5.1
8.0
Rainy season
-
14.1 ±1.6
-
14.1 ±1.5
-
18.0
-
18.0
3.8±0.8
4.2±0.6
2.2
5.1
2nd dry season
-
14.2 ±2.0
-
15.2 ±1.5
-
18.3
-
19.7
5.7±1.3
5.4±1.0
6.4
7.4
Note: nd = no data
At Locality 2, the mean
δ
13
C values of coral tissue
were higher than zooxanthellae during the 1
st
dry and
rainy seasons, while they were similar during the 2
nd
dry season (Table 2). During the 1
st
and 2
nd
dry
seasons, the mean
δ
15
N values of coral tissues were
higher than zooxanthellae, whereas they were lower
during the rainy season. However, only
δ
15
N values of
coral tissue of 2
nd
dry season were significantly
different compared to the rainy season.
At Locality 3, the mean
δ
13
C values of coral tissues
were higher than zooxanthellae during the 1
st
and 2
nd
dry seasons, but they were similar during the rainy
season. However, there were no significant differences
among them. The mean
δ
15
N values of coral tissues
were higher than zooxanthellae during the 1
st
and 2
nd
dry seasons, but were significantly lower during the
rainy season.
3.4 Comparison with POMs and zooplanktons
Twenty-six particulate organic matter (POM) and
eleven zooplankton samples collected during the dry
season were analyzed for
δ
13
C and
δ
15
N. POM
samples collected during the rainy season had widely
ranging carbon contents (2.3l–24.0%; mean = 9.3
±
7.0%). The mean
δ
13
C values of the POMs from
Locality 1 (–19.1
±
1.2‰) were lower than those from
Locality 3 (–15.9
±
4.3‰), but not significantly
different. The mean
δ
13
C values of POMs during the
dry season (–18.9
±
1.1‰) and the rainy season
(–19.0
±
4.3‰) were relatively similar.
During the 1st dry season, the mean
δ
15
N values of
POMs (5.4
±
1.0‰) were slightly higher than corals.
The mean
δ
15
N values of zooplankton and POMs were
similar or higher than corals during the 2
nd
dry season.
However, during the rainy season, the mean
δ
15
N
values of POMs were significantly lower than corals,
especially in Localities 1 and 3, suggesting that corals
tended to utilize POMs as nutrient sources.
Mean
δ
13
C values of zooplankton ranged from –22.3‰
to –18.0‰, while
δ
15
N values ranged from +4.1‰ to
+9.8‰.
δ
13
C values of zooplankton collected from the