Page 14 - 877-IJMS-vol3.no.36

International Journal of Marine Science 2013, Vol.3, No.36, 285-294
http://ijms.sophiapublisher.com
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must be environmental constraints and energetic costs
associated with the maintenance of symbiotic algae,
which may favor holozoic modes of nutrient
acquisition under certain circumstances. The corals
are able to obtain their food by ingesting complex
organic matter or uptake of dissolved organic nitrogen
(DON) (Muscatine and Kaplan, 1994).
According to Suhendra (2006), Locality 1 and
Locality 3 had different turbidity levels. The sediment
fraction at Locality 1 was dominated by silt (12.9%)
compared to Locality 3 (silt 8.7%) that may have been
transferred from the Berau River. Sedimentation rate
of the Locality 1 was higher (30.50 mg/cm2/day) than
Locality 2 (22.72 mg/cm2/day) and Locality 3 (8.67
mg/cm2/day). In this study, relationship between coral
host and zooxanthellae in difference sedimentation
level of the three localities were tested by isotopic
analysis. Sedimentation does not show significant
impact to the relationship between coral and
zooxanthellae. In particular, the branching corals at
Locality 1 appeared to have higher resistance to
sedimentation. Thus, the branching forms may have
the capacity to escape from sedimentation effects.
However, this study could not found genera of
Stylophora for the last data collection. Golbu (2008)
stated that the genus Stylophora is not usually found in
the turbid areas of Palau.
Concerning to differences in isotopic values among
localities, results of this study showed similar trends
as reported by Risk et al (1994) and Swart et al (2005)
in which δ13C increased toward offshore, while δ15N
had a different tendency. Spatial variation in isotopic
values of coral reefs was reported by Risk et al (1994)
who found that δ13C values of coral tissues were
higher in the offshore marine area compared with the
coastal area. In Acropora formosa and Porites lobata
from the Great Barrier Reef, the δ13 C values of coral
tissues and zooxanthellae increased with distance from
the shore (Risk et al., 1994). This trend probably
resulted from the uptake of 13C-depleted terrigenous
POM. Swart et al (2005) reported that mean δ15N and
δ13C values of the coral tissues and zooxanthellae
from inshore and offshore sites of Montastrea faveolata
in the Florida Keys were not significantly different.
Muscatine et al (1989) and Muscatine and Kaplan
(1994) noted that the δ13 C and δ15 N values of
zooxanthellae and coral tissues decreased with
increasing depth in most species. With increasing of
depth, mean difference of δ13C value between
zooxanthellae and coral tissue increased from less
than 1 in the shallow water (<10 m) and about 1.6 and
4.7 in the deep water (10 – 50 m). Peters and Pilson
(1985) suggested that suspended sediment reduces the
incident light intensity and photosynthetic activity.
The current study also found that the δ15N values of
coral tissues and zooxanthellae decreased as the depth
increases, but there was no significant difference in
the isotopic values at the 3 m and 10 m depths. In
shallow water, δ13C values of zooxanthellae and coral
tissue were similar probably due to translocation,
since more than 90% of the carbon photosynthetically
fixed by zooxanthellae is translocated to corals
(Muscatine et al., 1989). In the case of nitrogen, δ15N
values for both coral tissue and zooxanthellae tended
to be depleted as depth increased up to 30 m. δ15N
values for zooxanthellae ranged between -2.2‰ and
+3.5‰ and for the coral tissue ranged between +0.2‰
to +4.7‰. δ15N mean difference between coral animal
and the zooxanthellae in shallow water was 1.5±1.3‰
(Muscatine and Kaplan, 1994).
As a conclusion, the δ13C values of coral tissue and
zooxanthellae were affected by differences in genera,
seasons, localities, and depth, whereas the δ15N values
varied significantly with seasons alone. Although
corals depend on zooxanthellae, they were also able to
utilize POM. Corals were likely to be using POM as
their main source of organic matter during the time of
low nutrient availability. The corals are able to obtain
their food by ingesting complex organic matter or
uptake of dissolved organic nitrogen (DON). Lastly,
the branching forms of corals may have the capacity
to escape from sedimentation effects.
Acknowledgments
We gratefully acknowledge the fieldwork assistance provided by the Joint
Marine Program TNC-WWF Berau office. We thank the Indonesian Institute
of Sciences (LIPI) and the Directorate General of Forest Protection and
Nature Conservation (Ditjen PHKA, Ministry of Forestry) for providing
recommendation and permission letters to analyze coral reef samples in the
Kyushu University. We are indebted to members of the Laboratory of
Nature Conservation at Kyushu University for their help in this research. We
also thank Arisetiarso and Yudi Herdiana for discussions and inputs. We also
thank the two anonymous reviewers. This study was supported by a Japan
Wildlife Research Center (JWRC) scholarship.
References
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http://dx.doi.org/10.1016/S0022-0981(00)00237-9