Page 8 - 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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and coral tissue from the coral skeleton. This
successful separation was followed by isotopic
analyses of zooxanthellae and coral tissue. Carbon
isotope analyses indicated that the majority of coral
tissues had higher δ13C values than zooxanthellae
(Land et al., 1977).
The relationship between coral tissue and zooxanthellae
was studied by isotopic analysis, and focused on
resource partitioning in Jamaican reef corals using
δ13C (Muscatine et al., 1989) and δ15N (Muscatine and
Kaplan, 1994). These studies concluded that the δ13C
value of zooxanthellae was high in shallow water, and
became lower as depth increased. These investigations
illustrate depth-related spatial differences in nutrient
use by corals.
Risk et al (1994) studied scleractinian corals from the
central region of the Great Barrier Reefs to determine
the degree to which corals utilize terrigenous carbon
as an ultimate food source. δ13C values of coral tissue
and zooxanthellae increased linearly with distance
from shore. The study implied that inshore corals
derived much of their nutrients from terrigenous
sources, and these varied spatially.
Swart et al (2005) analyzed temporal and spatial
variation of Montastrea faveolata from the Florida
reef tract. This research revealed that the δ13C and
δ15N values of the zooxanthellae were less than in the
coral tissue. The study also discovered that there was
no significant difference between nearshore and
offshore coral in either δ13C or δ15N.
Heikoop et al (2000a) noted that the δ13C of coral
tissue can be used to determine whether their nutrition
is primarily autotrophic or heterotrophic. Autotrophic
corals typically have similar δ 13C values in
zooxanthellae and coral tissue. Heterotrophic corals
have lower δ13C that closely reflect the δ13C values of
their diets (Muscatine et al., 1989; Heikoop et al.,
2000a). An experimental study on the effect of
heterotrophy conditions under varying turbidity levels
with two coral species showed that Porites was
affected less than Goniastrea (Anthony and Fabricius,
2000). Porites corals were able to utilize suspended
particulate matter as part of its energy budget. An
investigation of Acropora coral using 13C and 15N
isotope tracers showed that algal photosynthetic
products were transferred to the host (Tanaka et al., 2006).
Heikoop et al (1998) suggested that light was a factor
influencing the nitrogen isotopic composition of coral
containing symbiotic zooxanthellae. Under conditions
of internal nutrient limitation due to light and nutrient
concentration, corals might exhibit minimal
fractionation of nitrogen, and δ15N could prove to be a
useful indicator during the dietary analysis of
seawater-dissolved inorganic nitrogen (DIN).
The δ 13C and δ 15N values of organic tissues have been
successfully used to trace the input of primary
producers by assuming that the δ13C of consumers
reflects the δ13C in their diet and that the δ15N values
of consumers are higher than the δ15N values in their
diet (Peterson and Fry, 1987; Yamamuro et al., 1995).
The δ13C composition of animals reflects their diet
with a small enrichment of 0.5–1‰ (Michener and
Kaufman, 2007), especially in shallow water of depth
1~10 m (Muscatine et al. 1989), while the δ15N values
of consumers are about 3‰~5‰ higher than their diet
(Peterson and Fry, 1987).
The current study investigated variations in the
biosynthetic relationship between corals and
zooxanthellae. Under normal conditions where
zooxanthellae produce sufficient photosynthetic
products, corals tend to function autotrophically and
obtain most of their nutrients from the zooxanthellae,
which results in the δ15N values of corals being higher
than zooxanthellae. However, zooxanthellae might fail
to provide sufficient nutrients to corals under turbid
conditions due to reduced light intensity and limited
photosynthesis production, which results in
differences in the δ13C and δ15N composition of coral
tissues and zooxanthellae. Thus, the objective of this
study was to identify where these differences occurred
temporally (rainy versus dry seasons) and spatially
(distance from a river mouth) based on a carbon and
nitrogen stable isotopes analysis of coral and
zooxanthellae. The river and rainy season are
discussed as likely sources of increased turbidity
which may affect the observed patterns in the coral
reef ecosystem.
2 Material and Method
The study was conducted in Berau, East Kalimantan,
Indonesia, which is known as part of the Coral
Triangle in the West Pacific (Green and Mous, 2004).
Spatially, the study area was divided into three
localities, as shown in Figure 1. Locality 1 was the