The Differences of Soft Corals Spatial Distributions between Sheltered and Exposed Sites at Pongok Island in South of Bangka and Tegal Island in Lampung Bay, Indonesia  

 Rozirwan1,2 , D. G. Bengen1 , N. P. Zamani1 , H. Effendi1 ,  Chaidir3
1. Program Study of Marine Science, Bogor Agricultural University, Kampus Darmaga, Bogor 16680, Indonesia
2. Program Study of Marine Science, University of Sriwijaya, Kampus Indralaya KM 32, Ogan Ilir, Sumatera Selatan 30662, Indonesia
3. The Agency for the Assessment and Application of Technology, Jakarta code pos10340, Indonesia
Author    Correspondence author
International Journal of Marine Science, 2014, Vol. 4, No. 65   doi: 10.5376/ijms.2014.04.0065
Received: 22 Jul., 2014    Accepted: 18 Aug., 2014    Published: 10 Nov., 2014
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Rozirwan et al., 2014, The differences of soft corals spatial distributions between sheltered and exposed sites at Pongok Island in South of Bangka and Tegal Island in Lampung Bay, Indonesia, India, International Journal of Marine Science, Vol.4, No.65 1-7 (doi: 10.5376/ijms.2014.04.0065)


This study is aimed to determine the differences of the soft corals between sheltered and exposed area in Pongok Island, Soulth of Bangka and Tegal Island in Lampung Bay, Indonesia. The physical-chemical parameters of waters were measured in the field and laboratorium. Soft coral types and covers were measured using line intercept transect (LIT) and quadrant transects methods. Eigtht types of soft corals classified in four genera (Lobophytum, Nephthea, Sarcophyton and Sinularia) were found in both sites, six species were identified in the waters of South Bangka (at 9 meters depth) and two species (at 3 meters depth). In Tegal Island waters (closed waters), only 3 speciesfrom the genus Sinularia were recorded (at 2-5m depth). There were 2 stations at Pongok Island namely, PGK1 and PGK2, while in Tegal Island, there were 4 stations namely MCN1, TGL2, GSN3 dan LHK4. Coral diversity was considered as medium category, similarity indexes were low to moderate, except at PGK2 station was considered high, and for the level of dominance, there were no type of coral that dominates. Principal component analyses showed that both waters can be classified based on their physical-chemical characteristic, which were turbidity, temperature, depth, currents, phosphate, nitrate and substrate type.

Coral Biodiversity; Soft corals; Pongok Island; Tegal Island

Coral reef ecosystem has a very important ecological role as feeding and nursery grounds, spawning, care and protection. This ecosystem consists of species of hard coral and soft corals (Nybakken, 1982). There are about 96 genera of soft coal, in 23 families in the Indo-Pacific (Fabricius and Alderslade, 2001). Soft corals in Indonesia reported about 219 species in 28 genera, 4 families (Manuputty, 2002).

The distribution of soft corals is strongly influenced by the characteristics of the aquatic environment such as temperature, turbidity, depth, salinity, currents, water pH, nutrients, and etc. (Wolanski, 2000). (Manuputty, 2010) found 30 species of Sinularia sp in the waters of the islands Derawan East Kalimantan, but it has not been proven that distance between coral habitat and mainland is influenced by human activity. The growth rate of Sinularia dura in the Pramuka Island waters was affected by th.e seasonal variations, turbidity and currents. (Arafat, 2009) recorded that Lobophytum strictum growth rate was varied throughout the year and the highest growth was in period from July and October.
The distribution of soft corals was decreased with decreasing the water quality. Changes in water quality led to multi-faceted shifts from phototrophic to heterotrophic benthic communities, and from diverse coral communities to low-diversity communities dominated by macroalgae. Turbidity was the best predictor of biota existence; hence turbidity measurements remain essential to directly monitor water quality on the Great Barrier Reef (GBR). The influenes of turbidity on hard corals is that it can decline their density four times compered to soft coral (Fabricius et al., 2012).
Temperature is one of the important factors in the growth of soft corals. Water temperature for coral growth ranges between 18 to 36 °C, however optimal growth are at an average water temperature of 26 to 28 oC annually (Birkeland, 1997). While (Nybakken, 1982) states the optimal growth temperature for coral is 23 to 25 ​​oC. Tolerance limit of coral growth in some places reaching 36 to 40 °C maximum and 18 °C minimum. Changes in water temperature variations can cause coral zooxanthellae out of the network. Zooxanthellae lost can cause coral bleaching and eventually kill the coral. Temperature range for soft coral growth is around 18 to 31 °C, but at 35 °C in Parsian Gulf at the height of summer (Fabricius and Alderslade, 2001).
Types of good substrates for coral ecosystems are hard substrates such as rocks, shells of mollusks, pieces of wood, clean metal. It is because attachment of planula larvae need appropriate subtrates to form colonies. Type of soft coral Sinularia sp and Lobophytum sp are found in the Pramuka Island waters which dominated by sand (Handojo, 2006).
Coral growth is also influenced by salinity. Optimum salinity for coral growth is in the range of 32 to 35‰, but coral can still thrive in high salinity such as in the Persian Gulf with salinity of 42‰ (Nybakken, 1982). Increasing salinity (2 to 3 ‰) is not growing an impact on the growth of soft corals in normal conditions, but if there are high differences; they will impact the type of dominance. As salinity below 30 ‰, soft corals will be dominated by the group of Xeniidae, and salinity below 25 ‰ will be lethal for most species of soft corals (Fabricius and Alderslade, 2001).
According to (Handojo, 2006), nitrate values in Pramuka Island waters were above normal conditions 0.30-0.48 mg.L-1 for NO3. It can cause threats for the survival of coral reef ecosystems in the waters.. PCA is used to associate a descriptive role in quantitative and qualitative restrictions (Legendre and Legendre, 1998). This analysis was carried out using Xlstat 2013 program.
1 Materials and Methods
1.1 Study Site
Pongok Island covers an area of ​​about 45 km2 located at the middle of the Gaspar Strait. This strait is strongly influenced by the open water, where the position at the north is bordered by Karimata Strait and the southern part is bordered by Java Sea. While on the west and east is flanked between two islands which include the Bangka Island and Belitung Island. In these waters, soft corals were found at both stations, where each station were coded PGK1 (with position 2° 50'50 .75 "S and 107 ° 1'44 .58" E), and PGK2 (2 ° 53'46 .26 "S and 107 ° 1'47 .34 "E).
Tegal Island occupies about 1.2 Km2. Geographically that island is located in Lampung Bay, the South Lampung regency. Tegal island is uninhabited by humans, but the marine area around the island there was highly exploited by human activities as; fishing, aquaculture floating cages and local transport lines. In this area, there were four stations of soft corals delineated, where station 1 (MCN1) is located on the eastern island to the position of 05034'23, 4 "S and 105016 '36.5" E, station 2 (TGL2) located in the south of the island of 05034'06, 1 "S, and 105016 '51.6 "E, station 3 (GSN3) in the southwest of the island which is about 1.2 km to the position of 050 34'16, 6"S and 105015' 25.5 "E and station 4 (LHK4) in the northwest near the island of Small Lahu with position of 05032'37, 3 "S, and 105015 '51.4" E. Water transparency at each station about 8 meters (Figure 1).

Figure 1 Map of the study site; A) Pongok Island South Bangka; and B) Tegal Island Lampung Bay

1.2 Sampling Time
The research was conducted in August 2012 in the Pongok Island waters, South Bangka and September 2012 in Tegal Island waters, Lampung Bay, Indonesia.
1.3 Water Quality measurements
Water quality parameters at each station were measured in situ include: temperature, turbidity, current velocity, pH, salinity and depth. Nitrate and phosphate contents were measured using Spectrophotometer UV-Visible 1240 Shimadzu in the laboratory.
1.4 Sampling of distribution of soft corals
Observations of ​​soft coral distribution were done using line intercept transect (LIT) method and transect quadrant refers to (English et al., 1994). Transect lines were installed parallel to each other and to the coastline with a length of 50 m for each. Placement of quadrant transects (1x1 m) using purposive sampling. Corals within each of the transect quadrants were recorded and photographed for documentation. In this research LIT were used measure diversity and coral cover. The collected data involved the percentage of live coral cover and the percentage of dead coral cover. Hard coral species were identified according to (Allen and Steene, 1996), (Veron, 2000) and (Suharsono, 2010).
Soft coral were sampled using a knife and wrapped with plastic bags. All samples were inserted into the cooler box and immediately taken to the laboratory. They were identified according to (Allen and Steene, 1996); (Fabricius and Alderslade, 2001); and (Manuputty, 2010).
1.5 Data analysis
The percentage of coral cover (Life form)
Percentage of coral cover (N) was calculated by summing (ni) coral species, and divided by (A) the transect area, and multiplied by 100% (Suharsono, 1995) with the formula:
   ……………………………… (1)
Coral covered were categorized into 0 to 24.9% in poor cover, 25 to 49.9% is moderate cover, 50 to 74.9% is good, and 75-100% is excellent (Gomez and Yap, 1988).
Diversity of soft coral
Shannon's diversity index (H') was calculated by multiplying pi (proportion of the i-th) and log pi, with the formula:
 …………………………….. (2)
Diversity index criteria is as follow: H'​​<1: low diversity, very strong environmental pressure, 1 <H' ≤ 3: moderate diversity, environmental pressures moderate, H '> 3: ​​high diversity, a balance ecosystem (Brower and Zar, 1984).
Equality (Evenness)
Shannon's Equality index (E) was calculated by dividing H’ by Hmax (here Hmax = ln S). Equality assumes a value between 0 and 1. Value 1 being complete evenness (represents excellent coral cover) according to the formula:

Dominance Index
Simpson's Dominance Index (D) was calculated by dividing species number (ni) by total species (N), according to the formula;
Dominance index values ​​between 0-1. If D is close to 1, it means that there are species dominate, if D close to 0 means no species dominate (Odum, 1971).
Principal Component Analysis (PCA)
PCA is used to examine the relationships of biophysic-chemical parameters of the water (temperature, depth, turbidity, flow velocity, sediment fraction, salinity, pH, nitrate and phosphate) with the percentage of coral cover. This analysis showed that there were influences of each parameter on the distribution of soft corals, and the similarity indices at each transect.
2 Results and Discussion
2.1 Result
2.1.1 Physic-chemical characteristics of waters
The results of physical-chemical parameters measurement of waters in each station showed relatively little variations. Of the six stations that were measured, at a depth of soft 9 meter corals diversity was very high. Temperature around was 29 °C, turbidity was 8,46 NTU, current speed was 0.5 ms-1, substrate type was generally sandstone, salinity about 31 ‰, pH of the water about 8.07, nitrate was 0.169 mgL-1, and phosphate was about 0.19 mgL-1 (Table 1).

Table 1 Physical-Chemical parameters of water

Distribution and types of soft coral
There were 35 spesies of hard corals belong to 8 families, and eigth spesies of soft corals belong to 4 genera recorded in the studied site (Table 2). The soft coral were distributed as follow; 2 species belong to genus Lobophytum, one species in Nephtea, 3 species in Sarcophyton and 2 species are belonging Sinularia. At Pongok Island, six soft coral species were recorded at PGK2 station and two species found in the PGK1 station. At Tegal Island only two species were recorded, one of them at MCN1 station, TGL2 and GSN3 while the other at LHK4 station (Appendix 1).

Table 2 the coral species in the study site

Appendix1 Types ofsoft coralsin the study site

Appendix1 Types ofsoft coralsin the study site

Tegal Island recorded the highest total coral cover (hard and soft) at GSN3 station with percentage of about 65.6%, about 36.3% of them represent the soft coral species; followed by LHK4 station (63.3%) with soft coral cover was 17% while, MCN1 stations recorded the lowest coral covers of about 47.7% and about 16.2% represents soft corals that categorized as moderate cover (Table 3). At Pongok Island, the highest coral cover was at PGK1 stations about 50.7% which is categorized as good with 4.6% soft coral cover, and PGK2 station about 37% which is categorized as lowest with soft corals 6.4%.

Table 3 Percentage of coral cover

Diversity indices indicate to two categories of high and medium coral diversities. PGK2 station showed the high diversity, meaning spread of high coral communities and high stability, while the five others were categorized as moderate diversity.
The rate of equality of the coral communities (E) showed that two stations (GSN3 and LHK4) with E values (<0.5) which includes a low rate, which mean that the coral communities threatened. Three stations (MCN1, TGL2 and PGK1) classified as moderate rates of quality, in distrubed coral communities. Station PGK2 recorded E> 0.75 that categorized as high rate, it means the coral community is stable (Figure 2).

Figure 2 Graph Diversity, Equality, and dominance of coral communities

Relationship between the characteristics of water environment with soft coral covers percentage
Based on of principal component analysis (PCA), cumulative Eigenvalues ​​were 85.62% and a variable minimum 0.495 squared cosines value illustrated that there were three groups of data with each identifier. Two groups were in axes F1 dan F2 dan another was axes F1 dan F3 of correlation circle (Figure 3).

Figure 3 Principal Component Analysis

Description of the three groups of PCA is as follows; First group includes PGK2 station, the identifiers is the depth, currents, turbidity and dead coral. Depth at this station reaches 9 meters, with dominance by dead coral cover (DC) of about 47%, hard coral is about 30.6% dominated by massive coral of the family Faviidae (22.7%). While the soft coral cover is only about 6.4%. The current speeds are strong enough about 0.5 m.sec-1. Turbidity is high but still below the quality standard for coral (>10 NTU). The second group involves PGK1 station with, the identifiers of phosphate average concentration at this station was 0.19 mg.L-1 above the quality standard for coral (0.15 mg.L-1). This group is dominated by the branching coral Acropora. Third group includes TGL2 station, the identifier is the type of substrate and nitrate. Subtract type is sandstone (70%). This was followed by nitrate concentrations about 0.156 mg.L-1, has been above standard quality
for coral (> 0.008 mg.L-1) (Tomascik et al., 1997).
2.2 Discussion
In Pongok waters, soft corals were more diverse than Tegal waters, but the percentage cover of soft corals in the Tegal waters is high than Pongok waters. Number of soft coral species in the two locations is lower than Ambon and Seram waters, Maluku, Indonesia (Manuputty and Ofwegen, 2007), and Derawan waters, East Kalimantan, Indonesia (Manuputty, 2010). It is thought to relate to the condition of physical and chemical parameters in the both waters. Such as, turbidity levels found slightly higher in Pongok waters, but still within tolerable limits for coral growth. In addition, the current speed at the site is quite strong in Pongok waters than in Tegal waters. Current function as a supplier of food for the coral and waste circulation (Fabricius and Alderslade, 2001).
The concentration of nutrients includes nitrate and phosphate in all stations fulfill quality standard for coral life. Compared to Pramuka Island waters of Jakarta, in most of location, subtrate types were generally sandstone. It is good for coral growth due to its hard and rough condition(Handojo, 2006).
3 Conclusions
Pongok Island and Tegal Island water have different physical-chemical characteristics. Percent cover of soft corals were dominate (16.2-36.3%) in Tegal Island waters compered to Pongok Island (4.6-6.4%), but the type of soft coral found in Pongok waters more diverse (6 species) compered to Tegal Island (2 species). Based on PCA, the factorsof identifier for type and soft coral distribution were depth, current, turbidity and nutrients.
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