CORAL REEFS IN THE SOUTHERN COAST OF THE DISTRICT OF LOMBOK TIMUR

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1 CORAL REEFS IN THE SOUTHERN COAST OF THE DISTRICT OF LOMBOK TIMUR Imam Bachtiar 1 and Karnan 2 Jurusan PMIPA, FKIP Universitas Mataram Jl. Majapahit 62, Mataram, NTB Abstrak Telah diteliti kondisi terumbu karang di wilayah pesisir selatan Kabupaten Lombok Timur yang meliputi Teluk Ekas dan Teluk Jukung. Metode yang digunakan adalah manta tow, transek garis dan transek sabuk. Hasil penelitian menunjukkan bahwa sebagian besar terumbu karang dalam kondisi jelek. Pengeboman ikan diduga merupakan penyebab utama kerusakan karang. Terumbu karang yang kondisinya paling baik dijumpai di Tanjung Segui. Karena di Tanjung Segui tutupan karang batu dan keanekaragaman karang serta ikan karang paling tinggi, sehingga diusulkan untuk dijadikan sebagai suaka laut. Abstract Coral reefs status in the southern coast of the District of Lombok Timur has been studied covering Ekas and Jukung Bays. Three survey methods were used for the study:,mantatow, line intercept transect and belt transect. Results of the present study show that most coral reefs on this area have bad condition. Blast fishing is likely the main cause of the bad reef condition. The best coral reef condition was found at Tanjung Segui with the highest coral cover, coral diversity and coral reef fish diversity. It is suggested, therefore, that coral reef of Tanjung Segui should be set up as a marine sanctuary. INTRODUCTION Coral reef is one of the most important and valuable coastal resources in tropical countries (Cesar, 2000). In Indonesia, however, coral reef condition is deteriorating. About half of reefs surveyed by P3O-LIPI, since the middle of 1980s, showed very bad condition (Sukarno et al., 1990; Tomascik et al., 1997). The present condition would be worse as more reefs are destroyed naturally or anthropogenicaly. Destructive fishing, overexploitation and sedimentation are the most common anthropogenic causal factors of coral reef degradation (Chou, 2000). Coral bleaching that ended up with mass coral mortality also has major contribution for the degradation of many reefs in Indonesia. At the province of Nusa Tenggara Barat (NTB) sources of reef degradation has been reviewed in Bachtiar (1997), before the 1998 bleaching event. Determining coral reef condition is one of the most important steps in coral reef management (Kenchington, 1988; Done, 1995). The information on present status 1 ibachtiar@hotmail.com 2 kar_nan@yahoo.com 1

2 of coral reefs will be very important in planning the management and as a baseline data to measure the succeed of the management actions. Southern coast of the District of Lombok Timur has been appointed to the site of pilot project on coastal fisheries management, the Co-Fish Project. Since coastal fisheries can not be separated from coral reef management, the present study was aimed to provide basic information about the status of the coral reefs, for planning management measures and future monitoring. MATERIALS AND METHOD in Gili Kere and Gili Maringke make the manta tow results can only describe coral reef condition at the reef flat. At Ekas and Batunampar, water visibility was so turbid that manta tow was not used during the survey. The line (intercept) transect using SCUBA equipments was used to measure macrobenthic coverage at a coral reef, for example hard coral, soft coral, sea anemone and sponges (English et al., 1994). The line transect used was 50 meter length. Two transect were made at each location. The present study was carried out at the southern coast of Lombok Timur covering Ekas, Serewe and Jukung Bays (Figure 1). The three bays are the main activities of the coastal fisheries in the District of Lombok Timur. Data collection was carried out twice: July 1999 (dry season) and February 2000 (wet season). There are three methods that were used in the coral reef survey: manta tow, line intercept transect and belt transect. The manta tow is used to get a general description on coverage of living hard coral and soft coral in a vast area within a short time (English et al., 1994). Data of fish abundance (roughly estimate) can also be obtained during the manta tow. The manta tow was applied on coral reef survey between eastern coast of Gili Kere to eastern coast of Gili Maringke, and between Tanjung Terong to Gili Kerate. The results of manta tow can describe general coral reef condition with moderate visibility (>6 meter). When the visibility is low, manta tow can only describe coral reef condition at the shallow reef flat, since coral reef condition at the slope could not been observed. The turbid water Figure 1. Location of study covering three bays: Teluk Ekas, Teluk Serewe and Teluk Jukung. Coral reef condition was determined based on proportion coverage of living hard corals (Acropora and non-acropora) as developed by Gomez and Yap (1988). The belt transect is used to carry out a visual censuses on coral reef fishes. The size of belt transect used is 50x5 m². The visual census on the belt transect was carried out at the same time with the line intercept transect. There were four observational stations on the coral reef survey (see Table 1). On each locations, 2

3 two transects were made at 3-5 meter depth and two other transects at meter depths. Table 1. Location of surveyed coral reefs in Kecamatan Keruak. Stations/ Code Position Locations 1. Gili Maringke Tk1 S ' E ' 2. Tanjung Segui. Tk2 S ' E ' 3. Batunampar Tk3 S ' E ' 4. Ekas Tk4 S ' E ' Identification of epibenthic macroinvertebrates was done using book references of Veron (1986) for hardcorals, Colin and Arreson (1995) for other macro-invertebrates. Identification of coral reef fishes was carried out using several books written by Debelius (1993), Kuiter and Debelius (1994), Kuiter (1992) and Lieske and Myers (1994). RESULTS AND DISCUSSION In general, coral reefs are in bad condition in Kecamatan Keruak. Coral reef in a good condition can only be found at Tanjung Segui and Gili Maringke. The good coral reef condition, however, was only at 3 (three) meter depth, while at 10 meter depth all coral reefs showed bad condition. The result of manta tow at eastern reef of Gili Kere to Gili Maringke shows that coral reefs in this location have low proportion of hard coral cover (10-30%), therefore classified as bad to poor condition (Table 2). Percent coverage of soft coral was also low. Fish abundance was estimated about fish per tow (one tow =2 minute, 2 knots, 6 meters wide). Since the visibility was bad (<8 m), the manta tow data was obtained from about 3-6 meter depth. Most reefs are covered with rubble indicating the intensive blast fishing sometime in the past. During the manta tow, some locations have percentage of coral cover about 50% at 3-6 meter depth. The living coral encountered was mostly tabulate Acropora, e.g. A. hyacinthus, A. cytherea, and branching Acropora, massive corals such as Porites, Montastrea, Goniastrea and Platygyra. Coral reef condition between Tanjung Terong and Gili Kerate is worse (Table 2). During the manta tow, hard coral coverage was estimated less than 10%, while soft coral coverage was about 11-30%. Coral reef fish abundance was also very low. The high coverage of rubble indicates the occurrence of blast fishing. Table 2. Coral reef condition on manta tow survey in Kecamatan Keruak. Location Gili Kere to Gili Maringke Tanjung Terong to Gili Kerate No. tow Medi an hardcoral cover * Med ian fish abun d.** Med ian soft coral * UW Visibi lity Note: *Hard- and soft-corals coverage: 1=0-10%, 2=11-30%, 3=31-50%, 4=51-75%, 5= >75%. **Fish abundance: 1=<100, 2=100-<1000, 3= individu per tow (5meters x 2miles/60 x2) Lines transect method results also showed the similar condition. Out of four locations of surveyed coral reefs, all of them were 3

4 showing fair or bad (poor) coral reef condition (hard coral coverage <50%). The beautiful coral reefs, such as at Tanjung Segui, can only be classified as in fair condition at the depth of 3 (three) meters, while at 10 meter depth, all coral reefs have bad condition. Excellent reef condition actually can be found at 1-3 meter depth at Tanjung Segui. Living coral cover at this location was dominated by branching Acroporidae. Since coral reef assessment was standardized in 3 and 10 meters depths, the pristine coral reef picture is not included. This place was very good for snorkeling tourism. Details of the line transect results as follows. At northern Gili Maringke, in July 1999, coral reef condition is fair at 3 (three) meter depth and is bad at 10 meter depth. Hard coral coverage is about 27.53% and 11.55% at three and 10 meters depths respectively (Figure 2). At Tanjung Segui, hard coral coverage is about 49.68% and 0% in 3 (three) and 10 meter depths respectively. These results suggest that at the two locations coral reef condition is in bad condition (coral coverage <25%) at 3 (three) meters depth, and in poor condition (coral coverage 26-50%) at 10 meters depth. Most abiotic coverage at 10 meter depth was sand in the two locations. Coral rubble is the second highest abiotic proportion at northern Gili Maringke. At Tanjung Segui, on the other hand, coral rubble is very low. The high rubble proportion is very likely due to blast fishing. The high proportion of sandy bottom and coral rubble may lead to low coral cover in 10 meter depth. Sedimentation inhibits coral larval recruitment and its survivorship (Hodgson 1990, Babcock and Davies 1991), reduce the reproduction efforts and the survivorship of living colonies. The low Benthic cover (%) visibility indicating low light penetration, may worsened the low coral recruitment on this area Benthic cover(%) m MK1 3 m MK2 A. Dry Season (July 1999) TS1 B. Wet Season (February 2000) TS2 EK1 Location EK2 BN1 BN2 Figure 2. Benthic coverage in coral reef of Keruak waters within two seasons. Spatial variation is very high at northern Gili Meringke in 10 meter depth. At the 10 m Acropora Non-Acropora Dead-scleractinia Algae Other-fauna Abiotik 10 m Location Acropora Non-Acropora Dead scleractinia Algae Other fauna Abiotik 4

5 first transect, for example, many hard corals were found patchy along transect separated by rubble or sandy bottom. At the next transect, however, the patchy corals was no longer encountered. Coral diversity was higher at Tanjung Segui than at Gili Maringke. Hard coral species found at Tanjung Segui were tabulate acroporiid Acropora cytherea, A. hyacinthus; branching acroporiid A. nobilis, A. microphthalma, A. tenuis, A. nasuta; submassive acroporiid A. pallifera; massive corals Porites, Montastrea, Goniastrea, Platygyra; submassive corals Pocillopora verrucosa, Pocillopora dammicornis, Pocillopora sp., Stylopora pistilata; branching corals Hydnophora rigida, Seriatophora caliendrum, S. hystrix and Porites cylindrica. There were three genera of soft corals found, Sinularia, Xenia and Sarcophyton. The giant clam (Tridacna sp.) and anemones were also found in three meter depths. At Gili Maringke hard coral species found were branching acroporiid A. nobilis, A. formosa, A. microphthalma, A. subglabra; foliose corals Echinopora mammiformis, E. lamellosa, Merulina and Oxypora; and mushroom corals Fungia. Soft corals found were Xenia, Sinularia and Sarcophyton. Zoanthiid colonies Palythoa and Zoanthus; and anemone Heteractis malii were also found at the line transect. At Ekas reef (Taket Ekas), coral reef survey was conducted in a shoal (patch reef) located at the eastern part of Awang Bay. The coral reef status was generally in bad condition, either in 3 (three) or 10 meters depths. The bad coral reef condition was very critical, as the living hard coral coverage was only <15%. There were nearly no corals growing at 10 meters depth. At the 10 m depth, coral rubble was a big proportion of the total coverage (44-73%) indicating the occurrence of blast fishing in the past. At 3 (three) meter depth, algae was relatively high (37-55%). This algae grows well on the remains of coral skeletons. The proportion of algal coverage varies a lot temporally. At the second survey, February 2000, algae coverage seems to increase. This result does not necessarily means that there is an increase in algal coverage. It is more likely that this due to spatial variation on the two sampling period instead of temporal variation. Coral diversity is relatively low. The hard corals found were massive corals Porites, Pavona and Galaxea; branching corals Seriatophora hystrix, S. caliendrum and Porites cylindrica; foliose corals Montipora sp. and Porites sp.; and mushroom coral Fungia. The new foliose coral colonies grow on the remains of dead coral skeleton. The dead coral was likely owing to massive coral bleaching in the El Nino The presence of these new colonies indicated that the bad coral reef is now in recovery process. Coral reef survey at Batunampar reef was also conducted in a shoal about in the middle of Awang Bay. Coral reef status is bad, either in 3 (three) or 10 meter depths. In the 3 meters depth, the reef was mostly covered with dead coral and coral rubble that was greenish by algae. The algae cover on this site was about 54-82%. In 10 meters depth, the reef was covered mostly with sand and silt. Some rubbles that have been covered with algae can also be found on this depth. The presence of rubbles in high proportion indicating the occurrence of intensive blast fishing in the past. There are not many coral species found on the Batunampar reef (Taket Batunampar). 5

Hard corals encountered on the transects were foliose corals Montipora and Porites; massive corals Porites, Galaxea, and Pavona; branching acroporiid Acropora tenuis; and fire coral Millepora.

6 Hard corals encountered on the transects were foliose corals Montipora and Porites; massive corals Porites, Galaxea, and Pavona; branching acroporiid Acropora tenuis; and fire coral Millepora. Between two consecutive surveys, July 1999 and February 2000, there are some considerably changes. At northern Gili Maringke reef, the proportion of other fauna (zooanthid and soft corals) was higher in the second survey than previously. At Tanjung Segui reef, algae coverage changes considerably at two depths. The same pattern was also occurred at Ekas and Batunampar reefs. All the changes do not necessarily indicating temporal variation or cyclical pattern of the reefs. It is more likely that the changes were owing to spatial variation between the two sampling period. In the present study the line transects was not permanent. In the second survey, therefore, it is unlikely to have line transects precisely on the same location with the ones on the first survey. This spatial variation should be minimized with greater number of replicates. Since the available funding was only allowed to have two replicates (transect) at each depth, the spatial variation is inherently still considerably high. The application of permanent transect may be good in future study. The high turbidity in most reefs visited, however, might sharply increase the cost of survey. It will take longer time for the divers to recognize any underwater marks of the permanent transect in turbid waters. Bad coral reefs are usually thought to be strongly associated with low abundance and diversity of fish communities. In the present study, however, the association is pretty noisy. Again, the low number of replicates may lead to the noisiness. In the dry season, August 1999, coral reef fish diversity was the highest in Batunampar reef at three meters depth (Figure 3). In this reef, fish diversity was 20 species per transect. Fish diversity in Tanjung Segui and Ekas at this time was 16 and 15 species respectively. In the wet season, the highest fish diversity was found in Ekas reef at three meters depth. In Batunampar reef, fish diversity was found 15 species. In the two surveys, therefore, fish diversity is high in Batunampar and Ekas reefs. On the dry season, coral reef fish abundance at Tanjung Segui reef is the highest one, while fish abundance at Batunampar reef is the third (Figure 4). Fish abundance is also high at Batunampar reef on the wet season that was followed by Ekas and Gili Maringke reefs. Figure 3. Coral Reef Fish Diversity in Keruak Waters. Error bars indicate 1 SD. MK=Gili Maringke, TS=Tanjung Segui, EK=Ekas, BN=Batunampar, xx3= 3 meter depth, xx10=10 meter depth Most of the coral reef fishes found in the belt transect were aquarium fishes, instead of commercial fishes. The commercial fishes species found were Acanthurus 6

7 nigrofuscus, A. piroferus, A. Surgeon, Apogon apogonides, A. semilineus, A. dispar, Caesio cuning, Epinephelus corallida, E. maculatus and Scarus. The commercial fishes were in low abundance and not distributed in all reefs. The Achanturidae was only found in Tanjung Segui, Batunampar and Ekas reefs. Caesionidae was found in Tanjung Segui and Batunampar reefs. The Epinephelus was found in transects of Batunampar and Ekas reefs. predominance. The difference does not necessarily mean temporal variation only, but also spatial variation. More replicates (transects and time) are required to get a good conclusion on temporal variation pattern. Results of the present study also show that coral reef at Tanjung Segui has the best condition among the all surveyed reefs. Anthropogenic threats are also low at present. On the other hand, most other reefs show some degree of blast fishing practices in the past. Simple explanation for this data is that coral reef of Tanjung Segui at proximate distance to pearl oyster culture, where boat patrols are intensively deter any approaching boats. No boats are allowed to stay or to deploy fishing nets on this area. This is the main reason why no blast fishing occurs on this area. This result supports Black (2000) hypothesis that pearl oyster culture may contribute to coral reef conservation at surrounding reefs. CONCLUSIONS Figure 4. Coral Reef Fish Abundance in Keruak Waters. Error bars indicate 1 SD. MK=Gili Maringke, TS=Tanjung Segui, EK=Ekas, BN=Batunampar, xx3= 3 meter depth, xx10=10 meter depth There were six indicator fishes, Chaetodontidae, found in all reefs. These are Chaetodon baronesa, C. guentheri, C. kleinii, C. meyeri, C. trifasciatus and C. unimaculatus. Gili Maringke and Ekas reefs have higher diversity and abundance of these indicator species than the others. The fish C. kleinii and C. meyeri can be found in all reefs. Comparison between the dry and wet seasons shows some differences in fish abundance, fish diversity and fish From the reef study, there were two main issues that should be prioritized. Firstly, all coral reefs surveyed have low hard coral cover, particularly at 10 meters depths. High proportion of coral rubble at 3 (three) and 10 meter depths indicating the occurrence of intensive blast fishing in the past and present. Low coral cover at 10 meters depth was likely owing to the low availability of hard substrate and low light penetration. Secondly, the best coral reef in the southern coast of Lombok Timur is at Tanjung Segui reef, either ecologically or esthetically. Coral reef in Tanjung Segui has high coral cover and diversity, high fish diversity and abundance, and good water clarity. But this description is only 7

8 applicable for 3 (three) meters depth. There is not any track of blast fishing in the past. It is suggested, therefore, this location is very good for snorkeling tourism. At Tanjung Segui reef, however, the size of the reef is too small for a marine protected area. The small size can enlarge if we could include the reefs surrounding Tanjung Segui, for example Gili Petelu. The surrounding reef is also have a good water clarity with pristine reef condition. Since complete data on surrounding reefs are not available at present, further detailed study on the surrounding reef is required. The study should addressed to assess the size of good coral reef, biological diversity, and diversity and biomass of fishery resources. Finally, coral reef rehabilitation is recommended on many places where coral rubble coverage is predominant, i.e. Ekas and Maringke reefs. The use of concrete blocks and volcanic stones as reported by Bachtiar (2001), and Fox (2001) should be considered. Acknowledgement: The study was funded by Co- Fish Project of Nusa Tenggara Barat. Field studies would never been completed without contributions of Bambang Arwono, Totok Sasbiyanto, Didik Santoso and Taufik Hidayat. REFERENCES Babcock, R. and Davies, P. (1991). Effects of sedimentation on settlement of Acropora millepora. Coral Reefs 9: Bachtiar, I Konservasi terumbu karang: permasalahan yang dihadapi di Nusa Tenggara Barat. Gema Rinjani 37: Bachtiar, I Promoting recruitment of scleractinian corals using artificial substrate in the Gili Indah, Lombok Barat, Indonesia. Proc. Int. Coral Reef Symp. Bali. In perss. Black, M Can pearl culture contribute to coral reef conservation in Indonesia. Jurnal Pesisir dan Lautan 3(2): Done, T.J Ecological criteria for evaluating coral reefs and their implications for managers and researchers. Coral Reefs 14: Chou, L.M Southeast asian reefsstatus update: Cambodia, Indonesia, Malaysia, Philipines, Singapore, Thailand and Vietnam. In: C. Wilkinson (ed.) "Status of Coral Reefs of the World: 2000". Australian Institute of Marine Science: Cape Ferguson. Pp Colin, P.L. and Arreson, C Tropical Pacific Invertebrates. Coral Reef Press. California. Debelius, H, Indian Ocean Tropical Fish Guide: Maldives Sri Lanka, Mauritus, Madagascar, East Africa, Seychelles, Arabian Sea, Red Sea. Aquaprint. Germany. English, S., Wilkinson, C. and Baker, V. (eds.) Survey Manual for Tropical Marine Resources. Australian Institute of Marine Sciences. Townsville. 8

9 Fox, H.E. and Pet, J.S Pilot study suggests viable options for reef restoration in Komodo National Park. Coral Reefs 20(3): Gomez, E.D. and Yap, H.T Monitoring reef conditions. In : Kenchington, R.A. and Hudson, B.E.T. (eds.) "Coral Reef Management Handbook". UNESCO-ROSTEA. Jakarta. pp Hodgson, G Sediment and the settlement of larvae of the reef coral Pocillopora damicornis. Coral Reefs 9: Kenchington, R Scientific Investigations for planning. In : Kenchington, R.A. and Hudson, B.E.T. (eds.) "Coral Reef Management Handbook". UNESCO-ROSTEA. Jakarta. pp Kuiter, R. H. 1992, Tropical Reef-Fishes of The Western Pacific: Indonesia and Adjacent Waters, Gramedia Pustaka Utama, Jakarta, Indonesia. Kuiter, R. H dan H. Debelius Southeast Asia Tropical Fish Guide: Indonesia, Philippines, Vietnam, Malaysia, Singapore, Thailand, Andaman Sea. Ikan- Unterwasserarchiv. Germany. Lieske, E. and. Myers, R Coral Reef Fishes. Harper Colin Publishers. Italy. Periplus Editions (HK) Ltd. Pp Veron, J.E.N Corals of Australia and the Indo-Pacific. University of Hawaii Press. Honolulu. pp Soekarno, R Comparative studies on the status of Indonesian coral reefs. Netherlands Journal of Sea Research 23(2): Tomascik, T., Mah, A.J., Nontji, A., and Moosa, M.K The Ecology of the Indonesian seas. Part Two. 9

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