Coral Communities of Outer Ambon Bay: a General Assessment Survey

BULLETIN OF MARINE SCIENCE. 31(3): 574-580. 1981

CORAL COMMUNITIES OF OUTER AMBON BAY: A GENERAL ASSESSMENT SURVEY

John W. McManus and Jacobus J. Wenno

ABSTRACT The deep waters of outer Ambon Bay are bounded by a narrow shallow-water shelf. Artisanal fishing villages and a rapidly growing city line the 51 km coastline. A visual and photographic survey of the shelf revealed patchy coral communities separated by stretches of silt, sand and loose rock. Regions of coastline characterized by soft or hard coral dominated communities were delineated and hard coral regions were subjectively ranked according to coral community development. This method efficiently provides crude baseline data for coastal management when time and resources are limited. Greatest fish abundances were in regions of highest coral community development. Coral damage, resulting in part from traditional fishing activities, was evident along some portions of the coastline. Future problems from increased siltation and pollution related to urbaniza- tion are anticipated. The deterioration of the coral communities may adversely affect the availability of food for the increasing human population.

Ambon Bay is a rapidly growing fishing and shipping port in eastern Indonesia. This study consists of a subjective analysis of the coral communities of the outer bay. The objectives of the study were to determine the general distribution of coral communities for future comparisons, to tentatively classify regions of coral community development as a basis for determining subsequent analytical methods, and to provide information on the status of the communities for immediate resource management applications.

Description of Ambon Bay Ambon Island (formerly Amboina) is located in the Maluku Region of Indo- nesia, south of Ceram (Fig. 1). The island is nearly divided by a bay oriented along a northeast-southwest axis (Fig. 2). A physical description of the bay can be found in Huwae (1971) and is summarized in part here. The elongate outer bay is connected to a small, shallow inner bay by a channel less than 1 km wide and 15 m deep. The outer bay reaches over 250 m in depth in the northeastern portions near Ambon City and over 700 m near the mouth. It is bounded on all sides by a shallow-water shelf, generally less than 200 m wide. Many rivers and streams drain the surrounding hills. The bay is subjected to a southerly monsoon from May to October, a northerly monsoon from December to March, and transitional westerly monsoons in April and November. Although squalls are common within the bay, the orientation of the land masses affords some protection from the monsoons. Rainfall is heaviest from May to August and varies during the year from approximately 11 cm to over 603 cm per month. Tides are mixed semi-diurnal and range from 220 cm to 230 cm. Air temperatures average slightly below 27°C with a maximum of approximately 35°C. Ambon Bay has been the site of considerable taxonomic work. It was the home of the Dutch naturalist Rumpf in the late 15th century (Sirks, 1945) and serves as the type locality for several of the marine species listed by Linne (Serene, 1971). The 19th century ichthyologist Bleeker published at least 26 papers on the

574 McMANUS AND WENNO: CORAL COMMUNITY ASSESSMENT SURVEY 575

I.EGEND: MAP OF AM80N ISLAND _llt.louafprtdo ••lnlllll,ftI14cDIDlcQIflIll~l\1l1•• D"·gIOnlof, ••• OMI"•••llrjJcronaucnco",,,,,,,nllln

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Figure \. (Left) Map of Ambon Island showing the deep and narrow outer bay. Figure 2. (Right) Map of outer Ambon Bay with regions of predominantly hard and soft coral communities indicated. Hard coral regions are subjectively ranked according to coral community development. Characters in parentheses refer to numbers and species of sharks sighted. The greatest frequencies of shark sightings were near the mouth of the bay.

fishes of Ambon Bay (Hutomo, 1971) and gave many of them the specific name amboinensis. In 1970, a cruise of the R. V. SAMUDERA resulted in publications on the physical aspects (Huwae, 1971; Birowo and I1ahude, 1971), plankton (Praseno, 1971), fishes (Hutomo, 1971) and brachyuran crabs (Serene, 1971) of Ambon Bay. Work is continuing on the bay under programs of the National Institute of Oceanology, and Pattimura University, in cooperation with the University of Washington and the U.S. Agency for International Development. The population of Ambon City was approximately 55,300 in 1961 (Landheer, 1967). Recently, it has risen drastically because of inter-island migration and, according to the estimates of local officials, may now be twice that number. Many of the people live in stilt houses built on hillsides and over shallow waters at the northeast end of the city, often with 20 or more people occupying a single house. Most of the refuse of the inhabitants passes into the shallow-water periphery of the bay. This includes a wide array of materials, especially organic wastes, plastic containers, rags, cans, bottles and soap. A major industry of the city is offshore skipjack tuna fishing. Most baitfish for this industry are captured within the bay with purse seines, beach seines and floating drift nets. Fishermen have reported a recent decline in available baitfish. Small fishing villages are scattered along the coastline of the bay. The artisanal fishermen often operate from dugout boats as small as 4 m long and 1 m wide. Fishing is generally done with hand lines, harpoons, nets or traps in shallow waters. The population of traditional fishermen is believed to have been greatly augmented during the recent waves of immigration. Deforestation is particularly evident along much of the coastline. Forests near Laha and along the southern coast from Ambon City to Batu Anjo Point have been cleared for lumber, construction and agriculture.

METHODS

The free swimming observer method was used because of the extent and continuity of linear coverage per unit time it provides (Kenchington, 1978), and its adaptability to investigating variables 576 BULLETIN OF MARINE SCIENCE, VOL. 31. NO.3, 1981 ranging in scale from gross community morphology to general substrate composition (Goreau, 1959). Arguments for a subjective approach to preliminary community classification have been summarized by Mueller-Dombois and Ellenburg (1974). On the basis of initial spot dives and boat observations, a sampling scheme for the survey was developed. A visual and photographic survey of the outer bay was then undertaken in a single transect approximately parallel to shore. Segments of the coastline were covered daily with respect to pre- vailing currents such that the total survey resulted in a nearly continuous line along the shallow-water shelf. Of the 51 km coastline of the outer bay, all but 4 km were surveyed during the period February, 16-March 3, 1980. Poor visibility and heavy boat traffic in the harbor area made survey work difficult and dangerous. For purposes of continuity, a single researcher made the primary observations throughout the study, with supplemental observations and verifications provided by a second worker. Data were recorded on a plastic slate and representative photographs taken with a 35 mm camera and 24 mm lens in a plastic housing. Mask, fins, and snorkel permitted investigation of phenomena to approximately 15 m depth. Since coral development was generally minimal at this depth, SCUBA gear was deemed unnecessary. The steep sandy walls and great depths of the bay made extensive deeper water coral community development unlikely. The edge of the dropoff was used as a guide. All coral communities encountered during the transect were traversed in a zig zag pattern. Information on both community structure and possible coral damage was gathered within the radius of visibility, which generally exceeded 10 m. Shelf width varied from approximately 1 to 200 m with depths along the shelf edge of 3 to 10 m. Some coral communities may have been overlooked in areas of widest shelf development, but in general, coral development appeared to be maximum along the edge of the dropoff. Records were made of changes in community dominance, gross coral community morphology, substrate composition, water clarity, depth and current direction. Current intensity was described in terms of very strong, moderate or weak, relative to the effort necessary for the diver to remain stationary for short periods of time. Species diversity was described in terms of high, medium, low or monospecific, based on species per unit area estimates and degree of apparent dominance. Obvious signs of recent siltation and physical damage to corals were recorded. Estimates were made of sizes of major coral structures and note was made of any patches of dead coral. Additional information on coral damage was obtained from local fishermen after each dive. Areas of high fish abundance were recorded, as were sightings of sharks and other large fishes as background data for fisheries management. The time of each observation or location relative to obvious landmarks was recorded. The 403 observation points were then located on a 1:50,000 hydrographic chart to within approximately 0.5 km. Regions of the bay with more than one coral community per 0.5 km (approx.) were delineated on the chart with respect to hard or soft coral dominance (Fig. 2) and degree of community development.

RESULTS A broad range of coral communities are scattered irregularly along the outer bay. Many of these showed signs of disruption related to human activities.

Coral Communities The distribution of coral communities in outer Ambon Bay is shown in Figure 2. The regions of hard coral dominance are grouped into four arbitrary classes and ranked from I to 4 (highest to lowest) based on coral community development within the bay, The criteria used for this evaluation are: a, major coral communities large relative to others in the bay; b, largest coral communities exhibit topographic relief relative to surrounding substrates; c, calcification between coral heads common; d, presence of large coral colonies; and e, absence of large ar'-'as of sand or gravel substrate within coral communities. Class I.-This region was characterized by patches of apparent high species/area diversity, mixed with a few monospecific stands often greater than 5 m in long axis dimension. In places, hard coral coverage was higher than 75% over an area of several hundred square meters. Zones dominated by tabular Acropora colonies were clearly defined, as were monospecific stands of branching Acropora and foliose Montipora. Fields of Galaxea extended more than 30 m across. Large McMANUS AND WENNO: CORAL COMMUNITY ASSESSMENT SURVEY 577 coral colonies were present and some dead coral heads and disrupted coral stands could be found. The long axes of most large colonies and mono specific stands were perpendicular to shore. Class 2.- Two regions were characterized by a predominance of mono specific coral stands greater than 5 m in axis length, associated with coral aggregations of moderate species diversity. Coral communities were interrupted by patches and channels of silty sand. North of Laha, stands of Goniopora and Euphyllia 2 covered areas 50-200 m • Mounds of Galaxea and Porites longer than 10 m and higher than 3 m were encountered. Stands of branching Acropora and foliose forms of Montipora, Echinopora, Mycedium and others formed large monospecific patches of varying size. South of Laha, long stands of branching Acropora were common, as were fields of Lobophyllia more than 20 m across. Many of the coral patches in both regions were oriented with their long axes approximately perpendicular to shore. Communities in both regions contained patches of dead branching Acropora representing as much as 15% of the total Acropora. Class 3.-Regions in this class contained a heterogeneous range of hard coral communities, most of which were divided into low patches by sand and gravel or clumps of aicyonaceans. Species/area diversity was moderate to high in most patches. Communities along the wider portions of the bay tended to have low topographic relief development, although some large coral heads (up to 2.5 m) were present. The Ambon Coral Gardens consisted of large aggregations of coral, interrupted by patches and channels of silty sand. Several dead faviid corals were observed, including heads larger than 1 m. A few disrupted patches of leafy Montipora were under Acanthaster planci predation. The coastline near Nama Point consisted of short cliffs jutting in towards the bay covered with various corals, including bush-like antipatharians taller than 1 m. Class 4.-These regions contain small and infrequent patches of corals. A community encountered along the northern shore of the channel leading to the inner bay was dominated by Seriatopora, Stylophora and Fungia. Micro atolls and Poriies heads less than 1.5 m in diameter were common in the same community to the southwest. Coral communities immediately southwest of Ambon City were mixed with alcyonaceans and dead coral patches. The wave exposed Nusanive Point region included short rock walls and stone blocks covered by stubby growth forms of Pocillopora, Acropora, Tubastrea, Stylophora, Distichopora (purple, yellow and white forms) and others in water less than 3 m deep. Other regions in this class were characterized by various fungiid accumulations, corals growing on stone boulder substrates and small patches of diverse coral aggregations separated by large sandy areas. Soft Coral Regions.-The most diverse aicyonacean dominated communities were along the open coast southwest of Laha. In the upper reaches of the outer bay, many communities were heavily dominated by Sarcophyton. These were frequently associated with silty substrates or regions near ship docks where oil pollution was obvious. Most of the patches of soft coral contained occasional scleractinians, particularly Turbinaria peltata. Unmarked Regions.-The most common scleractinian in some sandy regions was Wellsophyllia radiata Pichon, 1980. This was present on sand and submerged log substrates in unmarked regions of the upper coastline from Poka to Laha villages. The highest concentrations were on a sand and gravel slope on the southern shore of the channel connecting the inner and outer bays. 578 BULLETIN OF MARINE SCIENCE, VOL. 31, NO.3, 1981

Occasional rocks, boulders, logs and scrap metal were encountered with at- tached coral colonies. These were most commonly Porites, Pocillopora (especially P. verrucosa), Seriatopora, Stylophora, Turbinaria peltata, Acropora (especially A. humilis and various tabular forms) and some faviids.

Distribution of Fishes

The majority of fishes observed along the shallow-water shelf of the bay were associated with coral communities. This concurs with observations made in shallow waters of other tropical regions (Parrish and Zimmerman, 1977). Greatest fish abundances seemed to occur in regions belonging to classes 1 and 2. Com- monly encountered fishes over 30 cm in total length included some carangids (especially Caranx spp.), lutjanids, serranids, sphyraenids and acanthurids. Schools of smaller fishes (especially apogonids) were frequently dense enough to obscure the corals beneath them. Small coral-covered stone boulders appeared to attract disproportionately large numbers of small fishes per unit cover, particularly when isolated from other coral communities by more than 50 m. These small coral aggregations were commonly sites of cleaning activities by Labroides dimidiatus. Sandy and rocky portions of the shelf were often devoid of visible fishes for survey periods of more than 5 min. Large schools of Mugil, sphyraenids, or small clupeids were common but transient. Alcyonacean dominated communities also contained markedly lower numbers of actively swimming fishes. Cryptic and burrowing forms were not investigated. Forty-seven sightings were made of a black-tip shark species (?Charcarhinus melanopterus) and two ofa white-tip shark species (?Triaenodon obesus). Highest concentrations were along the distal portions of the bay. In all cases, the sharks were encountered within or near coral communities.

Apparent Perturbations Most of the observed coral damage can be attributed to predation by Acal1- thaster planci, fish predation and other natural causes as identified in coral reef systems elsewhere (Endean 1976). Schools of up to 20 Bulbometopon muricatus were frequently seen grazing among the coral patches. These and other fishes may be responsible for much of the displaced coral found in patches around the bay (Randall, 1976). Many coral communities showed indications of recent sediment encroachment, especially along the northern shore, east of Laha. Whether this was due to a natural change in sedimentation processes or is related to recent deforestation was not determined. Corals with large polyps may be able to withstand siltation better than some with smaller polyps (Roy and Smith, 1971). The predominance of large polyp Goniopora and Euphyllia colonies in several communities may be related to a generally high silt load. Much coral breakage throughout the bay was caused by local fishermen. Many fishermen break off small caespitose and corymbose corals to shake out small fish into their boat for food or bait. Corals were being damaged in the processes of disguising fish traps and in pulling the traps across coral communities. Some weighted nets may cause similar damage. Small massive corals were occasionally being used as building materials. The hook-like anchors of the traditional fishermen tend to break certain corals (Gomez, 1980). McMANUS AND WEN NO: CORAL COMMUNITY ASSESSMENT SURVEY 579

DISCUSSION The subjective ranking of coastal regions on the basis of coral community development is an efficient means of providing crude baseline data for future comparisons and can provide temporary guidelines for coastal development proj- ects when time and resources are limited. Subsequent studies may refine the community classification and lead to a better understanding of the processes of early succession and development in coral communities. With the rapid growth in population around the bay, some change in the status of the coral communities will probably occur. Destructive activities of traditional fishermen which may ordinarily be within the recoverability of a coral community might lead to broad-scale damage when the frequency of the disturbances is increased. As the urban regions expand, one may expect problems with pollution from industrialization, and siltation due to deforestation and construction. Be- cause of the high degree of association of the shallow-water fishes with the coral communities, the deterioration of these communities may have a significant im- pact on the availability of food for the rising population. In the body of literature on tropical shallow-water ecosystems, very little work has been published on small coral communities. Observations by one of us (McManus) in the Philippines indicate that small aggregations of coral are common along some coastlines exhibiting little reef development. As in Ambon Bay, these patches are often associated with large quantities of fish. If similar coral communities are abundant throughout Southeast Asia, then they may be impor- tant on a broad scale to fishery productivity. Unfortunately, the lack of topographic relief and close proximity to shore of these small coral patches may leave them especially vulnerable to damage from siltation. In order that the extent and status of these communities may be determined, some standards of comparison should be devised. The classifications used in the present study are based on a ranking of communities limited to the study area, and are most useful to spatial and temporary comparisons within the bay. For use on a national or international level, such classifications must be based on a much broader range of variability. It is proposed that research be initiated into the importance of small coral communities to coastal productivity and into their vulnerability to perturbations related to deforestation, industrialization and overpopulation.

ACKNOWLEDGMENTS

This study was funded by the United States Agency for International Development/Indonesia. The authors would like to thank the many people who made this study possible, especially Dr. A. Soe- giarto, Director, National Institute of Oceanology; Dr. A. Suwartana and Mr. L. Wenno of National Institute of Oceanology/LON; Rector Lestaluhu of Pattimura University; Fr. Nanlohy of the U.S. A.I.D. Project for the Aquatic Resources Component; Mr. W. Littlewood and Mr. J. Baird of U.S. A.I.D.; Mr. C. Angell of the University of Washington-U.S. A.I.D.-LON-Pattimura University Fisheries Program; Ms. L. Altea, Fisheries Program Director, and Co-Directors E. Abernathy and J. Abernathy of the U.S. Peace Corps/Philippines; and Dr. E. Gomez, Director, University of the Philippines Marine Sciences Center. Special thanks go to Mr. D. Sahetappy, University of Pattimura for sharing in the fieldwork, and to the people of Poka and other villages in Ambon for invaluable help and information. The authors gratefully acknowledge the advice of the following people on the preparation of the manuscript: Dr. A. Dahl, C. Glenn, Dr. B. Goldman, Dr. E. Gomez, Dr. M. Pichon, L. Talaue, and Dr. R. Tsuda. Manuscripts were typed by L. Talaue and E. Pagsaligan. This study was undertaken while J. W. McManus was a volunteer in the U.S. Peace Corps/Phil- ippines assigned temporarily to U.S. A.I.D./lndonesia. Contribution No. 31 of the Marine Sciences Center, University of the Philippines. 580 BULLETINOFMARINESCIENCE,VOL.31,NO.3, 1981

LITERATURE CITED

Birowo, S" and A. G, I1ahude. 1971. General hydrological conditions around Ambon Island. Pages 11-14 in Preliminary report on Ambon survey 1970. Institute of Marine Research, National Institute of Oceanology. Indonesian Institute of Sciences, 34 pp, Endean, R. 1976. Destruction and recovery of coral reef communities. Pages 215-254 in O. A. Jones and R, Endean, eds. Biology and geology of coral reefs. Vol. 3 Biology 2. Academic Press, New York. 337 pp. Gomez, E, D. 1980. Status report on research and degradation problems of the coral reefs of the East Asian seas, South China Seas Fisheries Development and Coordinating Programme, FAO, UNEP/WG. 41/INF. 15.68 pp. Goreau, T. F. 1959, The ecology of Jamaican coral reefs I. Species composition and zonation. Ecology 40: 67-90. Hutomo, M. 1971. Notes on fishes of Ambon. Pages 23-31 in Preliminary report on Ambon survey 1970. Institute of Marine Research. National Institute of Oceanology. Indonesian Institute of Sciences. 34 pp. Huwae, A. 1971. A brief description of Ambon. Pages 3-10 in Preliminary report on Ambon survey 1970. Institute of Marine Research. National Institute of Oceanology. Indonesian Institute of Sciences. 34 pp, Kenchington, R. A. 1978. Visual surveys of large areas of coral reefs. Pages 149-161 in D. R. Stoddart and R. E. Johannes, eds. Coral reefs: research methods. Monographs on oceanic method- ology 5. UNESCO. 581 pp. Landheer, B. 1967. Ambon. Page 628 in Collier's Encyclopedia Vol. 1. Crowell Collier and MacMillan Inc. 24 vols. Mueller-Dombois, D., and H. Ellenberg. 1974. Aims and methods of vegetation ecology. John Wiley and Sons, Inc., New York. 547 pp. Parrish, J. D., and R, J, Zimmerman, 1977. Utilization by fishes of space and food resources on an offshore Puerto Rican coral reef and its surrounding. Proc. 3rd Inter. Coral Reef Symp. I: 297- 303, Pichon, M, 1980. Wellsophyl/ia radiata n. gen., n, sp., a new hermatypic coral from the Indonesian region, (Cnidaria, Anthozoa, Scleractinia). Revue Suisse Zool. 87(1): 253-259. Praseno, D, P. 1971. Preliminary plankton observations in Ambon Bay and Piru Bay (Ceram). Pages 15-22 in Preliminary report on Ambon survey 1970. Institute of Marine Research. National Institute of Oceanology. Indonesian Institute of Sciences, 34 pp. Roy, K. J., and S. V. Smith. 1971. Sedimentation and coral reef development in turbid water: Fanning Lagoon, Pacific Science 25: 234-248, Serene, R. 1971. Observation on the brachyuran fauna of Ambon. Pages 32-34 in Preliminary report on Ambon survey 1970. Institute of Marine Research, National Institute of Oceanology. Indo- nesian Institute of Sciences. 34 pp, Sirks, M. J, 1945, Rumphius, the blind seer of Amboina. Pages 295-308 in P. Honig and F. Verdoorn, eds, Science and scientists in the Netherlands Indies. New York City Board for the Netherlands Indies, Surinam, and CuralYao, Vol. 102. Riverside Press, Cambridge.

DATEACCEPTED: May 14, 1981.

ADDRESS: (JWM) Marine Sciences Center, University of the Philippines, Manila, Philippines; (JJW) University of Pattimura, Poka, Ambon, Indonesia.