|Environment and development
in coastal regions and in small islands
Coastal region and small island papers 3
Buccoo Reef and Bon Accord Lagoon, Tobago, Republic of Trinidad and Tobago
Richard S. Laydoo, Kurt Bonair, and Gerard Alleng
Institute of Marine Affairs, PO Box 3160, Carenage Post Office, Republic of Trinidad and Tobago
Buccoo Reef and Bon Accord Lagoon are located on the leeward coast of southwestern Tobago. This is one of two localities in Trinidad and Tobago characterized by contiguous reef, seagrass, and mangrove ecosystems. The reef system is approximately 7 km2 in area and is characterized by an arc of five reef flats that enclose a shallow reef lagoon and the Bon Accord Lagoon. There is patchy distribution of coral communities within the reef lagoon, mainly staghorn coral and star coral. The Bon Accord Lagoon is characterized by macroalgae and seagrass communities. The mangrove wetland fringing the lagoon is primarily red mangrove. Seaward of the reef flats, the forereef slopes to depths of 15-30 m. Brain coral, star coral, and elkhorn coral are the dominant coral species on the forereef.
The Buccoo Reef and Bon Accord Lagoon system is located at the southwestern end of the island of Tobago between 11°08'N to 11°12'N latitude and 60°40'W to 60°51'W longitude (Fig. 1). The reef covers an area of 7 km2. It is a fringing reef, characterized by five insular emergent platforms to the north, a shallow sandy lagoon with a patchy distribution of coral communities, and the mangrove-fringed Bon Accord Lagoon in which a seagrass community is present. This system is the best example of contiguous reef, seagrass, and mangrove wetland in Trinidad and Tobago (Fig. 2).
|Fig. 1. Map of southwestern Tobago and location of Buccoo Reef|
|Fig. 2. Buccoo Reef and adjacent
seagrass and mangrove ecosystems, with
location of CARICOMP sampling localities.
The extant reef is of Holocene origin (ca. 10,000-12,000 years BP) lying on a Pleistocene carbonate platform. The platform, which is emergent to the south of the reef system, characterizes the terrestrial geology of the low-lying southwestern region of Tobago (Maxwell, 1948). The Buccoo Reef-Bon Accord Lagoon area is unique to the southern Caribbean due to its size, attractiveness, and easy accessibility (Goreau, 1967). It is located on the low-energy, leeward southwestern coast of Tobago. Such attributes have led to its development as a major tourist attraction.
Guided tours to the reef were initiated in the 1930s. Today, the primary activities associated with visitor use at Buccoo Reef include glass-bottom boat tours to the Outer Reef flat, the Coral Gardens, and the Nylon Pool, along with reef-walking and snorkelling on the shallow backreef areas of the Outer Reef flat. Sport-diving occurs at forereef sites, but this activity is not common at Buccoo Reef due to the presence of higher quality dive sites at other reef localities in Tobago.
The promotion of the Buccoo Reef area as a major tourist attraction, combined with hotel and residential development in adjacent coastal areas, has resulted in direct and indirect negative impacts on the ecosystems. Direct impacts are evident as physical damage over an extensive area of the Outer Reef flat; corals have been broken or crushed by trampling feet, falling anchors, and intermittent boat groundings (Goreau, 1967; Kenny, 1976). Indirect impacts are more insidious and are linked to the discharge of untreated sewage and to increased surface run-off (Laydoo and Heileman, 1987). Major population centers adjacent to the Buccoo Reef system are the villages of Buccoo and Bon Accord, as well as numerous hotels and guest houses along the coast from Plymouth to Crown Point (Fig. 1). Pollution threatens the viability of the reef through nutrient enrichment of the seawater and increased algal growth. This, combined with the effects of reef-walking, potentially reduces the possibility of coral regeneration in damaged areas. Sewage pollution at some localities presents a serious hazard to seabathers.
Recognition of the resource value of the Buccoo Reef system has resulted in its designation in 1973 as the countrys only marine protected area under the Marine Areas (Preservation and Enhancement) Act of 1970. However, no effective management has been implemented since its designation as a protected area, even though management proposals and draft plans have been developed. Only recently, the Institute of Marine Affairs, with assistance from the Tobago House of Assembly (the local government authority), developed a management plan for the proposed Buccoo Reef Marine Park.
Climate and Oceanography
Trinidad and Tobago have a humid, tropical climate. The mean annual temperature is 25.7°C, and precipitation is highest May to December. Southwestern Tobago generally gets little precipitation, with a maximum of 40 mm during the wet season and a maximum of 15 mm during the dry season (Berridge, 1981). Trinidad and Tobago, located at the southern extremity of the Antilles Archipelago, lie south of the hurricane belt. However, the islands occasionally experience tropical storms and hurricanes. The most recent hurricane in Tobago occurred in September 1963. The prevailing winds during the wet season are the northeast trades. In the dry season, winds are generally stronger and the prevailing wind direction is westerly. The Buccoo Reef system is exposed to the northeast trades throughout the year. Consequently, the Outer and Eastern Reef flats are subject to moderate to high wind and wave energy, particularly during the dry season when winds are stronger. Wave energy on the northeastern reef fringe is also high during the winter months, November-December, when strong oceanic swells are common. This generally results in increased turbidity in the reef area (Kenny, 1976).
Water movement in the Buccoo Reef area is predominantly wind driven; it is generally westerly, with some reversal in the Bon Accord Lagoon and the southwest channel near Pigeon Point during flood tide (Kenny, 1976; Fig. 1). Surface circulation to the west of Buccoo Reef, however, is apparently more influenced by northwesterly water movement between Trinidad and Tobago. The salinity and turbidity of this water is strongly influenced by Orinoco River discharge during the wet season. This has marked effects on the water quality at Buccoo Reef, where lower mean salinity (34 ) and higher turbidity (15 m visibility) are common during the wet season. In the dry season, a higher mean salinity (36 ) and clearer water is generally observed (Berridge, 1981). Seawater temperature is generally constant within depths less than 20 m, ranging from 24°C in winter to 27°C in summer (Berridge, 1981).
The Bon Accord Lagoon is bordered to the south and east by a mangrove wetland (Fig. 2) of lagoon fringe type, which forms a belt several meters wide and has an area of 77 ha. Indications are that this is a mature community, with conditions for growth close to optimum (Goreau, 1967). Red mangrove (Rhizophora mangle) predominates, but white mangrove (Laguncularia racemosa) is also common. Black mangrove (Avicennia germinans) and button mangrove (Conocarpus erectus) are also present.
In the northeastern sector, the mangrove fringe is connected by a small channel to another mangrove area located in the southern sector of Buccoo Bay. This is a basin mangrove community type located behind a sandy beach barrier. There are several perennial inlets into the system in this sector, but there are no outlets except the small channel connecting to the lagoon fringe community. It has been suggested that this basin area is a continuation of the Bon Accord Lagoon wetland system (Alleng, 1994). Although the land adjacent to the entire Bon Accord-Buccoo Bay wetland is privately owned, the wetland itself has been included in the Buccoo Reef Restricted Area and the proposed Buccoo Reef National Park. Adjacent land use is mainly agriculture, residential development, or scrub vegetation.
The system has been impacted by both natural and human factors. Most of the western part of the mangrove wetland was destroyed by Hurricane Flora in September 1963 but it has recovered since then. Some mangroves were also cleared at Sheerbirds Point for beach improvement in the 1960s, and gaps have been cut for jetties and drainage canals. In the past two years, a housing estate has been developed along the southwestern boundary of the wetland, with concomitant construction of sewage treatment ponds. It has been proposed that some enclosed lagoons in this area of the wetlands be utilized for the discharge of treated domestic waste.
An extensive seagrass bed is located in the western area of the Bon Accord Lagoon (Fig. 2). Turtle grass (Thalassia testudinum) is the dominant seagrass. The benthic community also contains macroalgae (Bryopsis spp., Dictyota spp., Chaetomorpha spp.), sea urchins (Lytechinus variegatus), mollusks (Strombus spp.), oysters (Pinctada radiata) and holothurians (unidentified) (Kenny, 1976).
North of the Bon Accord Lagoon is the extensive, shallow reef lagoon of Buccoo Reef (Fig. 2). Small coral formations, characterized by one or a few species, occur throughout the reef lagoon. Four types of these patch reefs have been identified (Hudson, 1984). Patch reefs of finger coral (Porites porites) occur in the Bon Accord Lagoon and south of it. The patch reefs in the western area of the reef lagoon are composed of thickets of staghorn coral (Acropora cervicornis), while those in the eastern area are composed of both staghorn and fire coral (Millepora spp.). The patch reefs in the northern area of the reef lagoon consist primarily of large formations of star coral (Montastraea annularis) and brain coral (Diploria strigosa). Due to the presence of sea fans (Gorgonia ventalina) and other octocorals, as well as numerous colorful reef fishes, this northern patch reef locality is popularly known as "Coral Gardens."
Five emergent reef flats arc seaward of the reef lagoon, from Pigeon Point in the west to Sheerbirds Point on the east, known as Pigeon Point Reef, Western Reef, Northern Reef, Outer Reef, and Eastern Reef (Fig. 2). The reef flats are separated by sandy-bottom channels, the widest and deepest of which is the Deep Channel between the Western and Northern Reefs. The reef flats are generally characterized by a narrow seaward reef crest and a more extensive backreef toward the reef lagoon. The reef crests coincide with a conspicuous breaker zone. Due to the turbulent nature of this zone, the faunal composition of the reef crests is limited to wave-resistant corals such as M. annularis, and elkhorn coral, A. palmata. Generally, the backreef areas are characterized by coral rubble (Kenny, 1976).
West of the reef flats, the forereef slopes gently to a depth of 20 m. To the east, the forereef slopes to a depth of 15 m, while to the north the forereef slopes gently to depths over 30 m (Laydoo, 1985). The benthic fauna of the forereef is dominated by large colonies of stony corals. In the shallow forereef zone (2-6 m depth) A. palmata is common. In deeper areas of the forereef, large colonies of Diploria spp., Montastraea spp., and starlet coral (Siderastrea spp.) are common. The substrate of the shallow forereef is mainly composed of rubble and dead standing remains of A. palmata (Laydoo, 1985).
The authors wish to acknowledge the assistance provided by the Tobago House of Assembly in the coordination and implementation of CARICOMP Level 1 field activities. In particular, the assistance and cooperation of the following members of staff of the Fisheries Section, Division of Agriculture, Forestry and Marine Affairs of the THA is sincerely appreciated: Mr. Erol Caesar, Fisheries Officer; Mr. David Shim, Buccoo Reef Park Manager; Mr. Euthan Yeates, Mr. Terrence Holmes, Mr. Isaac Augustine, Mr. Thomas Melville, Mr. Watson George, Mr. Glenford Waldron, Mr. Victor Solomon, Mr. Malcolm Morris, Mr. Levi James, and Mr. David Griffith. Also La Tours Estate, Tobago Marine Sports, Tobago Dive Experience, and Dive Tobago Experience. The authors thank Mr. Anthony Cummings and Ms. Hilary London for preparing the figures, and Dr. Avril Siung-Chang for reviewing the manuscript. This is Institute of Marine Affairs contribution IMA/CARICOMP No. 1.
Alleng, G. P. 1994. Advanced Application of Remote Sensing with Specific Reference to Caribbean Coastal Environments. Final Report to the Caribbean Development Bank, Barbados, 51 pp.
Berridge, C. E. 1981. Climate. In: The Natural Resources of Trinidad and Tobago (edited by St. G. Cooper and P. R. Bacon), pp 3-6 and 113-117. Edward Arnold, London, UK, 223 pp.
Goreau, T. F. 1967. Buccoo Reef and Bon Accord Lagoon, Tobago: Observations and Recommendations Concerning the Preservation of the Reef and its Lagoon in Relation to Urbanisation of the Neighbouring Coastal Islands. Memorandum to Permanent Secretary (Agriculture), Economic Planning Unit, Prime Ministers Office, Government of Trinidad and Tobago, 8 pp.
Hudson, D. I. G. 1984. Patch Reef Zonation on Buccoo Reef, Tobago. Proceedings of the Association of Island Marine Laboratories of the Caribbean, Number 18, 7 pp.
Kenny, J. S. 1976. A Preliminary Study of the Buccoo Reef/Bon Accord Complex, with Special Reference to Development and Management. Department of Biological Sciences, University of the West Indies, Trinidad, 123 pp.
Laydoo, R. S. 1985. The Forereef Slopes of the Buccoo Reef Complex, Tobago. Technical Report, Institute of Marine Affairs, Trinidad, 22 pp.
Laydoo, R. S., L. Heileman. 1987. Environmental Impacts of the Buccoo and Bon Accord Sewage Treatment Plants, Southwestern Tobago. A Preliminary Report. Institute of Marine Affairs and Crusoe Reef Society, 27 pp.
Maxwell, J. S. 1948. Geology of Tobago. Bulletin of the Geological Society of America, 59:801-854.