South China Sea

South China Sea

PII: Marine Pollution Bulletin Vol. 42, No. 12, pp. 1236±1263, 2001 Ó 2001 Published by Elsevier Science Ltd. Printed in Great Britain 0025-326X/01 $...

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PII:

Marine Pollution Bulletin Vol. 42, No. 12, pp. 1236±1263, 2001 Ó 2001 Published by Elsevier Science Ltd. Printed in Great Britain 0025-326X/01 $ - see front matter S0025-326X(01)00240-5

South China Sea BRIAN MORTON * and GRAHAM BLACKMOREà  The Swire Institute of Marine Science and Department of Ecology and Biodiversity, The University of Hong Kong, Cape d' Aguliar, Shek O, Hong Kong, China àDepartment of Biology, The Hong Kong University of Science and Technology, Hong Kong, China The South China Sea is poorly understood in terms of its marine biota, ecology and the human impacts upon it. What is known is most often contained in reports and workshop and conference documents that are not available to the wider scienti®c community. The South China Sea has an area of some 3.3 million km2 and depths range from the shallowest coastal fringe to 5377 m in the Manila Trench. It is also studded with numerous islets, atolls and reefs many of which are just awash at low tide. It is largely con®ned within the Tropic of Cancer and, therefore, experiences a monsoonal climate being in¯uenced by the Southwest Monsoon in summer and the Northeast Monsoon in winter. The South China Sea is a marginal sea and, therefore, largely surrounded by land. Countries that have a major in¯uence on and claims to the sea include China, Malaysia, the Philippines and Vietnam, although Thailand, Indonesia and Taiwan have some too. The coastal fringes of the South China Sea are home to about 270 million people that have had some of the fastest developing and most vibrant economies on the globe. Consequently, anthropogenic impacts, such as over-exploitation of resources and pollution, are anticipated to be huge although, in reality, relatively little is known about them. The Indo-West Paci®c biogeographic province, at the centre of which the South China Sea lies, is probably the world's most diverse shallow-water marine area. Of three major nearshore habitat types, i.e., coral reefs, mangroves and seagrasses, 45 mangrove species out of a global total of 51, most of the currently recognised 70 coral genera and 20 of 50 known seagrass species have been recorded from the South China Sea. The island groups of the South China Sea are all disputed and sovereignty is claimed over them by a number of countries. Con¯icts have in recent decades arisen over them because of perceived national rights. It is perhaps because of this that so little research has been undertaken on the South China Sea. What data are available, however, and if Hong Kong is used, as it is herein, as an indicator of what the perturbations of other regional cities upon the South China Sea are like, then it is impacted grossly and an ecological disaster has probably already, but unknow-

*Corresponding author. Tel.: +852-2809-2551; fax: +852-28092197. E-mail address: [email protected] (B. Morton).

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ingly, happened. Ó 2001 Published by Elsevier Science Ltd.

The De®ned Region The South China Sea is a marginal sea in the sense that it is largely surrounded by land with accesses to it, for example, between West Malaysia and Indonesia, at the Karimata Straits in the southwest and the Philippines and Taiwan, at the Luzon Straits to the northeast (Fig. 1). The sea has an area of 3.3 million km2 , not including the Gulfs of Thailand and Tonkin, but which, if included, would increase the area to 3.8 million km2 . It is sometimes referred to as the ÔAsian MediterraneanÕ. The countries around its rim, moreover, include some of the most densely populated, fastest growing and, until 1997, the most vibrant economies on earth. About 270 million people live in the coastal sub-regions of the South China Sea. Into it drain signi®cant rivers, the Pearl in Guangdong Province, China; the Red in North Vietnam; the Mekong in South Vietnam and associated with these are signi®cant cities, e.g., Guangzhou and Hong Kong, Hanoi and Ho Chi Min (Saigon), respectively. Many smaller rivers characterise East Malaysia and the Philippines, but population centres are still large, e.g., Manila (>10 million people). The South China Sea has signi®cant islands, including Hainan in the northwest and Palawan in the southeast, the latter separating it from the Sulu Sea. There are, however, hundreds of smaller islands, atolls, submerged reefs and banks in the South China Sea (Fig. 2). As will be described, moreover, the sea itself is of extraordinary structural diversity and can be divided into a number of geological divisions (Workman, 1991) and, thus, into sea areas which range from the shallowest coastal fringes to the Manila Trench with a maximum recorded depth of 5377 m. Between these extremes are wide continental shelves, especially to the north and west, and an abyssal plain at 4500 m. Arising from it are clusters and chains of seamounts of considerable size and which are believed to be extinct volcanoes (Fig. 2). The geology of the South China Sea and its formation in terms of plate tectonics have been described by Briais et al. (1993). The sea extends northwards from the equator to approximately 22°N at the southern coast of China and is thus contained within

Volume 42/Number 12/December 2001

Fig. 1 A map of the South China Sea.

most northerly atolls, Pratas Reef is 274 km southeast of Hong Kong, which itself, has 53 species of recorded corals. The South China Sea, therefore, has considerable habitat diversity and almost certainly species diversity. It also has large hydrocarbon, oil and gas reserves which are being tapped but about which little is published (Workman, 1991; Fig. 2.1). There are also signi®cant ®sheries, again about which little is published, and the biodiversity of the sea is largely unknown although there have been expeditions to the island groups mostly by Chinese and Vietnamese scientists, the results of which have been published usually in these languages and are, as a consequence, rarely referenced by other academics. The sea and its island groups are politically highly sensitive with disputed boundaries, for example, between Vietnam and China in the Gulf of Tonkin, between Malaysia and the Philippines o€ the coast of Sabah, and with numerous con¯icting claims for many of the sea's island groups (Chao, 1991), notably the Spratlys beneath which there is an estimated six million barrels of oil. Accounts of such claims are reported upon in Hill et al. (1991) that the sedimentary deposits which occur under shallow continental shelf of the northern, western and southern regions of the South China Sea, as a whole, contain between 10±14 billion barrels of oil, that o€ the coast of Borneo possessing 9-billion barrels alone. These Miocene (28 million years ago) deposits are immensely thick; that of the Red River Basic being 5000 m, the Mekong River Basin between 2500±3500 and the immense Saigon-Sarawak Basin 5000 in (Fig. 3). Since 1959, Vietnam, in particular, has been exploring and drilling for oil, in co-operation with Western companies and from its ®elds alone production was estimated to be 21 million tonned in 2000. Potential oil and gas resources for the various areas of the South China Sea have been estimated as follows: · · · · · · ·

Fig. 2 A chart of the South China Sea with the water removed to show topographical features of the seabed.

the Tropic of Cancer. Most low-lying mainland coastlines are (or were) mangrove-fringed, but the islands and islets have fringing coral reefs or are atolls. One of the

Southern China ± 1500 million barrels South of Hainan Island ± 210 million barrels Gulf of Tonkin ± 95 million barrels South Vietnam ± 2847 million barrels Sunda Shelf ± 180 million barrels Borneo/Sarawak ± 9260 million barrels Philippines ± 409 million barrels

Given such ®gures, it is not surprising that there are disputes for the rights over the mineral resources of South China. Add to these, the value of the ®shery resources of the sea and the potential for armed con¯ict is all too apparent. There is not, therefore, as one might expect, a large body of reputable research published on the South China Sea, although Gomez et al. (1990) provide an assessment of the pollution status. The reader is also referred to Morton (1978) for a general view of the ecology of Asian marine habitats and to Hotta and Dutton (1995) for a comprehensive overview of coastal 1237

Marine Pollution Bulletin

China Sea and head towards Vietnam in the west or the coast of Southern China in the north. The pattern of surface ¯ow in the South China Sea in winter is shown in Fig. 4. In winter (Fig. 4(a)), the Northeast Monsoon creates an anticlockwise pattern of circulation. The wind pushes cooler, coastal, waters down through the Taiwan Straits to circulate west and southwards along the coast of China and Vietnam and to either depart the South China Sea via the Karimata Straits or to be turned northeasterly and run along the coast of Borneo and Palawan and thus return to the northern rim of the sea. This creates an anticlockwise gyre in the central area. The Taiwan Current is cold coastal water but the Kuroshio Current entering the South China Sea via the Straits of Luzon, dampens its cooling e€ects, especially above the northern continental shelf by inputting into it north equatorial water which is much warmer (26±29°C). This joins the incurring Taiwan Current at the surface. In summer (Fig. 4(b)), from May to September, under the in¯uence of the Southwest Monsoon, current ¯ow is reversed in the South China Sea and water enters from the Java Sea via the Karimata Straits to sweep up into

Fig. 3 A map showing the sedimentary basins on the continental shell areas of the South China Sea and in which oil and gas resources are located.

zone management issues in the Asia±Paci®c region. One exception to this generalisation is Hong Kong and this review identi®es much of the more signi®cant literature on this area of the northern rim of the South China Sea, as a case study and, possibly, therefore, an indication of what the general situation might be in the wider body of the sea itself.

Seasonality, Currents, Natural Environmental Variables The South China Sea occupies the northern tropics, almost exactly between the equator and the Tropic of Cancer at 22°N. It thus experiences a monsoonal climate created by the in¯uences of the Southwest Monsoon in summer and the Northeast Monsoon in winter. The latter is a stronger and more constant dry wind, increasing average wave heights in Hong Kong, for example, by about 1 m. The former is rain-bearing, deriving moisture from evaporation over the South China Sea. Furthermore, in summer there are often intense low pressure cells built up in the Western Paci®c that develop into severe tropical storms or, in extreme cases, into typhoons (or hurricanes) which characteristically pass over the Philippines and either veer northeast towards Taiwan and Japan, or cross into the South 1238

Fig. 4 The surface currents of the South China Sea in: (a) winter and (b) summer.

Volume 42/Number 12/December 2001

the central area and exit through the Taiwan Straits. In so doing, a clockwise gyre is established o€ the coast of Borneo, above the Spratlys, and a smaller anticlockwise one o€ the coast of Vietnam. In totality, therefore, the southern coasts of the South China Sea, i.e., Borneo and much of the western Philippines, are a€ected by a prevailing northeasterly ¯ow while the coast of the northern rim, i.e., the southern coast of China and most of Vietnam are in¯uenced by a southeasterly ¯ow. The latter is in¯uenced, particularly, by the Coriolis Force, so that, for example, the prevailing ¯ow of water from the Pearl River, the major drainage of Southern China, is to the west (Morton and Wu, 1975). In summer, a major consequence of the northeasterly ¯owing waters of the central South China Sea is to keep the Kuroshio from entering the Straits of Luzon: rather, water from the sea joins this strong northwesterly ¯owing current to sweep up past the east coasts of Taiwan and Japan fostering there the luxuriant growth of corals at latitudes one would not normally expect to ®nd them. Currents in the Sulu Sea, isolated from the South China Sea by Palawan, are localised, reducing the in¯uence of the Sulawesi Sea and the tropical Western Paci®c Ocean. Similarly, the Gulf of Thailand is generally also isolated from the South China Sea, but by strongly ¯owing currents, not land, and water in it predominantly circulates as a clockwise-¯owing gyre. The currents of the South China Sea greatly in¯uence the ¯oral and faunal distribution of coastal marine species. For example, the Taiwan Current extends the East China Sea Province to along the southern coast of China towards Hainan. The complex ¯ow of currents along the coast of Vietnam also, for example, creates four biogeographic regions here (Vo, 1998) which are re¯ected in changes in coral community composition. The highly dynamic nature of the current ¯ows in the South China Sea, moreover, shifts biogeographic boundaries on a seasonal basis. Thus, although Hong Kong at 22°N is near the northern limit of tropical corals and mangroves in the South China Sea, it is also at the southern limit for other temperate species and communities. For example, the common intertidal sea urchin Anthocidaris crassispina is here at the southern limit of its range and grazes macrophytic intertidal algae only when, in winter, they too can grow. In the hot summer they die back, as do other intertidal elements such as barnacles (Liu and Morton, 1994). The arrival of South China Sea water into Hong Kong in summer is heralded by the appearance of the jelly®sh Cyanea nozakii in large numbers (Morton, 1988).

45 mangrove species out of a global total of 51 (Spalding et al., 1997); all of the approximately 70 coral genera now recognised (Tomascik et al., 1997; Vo, 1998); 20 of 50 seagrasses species (Sudara et al., 1994); and seven of nine giant clam species (Tomascik et al., 1997), occur in nearshore areas of the South China Sea. Here too occur three, of the world's four, species of horseshoe crabs (Xiphosura) (Chiu and Morton, 1999a,b). It is neither possible nor desirable to attempt to elucidate the total marine biodiversity of the South China Sea. Ng and Tan (2000), however, provide a detailed review of the biodiversity of the South China Sea. Here a few key marine communities and species are discussed. Mangroves Visitors to the tropics, including the South China Sea, encounter mangroves almost inadvertently because they (did) occupy virtually all but the most exposed and rocky shorelines (Fig. 5). In sheltered estuaries and lagoons, they are usually extensive and may even form a community up to several kilometres wide with a gradual transition to terrestrial rainforest vegetation (Tomlinson, 1986). Sadly mangroves were, for a long time, a forgotten ecosystem (Vannucci, 1989), considered unpleasant and dangerous swamps and, as a consequence, undervalued by governments and destroyed by developers. For example, as a result of the development of the new towns of Sha Tin and Tai Po in Tolo Harbour, Hong Kong, 42% of the mangroves in this inlet were destroyed (Hodgkiss and Yim, 1995). Mangroves, however, represent an interphase between two contrasting community types: terrestrial (lowland forests of various kinds) and marine (notably coral reefs and seagrasses).

The Major Shallow Water Marine and Coastal Habitats The Indo-West Paci®c biogeographic province, at the centre of which the South China Sea lies, is the world's most diverse shallow water marine area. For example,

Fig. 5 The dominating distribution of intertidal mangroves on the shoreline of the South China Sea (Redrawn after: Morton, 1978).

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Throughout the mangrove forests of Asia and the Western Paci®c, there are many examples of exploitation that have ended in disaster (Field, 1993). Clearfelled forests that will never recover, ®sh pond ventures that created wastelands, but were still advocated (Rabunal, 1977), mining areas that support no life, unchecked collection of foliage for fuel and poor paddy that produce lowered rice yields. In addition, urban development has removed vast areas of mangrove forest, often devastating far more land than is required and a€ecting adversely the lives of coastal dwellers unnecessarily. Despite an understanding in part by coastal dwellers that their existence is being threatened by these processes, attempts to restore productivity by local people fail to rehabilitate a€ected mangrove lands due to a lack of agronomic knowledge (Field, 1993). Seagrass beds Globally, there are about 58 species of seagrasses in 12 genera (Kuo and McComb, 1989). Seventeen species of seagrasses have been recorded from China (Sun, 1992) although it is not known how many occur in the South China Sea as a whole. Four species, i.e., Zostera nana ( ˆ Z. japonica), Halophila ovata, H. beccarii and Ruppia maritima have been recorded from Hong Kong (Hodgkiss and Morton, 1978a,b; Melville and Chan, 1992), where their status is considered precarious (Fong, 1999). Virtually everywhere, seagrasses are considered threatened through a combination of natural events such as tropical storms (Patriquin, 1972) but, mostly, human activities such as eutrophication, sedimentation and reclamation (Fong, 1999). Nowhere are the problems more obvious than in Hong Kong and, in recognising declines in seagrass communities due to these factors, Fong (1999) has suggested a conservation and management plan to protect local species. This involves the categorisation of shores, with their resident seagrasses and the perceived threats to them. A resulting ranking scheme focuses closest attention on seagrass beds of Rank I that have the highest priority for protection whereas the lowest Rank IV for a beach recognises that the resident seagrass will almost certainly disappear. Fringing coral reefs Coral communities occur principally around the numerous o€shore islands and archipelagos of the South China Sea (described below). Coral structures, ranging from simple non-reef-building communities along the mainland coast of southern China, e.g., Hong Kong, to complex fringing reefs in the Philippines, line nearly all the South China Sea coasts (Fig. 6). To the north, fringing reefs also occur around Hainan. The 24 km wide Hainan Strait separates this island from the mainland of China. Hainan is large (33 556 km2 ) and has a maximum altitude of over 1000 m. The great majority of the 6.7 million population live along the 1240

Fig. 6 The dominating distribution of sallow subtidal coral communities and reefs of the South China Sea (Redrawn after: Morton, 1978).

coast and use the resources of the sea extensively (Fiege et al., 1994). There are fringing reefs on the southern and southeastern coasts. The reefs are thought to be <10 000 years old and are <10 m thick. Although well-developed reefs were present along the southern coast in the 1950s, a survey in 1984 in the region of Sanya indicated that little of these remained, some 95% having been destroyed by being removed for building purposes, lime production, tourist souvenirs, dynamite ®shing and pollution (Zou and Wang, 1993). Lunya Bay, a sheltered inlet northeast of Sanya, had the best developed reefs with a high percentage of living coral, although extensive areas of dead coral were also present. Today, only scattered coral colonies survive but some 166 species of scleractinians in 43 genera have been described from Hainan and associated islands although a more conservative estimate is 110 species and subspecies and 34 genera. Twenty-six species have been recorded from the cooler waters o€ the northern part of Hainan. The most diverse areas are at the southern tip and include Luhuitou (87 species), Ximsozhou (77 species) and Xinchun lagoon (53 species) (Zou and Wang, 1993). The coral reefs of Vietnam have also been described (Latypov, 1995; Latypov and Malyutin, 1996; Vo and Hodgson, 1997). In contrast to those described above for Hainan, Vietnam's nearshore reefs are poorly developed; the highest diversity of corals has been described for the central region and o€shore islands (Vo and Hodgson, 1997; Vo, 1998). The distribution of coral reefs and species in Vietnam may be explained by poor larval recruitment, water temperature and frequent disturbance caused by high terrestrial runo€.

Volume 42/Number 12/December 2001

The east coast of Thailand borders the Gulf of Thailand. Much of the Gulf is shallow (generally less than 60 m and no more than 85 m deep), sedimented and highly productive. Most of the mainland coast consists of sandy beaches and rocky headlands with some muddy and mangrove fringed areas and few reefs, particularly in the north. O€shore are numerous islands with clearer water and areas of soft substrata, rocks and reefs. On the eastern side of the northern part of the Gulf of Thailand, the island of Sichang and numerous small islets support some coral reefs of low diversity, poor growth being due to freshwater run-o€ from the mainland. The number of islands increases south of Sichang, as does the quality and quantity of their reefs. Several coral-fringed islands occur o€ Pattaya. Numerous islands also lie o€ Sattahip and coral growth is good here, particularly Acropora in deep water. Further east, there is some coral growth in rocky areas o€ the coast of Rayong, and good coral growth on the islands o€shore from it. East of Rayong, the coastline is largely mangrove-fringed, particularly at Chantaburi. There are some o€shore islands but corals are not extensive as conditions are here not optimal. O€ Trat, near the border with Cambodia, there are again a number of o€shore islands, e.g., Kut and Thalu, with good reef development. Yet further east towards Cambodia and Vietnam, corals decline as the Mekong River is reached. Coral reef diversity is relatively low on the west coast of the Gulf of Thailand because of turbid conditions and muddy substata. On the western coast, there is a small fringing reef on the mainland at Khao Sam Roi Yot National Park. Near Pran Buri, there are numerous islands which had extensive coral growth in the recent past. The southern part of this coast has few small islands and few coral reefs. Gulf of Thailand reefs are less diverse than those on the west, i.e., Andaman Sea, coast of Thailand (Sudara, 1981). Peninsular and East Malaysia are situated on the Sunda Shelf in relatively shallow water. Shallow (to 15 m depth) fringing reefs are typical of Peninsular Malaysia but there are also isolated coral patches, most reefs occurring around o€shore islands. Pockets of coral reefs with no connection to land are reported to the east of Kota Baharu, in the Palau Redang area, east of Chukai and east of Pekan. East coast islands have more extensive reefs than those of the west. O€ Kuala Trengganu, reefs are found around the Pulau Perhentian group, Pulau Lang Tengah and Pulau Redang group. South of Pulau Redang, reefs occur around Pulau Bidong Laut, Pulau Belok, Pulau Yu, the Pulau Karah group and Pulau Kapas. Further south, there are reefs around the Pulau Tenggol group: 18 scleractinians and three other hard corals are recorded from reefs around Pulau Aur, South of Pulau Tioman (Dunn, 1970). At Tanjong Tuan, 36 species of hard corals have been documented with 32% live coral (Goh and Sasekumar, 1980). Reefs also occur around Pulau Paya and Segan-

tang group o€ Kedah, around Pulau Perek and in the Sembilan Islands. In East Malaysia, fringing reefs occur around the 40 or so islands lying in shallow waters o€ the west coast of Sabah but there is restricted reef development along the adjacent mainland coast. The Kudat area has 109 km of reef, the Kota Belud District 64 km, Kota Kinabulu 54 km and the Lubuan area 37 km. Reefs extend to a maximum depth of 17 m. The best reefs are in the Pulau Lubuan area around Pulau Kuraman, Pulau Rusukan and along the west coast of Labuan itself. The best coral reef development elsewhere is around Pulau Tiga, Deluar Shoals and Pulau Balambangan. In northeast Sabah, there is little reef development. O€ the southeast coast, there are extensive fringing and patch reefs and a small barrier reef associated with o€shore islands. On this coast, the water is clearer and reefs extend down to 25 m. In the Semprona area and around the island of Palau Sipadan, which lies o€ the edge of the continental shelf, corals occur at a depth of over 40 m (Wood, 1979). The only known coral atoll, Pulau Layang±Layang, occurs o€ the coast of Sabah. Sarawak lacks diverse reefs but coral communities have been recorded in some localities o€shore and away from the in¯uence of estuaries and siltation, such as Satang Besar, o€ Kuching. Owing to the somewhat turbid nature of Brunei's coastal waters and its sedimentary and mangrove-fringed coastline, coral formations are few and of limited extent. There are small reefs close to Pulau Punyut and the Pelong Rocks, but species diversity is poor. Potentially the most interesting site is Louisa Reef, 230 km o€ the coast. With the exception of embayments and large deltaic areas, virtually the whole coastline of the Philippines is dotted with either coral reefs or communities. Philippine reefs have been estimated to be about 27 000 km2 in extent, with the largest concentration in the southwest. The majority of the eastern seaboard of the Philippines faces the Paci®c Ocean and is characterised by steep slopes with no major reef areas. In contrast, the inland seas and the western seaboard, especially o€ Palawan, are lined with fringing reefs and numerous coral banks and shoals. Only two major islands are, however, in direct contact with the South China Sea and only the coral reefs and communities of these, i.e., Palawan and Luzon, are described herein. Around the largest island, Luzon, coral reefs are concentrated in the central western section from Bolinao, Pangasinan, down to Batangas Province. A poorly developed reef occurs around Pandil Island on the east coast of Bataan Peninsula north of Manila and small fringing reefs occur around the volcanic Capones Island slightly further north. Reefs and coral communities also abound on the Polillo Island shelf o€ the east coast of Luzon. The Babuyan Island group at the extreme north is characterised by narrow disconnected fringing reefs, 1241

Marine Pollution Bulletin

as at Fuga Island. Southwest of Luzon, reefs are found around Mindoro and Romblon. There is a dearth of information on the reefs of the southern edge of the South China Sea, such as the atolllike Scarborough reefs and shoals west of Luzon. Similarly, those west of Palawan are marked ÔDangerous GroundsÕ on nautical charts because of the numerous mainly uncharted, submerged coral stuctures. Palawan and its satellite islands have some of the best reefs in the Philippines. Good quality fringing reefs occur around Calauit Island and Maltanubong Island o€ the northern tip of Palawan. Green Island, north of Honda Bay and Ursula Island lying 30 km o€ the southeast coast, have good quality reefs (White, 1984). Marine mammals There are numerous species of cetaceans in the South China Sea, but little information is available on them and none on either the perturbations they are exposed to nor levels of contaminants in their tissues. Tanabe et al. (1994) review the global impacts of persistent organochlorines on marine mammals, allowing work on Hong Kong to be viewed in this context. The dugong (Dugong dugon) was once numerous in the South China Sea but is now restricted to the gull of Tanken between Vietnam and Hainan Island and from where sightings have been rare over the last few years (Morton, 2001). Construction of Hong Kong's new airport at Chek Lap Kok (completed in 1998) was associated with the stranding of two species of cetacean: the Indo-Paci®c Hump-backed dolphin (or Chinese White dolphin), Sousa chinensis, and the Finless porpoise, Neophocaena phocaenoides, on surrounding beaches. Parsons et al. (1995) provided an updated checklist of cetaceans recorded from Hong Kong waters, but the common feature of the above two is that both are resident. Since 1993, when accurate records of strandings of both species began to be collected, there has been an increase, which is continuing, in the strandings and which largely involves males and calves (Porter et al., 1997), particularly of S. chinensis. Although some strandings can be related to boat trac and ®shery accidents (S. chinensis commonly follows trawlers), pollution is suspected to be the prime cause of death. Parsons (1998, 1999) examined trace metal levels in the blubber, liver and/or kidney tissues of eleven S. chinensis and 20 N. phocaenoides stranded between 1993 and 1996. Most trace metal levels were similar to those recorded in cetaceans from elsewhere and deemed not to be of toxicological signi®cance. Cadmium and selenium were adjudged to be accumulated with age, concentrations of copper were highest in neonatal animals, but no metals were considered to constitute a health risk. In contrast, Parsons and Chan (1998) examined levels of organochlorines in eight S. chinensis and eleven N. phocaenoides also stranded between 1993 and 1996. Levels of total PCB were low and similar to values re1242

corded in cetaceans from elsewhere. Concentrations in calves were generally half those of the adults. A similar concentration was determined for a sample of milk obtained from the stomach of one calf. Levels of various PCB's were similar between the two cetacean species and levels of chlorinated benzene, hexa-chloro-cyclohexanes, dieldrin, chlordane and mirex were low (generally <1 lg g 1 lipid). Total DDT levels were high, however, with median values of 26:7 lg g 1 lipid and 50:3 g g 1 lipid recorded for S. chinensis and N. phocaenoides, respectively. Furthermore, relatively low DDE/DDT ratios (0.55 for adult S. chinensis and 0.32 for adult N. phocaenoides) suggested there had been relatively recent inputs of DDT into the cetacean's marine environment (Aguilar, 1984), even though its use was notionally banned in Hong Kong and China in the early 1980s (Wolfe et al., 1984). Parsons and Chan (1998) suggested that the high rate of, particularly, neonatal cetacean mortality might be due to compromised immune functions resulting from organochlorine exposure. Blubber samples from eleven S. chinensis and nine N. phocaenoides stranded in Hong Kong between 1993 and 1997 were analysed by Minh et al. (1999) for persistent organochlorines, repeating the work of Parsons and Chan (1998). Not surprisingly, the results were very similar between the two studies and the conclusions the same, that is, relatively high concentrations of PCBs and DDTs in the cetaceans pose a health risk to them. Such levels can be attributed to a continuous environmental input of these chemicals into Hong Kong waters. The above ®gures and concerns are not surprising. Very high levels of organochlorines were recorded from human breast milk by Ip and Phillips (1989) and which could be related to pesticides in vegetables produced, largely, in southern China, around Hong Kong (Ip, 1990). High levels of PCBs have been recorded in mussels, Perna viridis, in Hong Kong (Tanabe et al., 1987) while Connell et al. (1998) have shown that persistent organochlorines pose a signi®cant risk to local marine ecosystems. The plight of Hong Kong's two resident cetaceans, therefore, constitutes an example of the serious problem of organochlorine pollution in the coastal waters of southern China. Since those countries lining the rim of the South China Sea are similarly agricultural (pesticides), supplying the food resources of signi®cant cities where PCBs are still widely used in industry, it is possible that the above picture is more widespread in the region. Horseshoe crabs As noted earlier, three of the world's four species of horseshoe crabs (Xiphosura) occur in Asia. The fourth, Limulus polyphemus, occurs on the east coast of the United States of America (Fig. 7) (Sekiguchi and Nakamura, 1979). Everywhere, the four species are considered under threat. In Asia, all three species, i.e., Tachypleus gigas, T. tridentatus and Carcinoscorpius rotundicauda are consumed, their eggs being regarded as a

Volume 42/Number 12/December 2001

Fig. 7 A map showing the global distribution of horseshoe crabs.

delicacy, for example in Singapore, Malaysia, Borneo (Chatterji, 1994), Thailand (Kungsuwan et al., 1987), Hong Kong and China (Chiu and Morton, 1999a). In addition, the crabs' unique blood is the only source of a compound called Limulus Amoebocyte Lysate which is used widely to test for bacterial contaminants of drugs. Various components of the haemolymph have also proved to be of value medically, for example, lectin (Saito et al., 1997) and tachyplesin I (Morvan et al., 1997). Due to over-collecting as a ®sheries resource and for their pharmaceutical properties, therefore, horseshoe crab adult numbers are declining. Because also horseshoe crabs come ashore as mated pairs to lay eggs (Sekiguchi et al., 1977), they are highly vulnerable to artisanal collecting at this time. Moreover, juvenile horseshoe crabs spend something like 10 years on nursery beaches they hatched upon (Sekiguchi et al., 1988). These are usually mud/sand ¯ats dominated by seagrasses in front of mangroves and where the crabs feed on the larger elements of the meiofauna (Zhou et al., 2001). Beaches, as noted above, are being reclaimed everywhere in Asia and the breeding and nursery beaches of horseshoe crabs are thus disappearing too, and, if not, being polluted. Chiu and Morton (1999a) review this subject, noting that out of the formerly dozens of nursery beaches in Hong Kong, only three now remain and one species, T. gigas, no longer occurs in local waters (Chiu and Morton, 1999b).

Seahorses In 1995, at least 20 million dried seahorses were traded world-wide (Lourie et al., 1999). The majority of these were for use in traditional Chinese medicine. In China, the total annual trade volume is 20 t, which is equal to at least six million seahorses (Vincent, 1996). Thousands (probably several hundred thousand) are also sold each year for the aquarium trade and as dried souvenirs and curiosities. Around 45 countries currently trade in seahorses but the majority are derived from under-developed countries in Asia, especially those fringing the South China Sea, including China, Vietnam and the Philippines (Vincent, 1996). Exports of seahorses from Vietnam were estimated to be about ®ve t (dry weight) in 1996, particularly to China. The rapid growth in demand is seriously depleting seahorse populations. An even more serious threat may be the widespread destruction in the South China Sea of the seahorses' coral, seagrass and mangrove habitats (Vincent, 1996).

O€shore Systems The most important o€shore systems of the South China Sea are coral reefs (Fig. 8). The most abundant reefs lie in the waters to the south of Hainan, that is, the >20 atolls and islets of the Maccles®eld Bank (Zhongsha Qundao) and the 36 islands of the Paracel Islands 1243

Marine Pollution Bulletin

Fig. 8 A map of the South China Sea showing the continental mainland of Southeast Asia, the Philippines, East Malaysia and the islands of the sea.

(Xisha Qundao). Liang (1985) describes four groups of coral islands from the South China Sea, i.e., (i) Dongsha (Pratas Reef) (20°420 N); (ii) Xisha (18°N); (iii) Zhongsha (16°N) (Paracel Islands and Shoals and Maccles®eld Bank) and (iv) Nansha (Spratly Islands) (3°N). The Paracel Islands and Shoals (Xisha Qundao) are located southeast of the continental shelf and Hainan. Sovereignty of the area is disputed by China and Vietnam. There are 31 islets, the largest being Yongzing Dao (1:8 km2 ). Three others, Tong Dao, Zhongjian Dao and Taiping Dao, are over 1:5 km2 while the remaining 25 islets are all smaller than 0:5 km2 . Lagoon depth is 43 m in the Yongle complex atoll, 67 m in the Xuande com1244

plex atoll and 58 m in the Xuande Dong complex atoll. Shidao Islet has a maximum altitude of 15 m; 10 other islets reach 10 m and the remainder are <7 m. The islands and reefs have an atoll-like structure; complex atolls, simple atolls and table reefs having been described. Between 23 and 127 species and subspecies of scleractinian corals in 37±38 genera have been recorded from the Paracel Shoals. Species of Millipora are particularly abundant (Zou and Chen, 1983). The Zhongsha reefs lie 183 km southeast of the Paracel Shoals and comprise two large atolls: Zhongsha Atoll (53 km in diameter) is a drowned atoll, whereas `Yellow Rock' Atoll (15 km in diameter) is elevated 1±1.5 m above sea

Volume 42/Number 12/December 2001

level. Coral diversity on the Zhongsha reefs is lower than in the Paracel Shoals because most of the reefs lie 7 m below the surface. To the south of the South China Sea's central deep basin lies the vast area known to navigators as the Dangerous Grounds comprising many submerged hills and plateaux. The largest of these, with an area of 9000 km2 , is Reed Bank, which comprises more than 230 islands, sandbars, submerged reefs and shoals. These are a component of the Spratly Islands (Nansha Qundao) and over which there are regular, sometimes armed, con¯icts between China and the Philippines. The main island of the Spratly Islands (Nansha Qundao or Nan-Sha reefs) (Fig. 8) is Taiping Dao (or Itu Aba Island) located to the northwest of the Tizard Bank and its reefs. The southernmost reef is Zengmu (Tsan-Mou) Reef. Taiping Dao has an area of 0:5 km2 and is 3.8 m above sea-level. Sovereignty over the Spratly Islands and reefs is disputed by a number of countries, including China, Taiwan, Vietnam, the Philippines and Malaysia. Coral communities ¯ourish here and are diverse with a high percentage cover. Acropora is dominant. Over 100 species of coral have been recorded from Tizard Atoll and Dai and Fan (1996) recorded 163 species of scleractinians from Taiping Island in 1994. The reef ®shes are similarly rich with 400 species (>450 including midwater pelagic species) from 50 families recorded during a four day survey in 1994 (Chen et al., 1997). McManus (1994) considers that the Spratly Islands constitute one on the most biodiverse regions of the world's seas. Pratas reef (Dongsha Qundao) is the closest reef to Hong Kong (Fig. 8). It is 274 km southeast of Hong Kong and 386 km southwest of Kaohsiung, Taiwan. Pratas Reef covers an area 100 km2 and the atoll itself has an area of 1:7 km2 and a maximum altitude of 5 m. Sovereignty of the area is disputed by China and Taiwan with, at present, a garrison of Taiwanese troops stationed there. Hong Kong ®shermen and spear-®shing divers regularly visit the reef, but landing is not allowed. Pratas is a large submerged atoll with the small island of Dongsha Qundao situated on its western edge. The island is covered with sandy coral debris and has a lagoon (0:6 km2 ) opening to the sea on the west side. A shallow terrace that drops to 40 m or more at the outer edge surrounds it. The reef structure is typical of atolls and 101 species of corals have been recorded from here by Dai et al. (1995). Some 400 species (from 62 families) of reef ®sh have been recorded from here during 1990 (Chen et al., 1991) and 1994 (Chen et al., 1995).

Populations A€ecting the Area Many countries surround the rim of the South China Sea. Four of these, however, are most important in terms of their coastal margins, that is, China in the north, the Philippines in the east, Malaysia in the south and Vietnam in the west.

China is by far the biggest country of the South China Sea rim having an area of some 9 596 960 km2 , a land area of 9 326 410 km2 , but a relatively short coastline of 14 500 km. Only 14% of the land area remains as woodland and 41% is used for various agricultural practices. The 1998 population estimate for China was 1.2 billion with a gross domestic product (GDP) of US$ 865 billion. Despite having 1=4 of the world's population, China only accounted for 9.7% of the total global energy consumption with a per capita rate of 29.5 million British Thermal Units (Btu) (8.4% US value). Carbon emissions were 821.8 million t in 1997 giving a per capita output of 0.7 t (12.5% US value). Threats to the environment largely come from pollution as a result of the almost exclusive use of high sulfur coal, leading to acid rain that is damaging forests. Furthermore, <10% of wastewater receives any treatment and in common with the rest of Asia, deforestation and soil erosion are a problem. Malaysia is divided into two major land masses, i.e., Peninsular Malaysia and East Malaysia on the island of Borneo, and has an area of 329 750 km2 , a land area of 328 550 km2 and a coastline of 4675 km (Peninsular Malaysia 2068 km; East Malaysia 2607 km). In contrast to China, 63% of the land area remains as forest, although deforestation is a problem, and only 13% is used for agriculture. The 1999 population estimate for Malaysia was 22.7 million with a GDP of US$69.9 billion. In 1997, Malaysia accounted for 0.4% of the total world energy consumption with a per capita rate of 78.0 million Btu (22.6% US value). Carbon emissions were 28.3 million t in 1997 giving a per capita output of 1.3 t (23.2% US value). Threats to Malaysia's environment come from vehicular emissions and the discharge of raw sewage. Vietnam ¯anks much of the western rim of the South China Sea and has an area of 329 560 km2 , a land area of 325 360 km2 and a coastline of 3444 km. Forty percent of the country's land area remains as forest and 25% is used by some form of agriculture. In 1998, the population of Vietnam was estimated at 76.2 million with a GDP of US$27.0 billion. In 1997, it accounted for 0.2% of the total world energy consumption giving a per capita rate of 7.8 million Btu (2.2% US value). Carbon emissions were also low at 9.9 million t, 0.2% of the world total giving a per capita emission that was 2.3% of the US equivalent. Threats to the environment come from logging and slash and burn agriculture. Water pollution and over®shing are also problems. The Filipino islands of Palawan and Luzon border much of the southeastern and eastern South China Sea, respectively. In total, the Philippines has an area of 300 000 km2 , a land area of 298 170 km2 and a coastline of 36 289 km. Roughly 40% of the land is used for agriculture and a similar area remains as forest. In 1998, the population was estimated at 77.7 million and the GDP at US$77.5 billion. In 1997, it was estimated that the Philippines consumed 0.3% of total world energy 1245

Marine Pollution Bulletin

consumption with a per capita rate of 13.5 million Btu (3.8% US value). Carbon emissions were similarly low, i.e., 0.3% of the world total with a per capita output of 0.2 t (3.6% US value). The biggest threat to the environment comes from uncontrolled deforestation and associated soil erosion. Air and soil pollution is, however, a problem, particularly of those areas surrounding Manila. Furthermore, as the population has grown, coastal mangroves have become increasingly polluted. Several other countries have some in¯uence on the South China Sea. These include Brunei, Cambodia, Indonesia, Singapore, Thailand, Taiwan and the former colonies of Hong Kong and Macau. Although large in size, Indonesia and Taiwan only come into contact with small areas of the South China Sea in the south and north, respectively. The in¯uence of Cambodia and Thailand are mainly on the Gulf of Thailand. Cambodia, moreover, only has a coastline of 433 km. Brunei, Hong Kong, Macau and Singapore are important commercial centres but because of their small size, compared to the countries that surround them, are considered to have an insigni®cant physical in¯uence on the South China Sea basin. All of these countries and territories, however, have similar economies to those described above and, moreover, face many of the same environmental issues, namely, deforestation and soil erosion, pollution from rapid industrialisation and discharge of untreated urban, agricultural and industrial wastes, typically into the rivers and, thus, into the coastal waters of the South China Sea.

Rural Factors The richness and productivity of the environment of the South China Sea are seriously threatened by a high rate of population growth, pollution, excessive ®shing and habitat modi®cation. Such factors are resulting in the rapid loss of habitat and impairment of the regenerative capacities of the environment and its living systems. These impacts are signi®cant for the newly developed economies of this region. While economies become increasingly dominated by developments in the industrial and service sectors, food consumption patterns rely heavily on protein derived from ®shery resources. The agriculture sector (including ®sheries), therefore, remains not only a signi®cant source of revenue but also an important basis for food security in the countries bordering the South China Sea. The root cause of degradation of the South China Sea region is the growing Asian population and the concomitant demands made upon the marine environment as people strive to increase their standards of living. This socio-economic stress is manifested as over-exploitation of resources, e.g., ®shing and logging, dumping on land and in the sea, the otherwise inappropriate disposal of waste (urban, industrial and agricultural) and destruction of habitat during development, coastally from rec1246

lamation either for ®sh or prawn ponds or for urban and industrial land. Over the last 70 years, the area of mangrove bordering the South China Sea has been reduced by nearly 70%. At this rate, all mangroves will be lost by the year 2030. The main losses result from conversion of land to other uses, e.g., shrimp farms, urban development and logging (Li and Lee, 1997). Twenty-seven percent of the world's mapped coral reefs are in South East Asia and 84% of these fringe Indonesia and the Philippines. Over-exploitation, destructive ®shing methods (dynamite and cyanide ®shing), sedimentation and coastal development have degraded reefs in all countries in the South China Sea to, in some cases, incredible levels, for example, 95% of corals in Hainan. Fiege et al. (1994) reported upon dive surveys of Hainan reefs conducted in 1992 and compared the results to those of earlier surveys conducted by Hutchings and Wu (1987) in 1984 and Naumov et al. (1960) in 1957. Independently of Zou and Wang (1993), Fiege et al. (1994) verify such claims and describe scenes of massive devastation. Yu et al. (1998) consider that living corals have been reduced by >50% on some Hainan reefs, 30% of all reefs are degraded beyond recovery and another 30±60% are facing destruction! The main causes of damage are coral collection for building, making lime, tourist souvenirs, the aquarium trade, dynamite ®shing and pollution. A more subtle cause of damage is high nutrient and/or suspended solids, which either favour seaweeds, that subsequently overgrow the corals, or reduced light causing the corals to bleach via zooxanthellae loss. Coral bleaching, which may also be caused by slightly higher water temperatures, has occurred throughout the region. Reef loss has long-term implications, not just because of the loss of the corals themselves. The main concerns about coral reef degradation are: loss of biodiversity, reduction in reef ®sheries, loss of tourism revenue, threatened or endangered species, and the massive trade in coral skeletons but especially shells and other biota, e.g., pu€er ®shes, seahorses and sea fans. As an example of this, the Philippines Archipelago comprises about 7000 islands and 44 000 km2 of coral reefs situated around 17 460 km of coastline. In a survey of these reefs, it was estimated that 32% were in poor condition, 39% were fair, 24% were good and only 5% were excellent (pristine) (Munoz, 1998). There have been declines in ®sh production associated with reef loss due to destructive ®shing practices, tourism, pests and diseases, sea-level rise, land use conversion, pollution, sedimentation and degradation. Seagrasses are the least studied benthic community compared to other major coastal habitats, i.e., mangroves and corals. Their growth in shallow waters close to the shore, however, renders them sensitive to urban and industrial development. UNEP (1999) estimates that between 20% and 50% of seagrass areas in countries surrounding the South China Sea are damaged. As

Volume 42/Number 12/December 2001

with coral reefs and mangroves, the main issue is loss of biodiversity and ®sheries productivity.

breakdown of coral community structure, as well as those of associated coral-dominated communities.

Destructive Fishing Practices

Cyanide ®shing Observations made by Maclean (1988) during visits to Tubbataha Reefs in the Philippines identi®ed damage caused by blasting, as a method for capturing ®sh. The use of cyanide to stun ®sh, to be then sold as aquarium ®sh was also identi®ed. The problem of cyanide ®shing was identi®ed as widespread throughout the Asian region. Sodium cyanide (NaCN) has been in use by tropical marine ®sh collectors in the Philippines since 1962. Rubec (1986) reviewed the many detrimental toxic effects of cyanide on ®sh, which were published in the pet hobby and scienti®c literature. Interviews with scientists, ®sh collectors and aquarium industry personnel con®rmed that sodium cyanide is contributing to the destruction of Philippine coral reefs and the decline in aquarium and food ®shes. About 71% of Philippine reefs are in poor to fair condition due to excessive siltation caused by deforestation and the widespread use of sodium cyanide and explosives by ®shermen. There is a high mortality of ®sh captured by sodium cyanide squirted onto the reef and delayed mortalities throughout the chain of middlemen to the aquarium hobbyist. Pajaro et al. (1995) agreed that exploitation of tropical marine aquarium ®shes in the Philippine coastal waters has been going on for more than 30 years. The existence of these ®sh species has been threatened continually by the destruction of their habitat and unabated use of destructive ®shing methods such as sodium cyanide and dynamite ®shing. People from Luzon who are involved in the aquarium trade, such as gatherers, screeners and exporters, have also perceived a declining trend in the supply of certain species over the last 10 years. Based on interviews, catch data and sales records, it appears that the population of some species of pomacanthids, Blue tang (Paracantharus hepatus) and butter¯y ®sh (Chaetodon spp.) may have been a€ected by over-exploitation. Aquarium ®sh collection in the Philippines is a multimillion-dollar industry whose growth has been interrupted by major slumps over the last decades. These were attributed to the bad reputation of Philippine aquarium ®sh in the international market arising from the use of sodium cyanide in collecting them. Hingco and Rivera (1991) reviewed the industry in Bolinao, a major source of aquarium ®sh. The eciency of collection using cyanide and economic incentive systems support its continued use in aquarium ®shing. Fishermen are able to befriend law enforcers and/or avoid them so that the only method of e€ective control is to halt the supply of sodium cyanide. Originally developed for the aquarium trade, cyanide ®shing has grown into the live reef ®sh trade. Barber and Pratt (1998) consider that any live reef ®sh in captivity from the Indo-Paci®c region were most probably caught with some form of cyanide. Since the 1960s, more than

Dynamite ®shing Dynamite ®shing is practised in the South China Sea, including Hong Kong and yet relatively little is written about it. It typically occurs over coral reefs and, in some places, such as Indonesia it has been a widespread and accepted ®shing technique for over 50 years (Pet-Soede and Erdmann, 1998). In fact, the coral reefs of Indonesia are being destroyed rapidly by not just blast ®shing but also poison (cyanide), coral mining, sedimentation (through logging of rainforests) and over-®shing (Cesar et al., 1997). The problem of dynamite ®shing is widespread throughout Asia and the South China Sea, from Indonesia, to southern China, e.g., Hainan and Hong Kong. In Hainan, as in Indonesia, coral reefs are being destroyed by dynamite ®shing, coral mining, inappropriate tourism, over®shing and poisoning (Fiege et al., 1994). In Hong Kong, dynamite ®shing has been going on for decades, the ®rst law against it being published in 1903 (Cornish and McKellar, 1998). Morton (1990) ®rst drew attention to the scale of the problem and Cornish and McKellar (1998) have reviewed the history of dynamite and cyanide ®shing in Hong Kong. The same problems of mining, both o€shore and inland, dynamite ®shing, bottom trawling, coral collection and domestic, agricultural and industrial pollution have contributed to the deterioration of coral reefs in Thailand (Sudara, 1981). Most recent research on dynamite ®shing has been carried out in the Philippines and Alcala and Gomez (1979) calculated that, following blast ®shing in the Central Visayas, a recovery time of about 38 years would be needed to achieve 50% coral cover. Also in the Philippines, McManus et al. (1997) examined the e€ects of ®shing with explosives (blast ®shing) and sodium cyanide and anchor damage on live coral cover on a heavily exploited reef in Bolinao, from 1987 to 1990. A simple balance-sheet model indicated that approximately 1.4% yr 1 of coral cover may be lost to blasting, 0.4% yr 1 to cyanide and 0.03% yr 1 to anchors. The potential recovery rate was reduced by about one third from 3.8% yr 1 in the absence of disturbances to 2.4% yr 1 with them. Furthermore, McManus and Menez (1989) surveyed nine coral sites along the western coast of Lingayen Gulf, Philippines, to assess the status of coral reefs in the area. The study showed the reefs to be in relatively poor to fair condition, having 18±47% live coral cover. Reefs were being degraded by both naturally occurring and man-induced stresses, such as, poor land management (which brings about siltation) and destructive ®shing techniques. Blast ®shing and the use of sodium cyanide for catching aquarium ®sh was rampant in the area. The situation was so bad that it was considered the destruction of the reefs could cause a

1247

Marine Pollution Bulletin

one million kilograms of cyanide have been sprayed onto coral reefs in the Philippines to stun and capture ornamental aquarium ®sh bound for the pet shops and aquariums of Europe and North America and, more recently, the live reef ®sh trade. The increasing demand for live reef ®sh as seafood in Hong Kong and other major Asian cities has, in recent years, greatly increased the incidence of the practice. As well as capturing ®sh for the aquarium and live ®sh trade, however, cyanide kills the coral over which it is sprayed. This has been investigated by Jones and Steven (1997) and Jones et al. (1999). Jones and Steven (1997) subjected small fragments of the zooxanthellae corals Pocillopora damicornis and Porites lichen to a range of cyanide concentrations for various times. Doses encompassed those likely to be experienced by corals as a result of various cyanide ®shing practices. Following the highest doses, corals died: after medium doses, they lost their zooxanthellae resulting in bleaching; and at the lowest doses they lost zooxanthellae but not in sucient numbers to cause noticeable discolouration. Respiratory rates of P. damicornis were inhibited by 10±90% following exposure to cyanide but recovered to pre-exposure levels within 1±2 h after transfer to clean water. Jones et al. (1999) exposed branch tips of Stylophora pistillata and Acropora aspera to sodium cyanide concentrations estimated to occur during such ®shing. In S. pistillata, exposure resulted in an almost complete cessation of photosynthetic electron transport. Both species displayed a decrease in photochemical eciency following exposure to cyanide. Eciency returned to normal over a six day period during which time coral bleaching was observed. The reduced photochemical eciency is thought to be related to an inhibitory e€ect of cyanide on enzymes of the Calvin cycle. Impairment of photosynthesis occurs in the zooxanthellae and this causes the coral to release their symbionts following cyanide exposure. The annual retail value of the live reef ®sh trade in Southeast Asia is estimated at US$1.2 billion, US$1 billion of which consists of food ®sh. A 1995 report (Johannes and Riepen, 1995) conservatively estimated that some 20 000±25 000 t of wild live reef ®sh, caught with the application of hundred of t of cyanide, are imported/exported in Asia annually. This estimate, worryingly, did not include domestic trade, ®sh that did not recover from the cyanide or did not reach the market alive. Hong Kong is the centre for the live ®sh trade in Asia, annual imports into this Special Administrative Region of China in 1997 being estimated at 32 000 t of which between 3200 and 6400 t were re-exported to China. Local consumption is estimated at 25 600 and 28 000 t yr 1 . This represents a value of US$500 million (Lau and Parry-Jones, 1999). Other large markets include Taiwan and Singapore, importing 7000 and 1000 t, respectively. In Hong Kong, only ®sh arriving by air have to be declared by importers and since the majority un1248

doubtedly arrive by sea, the ®gures are probably gross underestimates. The scale of the problem is, therefore, poorly understood. It is clear, however, that it is huge. It is so pro®table, moreover, that the industry is booming. Having destroyed the reefs in the South China Sea, ®shermen, supported by business ventures, are moving further into the Western Paci®c and are now commissioning ®shing vessels capable of carrying 20 t of live ®sh (Lau and Parry-Jones, 1999). Cyanide ®shing has been growing over the last three decades and although other East Asian countries are involved, including Singapore, China, Taiwan and Japan, the major ®shing ¯eet involved is Hong Kong's with an estimated 60% of trade based here. Hong Kong's live ®sh trade, with landings of 15 000 t is, thus, sustaining the use of cyanide not only in the South China Sea but south to Australia and eastwards into the Paci®c Islands. Their targets are reef ®sh, notably, Grouper, especially Coral trout (Plectropomus leopardus) and Napoleon wrasse (Cheilinus undulatus) but, actually, anything that is worthwhile. The demand in Asia, especially Hong Kong and the fast-developing cities of southern China, appears insatiable and it is destroying the reefs of the Western Paci®c (Morton, 1996a). Traditional ®shing methods It is beyond the scope of this paper to review the ®shing activities prevalent in the South China Sea but in fact not a great deal is known about it. Information on Hong Kong is provided, however, as an example of potential impacts. Hong Kong's ®shing ¯eet comprises some 4460 ®shing vessels, employing about 192 000 ®shermen. In 1998, it produced 180 000 t of ®sheries products valued at HK$2 100 million (US$ 270 million) and with 90% of the catch coming from outside of Hong Kong, that is, mostly the South China Sea. Two thirds of the ¯eet comprises local, inshore vessels, and only the remaining third can ®sh o€shore waters with a range of approximately 650 km. The Chinese Government has a year round ban on trawling in its territorial waters down to a depth of 40 m and other areas have closed seasons for all ®shing. In 1999±2001, ®shing was banned in all of China's territorially claimed seas, including the South China Sea, for June and July. This has a€ected some four million Chinese (including Hong Kong) ®shermen and although the impacts of this action are unknown, it indicates clearly the extent to which over®shing is perceived to be a problem in the South China Sea. Hong Kong also has a mariculture industry occupying 26 ®sh culture zones with a sea area of 209 ha and some 1480 operators. Production in 1998 was only about 12 000 t, which catered for about 5% of local demand for live marine ®sh. The aquaculture sector, including freshwater production, was 6164 t in 1998, valued at HK$172 million (US$ 25 million) which accounts for 3% of the local catch by weight but 8% of the

Volume 42/Number 12/December 2001

value. The industry is sustained by 30 000 t of, locally so called, `trash' ®sh caught by the local capture ®sheries and which are fed, chopped up, to the caged seabreams, groupers and snappers. In reality, however, such Ôtrash ®shÕ are the ®ngerlings and juveniles of what would be commercially valuable species of they had ever reached maturity.

Coastal Erosion and Land®ll Inappropriate agricultural practices and deforestation may leave bare soil available to erosion by wind and rain. Land clearing of forests for agricultural crops is, therefore, a major supply of suspended solids and silt in rivers and coastal areas of the South China Sea (Hodgson, 1989). Inappropriate engineering practices also lead to large volumes of sediment being washed into rivers and the sea. The slopes of unprotected earth sea walls of shrimp and ®sh farms, causeways, bridge approaches and roadsides are potential sites for erosion. The increased suspended solid material reduces water quality and is manifested as less light to benthic plants and corals. In addition to the reclamation of mangroves for the construction of prawn and ®sh ponds throughout Asia, both Singapore and Hong Kong, in particular, have used coastal ®llings to create urban and industrial land. Since it was ®rst founded, Hong Kong has been engaging in coastal reclamation so that by 2000, some 20% of the coastline is estimated to be arti®cial. In Singapore the ®gure is nearer 100%. It is estimated, for example, that only 1% of the original mangrove forests remain on mainland Singapore (Chou et al., 1980), while an estimated 60% of total reef area has been lost through foreshore reclamation (Chou, 1995). Early reclamation in Hong Kong used soil from the land but between 1992 and 1995, the dredging of marine sand began. Marine sand was used in the construction of the footprint of Hong Kong's new airport at Chek Lap Kok on Lantau Island which was opened in 1998. The volume of ®ll required for the airport and associated infrastructure was estimated to be 500 million m3 and between 1992 and 1995 something like 70% of the worlds dredging ¯eet was operating in Hong Kong's territorial waters. In 2000, there are two additional local projects requiring substantial dredging and dumping works: for Container Terminal No. 9 in Victoria Harbour and at Penny's Bay on Lantau Island, this being the site of the now proceeding Disney theme park. For Hong Kong's Disneyland, some 209 ha of sea bed need to be dredged of all existing mud to a bedrock depth of 20 m. This was to be disposed of outside territorial waters but will now be inside. The next step requires 74 million m3 of marine sand ÔborrowedÕ to create the theme park's platform. Reclamation for the theme park will cost an estimated HK$13.6 billion (almost US$2 billion). Dredging began in May 2000. The second project is

Container Terminal No. 9 that will require 34 million m3 of marine ®ll. At the moment, therefore, for the two projects, there are seven suction dredgers operating in Hong Kong waters, although this will rise to nine next year, plus the addition of at least 10 grab dredgers, the latter mostly removing the uncontaminated and contaminated mud at the two construction sites. The present dredging rate for both projects is 7 million m3 month 1 but this, it is projected, will rise to 10 million m3 . When dredging for the marine ®ll required to create the Chek Lap Kok Airport footprint began, a team of scientists had just completed, in 1992, a benthic survey of the molluscs, prawns, crabs and ®sh in the southeastern waters of Hong Kong. They repeated the survey in 1995 when most of the dredging had ®nished and, again, in 1998 three years post dredging, prior to the present activities. For the crabs, few of which have any commercial value, Blackmore and Rainbow (2000a) showed that there was no support for the idea of signi®cant di€erences in community structure attributable to either the presence or absence of dredging. Lee et al. (2000) similarly showed that between 1992 and 1998 there had been a reduction in crab species diversity throughout the southeastern waters of Hong Kong, but this was equally true at both dredged and undredged sites. For the commercially valuable prawns it was concluded by Leung and Leung (2000) there had been some e€ects of dredging immediately after it ended in 1995, but that this was positive! That is, species richness and individual weights increased in the dredged areas because the holes in the sea bed created prawn refugia. Notwithstanding, this situation was transient and by 1998, there had been a return to the longer term pattern of resource over-exploitation due to intensive prawn trawling. For the epibenthic ®sh Leung (2000) showed that the southeastern waters of Hong Kong were homogeneous in terms of ®sh fauna, diversity, evenness and biomass and, despite some reductions in species richness and abundance in 1995 when dredging activity had just peaked, all population parameters continued to decline in 1998 due to, it was concluded, persistent over®shing. Only a few local benthic molluscs have any commercial importance, for example, species of the whelk Babylonia. Between 1992 and 1995, pre- and postdredging Leung and Morton (2000) showed that the total number of species of gastropods and bivalves had decreased from 67 to 47 and 47 to 36, respectively. It was concluded that dredging had destroyed the prey items (mostly polychaetes) of specialist neogastropods, notably representatives of the Turridae, and they had, thus, died out. Thin-shelled bivalves too had largely disappeared. But by 1998, numbers of gastropods and bivalves species had returned to 67 and 45, respectively, that is, to pre-dredging levels almost exactly and accounted for by the return of the predators and thinshelled bivalves, again, respectively. 1249

Marine Pollution Bulletin

There are, therefore, two important conclusions to be drawn for this research. First, the Mollusca are excellent indicators of short-term dredging impacts (Morton, 1996a). For example, the diets of the specialist predators can be determined from gut content analysis, while the bivalves, as mostly suspension feeders, are susceptible to su€ocation by silt, but both survive trawling e€ects. Second, as Morton (1995a, 1996a) and Leung and Morton (1997, 2000) point out, the Mollusca are also good indicators of trawling intensity, because their scavenging representatives, that is species of Nassaridae, feeding on by-catch, as noted above, survive the trawling process (unlike the crabs) and are returned to the sea bed alive. But the research on the prawns and ®sh (Leung and Leung, 2000; Leung, 2000), the two prime targets of trawlermen, also illustrate, unequivocally, that Hong Kong's seabed is over®shed. Although, therefore, Hong Kong is an extreme example of the relative degree to which the coastal waters of the South China Sea are dredged (for ®ll) and trawled over, it does demonstrate that wherever these two activities are occurring, they are probably acting synergistically to compound each others e€ects. They, thus, provide a picture of what the state of inshore dredgeable and trawlable coastal waters throughout the South China Sea might be like.

E€ects from Urban and Industrial Activities As with most seas, the majority of pollution that occurs in the South China Sea originates from the land, e.g., waste from large cities (sewage, industrial waste and hydrocarbons) and agricultural runo€ (nutrients, pesticides and sediment). Urban waste mainly consists of solids (plastic, glass, cans) and sewage consisting of organics, which increase BOD5 , nutrient and bacterial coliform levels. The populations of the countries that fringe the South China Sea generate about six million t of organic matter each year. Treatment plants in four countries remove some 11% of this. This inappropriate level of sewage management results in severe pollution through high BOD5 loading, eutrophication, ®sh kills, red tides, either damage to or loss of seagrass beds and other habitats, and public health hazards. Chou (1998) believes that the greatest threats to coral reefs throughout southeast Asia are posed by direct and indirect human pressures due to rapid population increases and economic growth concentrated mainly in coastal areas and, especially, around cities, e.g., Singapore, Manila and Jakarta. Urban centres are normally also the locations of major industries. Industrial pollution may be prevalent in the South China Sea, either due to a lack or poor enforcement of industrial pollution laws and regulations, poor facilities and the desire of factories to promote competitiveness in the international market by ignoring environmental and social costs. 1250

The reliance of countries fringing the South China Sea on agriculture for food and exports means that much of the land surface is used for either growing crops or rearing animals. Successful farming relies on adequate applications of fertiliser to enhance plant growth and the use of herbicides and insecticides to reduce pests that lower crop and animal yields. Fertiliser is often over applied and at the wrong time thus making it available to be washed away by monsoonal rains. This may exacerbate eutrophication problems. Animal wastes from livestock (pigs and poultry) farming and the e‚uents from aquaculture also contain nutrients which can damage marine ecosystems. Pesticides used to combat insects and weeds often enter waterways. These pesticides have varying e€ects on the marine environment. Some may be persistent and accumulate in animal and plant tissues, others may accumulate in the sediment and be released during storms. Surprisingly, oil-spills from wrecked ships are not the major cause of oil pollution in the sea. The South China Sea is a Ômaritime superhighwayÕ and a major transportational route for oil, mostly from the Gulf states to Japan (Fig. 9). One third of the 1.6 million tonnes annually discharged into the sea by shipping is released accidentally and the incidence of tar balls in the South China Sea, illustrated in Fig. 9, re¯ects this. Price and Smith (1986) reported that in 1980±1981, tar balls were the most common form of surface pollution in the South China Sea and others such as oil slicks were much less common. Other oil enters the sea from the regular discharge by ships of contaminated ballast water and water used for ¯ushing out tanks. Berger (1991) reviews the potential impacts of an oil spill upon the fragile coastal ecosystem of Palawan, the Philippines. Municipal and industrial wastes also represent a large source of con-

Fig. 9 The major pattern of oil tanker movements in the South China Sea (width of the arrows approximates relative volume) and the distribution of oil lumps.

Volume 42/Number 12/December 2001

tamination. In a study of dibenzothiophene (a major polycyclic aromatic sulphur heterocyles) in the sediment of the South China Sea (22 stations), high levels of from 11 to 66 ng g 1 dry sediment were believed to result from terrestrial runo€, crude oil pollution (from oil wells) and the input of airborne particulates formed from combustion processes (Yang et al., 1998). Hydrocarbon pollution may be limited in extent but be locally very important because some of the substances are not easily biodegradable and highly toxic (Zheng and Richardson, 1999).

Kong Island and in Kowloon, and more than one million in the areas of Tai Po and Sha Tin; (ii) widespread industrialisation, Hong Kong having over 2000 major and 200 000 minor industries (Morton, 1989); (iii) the former lack of stringent controls on the release of agricultural and industrial e‚uents and (iv) the asymmetry of anthropogenic supply. Many of these factors, in particular, dense population, rapid industrialisation and lack of controls are not unique to Hong Kong and characterise many of the countries surrounding the South China Sea.

Hong Kong

The port of Hong Kong Victoria Harbour is at the centre of Hong Kong's local, regional and international trade and, thus, its raison d'etre. Prior to the opening up of China in the mid 1970s, Hong Kong was a relatively small manufacturing entrepot territory but by 1989 it was visited by 19 000 ocean-going and 94 290 river cargo and passenger vessels (carrying 113 290 passengers) and a cargo throughput of 73.69 million t. In the peak year of 1997, vessel arrivals were 44,480 ocean-going and 188 980 river vessels (233 460 passengers), respectively, and a cargo throughput of 169.23 million t. Following Hong Kong's return to Chinese sovereignty on 1 July 1997, the Asian economic crisis, and with competition from new ports in China, in 1998, the number of ocean-going vessels fell to 41 690 although total river vessels increased to 189 610 (236 300) and cargo throughput fell to 167.17 million t. Statistics for 1999 continue to re¯ect a declining trend.

In contrast to the rest of the South China Sea, pollution in Hong Kong has been studied widely. We will review some of the more signi®cant literature and, in view of the paucity of reliable data from other areas, use Hong Kong as a case study to draw conclusions about pollution in the wider area of the South China Sea. Hong Kong is situated on the southern coast of China, adjacent to Guangdong Province, and consists of Hong Kong Island, Kowloon Peninsula, the New Territories and approximately 230 surrounding islands (islands are quickly being reclaimed and any exact ®gure is likely to be shortly incorrect) in a sea area of 1847 km2 . It is situated between latitudes 22°90 and 22°370 N and longitudes 113°520 and 114°300 E. The hydrography of the region is complex and varies seasonally. The western waters of Hong Kong are heavily a€ected by the Pearl River, which drains a 442 440 km2 area of southern China and has an annual discharge of 308 billion m3 yr 1 , over 80% of which is discharged in the summer months (Morton and Wu, 1975). During summer, coastal waters are also a€ected by the South China Sea Current which has moderate salinities (24±34.6½) and variable temperatures. In winter, this is replaced by the Kuroshio Current which is characterised by high salinities (34.4±35½) and high temperatures (26±29°C), originating from the Paci®c, and the East China Sea, or Hainan, Current, which has reduced temperatures (19± 23°C) and salinities (31±33½). The waters of Hong Kong have been divided into three zones, estuarine in the west and oceanic in the east with a transition zone between (Morton and Morton, 1983). This transition zone is essentially Victoria Harbour and other centrally located waters, such as Tolo Harbour, and various bays. Coastal reclamation continues throughout Hong Kong potentially exacerbating pollution e€ects by reducing tidal ¯ushing (Morton, 1989). Tolo Harbour is a semi-estuarine embayment and shows long water residence times correlated with poor oceanic exchange. Eutrophication has occurred subsequent to the construction of major cities; Tai Po and Sha Tin and, latterly, Ma On Shan. Factors contributing to the pollution of Hong Kong on a local scale include: (i) the dense population, of 6.7 million and at least three million of whom live on Hong

Butlytin compounds Organotin compounds are a highly e€ective class of biocide. Tributyltin (TBT), for example, is e€ective at the nanogram per litre level. Consequently, they often make up the active ingredient in antifouling paints (Champ and Seligman, 1996). Since entering the market in the 1960s, TBT paints have brought about large ®nancial savings to the shipping industry. It is estimated that reduced fuel consumption and the less frequent need to strip and repaint vessels, as a result of the paint's high performance, saves the shipping industry US$ 5.7 billion each year (Evans, 1999). As a consequence of fuel savings, 22 million t less carbon dioxide and 0.6 million t less sulphur dioxide are emitted to the environment annually (Evans, 1999). On the other hand, TBT is so toxic that it has had adverse a€ects on non-target organisms, notably abnormal shell thickening in oysters leading to the collapse of, for example, the French oyster industry in the mid 1970s (Krampitz et al., 1983). TBT concentrations all over the world are reported to range from <1 to >1000 ng l 1 (Bryan and Gibbs, 1991). More commonly, they were between 10 and 100 ng 1 and this range of concentration has been reported upon for the coastal waters of Hong Kong by Lau (1991). TBT also tends to be accumulated in benthic sediments (Langston 1251

Marine Pollution Bulletin

and Pope, 1995) and the average TBT level in the sediments of typhoon shelters and marinas in Hong Kong has been reported to be 500 ngSn g 1 (Ko et al., 1995). Similarly high concentrations of sediment TBT have been reported for Malaysia (Tong et al., 1996) and Thailand (Kan-Atireklap et al., 1997). TBT can be accumulated to a high level by some marine vertebrates, including ®shes (Kannan and Falandysz, 1997), ®sh eating birds (Guruge et al., 1996), and marine mammals such as dolphins (Iwata et al., 1994; Kannan et al., 1996; Tanabe, 1999). The greatest demonstrated e€ect of TBT, however, is the ability to induce imposex, or the imposition of male sexual characteristics, on female prosobranch molluscs. The literature on this subject is voluminous, but the most clearly at risk species include, importantly, keystone predators of the Muricidae and to date has been reported upon for 100 species worldwide (Gibbs et al., 1988, 1990, 1997). In Hong Kong, Li (2000), has shown how the most important predatory gastropod on local rocky shores, i.e., Thais clavigera, is particularly vulnerable to imposex and is a suitable biomonitor of it in the South China Sea region. T. clavigera has also been used as a biomonitor of TBT in Singapore (Tan, 1997), where imposex levels were shown to be lower than in conspeci®cs collected from Japan. In a later study, however, Tan (1999) demonstrated Thais gradata and Chicoreus capucinus collected from the Straits of Johore with severe imposex, presumably an indication of elevated bioavailabilities of TBT in this region. It is interesting to note that despite severe overall elevations of TBT concentrations in Hong Kong, T. clavigera is able to persist in Aberdeen Typhoon Shelter and Victoria Harbour (Blackmore, 2000). In severely TBTa€ected populations of Nucella lapillus, it was common for only large males to remain (Gibbs and Bryan, 1986; Gibbs et al., 1988), due to the selective sterilisation of females and a lack of recruitment. Blackmore (2000) provides statistical evidence to suggest that the population structure of T. clavigera has also been altered within Hong Kong's TBT contaminated areas, as the proportion of males was greater when compared to relatively una€ected areas. An important di€erence between N. lapillus and T. clavigera, however, is the method of recruitment. The former has a crawl-away juvenile while the latter has a planktonic larva. It is, therefore, possible that planktonic recruitment of juvenile T. clavigera occurs in heavily polluted sites from relatively clean ones. Population e€ects are exacerbated by the lack of a dispersive planktonic phase and, therefore, T. clavigera with only limited female reproductive functionality can persist in Victoria Harbour and Aberdeen, albeit in reduced numbers, while N. lapillus has vanished from many heavily TBT polluted areas in the Atlantic. So great are the indirect e€ects of TBT that it can radically impact ecologies. For example, Proud (1994) demonstrated the role of N. lapillus in structuring shore communities on the Isle of Man, UK. A decline in N. 1252

lapillus increased the abundance of the barnacle Semibalanus balanoides due to alleviation of predation pressure. Subsequently, high barnacle densities reduced the foraging eciency of the limpet Patella vulgata. This, therefore, allowed the alga Fucus vesiculosus to escape from limpet grazing and the size and longevity of algal clumps increased (Proud, 1994). Concern about TBT has grown worldwide and in 1982 France banned the use of TBT anti-fouling paints on boats of <25 m length. Subsequently, other countries have enjoined this ban (Champ, 1999) and in 1992 the Pesticide Ordinance was amended to prohibit the use of TBT paints on vessels of <25 m in length and on ®sh cages in Hong Kong. Elsewhere, such bans have been e€ective almost immediately, for example, in France where oyster farming has returned to former production levels (Alzieu, 1991). The use of TBT is not, however, regulated in other countries surrounding the South China Sea, e.g., the Philippines, Malaysia, Vietnam and China. In Hong Kong, the ban is not e€ective, because of the overwhelming preponderance of large vessels arriving daily that are not a€ected by the ordinance and no prosecutions have ever been made against small boat owners who also ignore it. TBT levels have not declined, therefore, and, to the contrary, imposex levels in the subtidal nassariid prosobranch Nassarius siquijorensis (Proud and Richardson, 1997) may be growing (Li, 2000). The very high levels of TBT in marina and typhoon shelter sediments in Hong Kong, moreover, con®rm that the ban on the use of TBT paints on smaller boats is ignored. At the 42nd Marine Environmental Protection Council (MEPC) meeting in November 1998, the Working Group on Harmful E€ects of the use of Antifouling Paints for Ships recommended that `the global instrument to be developed by the Marine Environmental Protection Committee should ensure a global prohibition on the application of organotin compounds which act as biocides on ships by 1 January 2003, and a complete prohibition on the presence of organotin compounds acting as biocides on ships by 1 January 2008' (http://www.imo.org, the IMO web site). This proposal was approved by the IMO Assembly in November 1999. Heavy metals The Hong Kong Government's Environmental Protection Department (EPD) routinely measures heavy metals in sediments (EPD, 1988, 1992, 1993, 1996, 2000). The EPDs sampling locations can be grouped into the following 10 water pollution control zones (WPCZ's 1±10): Deep Bay (2), Northwestern waters (3), Western Bu€er Zone (10), Victoria Harbour (9), Eastern Bu€er Zone (8), Port Shelter (6), Tolo Harbour (1), Eastern waters (5), and Southern waters (4). Concentrations of Cd, Cr, Cu, Hg, Ni, Pb and Zn, in sediment samples collected from Hong Kong's coastal waters during the period 1987±1995 are shown in Table 1. In

Year

Southern waters Eastern waters

Northwestern

Tolo Harbour

Victoria Harbour

Port Shelter

Deep Bay

Inner

Outer

Western

Central

Eastern

Inner

Outer

Cd 1987

<0:20

<0:20

<0:20±0.40

0.21±0.80

<0:21

<0:20±0.40

0.61±0.80

0.61±0.80

0.21±0.4

<0:20

<0:20

Cr 1987 1991 1992 1995

0±50 26±50 <25±40 <24±49

0±25 26±50 <25±55 25±49

0±100 26±75 26±70 <24±49

26±50 26±50 26±55 <24±49

0±25 26±50 26±40 25±49

0±75 76±>100 26±70 <24±80

26±>100 76±>100 41±>70 <24±80

0±100 51±>100 41±>70 25±>80

51±75 26±50 41±55 25±49

26±50 26±75 26±40 <24±49

0±50 26±50 26±55 <24±49

Cu 1987 1991 1992 1995

<50 <50 <50±100 15±99

<50 <50 <50 <14±100

<50±400 <50±100 <50±100 15±99

<50 <50±100 <50±100 15±59

<50 <50 <50 15±59

<50±400 <50±>400 101±400 15±>100

50±800 201±>400 101±>400 >100

100±800 201±>400 51±>400 15±>100

51±100 100±200 51±200 15±59

<50 <50 51±100 15±59

<50 <50 <50±200 <14±59

Hg 1987 1991 1992 1995

<0:25±1.00 <0:3 <0:03±0.14 <0:05

<0:25 <0:3±1.2 <0:05±0.08 <0:05

<0:25 <0:3 <0:05±0.14 <0:05

0.26±0.50 0.61±0.9 <0:05±0.08 <0:05

<0:25±0.50 0.61±0.9 <0:05±0.08 <0:05

<0:25±0.51 0.61±0.90 0.05±>0:14 <0:05±0.06

<0:25±>1:00 >1:2 0.08±>0:14 0.05±0.09

0.26±1.00 >1:2 0.05±0.14 <0:05

0.51±0.75 0.6±0.9 0.08±0.11 <0:05

0.26±0.50 <0:3±1.2 0.05±0.14 <0:05

<0:25 <0:3 <0:05±0.14 <0:05

Ni 1991 1992 1995

11±30 <15±30 10±24

<10±30 16±25 10±39

11±30 <15±30 10±24

11±20 16±25 10±24

11±20 21±25 10±24

11±30 16±30 10±40

31±>40 20±>30 10±>40

31±>40 20±>30 10±>40

11±30 21±30 10±24

11±30 16±25 10±24

<10±30 <15±30 <9±24

Pb 1987 1991 1992 1995

<50 <100 <30±70 30±59

<50 <75 <30±50 <40

<75 51±100 <30±70 <44

51±100 101±>125 >90 >60

<50 76±100 51±70 >60

<75 76±>125 31±70 30±44

51±>100 51±>125 51±90 30±>60

51±75 51±100 31±70 30±>60

<50 76±100 51±70 30±59

51±75 76±100 31±50 < 59

<50 51±75 <70 <44

Zn 1987 1991 1992 1995

0±100 101±150 <80±120 50±149

0±100 0±150 <80±100 50±99

0±150 <100±150 <80±140 50±149

100±200 151±200 >140 100±>150

0±100 101±200 101±120 50±149

0±150 101±200 81±>140 100±>150

0±300 151±>250 121±>140 50±>150

150±300 101±>250 81±>140 50±149

251±300 >250 >140 100±>150

0±100 <100±150 <80±100 50±149

0±150 0±250 <80±>140 50±>150

Volume 42/Number 12/December 2001

TABLE 1 Cd, Cr, Cu, Hg, Ni, Pb and Zn concentrations in marine sediments from Hong Kong's coastal waters in 1987, 1991, 1992, 1995 (EPD, 1988, 1992, 1993, 1996).

1253

Marine Pollution Bulletin

1987, sediment Cd concentrations were greatest in Victoria Harbour (0:61±0:80 mg kg 1 ) and lowest in outer Deep Bay, Southern and Eastern waters (< 0:2 mg kg 1 ). Levels of Cr were similar from all sampling areas (25±75 mg kg 1 ). There were, however, some elevated concentrations in Victoria Harbour sediments (maximum values of > 80 mg kg 1 ). Temporally, levels have remained relatively constant during the period 1987±1995. Concentrations of Cu in Hong Kong's marine sediments were greatest within Victoria Harbour, Inner Deep Bay and Northwestern waters (> 100 mg kg 1 ). There were reductions in Cu levels in sediments collected from Victoria Harbour and Northwestern waters since 1987. Concentrations of Hg in Hong Kong's marine sediments were low (< 0:05 mg kg 1 ). In 1991 and 1992, however, concentrations of > 1:2 mg kg 1 were measured in sediments from Victoria Harbour. Concentrations fell, however, until 1995 (< 0:09 mg kg 1 ). There were no apparent trends in concentrations of Ni in Hong Kong's marine sediments. Concentrations were, therefore, similar throughout the special administrative region and over time (10±> 40 mg kg 1 ). Concentrations of Pb in Hong Kong's marine sediments were greatest within Victoria Harbour and Tolo Harbour (> 50 mg kg 1 ) and lowest within Deep Bay, Eastern and Southern waters. Pb concentrations in Hong Kong's marine sediments were high, re¯ecting the large shipping trac. Reductions in sediment Pb concentrations were apparent in sediments collected after 1991. Concentrations of Zn in Hong Kong's marine sediment were greatest within Victoria Harbour, Inner Tolo Harbour and Inner Deep Bay (100±>150 mg kg 1 ) and lowest in the Eastern and Southern waters and Port Shelter (25 mg kg 1 ). Zn concentrations remained constant during the period 1987±1995, at < 300 mg kg 1 . The EPDs data, therefore, show that sediments from Victoria Harbour have higher concentrations of Cd, Cr, Hg, Pb and Zn, with Inner Deep Bay, Northwestern waters and Inner Tolo Harbour also having increased sediment metal concentrations. The data, moreover, show no consistent pattern of reduction in any metals during the period 1987±1995, although there is some evidence of area-speci®c reductions, e.g., Cu in Victoria Harbour. The sediments of typhoon shelters, in particular, are contaminated with metals (EPD, 2000). The Rambler Channel and Kowloon Bay typhoon shelters have consistently greater levels of all measured metals. The Chai Wan, Sai Kung and Yim Tin Tsai typhoon shelters have lower levels as compared to others, but levels within them are high, as compared with sediments collected from outside. Again there is no consistent pattern of reduction and levels in 1995 were still high. Core samples from polluted Hebe Haven in Hong Kong's eastern waters clearly demonstrate enhanced heavy metal levels as urbanisation and industrialisation occurred (Lo and Fung, 1992). Furthermore, Wong (1996) showed that Hong Kong sediments contained 1254

high levels of heavy metals, concluding that organic and heavy metal pollution is serious in marine sediments, and agricultural and industrial are probably the major sources of this contamination, respectively. Few studies have focused on measuring metals in seawater directly and those that have can largely be considered unreliable (Chan, 1992). A review of metals in seawater can be found in Blackmore (1998). Hong Kong has proven to be a key site in the development of biomonitoring techniques to assess the bioavailabilities of trace metals in sub-tropical waters, with pioneering work on oysters (Phillips, 1979; Phillips and Yim, 1981), mussels (Phillips and Yim, 1981; Phillips, 1985), and barnacles (Phillips and Rainbow, 1988; Chan et al., 1990; Rainbow and Smith, 1992) being carried out in its coastal waters (Rainbow, 1993; Blackmore, 1998). Although tissue burdens vary greatly between the different biomonitoring species, they all re¯ect the same basic pattern. We will, therefore, only discuss the organisms about which there is the most data, i.e., the barnacles. The barnacles Tetraclita squamosa and Balanus amphitrite were ®rst used in biomonitoring studies in Hong Kong in 1986 (Phillips and Rainbow, 1988; Chan et al., 1990) and since then samples of at least one of these species have been collected in 1989 (Rainbow and Smith, 1992), 1994 (Blackmore, 1996), 1996 (Blackmore and Chan, 1998), 1996±97 (Blackmore, 1999) and 1998 (Blackmore and Rainbow, 2000b). Furthermore, 20 sites have been visited twice or more. There is, therefore, a great deal of spatial and temporal information available. The biomonitoring data for barnacles presents a similar picture to that of the EPDs sediment data. Historically, there was an elevation of bioavailabilities of all measured metals in the central transitional, harbour region of Hong Kong. Victoria Harbour was the most uniformly metal-polluted, but other areas were hotspots for certain metals, e.g., Tsing Yi for Cu and Cr and Junk Bay for Cd and Pb. In the western waters, the bioavailabilities of many metals, in particular, Cd, are increased by the lowered salinities caused by the in¯uence of the Pearl River. It is interesting to note that in the past the Pearl River would not have been considered a source of pollution but it may now be as it drains a rapidly industrialising southern China (Liu et al., 1998). Both T. squamosa (Blackmore, 1999) and Perna viridis (Chan, 1988, 1989) showed no signi®cant seasonal differences in soft tissue metal concentrations and, presumably, no signi®cant changes in metal bioavailability. High variability characterised soft tissue metal concentrations in both species and these were much more important than seasonal variations. There is some evidence to suggest that metal bioavailabilities may be increased locally in the western waters during the summer months due to lowered salinities. Temporal patterns over a longer time scale (years) are, however, evident. Blackmore and Rainbow (2000b), present data for 1986, 1989 and 1998 and other studies

Volume 42/Number 12/December 2001

agree well with these (Blackmore, 1998). Since 1986, bioavailabilities of metals in Victoria Harbour have either generally fallen or otherwise not increased, with the possible exception of Zn availabilities to T. squamosa along the shore of Hong Kong Island. Bioavailabilities of Cd, Cr, Cu and Ni in Victoria Harbour have all fallen between 1986 and 1998. Although the bioavailabilities of Ag, As, Cu and Ni were still high in 1998 at Chai Wan Kok, Ag, Cu and Ni have fallen since 1986, as have availabilities there of Cd, Co, Cr, Pb and Zn. In Tolo Harbour, bioavailabilities of Cd, Cr, Cu, Pb and Ni have all fallen from 1986 to 1998. Evidence for changes in Tolo Harbour bioavailabilities of Ag, Co, Mn and Zn is more equivocal, and it cannot be concluded with con®dence that these availabilities have fallen in the harbour over the period. It is interesting to note that during the period 1986±1989 there was a large rise in the bioavailabilities of most measured metals to the barnacles, which makes the fall to 1998 more signi®cant. Blackmore (1998) provided an overview of metal pollution in Hong Kong's coastal waters and concluded that Tolo Harbour appears to becoming increasingly heavy-metal polluted. Elevated body concentrations of Cu and Zn have been recorded from barnacles and other biomonitors, for example, the supralittoral amphipod Platorchestia platensis (Rainbow, 1992), seawater (Chan, 1992), and the green alga Ulva lactuca (Ho, 1990a,b). In Victoria Harbour, levels of bioavailable heavy metal levels are either stabilising or falling. In Victoria Harbour, levels of pollutants in the sediment remain high (re¯ecting previous pollution) and metal levels in typhoon shelters remain extremely high (re¯ecting ongoing pollution) (EPD, 2000). Metal bioavailabilities have, however, been shown to be reduced in the water column (biomonitors). Scott (1990) showed that not only did the growth rates, species number, abundance and diversity of scleractinian corals declined between 1980 and 1986 in Tolo Harbour, a polluted embayment in the central transition zone of Hong Kong, but also that trace metal levels in the skeletons were very high as compared to cleaner locations elsewhere. Metal pollution in the greater South China Sea remains largely unstudied. Arima et al. (1989), however, measured mercury contents in ®sh collected from the southern South China Sea. Mean levels were 0:036 lg g 1 (highest 0:82 lg g 1 ) and these were lower than is ®sh collected from either Japanese coastal waters or the East China Sea (Arima et al., 1989). This is not unexpected as metal levels are usually enriched in coastal waters compared to the open ocean (Rainbow, 1985). Organic enrichment Hong Kong produces over two million t of municipal wastewater each day and until recently 50% entered watercourses and coastal waters without treatment (Chau, 1999). Total BOD loads were, therefore, high

until sewage treatment plants began to have some e€ect. Because the treatment plants do not remove N and P, levels of nutrients have continued to rise. Legislation to control animal wastes led to a control in pollution load from this source but did not lead to any signi®cant improvement in the water quality of Tolo Harbour, for example, because of the enormous sewered and unsewered human organic waste load. Due to this high load, urban runo€ has been estimated to contribute an insigni®cant 2% to the total BOD5 load. Red tides Among the thousands of species of phytoplankton are a few that produce potent toxins. These species are responsible for red tides or Harmful Algal Blooms (HAB) that discolour the water and at more inconspicuous concentrations damage is only noticed because of the harm caused by their highly potent toxins. Impacts include: mass mortalities of wild and farmed ®sh and shell®sh, human illness (or even death) from contaminated shell®sh or ®sh (Paralytic Shell®sh Poisoning or PSP), alterations of marine trophic structure through adverse e€ects on larvae and other life history stages of commercial ®sheries species and the death of marine mammals, seabirds, and other animals. ÔBloomsÕ of these algae are commonly called red tides, since, in some cases, they increase in abundance until water colour is changed by their pigments. The term ÔRed TideÕ is often used to describe detrimental e€ects and is, therefore, confusing because non-toxic species can bloom and harmlessly discolour the water. The term Ôharmful algal bloomÕ (HAB) is, therefore, now preferred. The impacts of HABs take a variety of forms. One major category is paralytic, diarrhetic, neurotoxic, and amnesic shell®sh poisoning. Toxic phytoplankton are ®ltered from the water, notably by bivalves, e.g., clams, mussels and oysters, which then accumulate the algal toxins to levels which can be lethal to humans or other consumers (Shumway, 1990). Except for amnesic shell ®sh poisoning (ASP), all are caused by biotoxins synthesised by dino¯agellates. ASP is produced by diatoms that until recently were all thought to be free of toxins and generally harmless (Bates et al., 1989). A ®fth human illness, ciguatera ®sh poisoning (CFP) is caused by biotoxins produced by epibenthic dino¯agellates attached to surfaces in many coral reef communities (Anderson and Lobel, 1987). Ciguatera toxins are transferred through the food chain from herbivorous reef ®shes to larger carnivorous, commercially valuable ®sh. Whales, porpoises, seabirds, and other animals can be victims as well, receiving toxins through the food chain via contaminated zooplankton or ®sh (Geraci et al., 1989; Anderson and White, 1992). Another type of HAB impact occurs when marine animals are killed by algal species that release toxins and other compounds into the water, or that kill without toxins by either physically damaging gills or by creating low oxygen conditions as bloom biomass decays. Smayda (1992) 1255

Marine Pollution Bulletin

areas of the South China Sea. Considering the degree of organic enrichment found in many of the coastal regions of the sea it is likely that blooms are occurring but go unreported. In the spring of 1998, a massive red tide killed over half, some 1500 t, of the ®sh inside Hong Kong's mariculture cages and which had a value of some HK$300 million (US$40 million) (Morton, 1998a).

Fig. 10 Histograms showing: (a) the yearly distribution of red tide occurrences over the period 1980±1999 in Hong Kong and (b) the seasonality of red tide occurrences in Hong Kong (Information courtesy of the Environmental Protection Department of Hong Kong, Hong Kong SAR Government, Hong Kong China).

proposed a model which represents the many ways in which HAB species a€ect other organisms within marine ecosystems, not just those that are either commercially important or easily visible to humans. In virtually all trophic compartments of the marine food web, there can be impacts from toxic or harmful blooms. Outbreaks of HABs are apparently increasing worldwide and an explanation for this is a re¯ection of increased pollution and nutrient loading in coastal waters. Tolo Harbour, Hong Kong, is a good example of this. Here the population within its watershed grew sixfold between 1976 and 1986. During that time, the number of observed red tide events increased eightfold (Lam and Ho, 1989). The underlying mechanism is presumed to be increased nutrient loading from pollution that accompanied human population growth. Fig. 10 shows the occurrence of red tides in Hong Kong from 1980 to 1999 and the accumulative numbers that have occurred in each month. The data correlate well with evidence from organic enrichment and other pollution data to suggest that the two may be linked. The seasonal pattern shows that most tides occur during the spring months (March±May) when the water starts to warm up but nutrients are not yet limited. Huang and Qi (1997) identify these factors as responsible for the outbreaks of red tides, notably caused by the holozoic Noctiluca scintillans in the eastern waters of Hong Kong. There are reports of red tides occurring in other 1256

Persistent organic contaminants Persistent organic contaminants include the chlorohydrocarbons, which are used in industry (largely polychlorinated biphenyls (PCBs) and hexachlorbenzene (HCB)) and agriculture (largely DDT isomers and metabolites and hexachlorocyclohexanes (HCH)), polycylic aromatic hydrocarbons, alkanes (both of which are derived from petroleum or combustion sources) and long chain alkyl benzenes which are the breakdown products of certain detergent components. The direct discharge of these products is currently uncommon in the developed world although trace amounts are usually present in stormwater and sewage discharges (Makepeace et al., 1995). Ip (1983) examined PCB and pesticide levels in human breast milk taken from Hong Kong patients and detected unusually high levels of HCH and DDT and its metabolites. Despite seafood being considered a major source of these contaminants, there is limited information available on organochlorines, notably PCBs and pesticides in Hong Kong's marine environment. Phillips (1985) measured organochlorines in the bivalve P. viridis and discovered there was widespread and signi®cant contamination of DDT and localised hotspots for PCBs, notably Junk Bay. In addition to work on marine mammals, organochlorines have been measured in ®sh (Chan et al., 1999). Levels of seven groups of organochlorines in 15 species of ®sh purchased from local markets were low, i.e., <0:1 lg g 1 . Since the source of local market ®sh cannot be identi®ed (they could have come from anywhere in the South China Sea, even the world!), their organochlorine loadings do not re¯ect contamination of Hong Kong but may shed some light on levels within the South China Sea. Worrying is the fact that DDE/total DDT ratios were highly variable suggesting the recent release of DDT into some areas of the South China Sea (Chan et al., 1999). Chiu et al. (1991) reported high levels of PCBs in the Shing Mun River, Sha Tin, suggesting either local industrial use or illegal dumping. Chan et al. (1999) reported lower levels possibly suggesting a decline in PCBs in the local environment. Connell et al. (1998) provide an overview of persistent organic contaminants in Hong Kong's marine areas. Data collected from 66 sites during the period 1987± 1996 were analyzed. Total PCBs and total PAHs were distributed widely in sediments at concentrations of 5±9:8 and 40±60 lg kg 1 , respectively. Elevated levels of persistent organic contaminants were identi®ed from

Volume 42/Number 12/December 2001

Victoria Harbour and several other areas. In particular, typhoon shelter sediments were heavily contaminated. The data, however, suggest that between 1987 and 1996 total PAHs were declining in most areas with an estimated half-life of between three and ten years. Petroleum hydrocarbons were, however, present in high concentrations in coastal sediments, especially in heavily industrialised and urbanised areas, e.g., Victoria Harbour (Zheng and Richardson, 1999). The main sources of these compounds are transportation of oil, shipping activities, spillages and industrial, stormwater and wastewater discharges. Chemical evidence suggests that the main source of petroleum hydrocarbons is via oil and its products and such sources appear to be stable and continuing when compared to previous data (Zheng and Richardson, 1999). Pollution in general There are a number of reviews on marine pollution issues in Hong Kong beginning with Morton (1976), e.g., Wu (1988), Morton (1989) and Blackmore (1998), and the subject in relation to the coastal zone was last discussed by Morton (1995b). Throughout the Special Administrative Region (SAR) of Hong Kong, no regional pollution gradients have been de®ned and pro®les are dominated by local sources (Phillips and Tanabe, 1989). Pollution in Victoria Harbour has resulted from the development of the fringing cities of Victoria and Kowloon. Entrepreneurial Hong Kong has created a large number of light industries. It is fortunate, however, that due to a lack of developable land, heavy industry has been inhibited (Morton, 1996a). For this reason, all major developments in Hong Kong have been on reclaimed land and, in the past, urban and industrial centres have grown together. As new towns, i.e., Sha Tin and Tai Po, developed, much of the industry previously polluting Victoria Harbour moved away from the central areas and, ®rst, into the New Territories and, subsequently, China. Prior to development, both Sha Tin and Tai Po were small villages and Tolo Harbour was subject to pollution only from agricultural wastes associated with the villages (Morton, 1996a) and, therefore, levels of metal contamination were low (Chan et al., 1973, 1974). Although the new developments had planned for and commissioned secondary sewage treatment plants, the long retention times in the semi-enclosed bay of the harbour have proved such measures inadequate. Inadequate treatment of waste has manifested itself as increasing contamination of this aquatic environment. Hong Kong industry is still moving, today into Southern China and other areas of Asia (Morton, 1996a) where land and labour costs are cheaper. The port of Hong Kong, however, remains ecient at transferring raw materials and trade products into and out of China. The Special Economic Zone of Shenzhen has, in particular, bene®ted from Hong Kong's high infrastructural costs. This shift is illustrated in the

number of workers employed in local manufacturing industries. Such numbers fell from 728 000 in 1971 to 446 000 in 1994 (Morton, 1996a). In contrast, numbers employed in the service industries rose from 639 000 to 2 214 000 over the same time period, enabling Hong Kong to handle some nine million visitors each year.

Protective Measures Unless countries realise that there is unsustainable exploitation and irreversible damage being done to the South China Sea, current rates of habitat loss and destruction will continue. To give countries a guide to what should be done to relieve the current situation, inventories of what is there and records of the state of the environment (determined by monitoring) need to be compiled (UNEP, 1999). To achieve collaboration and co-operation among countries it is usual to have legal frameworks that cover the areas of interest between participating parties. There is no legal framework that directly relates to forming a marine environment protection co-ordinating body, however, and few that relate to the marine pollution problems prioritised by the member countries of the South China Sea. The objectives of a legal framework (or protocol) are to protect and manage the marine environment and coastal areas of the South China Sea region (UNEP, 1999), including actions on: 1. Taking all necessary measures to prevent, reduce and control pollution of the South China Sea area, particularly dumping, land-based sources, activities causing habitat loss and airborne pollution. 2. Protecting and preserving rare or fragile ecosystems as well as the habitat of depleted, threatened or endangered species and other marine life in specially protected areas. 3. Co-operating in dealing with pollution emergencies in the South China Sea area. 4. Co-operating in assessing environmental impacts in the South China Sea area and in exchanging data and other scienti®c and technical information. 5. Establishing rules and procedures for the determination of liability and compensation for damage resulting from pollution in the South China Sea area. Coral reefs provide a substantial part of the protein intake in Southeast Asia. Reefs and non-reef coral communities within 15 km of shore are generally considered to be over-®shed and while o€shore subsurface atolls and pinnacles are often beyond the reach of smallscale ®shermen they are not to a growing ¯eet of larger vessels (McManus, 1988). For example, during the last two decades the biotically diverse and productive reefs of the Philippines have been subject to extensive destruction by sedimentation from deforestation, destructive ®shing methods, pollution, poor agricultural practices and the quarrying of reefs (McAllister, 1988). 1257

Marine Pollution Bulletin

150 000 kg of sodium cyanide is used on the coral reefs each year to catch ®shes for the aquarium and live ®sh food trades and at least 10% of inshore ®shermen use explosives to catch food ®shes throughout the year. The use of explosives in ®shing is illegal and punishable with large ®nes and prison terms. Nevertheless, it persists in coastal villages in Lingayen Gulf (Philippines) (Galvez, 1991) and presumably much of the rest of the South China Sea, as does cyanide ®shing, through combinations of increasing populations, a decline in ®sheries stocks caught in traditional ways, ignorance and corruption. Gomez et al. (1994) reviewed the status of the Philippine reefs since 1979. While the conditions of the reefs during the early surveys were assessed in terms of live coral cover per se, the `coral mortality index' was applied to the sets of data collected over the past seven years which may be a better gauge in determining the health of reefs. Generally, most reefs surveyed were considered to be only in `fair' condition. Major destructive factors described were sedimentation and siltation from coastal development and illegal activities inland and destructive methods of ®shing and over®shing. The destruction of coral reefs has grave environmental and economic consequences. Lost each year are conservatively estimated harvests of 160 million kg of ®sh (US$80 million). This translates into the loss of 127 000 inshore ®shing jobs leaving over 600 000 family members without support. The commercial food ®shery, aquarium ®sh, sports diving and tourist trades have also su€ered. The sociological e€ects are also far reaching and the destruction of coral reefs is a major contributor to poverty in coastal communities. From 1966 to 1986, while the productivity of coral reefs dropped by at least one third, the population of the Philippines has doubled. These changes have meant that the square kilometre of reef that largely supported 900 people in 1966 had to support 2631 in 1986 (McAllister, 1988). The current situation is likely to be much worse. Practical short-term and long-term alternatives exist to most of the problems that are causing destruction of coral reefs. Current attempts to manage these areas in the South China Sea through coastal-zone plans and ®sheries restrictions, however, have only been e€ective in a few isolated areas. The most promising approaches involve management and evaluation at the municipal level. This concept can be extrapolated to an adaptive management scheme involving community-based development specialists, cross-training in environmental and ®shery monitoring, and assisting municipalities in the development of regulations concerning local reefs and associated ecosystems. Reef management can be expedited in many areas with the establishment of alternative livelihood programmes to alleviate excessive demands on reef resources (McManus, 1988). An age old practice of artisan ®shermen in the IndoPaci®c has been the emplacement of ¯oating and dumped ®sh aggregating devices, using easily available 1258

natural materials into coastal ®shing areas to attract ®sh (Schoppe et al., 1998). More recently, arti®cial reefs have been used to counter the growing problem of over ®shing and have been deployed in the coastal waters of the South China Sea by many countries, i.e., Malaysia, the Philippines and now China and Hong Kong. The ®rst phase of arti®cial reef deployment in Hong Kong has been completed. Twenty vessels were prepared as arti®cial reefs and sunk in Hoi Ha Wan and Yan Chau Tong Marine Parks in 1998. Between July and September 1998, 216 tyre units were emplaced at eight sites in Hoi Ha Wan and Yan Chau Tong Marine Parks. Concrete modules (131), including ÔReef BallsÕ and eight quarry rock arti®cial reef units were deployed at two sites in Yan Chau Tong Marine Park between March and August 1999. A one-year arti®cial reef consultancy study to determine where to deploy the second phase of arti®cial reefs outside the existing marine parks was completed in June 1999. Five areas have been proposed, that is, the Soko Islands/Shek Kwu Chau, Po Toi, Nine Pins, Outer Port Shelter and Tap Mun/Shek Ngau Chau. Consultants have recommended that these arti®cial reefs areas should be designated as ÔMarine Special AreasÕ and managed under the Fisheries Protection Ordinance. As part of the mitigation for the temporary aviation fuel line at Sha Chau, arti®cial reefs will also be deployed in the Sha Chau and Lung Kwu Chau Marine Park. These reefs are designed to enhance ®sheries resources and promote feeding opportunities for the Chinese White dolphin that frequents the area (Porter et al., 1997). In addition, arti®cial reefs are being deployed in the Chek Lap Kok Marine Exclusion Zone. The work is scheduled to be completed in the summer of 2000. The Hong Kong e€ort to restore its over-®shed inshore resources by the deployment of arti®cial reefs re¯ects the broader picture of what is happening to marine resources in the South China Sea. Undocumented over®shing, using traditional gears, dynamiting, cyanide ®shing, the destruction of mangroves for ®sh and prawn ponds, combined with domestic, agricultural and industrial pollution are probably acting to destroy what is (was), probably, the focus of the greatest biodiversity of marine life on Earth. We conclude this from an analysis of the available literature. Hodgson (1999) analysed the results of a world-wide reef check and identi®ed Hong Kong as an example of coral reefs subjected to almost every form of disturbance. Even the best reefs are subjected to over®shing, poison and blast ®shing, pollution and sedimentation. Several formerly abundant species now appear to be e€ectively extirpated in Hong Kong (Morton, 1996b). In the Philippines too, reefs have been decimated largely by destructive ®shing practices (see earlier and Gomez et al., 1994). At three sites in the Sulu Sea, however, White and Vogt (2000) describe how signi®cant areas of reefs are legally protected and sustainable management schemes

Volume 42/Number 12/December 2001

are working e€ectively. This has been achieved through intensive education programmes, community participation and co-operation. Such success stories are few and far between in the South China Sea, however, and the full extent of the destruction that has gone on is hidden in grey literature because of either an unwillingness or inability to get such information published in reputable scienti®c journals and because of political sensitivity. Only, for example, in the democratic Philippines is there true freedom of expression in relation to the South China Sea. It is also dicult to work in the South China Sea (especially as there are so few resources for marine research anyway), because of the political sensitivity of its islands and waters. In some countries, as above in the Philippines, Vietnam and Malaysia, there are moves to establish marine parks and reserves and what is happening in Hong Kong is an example of this (Morton, 1998b). In reality, however, at the end of the last and the beginning of the new millennia, the South China Sea appears to be, largely, in a terrible state. In Hong Kong and in the broader picture of China, at least this is now recognised (Cheung and Xiao, 1991). Aguilar, A. (1984) Relationship of DDE/RDDT in marine mammals to the chronology of DDT input into the ecosystem. Canadian Journal of Aquatic Fisheries Science 41, 840±844. Alcala, A. C. and Gomez, E. D. (1979) Recolonization and growth of hermatypic corals in dynamite blasted coral reefs in the Central Visayas, Philippines. In Proceedings of the International Symposium on Marine Biogeography and Evolution in the Southern Hemisphere, Auckland, New Zealand, 1978. DSIR Information Services 137, Vol. 2. Alzieu, C. I. (1991) Environmental problems caused by TBT in France: assessment, regulations, prospects. Marine Environmental Research 32, 7±17. Anderson, D. M. and Lobel, P. S. (1987) The continuing enigma of ciguatera. Biological Bulletin 172, 89±107. Anderson, D. M. and White, A. W. (1992) Marine biotoxins at the top of the food chain. Oceanus 35, 55±61. Arima, S., Shimada, K., Uchiyama, M. and Hidaka, M. (1989) Total mercury contents in marine ®shes caught in the south-east region of the South China Sea. Memoirs of the Faculty of Fisheries, Kagoshima University 38, 63±67. Barber, C. V. and Pratt, V. R. (1998) Poison and pro®ts: cyanide ®shing in the Indo-Paci®c. Environment 40, 4±9. Bates, S. S., Bird, C. J., de Freitas, A. S. W., Foxall, R., Gilgan, M., Hanic, L. A., Johnson, G. R., McCulloch, A. W., Odense, P., Pocklington, R., Quilliam, M. A., Sim, P. G., Smith, J. C., Subba Rao, D. V., Todd, E. C. D., Walter, J. A. and Wright, J. L. C. (1989) Pennate diatom Nitzschia pungens as the primary source of domoic acid, a toxin in shell®sh from eastern Prince Edward Island, Canada. Canadian Journal of Fisheries and Aquatic Science 46, 1203±1215. Berger, K. J. E. (1991) The impact of South China Sea oil spills on the environment of Palawan. Philippines Science 28, 27±54. Blackmore, G. (1996) Biomonitoring of heavy metal pollution in Hong Kong coastal waters, using barnacles. Asian Marine Biology 13, 1± 13. Blackmore, G. (1998) An overview of trace metal pollution in the coastal waters of Hong Kong. The Science of the Total Environment 214, 21±48. Blackmore, G. (1999) Temporal and spatial biomonitoring of heavy metals in Hong Kong coastal waters using Tetraclita squamosa (Crustacea: Cirripedia). Environmental Pollution 106, 273±283. Blackmore, G. (2000) Imposex in Thais clavigera (Mollusca: Neogastropoda) as an indicator of TBT (tributyltin) bioavailability in coastal waters of Hong Kong. Journal of Molluscan Studies 66, 1±8.

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