Biodiversity of China’s seas, coasts and islands

Biodiversity of China’s seas, coasts and islands

4 Ecosystem diversity of China’s islands

5 Serious threats confronting the marine biodiversity of China’s seas

6 Efforts to protect the biodiversity of China’s seas, coasts and islands

1 Species diversity of China’s seas

The 20,278 species of organisms recorded from China’s seas belong to 5 kingdoms and 44 phyla. Of these, the Animalia includes 24 phyla, the most abundant species of which are the Arthropoda, Mollusca and Chordata with more than 2,500 species each. Of the six plant phyla, three are algae with 794 species and three are vascular plants with 413 species. Seven phyla of the Protista have nearly 5,000 species (Table 1).

Of the 24 animal phyla, 10 are exclusively marine. The number of species is more than in freshwaters but less than on land. Species numbers increase toward the south. China’s seas encompass both the southern boundary of many temperate species and the northern boundary of many tropical ones.

Table 1 The numbers of species recorded from China’s seas

Kingdom and phylun		Kingdom and phylum		Kingdom and phylum
MONERA	229	PLANTAE	1,203
Bacteria	79	Rhodophyta	443	Priapulida	2
Actinobacteria	18	Phaeophyta	153	Annelida	979
Cyanomyceta	131	Chlorophyta	194	Sipuncula	39
Prochlorophyta	1	Pteridophyta	11	Echiura	9
PROTISTA	4956	Gymnospermae	3	Mollusca	2554
Bacillariophyta	1395	Angiospermae	399	Arthropoda	29
Pyrrophyta	255	ANIMALIA	12794	Bryozoa	488
Chrysophyta	14	Porifera	106	Entoprocta	9
Xanthophyta	3	Coelenterata	989	Brachiopoda	8
Cryptophyta	1	Ctenophora	9	Phoronida	4
Ciliophora	291	Platyhelminthes	574	Chaetognatha	37
Sarcomastigophora	2997	Nemertea	52	Echinodermata	471
FUNGI	188	Kinorhyncha	10	Hemichordata	6
Yeast	61	Nematoda	122	Urochordata	125
Other fungi	127	Acanthocephala	32	vertebrata	3181
Mycophycophyta	1	Rotifera	17

2 Ecosystem diversity of China’s seas

Bordering mainland China are the Bohai Sea, the Yellow Sea, the East China Sea and the South China Sea with collective areas of 4.73 million km². The Yellow Sea and Bohai Sea are situated on the boundary of the north temperate region, and the East China Sea and South China Sea are in the subtropics. Each exhibits the characteristics of a large marine ecosystem. The Kuroshio Current, estuarine waters and up-welling areas in China’s neritic seas also show ecosystem level biodiversity.

(1) The Bohai Sea

The Bohai Sea is an inland sea on the mainland coast of China with an area of 80,000 km², a maximum depth of 70m and an average depth of 18m.

A total of 120 species of phytoplankton, dominated by eurythermal, low salinity, diatom species, have been recorded from the Bohai Sea. The dominant species are representative of the Coscinodiscacus, Chaetoceros, Rhizosolenia and Skeletonema costatum. There are also about 100 species of zooplankton, dominated by temperate low salinity and some oceanic species. The dominant species are Noctiluca scientillans, Calanus sinicus, Paracalanus parvus, Labidocera euchaeta, and Sagitta crasse. More than 100 species of benthic plants mainly warm temperate species with green algae dominant in the inter-tidal zone and brown and red algae dominant in subtidal zones, have been recorded. There are about 140 species of benthic animals which are also dominated by low salinity species. Of these, the species with a larger biomass and commercial fishing value are Scapharca subcrenata, Ruditapes philippinarum, Meretrix meretrix, Ostrea plicatula, Penaeus chinensis and Exopalaemon carinicauda. There are about 120 species of nekton, most of which are fishes, plus a few shrimps, crabs, squids and marine mammals. There are abort 20 main species of fish, such as Setipinna taty, Engraulis japonicus, Lateolabrax japonicus, Nibea albilora and Cynoglossus semilaevis.

(2) The Yellow Sea

The Yellow Sea is a semi-enclosed shallow continental sea with an area of 380,000 km², a mean depth of 44 m and a maximum depth of 140m. The circulation of the Yellow Sea is mainly influenced by the Yellow Sea Warm Current and coastal currents. Its continental shelf is mainly covered by pelitic and silty deposits. As it is located in the northern temperate zone, a unique biota which is characterized by an assemblage of elements from frigid, subfrigid, tropical and subtropical areas, in addition to native species.

A total of 386 species of phytoplankton have been recorded from the Yellow Sea which is dominated by representatives of the Coscinodiscacus, Biddulphia, Chaetoceros, Rhizosolenia, Nitzschia and Peridinium, with a variety of ecologies indicative of temperate seas.

A total of 130 species of zooplankton has been recorded. They are either warm temperate neritic species, typical of coastal currents, or warm water species from the Kuroshio. The dominant species are Calanus sinicus, Centropages memurrichi, Euphausia pacifica, Parathemisto gracilipes and Sagitta crassa.

Some 200 species of benthos have been recorded. Of these, the Polychaeta is the most numerous followed by the Mollusca, Crustacea and Echinodermata. There are also some widely distributed species such as Sternaspis scutata, Nereis longior, Eucymene annandalei, Ceratonereis erythraeenis, Tambalagmia fauveli, Leptochela gracilis, Amphioplus ancistrotus and Ophiura sarsii.

A total of 219 and 225 species of nekton have been recorded from the northern and the southern Yellow Sea, respectively. Fish are the most common species; together with shrimps, crabs, and squids. The most dominant species include Clupanodon punctatus, Setipinna taty, Harengula zundsi, Sardinella sp., Stromateoides argenteus, Ilisha elongatea, Cynoglossus semilaevis, Pseudodiaena polyactis, Nibea albiflora, Trichiurus haumela, Lateolabrax japonicus and Paralichthys olovaceus. There are, in addition, 15 species of whales, three pinnipedes and four turtles in the Yellow Sea.

(3) The East China Sea

The East China Sea has an area of 770 km² and a mean depth of 370 m over the continental shelf and a maximum depth of 2,719 m at the bottom of the continental slope. Coastal currents and the Taiwan Warm Current are important in the shallow waters of this sea.

A total of 64 species of phytoplankton occur in the waters near the estuary of the Yangtze River and 261 species occur off-shore in Zhejiang. The dominant algae are Skeletonema costatum, Coscinodiscacus spp., Chaetoceros lauderi and Nitzschia pungens. Neritic temperate species are the most common ecological type.

A total of 81 species of zooplankton occur close to the Yangtze River estuary and 223 species have been recorded from the coast of Zhejiang. Peaks in biomass occur in the summer. The main species are Calanus sinicus, Labidocera euchaeta, Pseudeuphausia sinica, Acartia pacifica and Sagitta enflata.

A total of 342 species of benthos have been recorded from the East China Sea. The Mollusca account for 77, the Polycheata 77, the Crustacea 95, the Echinodermata 136, the fishes 62, with 18 others.

There are 167 fishes recorded from the Yangtze River Estuary and shallow waters of the East China Sea. Of 203 species of nekton in the shallow waters of Zhejiang, common species of fish include Pseudosciaena crucea, Trichiarus haumela, Ilisha elongata, Stromateoides argenteus, Harpodon nekereus, Miichthys miiry, Muraenesox cinereus and Acetes chinensis. Other species include Exopalaemon carinicauda, Portunus trituberculatus, Charybdis japonica and Sepiella maindroni.

(4) The South China Sea

The South China Sea encompasses tropical and subtropical zones. It is a semi-enclosed sea with a continental margin and an area of 3.5 million km². There is a wide continental shelf, and 30% of the waters are deep with a mean depth of 1.4 km. Two main currents, a coastal current and the South China Sea Warm Current, occur in the northern South China Sea.

The number of phytoplankton species differs between regions and ranges from 104 to 260. They belong to two large groups, the diatoms and dinoflagellates, of which Chaetoceros and Rhizosolenia are dominant.

In the offshore waters of the northern and southern South China Sea, 130 and 250 species of zooplankton have been recorded, respectively, and of which the main ones are copepods. Zooplankton biomass forms a single peak over the course of each year.

Benthic organisms in the estuarine waters of the coast of Guangdong comprise 319 species most of which are tolerant of low salinities and occur in high numbers. In contrast, the benthos of the middle and western region of eastern Guangdong and the coastal waters of western Guangdong mostly comprise species with a high salinity tolerance, typical of the southern subtropics and tropics. A total of 820 species are dominated by the Mollusca, Arthropoda and Annelida. Most of the benthos along the coast of Hainan comprises tropical species, with a total of 755, dominated by corals, algae, molluscs and echinoderms. A total of 832 species recorded from along the coast of Guangxi are dominated by Turritella bacillum and Scapharca subcrenata. Of 135 species of benthos recorded from the Xisha Islands, 30.37% are crustaceans and the rest are mainly molluscs and echinoderms.

The nekton recorded from the northern South China Sea comprises 1,064 species, of which 100 are economically important, such as Decapterus maruadsi, Sardinella aurita, Pneumatophorus japonicus and Trachurus japonicus. It has been recorded that there are here some 200 species of shrimps belonging to Penaeus, Metapenaeopsis and Metapenaeus. Most of these are tropical and subtropical. The fishes comprise 535 species, and shrimps in the South China Sea are not characterized by dominant species. There are 58 species of cephalopod, of which 25 species, such as Todarodes pacificus, Nototodarus hawaiiensis and Sepiella sepia are of commercial value. Dominant species in the southern South China Sea are coral reef fishes and tropical oceanic fishes.

(5) The Kuroshio

The Kuroshio is the largest current passing along the continental shelf of China. As one of the strongest currents in the world, this hot water flow has a great influence on the shallow seas of China’s continental shelf. Based on the results of a survey of the current by Chinese scientists and a co-operative survey between China and Japan, 419 species of phytoplankton, 697 species of zooplankton, more than 180 larval and young fishes and 2,000 species of nekton have been identified from it.

Kuroshio organisms belong to different ecological groups. For example, the phytoplankton may include high thermohaline, low salinity and high thermophile, high salinity and low thermophile, and eurythermohaline species. Zooplankton may include warm temperate neritic and tropical oceanic species. Fishes may include pelagic, meso-pelagic and benthic species.

As is typical of high thermohaline waters, the Kuroshio can be detected by its indicator species, for example, phytoplankton such as Gossleriella tropica, Asterolampra marylandica, Cheatoceros dadayi, Ceratocorys bipes and Amphisolenia shauinslandi. More than twenty zooplankton species, such as Euchaeta concinna, E. marina, Pareuchatea russelli, Sagitta enflata, Liriope tetraphylla, Pseudoconchoecia concentrica, and Euphausia tenera, can also be used as indicators of the current.

(6) Estuaries

There are more than 1,500 rivers and streams draining into the seas along the coast of China. The huge input of freshwater and terrigenous material creates an unique estuarine ecosystem. In general, the species composition of an estuary is complicated and highly diversified. This can be demonstrated by reference to the species composition of three estuaries, i. e., the species of phytoplankton in the Pearl River, the Yangtze River, and the Yellow River estuaries are 64,103 and 224, respectively; the corresponding numbers of zooplankton are 105,66 and 133, benthos are 153,191 and 456, intertidal zone species are 41,195 and 189, and nekton are 189,144 and 356, again respectively.

The ecological types in these estuaries are different, e. g., the Pearl River Estuary is dominated by tropical and subtropical species with warm-water species as dominant nekton and the Yangtze River and Yellow River estuaries by cosmopolitan and temperate species with warm-temperate species as dominant nekton.

In spite of different ecological types, the uniqueness of the estuarine environment results in a similar community structure, i. e., they can all be divided into 3 categories: freshwater, brackish water, and marine water communities. For example, the composition of the fish fauna in the Yangtze River Estuary comprises: (1) 17.4% freshwater species mainly of the Cyprinidae and Cobitidae; (2) 21.6% brackish water species mainly of the Mugilidae and Gobiidae and (3) 57.2% marine water species mainly of the Clupeiformes, Beloniformes, Perciformes and Pleuronectiformes.

(7) Upwelling ecosystems

There are many up-welling areas in China’s seas, e. g., in the middle of the Bohai Sea the cold waters of the Yellow Sea, off-shore from the Shangdong Peninsula and Zhejiang the nearshore waters of southern Fujian, southwest of Taiwan, the nearshore waters of eastern Guangdong and along the southeast coast of Hainan. Some examples are as follows:

The offshore area in southern Fujian. Centered on the Nanpeng Archipelago, the upwelling area ranges from the Lishi Archipelago in Zhangpu, Fujian, to the Jiazj waters of Guangdong. In comparison to the open sea in summer, it is characterized by low temperature (2~4℃ lower than that of open sea), high salinity (some 0.5‰~1.5‰ higher), low dissolved oxygen levels (<4.4 ml/L) low oxygen saturation (<90%) and high nutrient levels (N⁺ 13.8 µmol/L, P⁺ 0.4 µmol/L). Pareuchaeta russelli, Euconchoecia maimai and Dolioletta gegenbauri are indicators of this upwelling water and appear in great numbers. The bacterial biomass may peak at 66.6 µg C/m³ and is dominated by coldwater luminescent species. In addition, phytoplankton density is high (>10⁸ cells/m³), with a high primary productivity [1.06g C/(m²·d)] and a total zooplankton biomass of more than 250 mg/m². Up-welling is a kind of wind-driven ascending current, i. e., a compensation current from the bottom water as a result of the southwestern land breeze occurring only in summer. Consequently, the fishing ground also only exists in summer.

The southern Taiwan Shoal. There exists, almost year round, a narrow band of low temperature, high salinity and high density water oriented in an east-west direction. The rapidly ascending isopleth trend in terms of temperature and salinity along the continental slope demonstrates the existence of a low pH centre and a surge of bottom water with high nutrient levels and low oxygen saturation. The indicator species, Calanoides carinatus, is found year round as is Callinitra emmae which comes from a depth of 5,000 m. High densities of eggs, larvae and young fishes, of which 9% are from the deep sea, enter this area. The upwelling climbs up with the bottom current along the slope, with the help of wind action in addition to the circulation pattern around the Taiwan Shoals. This upwelling is, thus, mainly topography-induced. Due to the permanent existence of upwelling in the area, a major fishing ground is present on the southern Taiwan Shoal year round.

Upwelling, as a special hydrological phenomenon, results in a special ecosystem. An upwelling ecosystem is generally characterized by its high productivity, a short food chain, a fast nutrient cycle and efficient energy transfer.

3 The diverse coastal ecosystem

(1) Intertidal ecosystems

According to an intertidal zone survey conducted during the period from 1981 to 1986, a total of 1,590 species, but probably several times that figure in practice, has been recorded from the shores of China. The number of species increases towards the south, i. e., it starts at 251 species in the Bohai Sea and reaches more than 971 in the South China Sea (Table 2). Except for those dominant eurythermal, euryhaline and cosmopolitan species, some are typical of temperate waters, such as Chthamalus challengeri, Stenothyra glabar and Styela clava, whereas others are typical tropical and subtropical species such as Euraphia witherisi, Nodilittorina trochoides and Styela plicata. The species on hard substrata of reefs and piles are different from species on soft bottoms of sand and mud.

Table 2 The numbers of intertidal species along the coast of China (1981-1986)

	Bohai Sea	Yellow Sea	East China Sea	South China Sea	Total
Cnidaria	6	12	9	22	38
Polychaeta	45	101	142	78	218
Mollusca	83	180	296	335	513
Crustacea	54	116	196	202	308
Echinodermata	8	22	30	54	78
Pisces	17	12	35	40	61
Algae	34	147	97	235	358
Others	4	15	6	5	16
Total	251	605	811	971	1590

The weight and diversity of the benthic biomass varies much between areas and sediment types, e. g., the wet weight of biomass in the Yellow Sea is as high as 2.199 g/m², compared with 217g/m² in the East China Sea. Density reaches 1,013 individuals/m² in the Bohai Sea but only 317 individuals/m² in the South China Sea. This also demonstrates that a discrepancy exists in terms of biomass on different substrata. The number of animals is much higher on a hard bottom than on a soft one. For example, the biomass of a coral reef is 41 times that of a mangrove mudflat. The same situation occurs with density. This is mostly due to the gregarious attachment of shells, such as barnacles and oysters, on hard substrata. The biomass of the intertidal zone is much higher than that of the shallow water benthos, demonstrating the high productivity of the intertidal zone.

Intertidal communities can be divided distinctly into 3 vertical zones: high, middle and low, related to the tidal exposure of the substratum. Species numbers and biomass are low in the high intertidal zone while they vary with location and substratum type in the middle and lower zones. This discrepancy between tidal zones cannot be generalized, or simply averaged. Biological zonation on a rocky shore is, however, clear. Usually, a littorinid-lichen-barnacle zone forms on the high intertidal. The dominant species of this zone are similar to those which occur in the Bohai and Yellow Seas. Here it is characterized by Chthamalus challengeri but this species does not occur in the East and South China Seas where the warm water species Nodilittorina, trochoides and Capitulum mitella take its place. Species inhabiting the middle tidal zone include the oyster Saccostrea sp., barnacles and green algae. Brown algae and red algae inhabit the low intertidal zone. In the Bohai Sea and Yellow Sea, Chthamalus challengeri is the exclusive dominant species of this zone. In contrast, species like Saccostrea echinata, S. mordax, Tetraclita squamosa squamosa, and species of Ulva and Gelidium, occur in great quanties in the East China Sea and South China Sea. Brown algae and red algae inhabit the low intertide zone. Sargassum pallidum is typical of the Yellow Sea. Warm water species, such as Sargassum henslowianum, Ishige okamurae, Hypnea japonica and Symphyocladia marchantioides can only be found to the south of the East China Sea.

(2) Coastal marsh-wetland ecosystem (Boreal)

There are many saline marshes and mudflats in estuaries to the north of Zhejiang. This kind of wetland, i. e., a biotope covered with grass vegetation high in the intertidal zone, mid tidal zone and supratidal zone, are mostly the habitat of birds and make up a marsh-wetland ecosystem. Such ecosystems can be found in the mudflats of the Yalujiang River Estuary, the Liaohe Delta, the Yellow River Delta, Laizhouwan Bay, Tianjin Beach in Bohai Bay, Dagu Estuary in Shandong, Yancheng Estuary in Jiangsu, Chongming Estuary of the Yangtze River, Nanhui district of Shanghai, the beaches of Hangzhou Bay and the beaches of the Yongjiang and Oujiang Rivers.

In marshes connecting freshwater and estuarine areas beyond the supra-tidal zone, wide areas of lush reeds (Phragmites communis) are distributed from the Yalujiang Estuary in the north to Hangzhou Bay in the south. Small patches of reed bed also occur in Guangdong. The area of reed bed in the Liaohe Delta is 67,000 ha. Seaward of the reed bed in the high intertidal zone, vast areas of short vegetation such as Salsola glauca and Salicornia europaea are found. In the high intertidal zone of the Yangtze River Estuary and Hangzhou Bay, Scirpus marigueter grows in large areas of marsh. For example, its community of Jin Si Niang Bridge, Pin Hu, on the northern coast of Hangzhou Bay has an area of 500×3,000 m², a height of 20 cm and 85% cover.

Up to 1992, the grasses Spartina anglica and S. alterniflora introduced from England in 1963 and from America in 1979, respectively, have grown and spread to cover 6,000 ha of the high intertidal zone along stretches of the coast from Liaoning to Guangxi. They form an artificial biotope, especially in Jiangsu and Zhejiang.

Table 3 lists 8 representative wetland grass communities with their relevant migrants from the Yalujiang Estuary to Hangzhou Bay.

Table 3 Some representative wetland grass communities and birds

along the coastal regions of northern and middle China

Mud flat	Vegetation		Birds recorded and species numbers
Mud flat	Reed bed	Others	Birds recorded and species numbers
Yalujian River Estuary	11,000 ha	Salsola glauca, Salicornia europaea	>70 species, Cygnus cygnus, Egretta eulophots
Liaohe Delta	67,000 ha	S. glauca, S. europaea	137 species, Grus japonensis
Yellow River Delta	Large areas	S. glauca, S. europaea	Egretta, Cygnus, Anser and Anas
Dagu Estuary	Large areas	S. glauca, S. europaea	206 species, Haliaeetus albicilla, Gavias stellata
Yancheng, Jiangsu	Large areas	S. glauca, S. europaea Zoysia japonica, Imperata cylindric var. major, Spartina anglica	226 species, 535,000 individuals in January, some species of Anser and Anas
Dongtan, Chongming Island, Shanghai	Large areas	Scirpus trigueter, Carex spcabrifolia, Juncus effusus, Zoysia japonica	241 species, more than 2 million Cygnus columbianus, Anser and anas, Larus argentatus
Nanhui, Shanghai	Large areas of width 300～500m	Scirpus mariqueter over more than 200～400m of mud flats	Many species
Opening of Hangzhou Bay	Large areas and 20 km² in Andong	Scirpus mariqueter, Salsda glauca, Zoysia japonica, Aeluropus littoralis	Anser, Anas, and Larus

(3) Mangrve ecosystem

A mangal is a kind of woody plant that grows in the intertidal zone and is under the influence of tides for most of the day. Some woody plants, however, the so called semi-mangrove, can grow either in the intertidal zone, where they become dominant mangroves, or inland as normal trees. All kinds of herbs and vines grow among the mangroves and are called mangrove associates. The mangal is a primary producer with adherent organisms such as Balanus spp., Euraphia withersi, Saccostrea spp., and borers such as Bankia spp., and Teredo spp., growing on their leaves, stems and roots. Great numbers of crabs (Uca spp.) and the muds kipper Scartelaos spp. also inhabit mangroves. Producers, consumers, and decomposers all exist in the mangrove ecosystem.

There are 26 true mangrove plants growing in China (Table 4) and these account for 43% of the 60 species in the world. There are also 11 species of semi-mangroves and 19 species of associated plants. China is located on the edge of the Western Pacific biogeographic boundary for mangrove plants. They spread contiguously from Yulin Harbour, Hainan (18^o90’N), up to Fuding in northeast Fujian (27^o20’N). Mangroves are also scattered naturally in northern and western Taiwan (Fig. 3.9.1). The transplantation of Kandelia candel into Pingyang, Zhejiang Prowvince (28^oN), was successful. The number of mangrove species decreases from south to north, i. e., 24 in Hainan and only one in northern Fujian and northern Taiwan. The same is true of the semi-mangroves. The existing area of mangroves in China is now between 13,000~15,000 ha, i. e., only 1/2 that historically.

Table 4 The species of mangroves in China and their distributions

Family	Species	Distribution
Family	Species	Hn	Hk	Ma	Gd	Gx	Tw	Fj	Zj
Rhizophoraceae	Bruguiera cylindrica	+
	B. gymnorhiza	+	+		+	+	+	+
	B. sexangula	+
	B. s. var. rhynchopetala	+
	Ceriops tagal	+			+	+	+
	Kandelia candel	+	+	+	+	+	+	+	+
	Rhizophora apiculata	+
	R. stylosa	+	+		+	+
	R. mucronata						+
Acanthaceae	Acanthus ebracteatus	+		+
	A. ilicifolius	+	+	+	+	+	+	+
	A. xiamenensis						+
*Barringtoniaceae	Barringtonia racemosa	+
Combretaceae	Lumnitzera littorea	+
	L. racemosa	+	+		+	+	+
Euphorbiaceae	Excoecaria agallocha	+	+		+	+	+	+
Meliaceae	Nylocarpus granatum	+
Myrsinaceae	Aegiceras corniculatum	+	+	+	+	+	+	+
Palmaceae	Nypa fruticans	+
Rubiaceae	Scyphiphora hydrophyllacea	+
Sonneratiaceae	Sonneratia alba	+
	S. caseolaris	+
	S. hainanensis	+
	S. ovata	+
Sterculiaceae	Heritiera littoralis	+
Verbenaceae	Avicennia marina	+	+	+	+	+	+	+
Total	26	24	9	4	10	9	9	7	1

Ab.: Hn: Hainan; Hk: Hong Kong; Ma: Macao; Gd: Guandong; Gx: Guangxi; Tw: Taiwan; Fj: Fujian; Zj: Zhejiang.

*. Another species: B. asiaitca is reported from Taiwan.

4 Ecosystem diversity of China’s islands

There are over 6 500 islands within the jurisdiction of China. Their isolation from the mainland results in unique island faunas and floras. Many islands in the South China Sea have characteristic coral reefs. Owing to island effects, surrounding waters have a high biodiversity, as follows.

(1) Islands

The biodiversity of islands along the coast can be demonstrated using the examples of Dongdao Island in Xisha, Dazhou Island in Hainan and Snake Island in Dalian.

a. Dongdao Island, Xisha. As the second largest and one of the two reef islands in the Xisha Archipelago, with an area of merely 1.55km² and an altitude of 4.5m above sea level, Dongdao Island is composed of raised reefs, and coral and shell debris. In the centre of the island, guano piles up to a maximum height of 2.5 m. Evergreen rain forest typical of tropical coral reef islands, dominated by Pisonia grandis, Guettarda speciosa and Scaevola sericea, grow on the island with a maximum height of 16 m. A large group of boobies, Sula sula rubripes and S. leucogaster, inhabit these trees.

There are three underwater reef terraces around the island at depths of 3～5m, 15～25m, and 40～50 m, respectively. The zonation of organisms on the terraces is striking and differs with direction and diversity of inhabiting species. For example, the northeastern terrace is well developed, 500m in width, and three zones can be recognized, i.e., (Ⅰ) porites lutea associated with great numbers of algae; (Ⅱ) Heliopora coerulea, and (Ⅲ), coral debris with poor algal cover. In contrast, the southwestern terrace is less developed , 150 m wide and zoned into broken corals and a zone of Goniastrea-Favia spp..

On such a small island and its surrounding waters, there are more than 200 higher plants, 400 benthic algae, 1800 invertebrates, more than 500 fishes and 60 bird species.

b. Dazhou Island, Haian. Daxhou Island is located in the waters of Wanning County in southern Hainan and has an area of 7,000 ha. Cliffs towering over the southern part of the island where a famous cave, Nanluodong, is the only place in China inhabited by swallows (Collocalia sp.) which produce Dazhou bird nests.

Tropical Indonesia and some other areas have some species of swallows that can produce high value nests. Among them, Collocalia juciphaga flies to Nanluodong Cave in spring every year and breeds there. This suggests that the southern coast of Hainan Island is the northern limit for the breeding of this tropical migratory bird.

c. Snake Island. An unusual island off the coast of Liaodong Peninsula, Liaoning Province, Snake Island has an unique ecosystem and is a snake poison resource. It is located near Lushunkou, 7 miles fron the mainland, and has an area of 0.73km². On the island occurs one sub-species of snake, Agkistrodon qianshanensis shedaoensis. According to a recent estimate, there are as many as 14,000 snakes between 73～102 cm in length living on the island where they feed on small birds resting during their migrations. Their predatory behavior is to hold their heads high and keep their mouths open in a fixed place waiting for their prey. The snake is on the valuable medicinal resource and there is a factory for snake poison processing, a Snake Island hospital and a snake museum island. A total of 283 species of migratory birds, in numbers of more than 2 million, fly over the island and nearby waters annually. Some of the birds are fed on by snakes which in turn become the prey of predatory birds, such as eagles. It is recorded that there are 122 species of insects and 210 plants on the island and a lush growth of Pueraria thomsonii permits the development of the snake population. Animals in the air, on land, and on the beach are different links in a unique food chain, as follows:

coastal organisms—＞small birds—＞snakes—＞birds of prey

(2) Corals and coral reef ecosystems

More than 200 species of reef building corals are recorded from China (Table5) and comprise 1/3 of the world’ s total. The area of China’s coral reefs also makes up a great proportion of the world total. The northern boundary of coral reefs, mostly fringing reefs, is on the coasts of Hainan and Taiwan. The islands of the Dongsha, Xisha, and Nansha reefs are largely made up of barrier reefs. A small number of reef builders are scattered along the shores of Guangdong, Guangxi, Hong Kong, northeast Taiwan and southern Fujian, although they do not here form reefs.

Table5 The numbers of reef building corals recorded from Cnina’s seas

Location

Genera

Species

200

127

230

110

>10

Ns: Nansha Islands; Ds: Dongsha Islands; Xs: Xisha Islands; Hy: Huangyan Islands; Tw:Taiwan;

Hn: Hainan; Hk: Hong Kong; Lg: Guangdong and Guangxi; Fi: Fujian.

Coral reefs can compete with tropical rain forests in terms of their unique structures and luxuriant diversity. The reef builders of the Nansha Islands consist of about 94 species in 33 genera and 11 families. Though there are no algal ridges, reef builders such as Corallina officinalis, Halimedo opuntia and bryozoans can be seen everywhere.

Coral reefs are stereo-biotopes where many organisms live on them close to the surface, in crevices of the reef body, and in the surrounding waters. A total of 3.,372 species of organisms has been recorded from the coral reefs of Nansha. Bright colors and diverse skeletal structures, consisting mainly of limestone, are features of the reef builders.

(3) Biodiversity of off-island seawater

Some 6,500 Islands are scattered along the coast of China. Except for some islands consisting of sand, mud and corals, most are rocky. In addition to the islands and islets of the South China Sea, most occur near the mainland in regions where there is a strong interaction between coastal currents and open seawater masses. Waters surrounding such islands and nearby seas are, therefore, rich in nutrients providing an environment favoring the growth of aquatic organisms. Intertidal and subtidal zones possess many species occurring in high biomasses.

A comprehensive investigation of the island resources of China has identified 633 species. Levels of biodiversity increase from the north to the south ending up with highest values around the Xisha and Nansha Islands. However, species dominance and biomass are opposite, that is, from a few significant dominant species in Xisha and Nansha to more dominant species and high biomasses in boreal areas to the north.

A total of 615 species of zooplankton has been identified. Such organisms in boreal areas are temperate and warm temperate neritic species whereas in the south the species are warm water, high temperature and high salinity oceanic species. The zooplankton in waters surrounding islands near an estuary are mainly low salinity, brackish-water and freshwater species.

Though the area of the intertidal zone is rather narrow and steep, resident organisms of this and their neritic waters are abundant. Based on a survey of the islands, a total of 2,377 species occur in the intertidal zone and 1,872 in the shallow subtidal benthos. Of these, 30% are species of Mollusca.

The nektons of waters surrounding islands are estimated to comprise 1,126 species of fishes and 291 large invertebrates.

5 Serious threats confronting the marine biodiversity of China’s seas

(1) Overfishing

In the recent two decades, the fishery resources of the nearshore and offshore areas of China have come under serious threat due to increasing fishing efforts, in terms of both boats and horse power, specially for the so-called four main products, Pseudosciaena crocea, P. polyactis, Trichiurus haumela and Sepiella sepia. The production of these resources has dramatically decreased of late.

(2) Pollution

Seawater pollution and eutrophication induce red tides. In China there were 221 red tides incidents in the 1980’s and 127 red tide species were recorded. Red tides kill fishes, crustaceans and shellfish. In some areas, such as the intertidal zone, polluted, for example, by industrial discharges, no species can be found.

(3) Biotope deterioration

Marine engineering in the coastal zone has also destroyed habitats and ecosystems. In the last 40 years, 660,000 ha of mudflats and beaches along the coast of China have been reclaimed and many endemic wild species have lost their habitats.

(4) Introduction of exotic species

Exotics include species transplanted deliberately or usually, accidentally, by boats. Introduced species invade the habitats of native species and displace them. Examples of introduced species include a variety of barnacles, polychaetes, the bivalve Mytilopsis sallei, Styela spp., and Spartina spp., On the coast they occupy habitats and exclude native species.

6 Efforts to protect the biodiversity of China’s seas, coasts and islands

Fifty-nine marine reserves with a total area of 129.2 million ha have been established since 1963 and are aimed at the protection of China’s marine biodiversity. At the same time, laws and regulations with regard to fishery sanctuaries and closed seasons, the banning of bottom trawling and the protection of marine environments and resources have been issued by the Government and make up a series of important measures for marine biodiversity protection.