South China Sea Institute of Oceanology, The Chinese Academy of Sciences

Guangzhou, CHINA

qmzhang@scsio.ac.cn

　

Since 1984, the Multidisciplinary Oceanographic Expedition Team of Chinese Academy of Sciences to Nansha Islands, consisting of South China Sea Institute of Oceanology of the Chinese Academy of Sciences and about 20 other institutes or universities, has been carrying out multidisciplinary oceanographic expedition to Nansha Islands and its neighboring waters, including 22 cruises, 1000 survey stations and voyage of 100,000km, and as results 48 research reports and monographs and many papers had published (Chen Qingchao, 1999). Here we introduce some results about coral reefs, seawater quality, sediments pollution and oil pollution of Nansha Islands and its neighboring waters.

　

Nansha Islands of China are characterized by more atolls or table reefs (more than 100 in total), of which more drowned atolls or table reefs (more than half of total), but less islands (only 23 in total) and less area of islands (only about 2.0 km² in total) (Zhong Jinliang et al., 1996; Zhao Huanting, 1996; Zhao Huanting et al., 1999). The total area of coral reefs and nearby shallow waters in Nansha Islands is about 25,000km², 7.2% of total area of Nansha waters. Coral reefs are ecologically critical area of highly concentrated biological activity of a type that is especially valuable for maintaining biodiversity and/or resources productivity (Clark, 1996), and become the most important ecosystem and landform in Nansha Islands. About 40 reefs in Nansha Islands have been surveyed by geomorphologists (Zhong Jinliang et al., 1996) or biologists (Chen Ruiqiu, 1994a, 1994b; Chen Ruiqiu and Li Changrong, 1996). In general the coral reefs in Nansha Islands are quite good and healthy especially in comparison with the rest part of Southeast Asia and East Asia (Wilkinson, 2000). They still found that part of coral reefs had been destroyed by destructive fishing methods (e.g. blast and poison fishing), storm damage and predator infestation.

Especially corals on the reef flats were more seriously damaged and its live coral cover in some places was only 20%. Over harvesting for high-value and edible species and collecting for curio trade had made some species (e.g. Cassia cornuta) endangered (Chen Ruiqiu, 1994b) and made reef ecosystem lost its balance.

¹ Supported by National Special Program for Social Public Welfare in Tenth Five Year Plan, No: 2001 DIA 50041

　

According to the results of survey of sea water quality in about 190 stations of 6 cruises during 1987-1994 (Li zhongqing, 1996), sea water quality of Nansha Islands waters is good and belongs to that of the clean sea area. The contents of pH, DO, Cu Pb, Zn, Cd, T-Hg and the organic chlorine pesticide meets the first class of sea water quality standards, except PO4³￣P, IO-N and Oil of individual station. In cruises of December of 1993 and September of 1994, the contents of Cu, Cd, BHC and DDT are not detected. The criteria of assessment factors for the first class of sea water quality in national standard (GB3097-82) is: pH 7.5-8.4; DO 5 mg/dm³; IO-N 0.10 mg/dm³; PO4³￣P 0.015 mg/dm³; Cu 0.01 mg/dm³; Pb 0.05 mg/dm³; Zn 0.10 mg/dm³; Cd 0.005 mg/dm³; T-Hg 0.0005 mg/dm³; Oil 0.05 mg/dm³.

　

According to the results of survey of sediment quality m about 121 stations of 6 cruises during 1987-1994 (Li zhongqing, 1996), the pollutant contents in sediment of the Nansha Islands waters are higher than that in seawater. The sediment of Nansha Islands waters suffered generally light pollution but middle pollution in local area The main pollutants in the sediments of Nansha Islands waters are heavy metal. Among them Cd is the most important pollutant. The content of Cd in all station is overproof and the average content is 3.5 times of the standard content. Pb and Zn are the next most important pollutants, most of stations are overfroof The Cu contents in most stations meet the standard The contents of T-Hg, organism, oil, Sulphide and organic chlorine pesticide are lower. The main factors affecting the pollutants distribution in the sediment of Nansha Islands waters are the source of pollutants, grain size of sediments and the background level. The organic chlorine pesticide mainly originates from land, and its high value area is southwest waters near to large river system and delta. The high content of Cd correlated closely with high background level or high natural source of pollutant (Li Zhongqing, 1996). The assessment standard of sediment pollution is from Concise Regulation for Multidisciplinary Resources Investigation of Coastal Zone and Tidal Flats. The criteria of its assessment factors is: T-Hg 0.2 x 10^-6; Cu 30 x 10^-6; Pb 25 × 10^-6; Zn 80 ×10^-6; Cd 0.5 ×10^-6; Oil 1000 ×10^-6; BHC 0.5 ×10^-6; DDT 0.02 ×10^-6; sulphide. 300 ×10^-6; organic matter 3.4%.

　

The influence of energy source exploitation of the abundant oil and gas resources in Nansha Islands waters on the environment quality is a question concerned generally for long time. A vast amount of investigation data expresses that both water and sediment don't suffer the pollution from oil. The content of oil in water meets the first class of water quality standard except that of individual station. The content of oil in sediment is lower. The experiment results of the oil species identifying by fingermark method of gas chromatography and mass spectrography from 101 microfurface and subsurface samples collected in Nansha Islands waters during cruises of December of 1993 and September of 1994 showed that most of sea water have not been found to suffer the pollution from crude oil, fuel, heavy oil and lubricating oil. The only sea area in the west (Wananxi basin) and the south edge regions of Nansha Islands suffered the pollution from oil hydrocarbon related to oil exploitation or natural leak of bottom oil.

　

Nansha Islands waters have vast area, strong water exchange and self-purifircation ability, and are remote from population center and land-based pollution, so the status of coral reefs and enviromnent quality are good in general. In addition the coral ecosystem degradation, Iocally PO4³￣P, IO-N and Oil sea water pollution and notable metal pollution of Cd, Pb and Zn in sediments were the main current problems. Along with increasing populations and growing food and energy demands in this Paciflc Century, we need pay more attention to environmental and ecological potential stress andtake preventive measures.

　

Chen Qingchao. Progress in multidisciplinary oceanographic expedition to Nansha Islands and its neighboring waters. In: Yang Wenhe (Chief editor). Chinese Ocean Yearbook 1997-1998. Beijing: Ocean Press, 1999, 259 (In Chinese)

Chen Ruiqiu. A study on mollusc diversity and its protection near the atolls of Nansha Islands. In: The Multidisciplinary Oceanographic Expedition Team of Chinese Academy of Sciences to Nansha Islands (Editor). Studies on Marine Biodiversity of the Nansha Islands and Neighboring Waters (1). Beijing: Ocean Press, 1994a, 51-57 (In Chinese with an English abstract)

Chen Ruiqiu. The countermeasure for the endangered Cassia cornuta (Linne) in Nansha Islands. In: The Multidisciplinary Oceanographic Expedition Team of Chinese Academy of Sciences to Nansha Islands (Editor). Studies on Marine Biodiversity of the Nansha Islands and Neighboring Waters (1). Beijing: Ocean Press, 1994b, 58-60 (In Chinese with an English abstract)

Chen Ruiqiu and Li Changrong. Conservation and sustainable utilization of biodiversity in the atoll reefs of the Nansha Islauds. In: The Multidisciplinary Oceanographic Expedition Team of Chinese Academy of Sciences to Nansha Islands (Editor). Studies on Marine Biodiversity of the Nansha Islands and Neighboring Waters (2). Beijing: Ocean Press, 1996, 51-59 (In Chinese with an English abstract)

Clark, J.R. 1996. Coastal Zone Management Handbook. Boca Raton: CRC, Lewis Publishers, 653. Li zhongqing (Chief editor). The Research on Enviroument Quality in the Nansha Islands and Adjacent Sea Area. Beijing: Ocean Press, 1996, 1-111 (In Chinese with an English Chapter 9 with conclusion)

Wilkinson (Editor). Status of Coral Reefs of the World: 2000. Queensland: Australian Institute of Marine Science, 2000, 7-20, 117-140

Zhao Huanting (Chief editor). Physical Geography of Nansha Islands. Beijing: Science Press, 1996, 1-402

(In Chinese)

Zhao Huanting, Zhang Qiaomin, Song Chaojing et al. Geomorphology and Environment of the South China Coasts and South China Sea Islands. Beijing: Science Press, 1999, 370-453 (In Chinese)

Zhong Jinjiang, Chen Xinshu. Zhang Qiaomin et al. Geomorphology Research of Coral Reef of Nansha Islands. Beijing: Science Press, 1996, 1-84 (In Chinese)