BEIJING -- China's seabed is undergoing rapid desertification due to an excessive discharge of sewage and pollutants, an investigation by the Chinese Research Academy of Environmental Sciences has revealed.

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"One third of the samples collected from China's seabed had no sign of benthos, which means that the seabed is undergoing serious desertification," said Dr. Zheng Binghui, director of the academy's water environment institute.

The investigation, which began in 2005, covered 103,600 square kilometers of land, mostly in China's densely-populated east and coastal provinces, and 38,000 square kilometers sea areas.

According to the investigation, 79 percent of the sea water covered in the research is worse than Grade Four (medium-polluted).

The areas investigated include the Yangtze River Basin and its surrounding sea areas, including eight cities along the Yangtze River in east China's Jiangsu Province, six coastal cities in eastern Zhejiang Province, Shanghai and sea areas bordering Hangzhou Bay.

Inorganic nitrogen and active phosphate were the two major pollutants in the sea water, 11.1 times and 3.1 times higher than the national standards, according to the investigation.

In 2005 alone, 9.07 billion tons of waster water was poured into the sea from the Yangtze River basin and its neighbouring industrial areas, the investigation shows.

Sources with the State Environmental Protection Administration said the administration will work on a sewage quota system for Zhejiang, Jiangsu and Shanghai based on the result of the investigation and set up a joint mechanism to curb sea water pollution.