Increasing stretches of China's coastal waters were seriously polluted in 2012, mainly from excessive polluting discharges from land, the State Oceanic Administration reported on Wednesday.

The area of severely polluted Chinese coastal waters surged to 68,000 square kilometers in 2012 from 44,000 sq km in 2011, according to the country's 2012 marine environment report.

Guan Daoming, director of the National Marine Environmental Monitoring Center, blamed the worsening marine environment on surging human activity.

The report showed that the water quality near coastal regions that are crowded with factories and buildings has been worsening in recent years.

"Human activity is posing an increasing threat to marine life and habitats as the pollution escalates," Guan said.

According to the report, more than 17 million metric tons of pollutants from the 72 monitored rivers flowed into the sea in 2012. This included 46,000 tons of heavy metals and 93,000 tons of oil.

As the marine economy becomes a new growth area for China, coastal waters face great risks from booming offshore development and coastal construction.

According to the State Oceanic Administration, more than 80 percent of the Bohai Sea coastline was crowded with factories and construction projects, and less than 5 percent of the Bohai Bay's shoreline remained in a natural state.

The environmental impact from a Bohai Bay oil spill in June 2011 is still felt, with increased oil level in the waters near the accident site since the spill, the report said. Some marine experts said that it could take about 30 years for the bay to recover.

Besides Bohai Bay, about 53,074 cubic meters of drilling mud from offshore oil platforms was discharged into the nation's coastal waters, a year-on-year increase of 11 percent.

Plastic refuse accounted for 80 percent of the litter in the coastal waters.

Nearly 4,400 pieces of plastic refuse are found per sq km of water, and beaches have 50,000 pieces per sq km, the report said.

To better protect the fragile marine environment, Li Xiaoming, director of the department of marine environment protection under the SOA, said the oceanic watchdog is taking a series of measures to increase supervision and restrict pollutants discharged into the sea.

He added that a system will be set up to strictly control the effect of human activities on the bay.

More than 720 barrels of crude oil and 2,610 barrels of oily mud were released into the bay by spills in June, and together they polluted 6,200 sq km of water, the SOA estimates.

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