China's marine environment has been rapidly deteriorating in recent years due to increasing discharge of pollutants and rampant human activities, according to an annual report released by the country's ocean watchdog.

The severely polluted sea area amounted to 44,000 square kilometers in China in 2011 from 25,000 sq km in 2003, according to China's 2011 marine environment report released on Monday by the State Oceanic Administration.

Li Xiaoming, director of the department of marine environment protection at the administration, blamed overdevelopment in the coastal area for the country's worsening water quality.

"Just one number can tell you how serious this is. More than 80 percent of the coastline in Bohai Bay has been crowded by factories and buildings," Li said.

The construction of offshore projects across the country represented about 110 billion yuan ($17.46 billion) in 2011, approximate 15 percent year-on-year increase, according to the data.

As coastal development has become a new growth area in China's economy, offshore development and coastal construction are threatening the country's marine environment.

A Bohai Bay oil spill in June 2011 polluted a 6,200-sq-km water area, about nine times the size of Singapore. The report said that a year after the oil spill, the environmental impact of the incident still exists. Some marine experts warned that it will take about 30 years for the bay to recover.

Many scholars and experts have also expressed concern over the worsening marine environment and the new round of marine exploration and development during the country's 12th Five-Year Plan (2011-15).

Ma Chaode, project manager of the United National Development Program, said that local governments must find an effective way of balancing economic development and environment protection.

Feng Jinan, chief engineer of the Guangdong Administration of Ocean and Fisheries, said that methods for protecting marine ecosystems are still under study. He believes that a way to both protect the environment and guarantee economic development will be worked out. But before that, slowing down development is needed, he added.

The statistics from the State Oceanic Administration show that nearly 83 percent of the country's coastline has a fragile ecosystem, while coastal areas contribute to 70 percent of the country's GDP.

"It's a hard choice for the authorities to make, between environment and economy," Ma said.

In 2011, China's oceanic sector saw an annual growth of more than 10 percent, reaching about 4.6 trillion yuan.