Local residents in Qingdao, Shandong Province, have questioned whether authorities have taken enough steps to deal with the algae invasion, with experts still disagreeing as to the exact cause of the annual seaside scourge. 

The carpet of green weed, while not harmful to health, has covered an area of 28,900 square kilometers, twice that of 2008's invasion at 13,000 square kilometers, according to State oceanic authorities, the Xinhua News Agency reported Friday.

It's the fifth consecutive year since Qingdao saw its first algae invasion in 2008, and the local residents said the invasion has gotten worse year after year.

"It came earlier this June, in small amounts first, but now it looks like grassland along the coastline," a Qingdao resident surnamed Wang told the Global Times. "The smell is disgusting, as if something is rotten."

Teams, dispatched by local authorities, had cleaned up 70,000 tons of algae until Friday.

They have also fixed fishing nets in certain sea areas to prevent the algae from reaching the shore, the Qingdao Daily reported on Sunday.

Li Delin, an engineer with the Commission of Urban-rural Development in Qingdao, in charge of cleaning up the algae from the shore, told the Global Times that all the collected algae is dehydrated and compressed and sent to factories to be made into feed additives and organic fertilizers.  

Feng Yongfeng, founder of Green Beagle, a Beijing-based environmental watchdog, said that the clustered algae was a result of eutrophication, a process in which bacteria consume oxygen causing fast growth, as a result of wastewater discharged from factories in Shandong.

Pang Shaojun, a research fellow from the Institute of Oceanology under the Chinese Academy of Sciences, told the Jinan-based Dazhong Daily on June 19 that the algae could be caused by an increased amount of fermented chicken manure used as fertilizers in the area.

"Every March to May since 2005, about five tons of waste fertilizers rich in ammonia nitrogen are discharged into the water," said Pang. "The nutrients in the wastewater together with the unique geological terrain in the area contributed to the algae invasion."

While some experts have said it may affect sealife, others have said the plant may cast a positive effect on local environment.

"It is actually good for the sea environment, since the algae will take in the pollutants as they grow. In this case, when they are removed from the sea, so are the pollutants," said Feng, "but it looks bad, especially in Qingdao as the city relies heavily on the tourism industry."

However, some beach resorts have not been so heavily affected. A staff worker from Shilaoren Beach told the Global Times that all the algae was removed by Monday.

While local residents may be annoyed, many tourists have been pictured playing and swimming in the weed, which has become somewhat of a tourist attraction itself.