A large expanse of green algae is floating towards east China's coastline, an oceanic official said Tuesday.

The green algae, namely enteromorpha prolifera, presently covers about 200 square kilometers of sea off China's Shandong Province. The green mass is about 13 kilometers from Jiaonan City and 16 km from Dagong Island, according to the North China Sea Branch (NCSB) of the State Oceanic Administration.

The NCSB first detected the green expanse in the sea off the coast of Rizhao City in Shandong last Monday and since it has continued to drift north.

It would move northward, according the sea's flow, at a speed of 7-9 kilometers per day and would come closer to the coastline, said Liu Fenglin, spokeswoman of NCSB.

The NCSB has started an emergency response. Local governments have dispatched vessels to clear the algae from the sea.

Though not poisonous and with no affect on water quality, the algae can consume large amounts of oxygen, threatening marine life, according to Pang Shaojun, professor of Chinese Academy of Sciences.

If the green algae was not cleaned in time, it could affect the development of the tourism sector in the coastal area as the rotten algae emits a foul smell, according to Pang.

Green algae emerged in the Yellow Sea in 2007. Local residents and soldiers removed tens of thousands of tonnes of the algae in 2008 before the Beijing Olympics' sailing competitions kicked off in Qingdao of Shandong.