A large expanse of green algae is moving toward China's east coastline, local maritime officials said Tuesday.

The green algae, namely enteromorpha prolifera, covered 130 square kilometers of sea off east Shandong and Jiangsu provinces by Monday, said Liu Fenglin, spokesman with the North China Sea Branch (NCSB) of the State Oceanic Administration.

The NCSB first detected the green algae expanse when it covered 6.8 square kilometers off the city of Yancheng in Jiangsu on May 28.

It will move northward and reach the coastline of Chaolian Island, 31.4 kilometers from the city of Qingdao in Shandong, on Thursday, Liu said.

Although the green algae is non-poisonous and harmless for water quality, it can consume large amounts of oxygen. Thus, a large expanse of green algae could threaten marine life and affect coastline tourism as the rotten algae emits a foul smell.

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