QINGDAO, Shandong - Chinese marine authorities are working to protect China's eastern coasts from a "green tide" of algae currently drifting on the Yellow Sea.

The North Sea branch of the State Oceanic Administration on Tuesday said the algae had been found in an area of 14,130 square kilometers of the Yellow Sea, and that a dense 165-square-kilometer-patch was of particular concern. It is invading coasts of Qingdao and Rizhao cities, both in Shandong province.

Authorities in Qingdao have deployed manpower to build barriers to stop algae from carpeting the shore and have mobilized people to clear the matter.

The algae, though not toxic nor detrimental to water quality, ravages the ecosystem because it consumes large quantities of oxygen, thus suffocating other marine lives. It also has an impact on local sea tourism in summer travel seasons.

The algae density increases as water temperature and salinity rise, and the outbreak may cause damage to fishery and aquaculture industries.

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 Olympic Games' sailing events in Qingdao.

However, the green tide is not everyone's nemesis. Some garment factories have found a use for it - making fibers for hi-tech fabrics.