A boy wades into the algae-swamped Chaohu Lake in east China's Anhui province on July 4, 2006. [File photo/sohu.com]

Green algae blooms frequently cause havoc in China's waterways and threaten marine ecology systems and fisheries.

An algae outbreak almost halted the sailing competitions of the 2008 Olympic Games in Qingdao. Local authorities had to mobilize soldiers and volunteers to clear it.

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Almost a million tons of algae was cleared from the sea and buried underground.

This year, a large expanse of green algae appeared along Qingdao's coastline in June and July. Though not toxic, the algae consumed large amounts of oxygen, threatening marine life and fisheries.

Tourism was also affected when an algae strip hundreds of meters long formed at a beach on Xuejia Island, Qingdao, on June 30.

In 2007, an algae outbreak in China's third-largest freshwater lake, Taihu, stopped tap water supplies for more than a million people in Wuxi, Jiangsu Province, for about 10 days.