Seaweed farming linked to Qingdao's green tide of algae

When Jiangsu seaweed farmers won the right to sell their produce to Japan in 2005, few expected their victory to bring such big changes to one of the mainland's most popular seaside resorts.

But as the tourist city of Qingdao in neighbouring Shandong copes with its sixth massive summer algal bloom in as many years, scientists are pointing to the expansion of seaweed farming along the coast as a possible culprit.

Qingdao's beaches began to look more like grasslands as they were swamped by the annual "green tide" last month, with this year's outbreak covering an unprecedented 28,600 square kilometres.

While the algae appears harmless to humans, it can choke off oxygen supplies for marine life, and the smell as it rots does little to attract tourists to a city long famed for its local Tsingtao beer and beaches.

The algae first hit in earnest in 2008, weeks before Qingdao was in the international spotlight as host of the sailing events for the Beijing Olympics, yet no convincing explanation for the algal bloom has emerged.

Many cite coastal pollution as a likely factor. However, a study published in May in the journal Estuarine, Coastal and Shelf Science concluded that the "green tide" originated from the Jiangsu coast and proliferated in the Yellow Sea before being swept north by the tide towards Qingdao. The study by scientists from the Yantai Institute of Coastal Zone Research under the Chinese Academy of Sciences cited satellite images and field observations to support its claims.

But the findings are already proving controversial, with scientists involved in the research reluctant to speak publicly due to its "sensitivity". Not only does the study cover relations between two provinces, but it also has implications for a fast-growing and lucrative industry.