Tourists take photos last week in seawater covered in algae near a beach in Qingdao, Shandong province. The algae outbreak is now under control. Li Ziheng / Xinhua

Pang Shaojun, another ocean university researcher, said pollution and eutrophication are the primary cause of algae blooms, and the algae appearing in Qingdao has mainly drifted from South China.

Pang also said that how to deal with algae outbreaks has become a hot research point for scientists around the world.

"Harvested" algae is transported to local processing centers and used to make feed and fertilizer by companies, including China Ocean University Organism Project Development.

The company uses algae in three ways, namely feed additives, organic fertilizers and materials for healthcare products, said Shan Junwei, president of the company.

"Since 2008 we have developed quality algae fertilizers for fruit trees, vegetables, organic agriculture and urban gardening," he said.

"Hundreds of tons of bio-fertilizers made of algae have been sold to more than 20 provinces and regions."

The company is researching a method to extract polysaccharide from the algae for nutritional products.