The waters off Qingdao, a major port city on the Yellow Sea, have been blanketed by green algae since late June.
The city has dispatched thousands of boats to scoop up the plants, which cover 1,746 square kilometres, according to Jiemian. So far, 310,000 tons have been collected.
This is the biggest Qingdao bloom so far. The algae was a particular embarrassment in 2008, when the city hosted the Olympic sailing. In 2017, research identified purple laver farming in neighbouring Jiangsu province as the root cause. When farmers harvest the edible seaweed, they inadvertently release the algae, the research found. The green algae then starts its journey north until it eventually reaches Qingdao hundreds of kilometres away.
That conclusion was heavily disputed by experts in Jiangsu, who say the province has prohibited farmers from dumping algae into the ocean since 2014. This year, the scale of purple laver farming in northern Jiangsu fell 38% compared to last year, they said. “Jiangsu’s control effort is considered the strongest in 2021, and yet Qingdao’s algal bloom turned out to be the worst in years, indicating a weak link between the two,” said Dai Weiping, secretary general of Jiangsu province edible seaweed association. He said eutrophication and climate change were more important factors.
As the debate continues, the short-term solution appears to be better forecasts and preemptive clean-up. “We should make preparations for algal blooms like we do for typhoons,” expert Sun Song told Jiemian.