Scientists and cleanup crews are doing battle with a massive algal bloom in China's Taihu Lake, a source of drinking water for more than two million people.
In early June this year, a bloom of cyanobacteria — blue-green algae — spread across Taihu.
Algal blooms arrive in Taihu every summer, encouraged by warm conditions and nutrient-rich agricultural run-off and sewage that accumulates in the lake.
Some cyanobacteria make toxins that can damage the liver, intestines and nervous system if ingested, forcing locals to use bottled drinking water.
Clean up crews have removed more than 6000 tons of algae from the lake and laid a barrier to stop the algae from reaching a drinking water plant. Scientists are conducting experiments to determine how much nutrient levels must fall to stop bloom formation.
But the biggest challenge is preventing nutrient-rich waste from entering the lake, which will require tough emissions standards for surrounding factories and farms.