When the normally murky brown Mekong River turned a brilliant blue late last year, villagers in northeastern Thailand were surprised.
Then, this week, unusually large patches of green algae appeared, clogging up nets and making it almost impossible to fish.
Both the Mekong’s strange colour and the algae have heightened worries about the health of the river that more than 60 million people in Southeast Asia depend on for their livelihoods.
“This is unnatural,” fisherman Tongchai Kodrak said of the algae and the blue waters, which both signal a lower level of life-bringing sediment in the water.
He says a bit of algae appears every dry season but this year it is more than anyone can remember.
Panu Wongcha-um and Kay Johnson