Since Tuesday, Olympic organizers have repeatedly assured athletes and fans that the pool is safe and that the situation was under control. Rio organizing committee spokesman Mario Andrada told reporters on Wednesday that “the pool should go back to its classic blue color during the day.”
That clearly didn’t happen. Instead, reports trickled in that the adjacent pool used for water polo and synchronized swimming also began to turn green.
The cause of the emerald tides is still murky. Officials have discussed running out of an unnamed chemical used to treat the pool, algal blooms, too many people using the pool, and apH imbalance. All of those may be factors. It’s conceivable that the organizers ran out of a chemical, such as muriatic acid, used to balance the pH of the pool, normally kept around seven, and wound up with a higher, alkaline pH. With the acidity out of whack, the disinfecting power of the chlorine would decrease and give algae a chance to get a foot in the door. When combined with hordes of microbe-toting swimmers and warm temperatures, all of this could lead to a jade lagoon.