Science Has a Name for What’s Plaguing the Reflecting Pool

Testing reveals that efforts to suppress one algal bloom seem to be fueling another.

By Matt Viser

https://cdn.theatlantic.com/thumbor/tjz1Zwg5U87x_GnEmzY1jyOqnIE=/0x0:4000x2250/828x466/media/img/mt/2026/06/2026_06_19_Algae_Reflecting_Pool_3/original.jpg
Workers clean up the Reflecting Pool with a reflection of the Washington Monument
Aaron Schwartz / Bloomberg / Getty

June 19, 2026, 3:50 PM ET

Donald Trump has a new nemesis, with a name worthy of a supervillain: Scenedesmus.

The Reflecting Pool on the National Mall has become the country’s most high-profile science experiment, with workers battling against nature. After a week of combat, they have essentially killed off one type of algae infesting the pool, only to create the conditions for a new type to take over. And Scenedesmus, a genus of green algae nicknamed “Skinny Dead Mouse” by scientists, is now flourishing, according to testing that was run at the request of The Atlantic.

The pool, at the moment, looks like a strange bit of modern art. As workers treat different sections, the areas where they succeed in reducing the algae turn lighter shades of green. In some places, the water is relatively clear. In others, it’s an oily sludge. A quick glance, though, is enough to confirm that this is not the American-flag blue it was supposed to be.

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