Algae Blooms: Unsightly for the Reflecting Pool, Potentially Toxic Elsewhere
June 25, 2026 | Source: ewg | by Adam Levin
Algae is making headlines after the Trump administration’s $14.2 million renovation of the Lincoln Memorial Reflecting Pool turned its water closer in color to the Chicago River on St. Patrick’s Day – an unmistakable bright green.
But the color of the Reflecting Pool came not from thousands of tons of green dye but from an algae bloom consuming the 6.5 million gallon basin.
Over half of all U.S. lakes now suffer from worsening algae blooms, a problem that has intensified dramatically since 2015. Not all algae blooms are toxic, and that includes the current reflecting pool growth.
It’s the toxic blooms elsewhere that prompt health concerns.
A toxic algae bloom is not algae at all. It’s an overgrowth of algae-like bacteria in an aquatic ecosystem. It can kill fish, birds and other wildlife, and cause severe kidney and degenerative diseases in humans.
It’s impossible to know by sight alone whether an algae bloom is toxic. Green-blue scum, thick mats on the water’s surface, or foul odors can signal danger. But the problem often starts upstream, when fertilizer, manure and climate-driven runoff fuel rapid algae growth.