06/24/2026
By now, everyone's heard about the (wrong color of the) Lincoln Memorial Reflecting Pool on the National Mall in DC.
The science behind the "wrong color" is explained by multiple experts, including professor of aquatic ecology Rosalina Stancheva Christova, who had taken water samples from the pool for analysis.
Christova confirmed that the algae belongs to the genus Desmodesmus, which she said is "growing in excessive amounts" but is not toxic or harmful. However, she would like to see the water monitored weekly.
"If we don't have any control over algal growth, we don't know what is growing," she said, adding that not all types of algae are as harmless as the one currently blooming in the pool.
Read the NPR story (heard on All Things Considered): https://www.npr.org/2026/06/19/nx-s1-5863044/dc-reflecting-pool-algae-green-trump
Potomac Environmental Research and Education Center
College of Science at George Mason University
The shallow, sunny waters of the reflecting pool are an ideal incubator for algae growth in the summertime. Experts say the recent renovation may have helped accelerate it.