Algae bloom turns Washington's Lincoln Memorial Reflecting Pool green after recent renovations
The reflecting pool turned green due to rapid algae growth fueled by nutrient-rich water, high temperatures and recent changes to its color, prompting the National Park Service to apply chemical treatments.
The Lincoln Memorial Reflecting Pool has developed a vivid green hue within days of a renovation that darkened its water to a flag-blue shade. Officials said the still water creates an ideal environment for algae, which thrive on nitrogen and phosphorus that enter the pool from the Potomac River, a waterway that receives runoff from urban and agricultural areas.
The Department of the Interior noted the algae were "residual" from the pool's supply lines. Experts added that the darker water absorbs more heat, and with daytime temperatures in Washington reaching 95 degrees Fahrenheit, the warmer conditions accelerate algal metabolism.
To curb the bloom, National Park Service workers have been applying gallons of hydrogen peroxide and testing a high-tech nanobubble ozone system that injects tiny ozone bubbles to damage algal cells. While these measures address the immediate discoloration, longer-term solutions would need to reduce nutrient inflow and consider the pool’s depth and coloration, which together make it a favorable habitat for algae.
