The Lincoln Memorial reflecting pool in Washington DC has been in the news since April when President Trump vowed to renovate it and paint it 'American flag blue' by 4 July. Despite stripping, cleaning, coating, and refilling the pool, the algae that has plagued it for decades returned within days.
Why Does Algae Bloom in the Reflecting Pool?
Dr Linda May, a freshwater ecologist at the UK Centre for Ecology & Hydrology, explains that algae blooms occur due to a combination of factors. The pool is shallow, allowing sunlight to penetrate and warm the water, creating ideal conditions for algae growth. Nutrients like phosphorus and nitrogen, often from bird droppings or decaying organic matter, fuel the blooms.
Why Is It So Difficult to Tackle?
May notes that the pool's design—a large, open basin with limited water circulation—makes it a perfect habitat for algae. Traditional treatments like algaecides can be harmful to wildlife and are often only temporary. The pool's location in a busy urban area also means runoff and debris constantly introduce new nutrients.
What Could Trump Try Next?
According to May, long-term solutions include installing a filtration system, adding aeration to circulate water, or using barley straw, which releases compounds that inhibit algae growth. However, these methods require significant investment and maintenance. The pool's historical status also limits alterations.
The saga has turned the pool into a metaphor for the challenges of managing urban water bodies. As May puts it, 'Algae are a natural part of aquatic ecosystems, and controlling them in such a high-profile location is a complex scientific problem.'
