what is the reason for all the algae in the reflecting pool in washington

The algae is there because the Lincoln Memorial Reflecting Pool has the exact conditions algae love: warm, still water plus nutrients such as nitrogen and phosphorus. Reports also say the recent dark-blue lining may help the pool absorb more heat, which can speed up algae growth even more.

Why it happens

• The water is relatively calm, so it does not circulate enough to discourage blooms.

• Nutrients in the water, including nitrogen and phosphorus, feed algae growth.

• Summer heat in Washington makes the problem worse by speeding up algae metabolism.

What people are saying

Some reports note that the administration has blamed vandalism, but scientists and reporting suggest the green water is mainly an environmental and maintenance issue rather than a mystery event.

What helps

Officials have used treatments like hydrogen peroxide and ozone nanobubbles to reduce the algae, but those are mostly short-term fixes. Long-term control would depend on changing the conditions that keep the pool algae-friendly.

TL;DR: the pool turns green because warm, nutrient-rich, still water is a near-perfect setup for algae growth.