Why is newly renovated Reflecting Pool in Washington DC full of algae?

The Lincoln Memorial Reflecting Pool in the US capital has turned green with algae days after it was refilled with water following renovations.

President Donald Trump ordered the revamp last year, claiming the pool had been left in a poor condition by President Joe Biden.

It's had issues with algae for decades. BBC Verify's Jake Horton has looked into what's behind the latest problem.

Produced by Ian Aikman, graphics by Leo Scutt-Richter