Trump's $14.2 million blue Reflection Pool turns green as four theories emerge on why

A project around Washington DC has finished, and now people are already coming with theories as to what may have gone wrong.

No, we're not talking about Donald Trump's controversial staging of a UFC championship on the South Lawn to celebrate his 80th birthday and the USA's 200th anniversary.

And it's not his ongoing project to construct an enormous ballroom, including demolishing parts of the the historic structure, either.

This is concerned with the recent renovation of another part of the historic architecture around Washington DC - the Lincoln Memorial reflecting pool, which has reportedly cost a whopping $14 million to complete.

One part of this renovation has now drawn attention, as the waters in the pool have now suddenly turned a very fetching shade of green.

The immediate cause of this is clear, it's an algal bloom, with the microscopic plants multiplying in the water and their chlorophyl turning the pool green.

But there are some broader questions about this as well, which are what has caused the algal bloom itself? Let's look at some theories, according to Christopher Lowe, senior lecturer in marine biology at Swansea University in the UK, who shared them with Newsweek.

Employees at the National Parks Service in the reflecting pool (Tasos Katopodis/Getty Images)

The Coating

This has been changed to 'American flag blue', and Lowe suggested that it could be a factor due to how different colors react to heat.

Darker colors absorb heat and light, meaning that over time this could result in the water temperature rising.

That in turn could make it more susceptible to algal blooms as it may create 'perfect conditions for algae to bloom'.

Water flow

With an artificial body of water the size of the reflecting pool, a large water treatment system is necessary to keep the water from becoming stagnant - think like the filter on a pond or fish tank, but much bigger.

When this isn't working correctly then it could interrupt the water flow, and make algal blooms more likely.

If this is what has happened, then it would be a case of further work and tweaking being carried out on the system to get it running correctly.

The pool is a very bright green color (Aaron Schwartz/Bloomberg via Getty Images)

Weather

Washington DC can get hot, and is famously a very humid city due to its location.

This is a factor which can also influence algae growth, with Lowe saying: “When nutrients, light and temperature are all high, algae can reproduce extremely quickly."

Residual Algae

This is the explanation according to a spokesperson from the Interior Department, who told Politico that the algae is 'residual'.

That means that while the construction process was going on it had been sitting in the pipes for eight weeks, and now that the pool is functional again it has erupted into a bloom.