In April, President Trump ordered that the Lincoln Memorial Reflecting Pool in Washington, D.C., be emptied, painted “American flag blue,” and refilled with glistening blue water in time for the country’s 250th anniversary this July.
Instead, the pool turned a vibrant blue-green colour as a swift algae bloom overtook the pool’s surface following its refilling in early June, undermining the two-month-long $14.2-million resurfacing job. Then, in mid-June, workers began dumping hydrogen peroxide into the reflecting pool in hopes of clearing the bloom.
We asked Paul Hamilton, a senior research assistant and the curator of Canada’s National Algae Collection at the Canadian Museum of Nature, to answer a few key questions about the fiasco, including “Should I be dumping hydrogen peroxide in my lake?”
What is causing the algae bloom at the Reflecting Pool?
The Reflecting Pool is filled with fresh water from the Potomac River, which is already contaminated. And it sits in the Reflecting Pool’s shallow, warm water. In those conditions, the water’s naturally occurring fertilizers, such as nitrogen and phosphorus, allow the algae to take off and go crazy. Painting the pool that darker “American flag blue” colour would have made the water even warmer, potentially accelerating the bloom.
They tried to stop the bloom by dumping hydrogen peroxide into the water. Does this actually work?
Hydrogen peroxide can be a solution to blue-green algae blooms, which is what initially covered the pool’s surface. It works by releasing high levels of reactive oxygen that breaks down algae cells, causing them to die off. In this case, it was successful, but when the blue-green algae died off, it released a layer of nutrients that then kick-started a second bloom, of green algae. These blooms can be harder to get rid of. They also likely used a 10 to 15 per cent hydrogen peroxide, which is strong enough to strip paint. That might have contributed to the peeling of the fresh paint job.
9 ways to get a beautiful shoreline and a healthy lake
Does this type of green algae occur in cottage country lakes and rivers?
Yes, it’s quite common. In cottage country lakes, it would typically be near shore alongside aquatic plants and sandy soil. It tends to be found in that kind of environment as opposed to out in the middle of the lake.
What causes the blooms?
The primary cause of algae blooms is fertilizers (in addition to sunlight, of course). Whenever you have elevated levels of nitrogen and phosphorus, you’re going to get algae growth. It’s just like your lawn or your garden—if you get too much fertilizer, everything’s going to grow like crazy. Fertilizers often make their way into our lakes and rivers via surface runoff that carries excess nutrients from agricultural land and residential lawns.
Is this type of algae harmful to people or pets?
No. Blue-green algae is toxic because it’s a type of bacteria called cyanobacteria, but green algae is closely related to other plants, and can usually coexist among them.
Cottage Q&A: Giraffe legs in the water?
Does it smell?
Certain kinds of algae smell more than others. This particular species, if it gets in high numbers and then starts to die, you’re going to get a rotting smell. Golden-brown algae, which is also found across cottage country, produces a smell on its own and can affect the taste of drinking water.
What can cottagers do to minimize algae blooms on their lakes?
You can’t really control temperature, and temperatures are getting warmer on average, which will lead to more frequent algal blooms. But what cottagers can and should do is reduce the amount of nutrients going into the lake. You can do that by making sure your septic tank isn’t leaking into the water, avoiding the use of fertilizers on your property, and leaving trees in front of your cottage and along the shoreline untouched. If you cut down all the trees around your cottage, and there’s a massive rainstorm, all the fertilizer in the soil is going to wash into the lake. Trees help control that. Then there’s the golden rule we laugh at: don’t pee in the lake. We’re packed with nutrients.
So, should cottagers be dumping hydrogen peroxide in their lake during a blue-green algae bloom?
Absolutely not. If the blue-green algae are producing toxins, the toxins will be released into the water and cannot be filtered out.
Related Story Cottage Q&A: What happened to our frog population?
Related Story Cottage Q&A: Do dock lights cause blue-green algae?
Related Story Q&A: How can I make wooden steps less slippery?