Reflecting pool algae: the science Trump needs to know

0:00This is The Guardian.

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1:51On Saturday, the USA will celebrate its 250th birthday. And to mark the occasion, Donald Trump had a special gift in mind. It was supposed to be a quick, easy and cheap job to transform Washington, D.C.'s Lincoln Memorial Pool to an American flag blue all in time for America's 250th birthday. At first, Trump's renovation efforts seemed to be going well. We haven't finished the waters pouring in as we speak. And maybe we'll show that what it looks like because I'm sure the fake news will be thrilled. But then everything started to go a bit green and smelly. Two weeks after it was refilled, the Lincoln Memorial reflecting pool is going through some things.

2:40It's brand new$14 million blue coating, a color personally picked by President Donald Trump, is obscured by bright green algae. Over the past week, the administration has thrown everything at it from innovative new technology, hydrogen peroxide and even vacuuming. And finally, on Sunday, Trump took to Truth Social to announce the reflecting pool is now in full use and the criminally made algae is gone.

3:15The fight against the algae is basically a huge science experiment happening in real time and it got us wondering, what is the science behind algal blooms? And given its size and location, will the pool really ever be American flag blue? From The Guardian, I'm Ian Sample and this is Science Weekly.

3:42Maddy, today we're getting into the science behind the ongoing Reflecting Pool saga. Give me a bit of background about the pool itself. So this is the Lincoln Memorial Reflecting Pool in Washington, DC. At one end of the pool, you've got the Washington Monument, so that's kind of the big pointy stick. And then at the other end, you've got the Lincoln Memorial, super famous. and across both sides you've got this promenade of elm trees. So it's such a beautiful spot. It was completed in the early 1920s and since then it's been a site for so many big historical moments. So one example, it's where Martin Luther King Jr.

4:27did his I Have a Dream speech. He was looking out over this reflecting pool and actually it's had a lot of renovations over the years, including a big one in 2012 that actually also caused an algae bloom. So let's get into the science here. What actually is algae? These are plant-like organisms. They photosynthesise and they're typically aquatic, so you find them in water. They tend not to have true plant structures, so things like roots and stems and leaves, and they're often referred to via their colour. So you might hear about green algae, brown algae, red algae, but really they're this huge, diverse group with tens of thousands of species.

5:13So you go from the very, very small, so plankton, but it goes all the way up as well to seaweeds like kelp. And obviously things that photosynthesize are really helpful for us, turning carbon dioxide into oxygen. But I wanted to find out a little bit more about algae and the role that they play in our ecosystems. So I got in touch with Dr. Linda May. She's a freshwater ecologist from the UK Centre for Ecology and Hydrology. I divide them into nice algae and bad algae. So the bad algae that cause the scums and become toxic and cause problems for people are the sign of bacteria are one thing. But just like any other system, you need plants to feed your smaller animals that are eaten by your bigger animals and so on.

5:59It's the same in a lake or a pond. Selgi are really important in trucking the sun's energy and providing food and energy for ecosystems. They feed larvae and things that fish feed on. And if they're not there, then the fish can't grow. They feed this small zooplankton. You need the small zooplankton because when the fish first hatch out of their eggs, then they've got tiny, tiny gape sizes, we call it, tiny, tiny mouths. And so for the first four or five weeks, They need the tiny, tiny zooplankton because they can't eat the bigger ones. And those are all fed by the algae. We need them, but we don't need too many.

6:33It's like a lot of things. Now, going back to what Linda referred to as the bad algae, you often hear about blue-green algae. This is also called cyanobacteria, and that's actually a little hint that it's not really an algae at all. It's a bacteria. Do we know what kind of algae this is and where it came from? Well, some scientists have sneakily, I guess, tested the water over the past few weeks, and they seem to have identified it as a kind of green algae called cenodesmus. Now, this hasn't been officially confirmed by the administration. There were concerns at first that it might be this kind of bad algae called cyanobacteria.

7:17And the reason that some people were suspicious of this is because unfortunately in the water they have found dead ducks and dead ducklings and cyanobacteria produces a lot of toxins but it may be that these ducklings died because of what they were doing to treat the algae or just the disruption to their habitat and Trump did imply that this algae came from vandals and criminals maybe putting nutrients in the water. But what I would say is that algae spores are absolutely everywhere. They're travelling along in the wind. If you've got any kind of body of water, you're probably going to find an algae spore in there.

7:56And the water itself, now there are a few different sources on this. When I was looking, it seems like the water used to actually be the same as the city's drinking water, the stuff that comes out the taps. But now it seems as if the water comes from this reservoir known as the tidal basin, which is connected to the Potomac River, you'd assume that there's some kind of filtration system going on before it enters the reflecting pool. But perhaps there isn't a filtration system, or at least it isn't working well enough. So what causes the kind of bloom that we've seen in the reflecting pool? Right.

8:34So algae love three things. So algae love light because they're photosynthesizing. They love warmth and they love nutrients, in particular phosphorus and also nitrogen. It's kind of like if you wanted to build a structure that caused an algae bloom, build a reflecting pool. It's shallow, so the water gets really nice and warm. It's wide, so it has all the light and it's stagnant water. It's the perfect place for algae. And so actually there have been lots of blooms over the years. This is not the first time this has happened because algae is everywhere. And what causes the actual blooms themselves is things like agricultural runoffs.

9:22So that's when you're getting a lot of nutrients into the water. Linda told me that scientists like her, when they're called to take a look at these algal blooms, the first thing that they do is try and work out where these additional nutrients are actually coming from. Because if you want to do something about an algal bloom, that's really the root cause that you have to get at because you're not going to do anything about the sun. And some people have wondered whether this botched paint job has been anything to do with it. Is there any chance of that? I saw one theory that was talking about the kind of texture of this paint job, which is quite rough, and maybe that was helping the algae.

10:01I'm not sure that's true. So algae might like rough surfaces when it's things like bricks or paving slabs, because those little, you know, divots and dents that you would find in there are collecting water. And that's where you find most algae. So I don't really think that's the issue. Some people have also said, and this is more plausible, is that the paint job itself, because it's been painted dark blue, that's making the water much warmer. I mean, before now, the reflecting pool was a kind of grey slab, so it was reflecting off the light and the heat. And so maybe the water is a little bit more warmer than usual.

10:38But to be honest, it's the summer. So how much difference that colour of paint is making to the temperature of the water and the algal bloom, I'm not sure.

10:54Maddy let's talk through what the administration says they've been doing to try and get this under control and the interior department said it was using the wonderfully named advanced nano bubbler technology to kill algae which the National Park Service then goes and sort of vacuums up what is this? It does sound made up doesn't it it sounds like a made-up technology but it is it's real and it's actually very new. Basically, you have this specialised equipment and it injects air, like ozone, oxygen, into the water. And it does that through injecting millions, billions of these tiny, tiny, tiny little nanobubbles.

11:33So each nanobubble will probably be 100 nanometres in diameter on average. And that's about a thousandth of the thickness of a human hair. And when you inject all these like tiny little bubbles, because they're so small, they don't have much buoyancy and they're able to kind of really get into the water and spread and stay. And what they do there is they oxygenate the water. And this has two effects, really. So one is that it can promote the growth of aerobic bacteria, which consumes the nutrients that the algae might and kind of out competes the algae and keeps the algae in check. Alternatively, what it might do is when you're delivering all these nanobubbles, all this oxygen, this ozone gas, that's very reactive.

12:23And what it does is it can break down the cells of the algae and kill it. They've also tried pouring in hydrogen peroxide, which I thought was used for bleaching hair. Yeah, hydrogen peroxide is the same chemical process that makes your hair blonde as works as a pretty good algicide. It's kind of breaking down the algae cell walls. And actually, hydrogen peroxide is really good in this instance, because it breaks down into oxygen and water. So it's not toxic when you pour it in there for the other aquatic life that might be present. like the nanobubbler technology it is a kind of short-term corrective it's not going to last that long and unlike the nanobubbler technology which is really good at spreading out in the water hydrogen peroxide when you pour it in it's not going to diffuse that well it's probably not going to go that deep and it's not going to get that far in and one of the issues there is that when you break down the algae you're releasing the nutrients that that algae has sort of taken in back into the water.

13:30And so what you might do is actually cause another bloom. So you're providing more food for the algae that's still in there. Coming up, could Trump turn the pool blue by embracing a green solution?

13:57Your call has been forwarded to an automatic voice message system. A missed call doesn't feel like anything. No red flag, no notifications screaming at you. It just disappears into your call log. And nine times out of ten, that was someone ready to hand you money. That's why today's episode is brought to you by Quo. spelled Q-U-O. The business phone system built so you never miss a call. Here's what I like about it. All your calls, texts, and voicemails live in one place, so anyone on your team can pick up a conversation, see the full history, and respond fast. No more, wait, who talked to this customer last?

14:33And if you're worried about after-hours leads slipping through, Quo's optional built-in AI agent can answer questions and even book appointments while your team's offline. It's the number one rated business phone system on G2, and over 90 ,000 businesses already trust it to stay reachable. Money is on the line. Always say hello with Quo. Try Quo for free. Plus get 20 % off your first six months when you go to quo.com slash tech. That's Q-U-O dot com slash tech.

15:06Maddie, there's not much time now before the 250th celebrations. Trump says the pool is now in full use and that they'll drain it again after July 4th to fix any issues once and for all. Should it start going green again, is there anything else they can do? When I asked Linda about this, she really sold me on this idea of introducing water fleas. and these are also known as Daphnia and they're found all around the world and as she described it they are absolutely brilliant at tackling algae. If you wanted to this is going to be your most effective method. In Lockleaven which is my main stomping ground up in Scotland we've been looking at what happens there and one of the things we have noticed is that the Daphnia, the water fleas when they're there.

15:57On a summer's day, the entire population of water fleas will remove the algae from about 60 % of the entire loch every day. They work like little hoovers, and they're really very cute. So if you've got a really good population of them, then that works very well, but they are very, very sensitive to pollution. And so in Loch Leven, for example, between 1954 and 1971, we lost all of the daphnia because of pesticide pollution. which was then stopped. And the difference when the Daphne weren't there to when they reappeared in 1972 is absolutely amazing. We had lots and lots of algal blooms. Daphne came back and the algal blooms just disappeared in 1972.

16:41Okay, so Ian, I've actually got a radical suggestion. If you wanted to create a system which eventually sort of looked after itself, so you don't have to have these nanobubbler technology machines around the side. You don't have to come up with this incredible filtration system. You could turn the reflecting pool into a functioning ecosystem. You could put in the Daphnia. You could put in some plants. Hey, you could put in some fish. I think that would be quite fun. I don't know if it's appropriate for a national monument. So if you don't want to do that and you want to get rid of the algae or keep them at bay, you just have to tackle the nutrients.

17:21And how is that brought down to a level where these algae blooms aren't going to suddenly take off? It's hard to see them really going for something that would inevitably become known as the flea pool. Yes. Which is better, the algae swamp pool or the flea pool? I don't know. A lot of political people have called this the perfect metaphor. thought, what do you think we should take from this saga, scientifically speaking? So obviously, this redo of the reflecting pool was to mark the 250th. And when you think about the incredible scientific and technological advances that we've had over the last 250 years, it's truly amazing.

18:05And yet, what's also quite fun to think about is that occasionally still, we are bested by ancient, simple organisms like algae. And in honour of our World Cup hosts at the moment, I'll just say, algae won, Trump nil. Thanks to Maddy, who also produced this episode. The sound design was by Ross Burns, and the executive producer was Ellie Burie. And if you'd like to hear more about the Reflecting Paul's saga, listen to the latest episode of Politics Weekly America, where host Johnny Friedland talks to Awa Madawi about why the project has proved so embarrassing for Trump. Just search wherever you're listening to this.

18:51We'll be back on Thursday. See you then.

18:57This is The Guardian.

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