algae

WASHINGTON — The paint is peeling from the Lincoln Memorial Reflecting Pool after the renovation ordered by President Trump, and he is now alleging, without substantiation, that someone damaged it intentionally.

“We’ve had some real problems with Vandalism at the beautiful Reflecting Pool,” he posted on his social media site Friday night. “Just like three days ago, they destroyed the grass outside of the Pool, they’ve also done everything possible to hurt the inside surface that was just installed.” He offered no details to substantiate his claim.

Agencies responsible for law enforcement and upkeep on the National Mall — the U.S. Park Police, National Park Service and Department of the Interior — did not immediately respond to requests for comment.

The Washington Post reported that Park Police officers arrested someone Friday who they said was peeling paint from the pool, an act that would not explain the clouds of algae in green water and swaths of loose blue paint detached from the bottom.

Trump insisted something nefarious was going on. “No different than the chemicals that were used on the National Mall, they used something similar in the Reflecting Pool to try to destroy and demean our beautiful work,” he posted.

That was a reference to the discovery of large numbers etched in discolored grass on the National Mall the week before: “86 47,” apparently advocating to “86” — get rid of, in restaurant lingo — the 47th president.

Authorities claimed the numbers may be a threat against Trump, and they are investigating. Trump’s Department of Justice has tried — unsuccessfully so far — to prosecute Trump foe and former FBI Director James B. Comey for posting a photo of seashells arranged in the numerals “86 47.”

Trump’s claims of vandalism came after days of negative attention to the state of the Reflecting Pool, which has raised concerns about the no-bid contract of more than $14 million to refurbish. The president has said the pool rehab was needed as the nation’s 250th anniversary celebrations ramp up.

The pool was swiftly beset by an algae bloom that returned its waters to the greenish color that Trump had tried to replace by having the bottom painted “American flag blue.”

Federal workers treated the pool with hydrogen peroxide to kill the algae. Now, chunks of the blue paint are gone, exposing its rocky bottom.

U.S. National Park Service employees are pictured using a vacuum pump to clean algae off the bottom of the newly repainted Lincoln Memorial Reflecting Pool on the National Mall in Washington, D.C., on Wednesday, which on Friday started peeling and floating to the top of the pool. Photo by Bonnie Cash/UPI | License Photo

June 19 (UPI) — After cleaning algae from the Lincoln Memorial’s Reflecting Pool weeks after its $15 million renovation, the Interior Department now has to deal with blue paint applied to its bottom peeling off.

President Donald Trump‘s renovation of the national monument was meant to clear the water and prevent algae, and included painting the bottom of the pool “American Flag Blue” in the effort to improve it’s look.

The Reflecting Pool has for decades been known for some algae and unclear water, though it was designed to reflect the Washington Monument and sky rather than appear similar to other fountains and water features at monuments that have filtration systems that prevent water from being still enough to reflect their surroundings.

The pool’s new paint job was meant as an upgrade ahead of celebrations for the 250th birthday of the United States of America but after it was refilled following the paint job, green sludge started appearing on the water’s surface — and on Friday, chunks of paint could be seen floating to its top, as well.

The Interior Department on Friday told The Washington Post that it is treating the pool with hydrogen peroxide and a “high-tech nanobubble ozone technology” to prevent algae growth.

Swimming pool experts told The Post that it is possible the resurfacing was improperly installed, or that there could be water seeping under the repainted surface that is causing it to peel.

In posts on X on Wednesday, as the department started treating the water to reduce algae blooms, officials reported that some parts of the pool had seen clearer water as a result.

“The nanobubbler technology and vacuuming have been incredibly effective,” the Interior Department said in one post, “making the water crystal clear with the American Flag Blue coating shining brightly on the bottom of the pool.”

The cost to repaint the pool, along with other enhancements the administration has made, cost more than $14.65 million for the main contract on the work, with another $1.74 million paid to a separate company for the nano bubble technology that is expected to kill algae in the pool, ABC News reported.

According to a lawsuit filed by The Cultural Landscape Foundation, a thorough review of the renovation plans before the administration started work may have identified “potential problems — like algae and exfoliating paint — and, perhaps, suggest solutions.”

“Instead, the Park Service granted themselves a ‘streamlined review,’ which they admitted was done under pressure from ‘White House leadership,'” the TCLF’s CEO Charles Birnbaum told The Post.

Just days after the Trump administration completed millions of dollars in renovations on the Lincoln Memorial Reflecting Pool to make it American flag-blue, residents and online users noted it had turned a phosphorescent green.

Here’s why:

The calm, still waters of the Reflecting Pool make it an ideal nursery for algae growth. Algae need nitrogen and phosphorus to grow, and the Reflecting Pool is primarily fed by the Potomac River, which gets heavy doses of those nutrients from nearby urban and agricultural lands.

The Potomac also absorbed one of the largest sewage spills in U.S. history earlier this year when a pipe burst five miles upstream of Washington, although that event probably happened too long ago to contribute to the algal bloom today.

Untreated sewage is high in nitrogen and phosphorus. When nutrient levels are high, feasting algae can quickly reproduce.

The Department of the Interior said when the algae first appeared that it was “residual,” from the supply lines to the pool.

Experts also speculate that the darker blue color may be helping the Reflecting Pool absorb more heat. The higher temperatures promote algae growth by allowing their metabolisms to shift into overdrive.

Summer temperatures in D.C. aren’t helping. This week, temperatures are as high as 95 degrees in the city, prompting a heat alert.

The combination probably explains the excessive growth, turning the water surface an opaque green and preventing onlookers from seeing the new blue hue of the concrete basin.

Algae are important and beneficial organisms when the ecosystem is in balance. They’re the base of the aquatic food chain, fed on by herbivores of all shapes and sizes, including shrimp and juvenile fish, which in turn feed organisms higher up the food chain. The single-celled organisms use the power of the sun to produce energy through photosynthesis, similar to houseplants on your balcony.

In an effort combat the algae in the Reflecting Pool, employees of the National Park Service were seen pouring in gallons of hydrogen peroxide, a chemical commonly used in pool maintenance.

The Department of the Interior also is employing a “high-tech nanobubble ozone technology” to destroy the cells of the algae.

Ozone — yes, the same irritant that is in smog — is a gas composed of three oxygen molecules, and the small size of the bubbles allow the most gas transfer into the water, where it can damage algal cells, similar to how it irritates our lungs.

This only treats the symptoms, however. Generally, ozone nanobubbling is effective as a temporary solution for algae blooms. Longer-term fixes would have to address what makes the Reflecting Pool so ideal for algae, such as its depth, darker color and inflow of nitrogen and phosphorus.

In California, ozone nanobubbles also have been used in a project to improve water quality in the Tijuana River. The 120-mile river that runs near the border in northern Mexico and Southern California was the site of a pilot study in 2025. The U.S. section of the International Boundary and Water Commission reported that the nanobubbling reduced “odors and bacteria,” but the project concluded prematurely after a flood swept some of the instrumentation into the river.

WASHINGTON — President Trump’s remodeled Lincoln Memorial Reflecting Pool with its “American flag blue” bottom has turned chartreuse from an algal bloom that park service workers struggled to address Tuesday just days after its more than $14 million renovation.

The Washington Monument is once again visible in the refilled pool, but Trump’s vision of an azure expanse between the D.C. landmarks has been complicated by the harsh realities of chemistry and biology known to any backyard pool owner. The work has been confounded by the unique challenges posed by the scale of the structure, bigger than 10 Olympic-sized pools — which Trump has called a lake — and the source of its water: the often-fetid Tidal Basin.

Algae has plagued the site since it opened more than 100 years ago, but Trump set his sights on addressing it as part of his aggressive push to beautify Washington as the country approaches its 250th anniversary. Contracts worth at least $14.8 million have been awarded for the project, announced in April by Trump, who said he was inspired by complaints from a friend visiting from Germany who called the pool dark and disgusting.

Teams of National Park Service employees and contractors deployed chemicals and ozone nanobubbles Tuesday in a bid to keep the algae in check, not dissimilar from efforts to clean the pool before Trump’s renovation kicked off.

“What do you expect?” asked Cochise Wanzer II, president of the Pool Service Company in Arlington, Virginia. “You’re basically taking natural, untreated river water, pumping it in and expecting it to do something different from what it would do out in the open.”

And the new coat of paint on the bottom of the pool has added an additional twist to ensuring the cleanliness of one of Washington’s most memorable destinations: “Now that the bottom is nice and dark, it elevates the temperature and the algae grows better,” said Wanzer.

The chemicals and ozone nanobubbles — a water purification treatment used to avoid some harsh chemicals — were one part of the effort underway to clean the Reflecting Pool. Workers used a swimming pool-type vacuum cleaner to suck up algae from the bottom, leaving behind clean patches of American Flag Blue paint adjacent to enormous swaths of green algae in a pattern familiar to anyone who has ever vacuumed a carpet before.

The park service said in a statement it is also using hydrogen peroxide, a milder treatment than chlorine and one used in spas and natural swimming pools. “There are no harmful side effects to marine life or to the environment,” it said.

As the mitigation work continued, a contractor took off his socks and shoes and rolled up his pants to his knees and proceeded to wade into the pool to place an ozone nanobubble tube as tourists and locals milled about on a sunny morning.

Rick and Ariana Pettit, a couple from Las Vegas who are road tripping in their RV across the United States, posed for photos at the iconic site of protests and marches as cleaning continued. Dressed in American flag-themed leggings and a Make America Great Again leotard, Pettit remarked to her husband, attired in an “Veteran for Trump” American flag button-up: “Look, it’s already looking more blue.”

Wanzer was blunt in his assessment of what it would take to maintain the pool as an algae-free space: “They may want to drain it, hose it all down, and start from the beginning with fresh water and treat it as the water comes in.”

Vogel and Martin write for the Associated Press.