A toxic algal bloom is putting a damper on Fourth of July festivities at Lake Powell, one of the Southwest’s most iconic recreation destinations. The National Park Service recently confirmed elevated levels of harmful cyanotoxins in the Arizona portion of the lake, specifically near Antelope Canyon.
Lake Powell, which stretches 186 miles across the Glen Canyon National Recreation Area, straddles the border of Arizona and Utah and attracts millions of visitors annually. In 2023 alone, the area welcomed 5.2 million tourists. This year, however, park officials are urging caution due to potentially dangerous water conditions caused by cyanobacteria, often referred to as blue-green algae.
According to the Park Service, cyanotoxins found in the water are approaching the upper limits of what is considered safe for human exposure. These toxins can pose health risks to both people and animals. Though severe health reactions in humans are relatively rare, symptoms may include rashes, respiratory irritation, stomach issues, and in more extreme cases, liver or kidney damage. Ingesting or inhaling contaminated water is the most common route of exposure during activities like swimming, boating, or water skiing.
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Microcystin, the most common cyanotoxin, is particularly hazardous. It’s recognized as a potent liver toxin and is also suspected to be a human carcinogen. Officials advise anyone experiencing symptoms such as vomiting, nausea, unexplained illness, breathing issues, or seizures after exposure to seek medical attention immediately. The toxins can also be fatal for pets or livestock if they drink from the contaminated lake.
While Lake Powell remains open for recreational use, the Park Service warns against swimming in or boating through areas where algal blooms are visible. Stirring up the water can release toxins into the air, increasing the risk of inhalation.
This isn’t the first time the lake has battled algal blooms. Similar conditions were recorded last fall, and experts say climate change is making such blooms more common and more severe. Rising temperatures and stagnant water create ideal environments for cyanobacteria to thrive. Add in nutrient-rich runoff from agriculture or development—especially nitrogen and phosphorus—and you have a recipe for rapid bloom growth.
Lake Erie in the Midwest has also seen a spike in harmful algae events. Gregory Dick, a biologist at the University of Michigan, says warming waters have extended the life cycle of blooms there. He pointed to a 2022 event that lingered into November—an unusually long duration for a freshwater bloom.
In response, Michigan officials are working on strategies to reduce nutrient pollution that fuels these outbreaks. Despite these efforts, rising air and water temperatures continue to make the problem worse.
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The National Park Service emphasized the importance of awareness and personal responsibility. “Warm, still waters combined with excess nutrients create the perfect environment for cyanobacteria to flourish,” officials stated. Swimmers and boaters are urged to avoid visibly discolored or scummy water and report any sightings of potential blooms.
As climate conditions intensify, harmful algal blooms are expected to become more frequent and widespread, posing growing challenges for water recreation, wildlife, and public health across the U.S.
