Growing Bacterial Threat Puts US Beach Vacations at Risk

Beachgoers across the United States face an unexpected threat this summer as deadly bacteria fueled by climate change lead to widespread lake and river closures. Rising water temperatures and increased rainfall create ideal conditions for harmful bacteria, such as E. coli and cyanobacteria, to thrive, putting public health and local economies at risk.

In recent decades, lakes and ponds have been warming at an average rate of 0.6°F (0.3°C) per decade, significantly increasing the likelihood of bacterial blooms even in historically colder regions. These bacteria can cause various health issues, from rashes and diarrhea to severe conditions like liver damage. The impact extends beyond human health, as these outbreaks also disrupt ecosystems. Between 2010 and 2020, these outbreaks cost the US over $1 billion in prevention and treatment efforts—a figure expected to rise with ongoing global warming.

According to Kaitlin Reinl, a limnologist at the National Oceanic and Atmospheric Administration, heavy rainfall plays a crucial role in these bacterial outbreaks. Rainstorms wash phosphorus and nitrogen into lakes and rivers, which, when combined with heat waves, stimulate the growth of harmful bacteria and algae.

“Temperature accelerates everything,” notes Hans-Peter Grossart, a professor of aquatic microbial ecology at Potsdam University. He explains that the increased atmospheric CO2 and higher nutrient concentrations in water exacerbate the problem.

One of the most common bacterial threats is diarrheagenic E. coli, which sees an 8% increase in incidence with each one °C rise in monthly average temperature. Cyanobacteria, also known as blue-green algae, blooms under similar conditions, releasing toxins that can cause respiratory, gastrointestinal, and skin issues, with more extreme cases leading to seizures or liver damage. The US Centers for Disease Control and Prevention reported that these blooms can be fatal to pets and wildlife.

This summer, areas not typically associated with such bacterial blooms are experiencing unprecedented contamination levels. Massachusetts has seen a record 55 beach closures due to bacterial spikes, while Vermont’s cyanobacteria tracker has more than 40 active alerts. Even Lake Tahoe, known for its crystal-clear waters, has faced warnings of toxic algal blooms, though no significant outbreak has occurred so far.

Jeff Cowen, a public information officer at the Tahoe Regional Planning Agency, highlighted the economic risks posed by these environmental changes. “The 1.4-degree rise in annual water temperature is impacting parts of the lake we never thought would be a problem,” Cowen said, noting that Tahoe’s $5.1 billion annual tourism revenue, which constitutes 60% of the area’s economy, is at stake.

Lake Elsinore has been grappling with harmful algal blooms in Southern California for years. In 2022, a six-month closure due to a bacterial bloom cost the city $300,000 in lake use fees, with even more significant losses for local businesses reliant on tourism. To combat the issue, the city invested $2 million in nanobubble technology to inject oxygen into the lake and reduce phosphorus levels. However, scaling these technologies for large bodies of water like Lake Elsinore remains challenging.

Experts agree that the most effective strategies to combat harmful bacterial blooms involve reducing nitrogen and phosphorus pollution and lowering emissions to mitigate climate change. These measures are necessary for communities that depend on tourism to avoid dire economic consequences.

“The lake’s beauty, scenic quality, blueness, and clarity attract people in the first place,” said Cowen. “But it goes beyond that: Here, the economy is the environment, and the environment is the economy.”

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