Deadly bacteria have perfect conditions for outbreaks

Bacteria tend to grow in warm conditions, and between 1985 and 2009, lakes and ponds warmed at a rate of about 0.6F (0.3C) per decade. This change increases the risk of flowering in historically cold sites. The bacteria can cause a number of symptoms, including blisters, rashes, diarrhea, muscle weakness, and liver damage, to name a few. Outbreaks can also tax ecosystems.

Everything comes at a price: In the US alone, preventing and treating harmful cyanobacterial blooms cost more than $1 billion between 2010 and 2020, and the figure is likely to rise due to global warming.

Heavy rain often provides “fuel and supplies” for bacterial spikes, according to Kaitlin Reinl, a limnologist at the National Oceanic and Atmospheric Administration. Stormwater encourages bacterial growth by washing phosphorus and nitrogen into lakes and rivers, where heat waves can lead to bacterial and algal growth.

“Basically, temperature accelerates everything,” says Hans-Peter Grossart, professor of aquatic microbial ecology and biodiversity at the University of Potsdam. “The balance of carbon dioxide in the water has been altered because we now have higher concentrations of CO2 in the atmosphere. The greenhouse (effect) increases the concentration of nutrients (for example the presence of phosphorus and nitrogen in the water) and the concentration of CO2.”

One of the most common bacterial threats to water quality is diarrhea E. colithat thrive in warmer conditions: Every 1C increase in average monthly temperature increases its incidence by 8%.

Cyanobacteria – called blue-green algae – also thrive in high heat. When algae decomposes, it releases harmful toxins that cause respiratory and gastrointestinal problems, as well as skin and eye irritation. More extreme impacts include seizures and liver damage, and the algae can even kill pets and wildlife, according to the US Centers for Disease Control and Prevention.

In historically warm climates such as Florida, precipitation is the biggest factor causing cyanobacterial blooms. But rising temperatures are affecting waterways in colder climates that are not typically associated with cyanobacterial blooms. Massachusetts hit a season high with 55 beach closures since Aug. 16, 87 percent of them due to bacterial growth, according to the state’s Interactive Beach Water Quality Dashboard. The Vermont Cyanobacteria Tracker currently lists over 40 active alerts.

Even Lake Tahoe, famous for its clean waters, showed warning signs of toxic algae blooms earlier this summer. While these concerns were a false alarm, the risk of a real outbreak hangs over the lake. Algal blooms have become a growing problem in recent years, and dangerous toxins have been detected in a pond on the shores of Lake Tahoe Nevada, although it was not connected to the lake.

“The 1.4 degree increase in annual water temperature is impacting parts of the lake that we thought would never be a problem,” says Jeff Cowen, public information officer for the Tahoe Regional Planning Agency.

It also threatens Tahoe’s $5.1 billion in annual tourism revenue, which accounts for 60 percent of the area’s economy, according to Cowen. While Tahoe can mitigate any potential summer problems with its prolific winter ski season, many lakefront economies depend on visitors flocking there to take a dip on hot days.

Adam Gufarotti, community outreach manager for the city of Lake Elsinore, says harmful algal blooms are a major concern. As the largest freshwater lake in Southern California, Elsinore attracts visitors from all over the region. But in 2022, the lake was closed for six months due to a dangerous bacterial bloom. The city lost $300,000 in lake use fees alone. Gufarotti noted that the tax was even higher for local merchants dependent on tourism revenue.

To prevent a repeat, Lake Elsinore began a $2 million investment in February to pilot what is known as nanobubble technology from Moleaer Inc. By injecting the lake with pure oxygen, Moleaer’s nanobubble barges increase lake levels of the element and limit the release of phosphorus that allows bacteria to thrive. The lake purchased two more barges in June.

But technological solutions for large bodies of water remain few and far between. Gufarotti says new water quality solutions are constantly being proposed, but many can’t handle a lake the size of Elsinore. “Most of the time, the largest body of water they’ve cleaned is an acre or 50 acres. Lake Elsinore is 3,000 acres,” he says. The cost of using these technologies at that scale can be prohibitively high, with some startups asking for tens of millions of dollars.

Ultimately, the best strategies for reducing the risk of harmful bacteria are to reduce nitrogen and phosphorus pollution to reduce algae fuel needs and reduce emissions. Failure to do so could leave tourism-dependent communities at a trickle.

“The beauty of the lake, the quality of the scenery, the blue and the clarity is what draws people in the first place,” says Cowen of Tahoe. “But it goes beyond that: here, the economy is the environment, and the environment is the economy.”

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