Harmful algae bloom in Ohio River could impact Louisville IRONMAN triathlon

A harmful algae bloom has formed in the Ohio River near Louisville, state officials announced Saturday, harming water quality two weeks before the IRONMAN triathlon.

Scientists detected the algae bloom near Towhead Island and the mouth of Beargrass Creek, just upstream from Waterfront Park.

Algae can thrive in waterways during warm, low-flow conditions and are often fueled by nitrogen and phosphorus pollution from agriculture, sewage and other sources.

Blue-green algae and cyanobacteria are a natural part of freshwater ecosystems and not all are toxic, but state scientists took samples from the nearby bloom on Aug. 1 and detected microcystin toxins harmful to humans and aquatic life.

Authorities issued a public health advisory over the weekend, warning people to avoid contact with the water. On Monday morning, algae was still visible on the surface of the water near Towhead Island.

If it continues, this toxic algae outbreak could once again derail the first leg of the upcoming Louisville Triathlon and highlight a legacy of water quality problems on the Ohio River.

In 2019, a similar algae bloom in the Ohio River led to the cancellation of the swimming portion of the 2019 IRONMAN Louisville race due to concerns about athlete safety.

Organizers called off the race in Louisville the following year, citing the COVID-19 pandemic. This year’s 70.3-mile Half IRONMAN, scheduled for Aug. 18, is the organization’s first event in Louisville since 2019.

It is planned to begin with a 1.2-mile swim in the Ohio River from the Louisville Community Boathouse to Waterfront Park, directly through the area currently affected by algae.

Race organizers did not immediately respond to a phone call or email about the water quality advisory.

It’s unclear how big the algae bloom will be or how long it will last, but scientists will continue to monitor it, the state’s announcement said.

Cyanobacteria can survive in “a wide range of conditions,” said Andrew Mehring, a professor in the Department of Biology at the University of Louisville.

But factors such as high water temperatures, low river flow and nutrient pollution (especially phosphorus) help algae “grow out of control,” he said.

Health risks from harmful algae blooms

Harmful algae blooms typically “appear as opaque, bright green paint blobs, but closer inspection often reveals the grainy, sawdust-like appearance of individual colonies,” according to the state Division of Waters. “The color of the algae may also be red or brown.”

People can be exposed to algae toxins by swimming or wading in contaminated water or by eating contaminated food or drinking water, according to the U.S. Environmental Protection Agency.

No toxins were detected in Louisville’s treated drinking water, and the state Water Division is working with Louisville Water Co. to monitor water quality.

Symptoms can include rash, irritation of the eyes, nose and throat. Ingesting the toxins can also cause stomach pain, vomiting, liver damage and other health effects, according to the Centers for Disease Control and Prevention.

The state recommended the following measures to stay safe from harmful algal blooms and avoid polluted waters:

• People should avoid activities such as swimming, wading, rowing, diving, jet skiing, and water skiing in affected waters that have a visible bloom, unusual color, or a layer of algae scum forming on the surface.

• People prone to respiratory allergies or asthma should avoid areas with harmful algal blooms. Children may be at particular risk.

• If contact has occurred with water containing visible blue-green algae, rinse with fresh water. In some cases, skin irritation may occur after prolonged exposure. If symptoms persist, consult your doctor.

• If fishing in affected waters, fish fillets (not organs) may be consumed after rinsing with clean drinking water.

• Prevent pets and livestock from ingesting or coming into contact with water sources where harmful algal blooms are present or suspected.

Reducing future algal blooms in the river will require a collective effort by the entire Ohio River watershed to limit nutrient pollution, Mehring said.

“We have to do our part here in Louisville by controlling stormwater runoff, picking up pet waste and using fertilizers responsibly,” she said. “But it’s also up to everyone in the Ohio River watershed to limit these things and use best management practices.”

Connor Giffin is an environmental reporter for The Courier Journal. Contact him directly at [email protected] or in X @byconnorgiffin.

This article originally appeared in the Louisville Courier Journal: Louisville IRONMAN: Toxic algae in Ohio River could affect swimming