Updated: Monday, 1:12 p.m.
On Friday, a green-ish scum began forming in places along the banks of the Ohio River. At the time, the executive director of the Ohio River Valley Sanitation Commission (ORSANCO) wasn't concerned, but that changed this weekend.
On Saturday, the Kentucky Division of Water urged caution for recreational use of the Ohio River. The DOW issued the warning to avoid direct contact based on the sighting of algae, cyanobacteria cell counts and cyanotoxin screening results.
And The Great Ohio River Swim was postponed until Oct. 13 because of the algae.
Richard Harrison says ORSANCO personnel first took samples of the algae on Thursday. "There were lower levels of toxins in the results," he says of those tests. The samples they took Friday weren't available until later.
Algae is almost always present in the Ohio River but sometimes it explodes in what's called an algal bloom. There was one in the Ohio River in 2015. Earlier this summer, algae without signs of a bloom was blamed in the deaths of dogs in North Carolina.
When that happens, "the states may issue precautionary advisories or actually contact recreation advisories," Harrison explains. "What we're looking at are levels in the river that might come into play with recreation."
On Friday, Harrison said conditions were favorable for a bloom. "We've had a pretty long period now of warm, dry weather. If you notice the river is very clear, which allows sunlight to penetrate which helps with the growth or formation of algae blooms."
Whether the bloom grows is hard to predict. "We're seeing indications of algae activity really in different places all up and down the river. Conditions are really favorable right now," he says.
The most up-to-date information can be found at ORSANCO's website, which has links to each member state's EPA page.
This article was first published on Friday, Sept. 20 and has been updated.