The Ohio River is free from harmful levels of toxic algae after more than a month of recreational public health advisories, according to the Kentucky Energy and Environment Cabinet.
The cabinet lifted recreation public health advisories along the Ohio River on Thursday after recent water samples showed a decline in toxic algae.
The algae first formed in late September when drought conditions paired with hot temperatures produced blooms along a 300-mile stretch of the Ohio River. The blooms resulted in the cancellation of the Great Ohio River Swim in Cincinnati and the swimming portion of Louisville’s Iron Man Competition.
“We’ve been testing for more than a month and after the Iron Man competition we’ve continued to test to make sure that we could tell people, recreational users of the river, when they could safely return,” Mura said. “And the algal blooms have finally cleared up.”
Blue-green algae can produce a toxin known as microcystin that’s harmful to people, and especially to pets. When touched or consumed, the toxin can cause stomach pain, nausea, vomiting and other health effects.
The algal blooms were growing throughout the river, often appearing as green, paint-like scum on the surface. The highest sample seen this year was greater than 5,000 micrograms per liter on October 9 in Madison, Indiana. That was 625 times higher than the recreational advisory threshold in Kentucky and Indiana.
But recent wet weather has helped return the river to normal, Mura said.
“We’ve had more flow because of the rains and we’re not getting the intense sunlight and heat we were getting that caused these blooms,” he said.
Kentucky officials said that although samples are below the hazardous concentrations, people should still avoid waters with visible algal blooms.
Hundreds of miles of the Ohio River are still contaminated with unsafe levels of toxic blue-green algae, though seasonal changes have helped to improve conditions over the last week or so.
Drought conditions across the Ohio Valley in September helped fuel the growth of harmful algal blooms. The algae led organizers to cancel the Great Ohio River Swim in Cincinnati and the swimming portion of Louisville’s Iron Man competition earlier this month.
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.
Though the recent rain has helped the Ohio River avert a possible harmful algal bloom, a handful of Greater Cincinnati agencies continue to monitor the river for the presence of the toxic scum-like organism that can potentially kill fish and other wildlife.