That’s what’s happening right now in Ketchum Cove on Grand Lake in northeastern Oklahoma. People should avoid the bloom, and residents should not consume water from that area of the lake.
The Grand River Dam Authority confirmed the presence of a blue-green algal bloom at the lake last week. Over the weekend, they determined that the water around the bloom contained harmful levels of toxins and said that lake goers should be careful to avoid the bloom.
An algal bloom occurs when abnormally high levels of algae accumulate on the surface of a lake, pond or ocean.
“The algae cells are always there, just generally at low concentrations,” said Dr. Andy Dzialowski, an aquatic zoologist at Oklahoma State University. “A bloom is when they increase in abundance.”
These blooms often look like paint floating on top of the water, but they’re not necessarily as blue-green as their name suggests. They can appear blue, green, brown or even red.
Not all algal blooms are harmful to people. Blue-green algae can release chemicals that cause rashes, induce nausea and even impact neurological function, but they don’t always produce enough to be dangerous.
“We don't have a good understanding of what environmental conditions may influence it, when they’re produced or how much is produced,” Dzialowski said.
On Saturday, the water around Grand Lake’s current bloom contained almost 17 micrograms of toxin per liter—over twice the Environmental Protection Agency’s recommended limit. The EPA recommends people avoid any contact with water containing more than 8 micrograms per liter.
The Grand River Dam Authority is urging lake goers not to touch water near the bloom in Ketchum Cove. Residents should not consume water from that part of the lake; boiling water might kill algal cells, but it does not remove toxins. People should make sure children and pets do not swim in or drink water that looks like it might contain blue-green algae.
The Grand River Dam Authority was quick to confirm the presence of the blue-green algal bloom after it was first spotted Wednesday morning. But not all lake managers have the resources to monitor so closely.
“It costs a lot of money,” Dzialowski said. “You can't just go out and say, ‘Oh, it's green, there's a bloom.’”
To determine whether there’s a bloom, the municipality or state agency that manages a lake would need to pay a lab to measure how much algae is present. Then they have to run more tests to measure toxin levels and determine whether the bloom poses a danger to people.
Sometimes blooms are stealthy. An algal bloom might cause rashes one day and then mix back into the lake water by the time someone comes to collect a water sample. This can add another layer of difficulty to identifying harmful blooms, Dzialowski said.
Because it’s so tricky to officially diagnose a harmful algal bloom, Dzialowski recommended that people enjoying lakes and ponds across the state keep an eye out for gross-looking surface scum.
“If the water doesn't look safe, it probably is good to stay out of it.”
