Low water levels, high temps fuel algae blooms on Lake Okabena
According to testing of water samples, recent blooms have not been toxic.
WORTHINGTON — After two years of nearly pristine waters, Lake Okabena has once again taken on a blue-green hue this month. The colorful algae blooms have been prominent on lakes across Minnesota this summer.
Okabena-Ocheda Watershed District Administrator Dan Livdahl said the algae growth can be blamed on a couple of things — a severe drought that has caused lake levels to drop, and rising summer temperatures that are, this week, slated to reach triple digits.
“We had a big bloom at the beginning of June and then the algae went away for about a month,” Livdahl said Monday afternoon. “In July, it’s been coming and going. If the water warms up on a sunny day and it’s calm, you get an algae bloom somewhere.”
What’s new this year is that the watershed district is collecting one-liter samples from popular lake spots like Centennial Park and Sailboard Beach and testing a milliliter of each sample for the presence of microcystin toxins. Microcystin algae is toxic and can be fatal to pets who ingest affected waters. It can also cause skin irritation or harmful reactions in humans.
Thus far, Livdahl has conducted three tests from Lake Okabena (twice from Centennial Park’s swimming beach and once from Sailboard Beach) and collected one sample from Lake Ocheda, which has had consistent algae blooms this summer. All of the tests revealed either no microcystin or levels below the testing limit, he reported.
Still, Livdahl encourages people to find other areas to enjoy when the lake is in the midst of an algae bloom. Rather than letting kids swim in the lake, let them play on the sandy beach and cool off in the splash pad at Centennial Park.
“When that water is thick green, that’s potentially toxic,” he said. “You should just stay out and certainly keep pets and kids out of the water. It’s not necessarily toxic, but you shouldn’t take the risk. It’s unpleasant.”
Livdahl said he has received some questions from local residents about the green scum-like substance in Whiskey Ditch. He inspected the area and found the ditch to have filamentous algae and duckweed. The algae there is again due to low water levels, while the duckweed is often seen in healthy water bodies. Livdahl said both work to clean up the water, and without them the ditch would also contain blue-green algae. Decaying blue-green algae creates an odor similar to rotten eggs.
“We’ve avoided this for about two years and we’re kind of back to normal conditions this year,” Livdahl said of the algae blooms. “The water in the lakes is warmer overall and on those calm, hot days you get the warmer water on the surface and that’s where you get those blue-green algae blooms. Any lake, with the warmth and the low water this year, you get that in abundance.”
He will continue to monitor the blooms and test as needed for microcystin toxins in the water. Earlier this year, the Okabena-Ocheda Watershed District authorized the purchase of 10 test kits specifically to monitor water for the dangerous toxins. Livdahl said he will focus testing efforts on Centennial Park and Sailboard Beach the remainder of the season.