Blue-green algae returns to Lake Okabena
WORTHINGTON -- A walk along Lake Okabena's Sailboard Beach Wednesday night yielded some rather impressive views of the lake's first significant algae bloom of the season, but by Thursday morning -- thanks to a shift in the wind direction -- the green muck had moved across the lake to settle in the area around Ehlers Park.
The bloom comes at a poor time, just when people are gearing up for Fourth of July celebrations, backyard barbecues and a little lake-inspired fun on jet skis and ski boats.
And then there is the impact to fishermen, whose lines and lures seem to be a magnet for the little green bacteria.
Algae blooms this early in the season are usually short-lived, according to Okabena-Ocheda Watershed District Administrator Dan Livdahl. Still, he said people should take precautions to stay clear of the bacteria-laden areas of the lake.
"When we have an algae bloom where it's blue-green or dark green -- that pea soup color -- and the water looks bad near the shoreline, people should keep themselves, their children and their pets out of the water," Livdahl said. "The algae blooms can develop toxins, and if pets ingest the water, they can get very sick or die."
It isn't quite as serious for people, although those with sensitive skin could develop a rash, and throat or nose irritation is possible if any of the affected water is ingested.
"Generally, people won't swallow enough of the water for it to be a very serious issue," Livdahl said.
While evidence of an algae bloom on the lake became most evident on Wednesday, Livdahl said he noticed signs of a bloom earlier this month.
"The algae have been growing for the last couple of weeks faster than we'd expect it to grow in a normal June," he said, adding it came to a critical point on Wednesday. "On Saturday night, the east end had a lot of clumps of algae and the western two-thirds was clearer."
The typical peak time for algae blooms on Lake Okabena is August through September. Last year, the largest bloom occurred in September, spawned primarily by a large rain event in July that funneled lots of dirt and nutrients into the lake.
This year's early bloom is likely the result of large rain events in May.
"The rain came at the worst time for erosion and sediment transport toward the lake," Livdahl explained. "The fields were bare and a lot of tillage had occurred."
The soil particles carried by washouts in farm fields ended up in streams and ultimately traveled through Whiskey Ditch and into Lake Okabena. Livdahl described the scene in May as "a plume of sediment coming in."
"Our algae blooms really are dependent on the amount of runoff that comes into the lake, along with other pollution," he said.
Livdahl cautioned farmland isn't the only contributor to nutrients getting into the lake to spawn algae growth. The habits of urban dwellers also impact the lake's health.
"We have grass clippings and nutrients from people's yards and dust and dirt from streets that get into the storm sewers," he said. "I think one of the problems with asking people, whether they be farmers or urban people, to manage their land in a way that keeps pollution out of the waterways (is that) people look at what's coming off their property and say, 'That's so little that it doesn't matter. It's just a few grass clippings or it's just a little gully, it's not going to cause a problem.' The problem is that adds up -- city-wide or watershed-wide -- and becomes a bigger problem."
Efforts in the Okabena-Ocheda Watershed District, Livdahl said, are working. Much of the land along Okabena Creek is planted in filter strips, the sedimentation pond northwest of town helps to keep nutrients from being carried downstream and educational programs for urban landowners are helping, he shared.
"We are getting cleaner water during normal rain events," Livdahl said. "In years when we have small amounts of runoff coming into the lake, the water quality is better. The last two years we've had a lot of runoff coming into the lake and the water clarity has been quite poor.
"As long as people are using the landscape, there will be some pollution getting in the lake," he added. "We just have to find ways to continue to farm and live here without contributing extra pollution."
With in-lake treatments to reduce algae blooms expensive and not guaranteed to be effective, getting people to do their part to reduce pollution is the best option. That includes keeping storm sewer grates clear of grass clippings, dirt, debris and chemical run-off, such as the soaps from washing cars in driveways and streets.
Now the algae bloom has already occurred on Lake Okabena, there really isn't anything people can do but wait for it to clear up.
That may take a while if the winds stay calm and the heat continues.
"This hot weather that we have right now is really conducive to the algae growth," Livdahl said. "Algae likes warm temperatures, it likes still water or light winds and high nutrients. If we keep those conditions over the next week or so, we'll have a greater algae bloom or more algae than we hope for."
On the flip side, winds and waves will help to disperse the bacteria away from the shores and cause it to decay over time, reducing the potential for the rotten egg smell often produced by dying algae on the shoreline.
While the smell alone is enough to keep people out of the water, Livdahl said, "if it looks bad, don't swim there. Things may be different tomorrow."
Daily Globe Reporter Julie
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