SPICER –– Last fall when docks and boat lifts were pulled from Green Lake, there was just a handful of the tiny zebra mussels stuck onto the pipes and beams.
This year docks and lifts are covered with them.
“There are billions of them,” said Mike Schoffman, from Mike’s Dock and Yard in Spicer. “They are in every nook and cranny.”
Last fall his crews found about three zebra mussels on docks and boat lifts they were hired to remove for lakeshore owners on Green Lake.
“There were hardly any - about zero zebra mussels in Green Lake,” Schoffman said, who was shocked to see the clusters of zebra mussels on underwater structures this year.
“They are that prolific. That’s how fast they multiply,” he said.
Oscar Oakes, from Oakes Lawn Care, has a similar story to tell.
Last fall his crews saw maybe 15 to 20 zebra mussels - total.
“It was really minimal,” Oakes said.
His crews recently removed boat lifts from the north side of Green Lake, by the Olde Mill Inn, that are thick with zebra mussels.
Oakes and Schoffman said this fall they have not seen one single dock or boat lift without zebra mussels attached.
“It’s really exploded in population in one year,” Oakes said.
After the discovery in the summer of 2014 of a single adult zebra mussel in Green Lake, the state Department of Natural Resources did an intensive investigation and declared the lake infested.
Dave Coahran, supervisor for the DNR Spicer Area Fisheries office, said he was surprised how many adult zebra mussels that homeowners are finding this year.
“It’s more than I expected,” he said.
It’s hard to predict what will happen in another year in Green Lake, but according to the DNR, a female zebra mussel can lay up to 500,000 eggs in a year.
Coahran said he’s observed vegetation from Green Lake full of zebra mussel babies. A little larger than a grain of sand, Coahran said there are “a lot of tiny ones attached to vegetation out there.”
He said zebra mussel-infested vegetation “appears to be very widespread” in Green Lake and transporting even “a sprig of vegetation” could easily carry zebra mussels to another lake.
There are restrictions for transporting structures removed from infected lakes for winter storage.
Unless they are decontaminated - which is a service many dock-removal companies provide - structures must be out of the water for 21 days before they can be moved to another site.
The additional steps take extra time and money for the dock removal process, Schoffman said.
Many companies remove docks and boat lifts mechanically, but homeowners who do the job themselves could be sliced up by the sharp edges of zebra mussels attached to the pipes.
Oakes said he’s talked to residents who were “really scratched up on their forearms” from the zebra mussels.
Docks and boat lifts, such as the ones by Olde Mill Inn, can legally be pulled out of a lake and stored on a homeowner’s adjacent lakeshore property even if zebra mussels are still attached.
Both Schoffman and Oakes said people should be cautious before buying and selling lake equipment to make sure rules are followed to prevent the spread of aquatic invasive species.
Oakes said his observation of zebra mussels in other lakes has him hopeful that Green Lake won’t get too much worse. He said the lake’s sandy bottom may be an advantage because zebra mussels prefer rocks and other ragged objects to which to cling.
Coahran said his office will take a lot of samples of zooplankton and phytoplankton next year to study the effect of zebra mussels on the food source for young fish in Green Lake.
The study will be part of the DNR’s efforts to determine the long-term ecological impact of zebra mussels on the lake.
Kandiyohi County has an Aquatic Invasive Species Task Force and, with the help of local lake associations and volunteers, launched education and enforcement plans to limit the spread of zebra mussels.
Decontamination stations were set up to powerwash boats with hot water to kill zebra mussels, and extra law enforcement was hired to make sure boaters were following rules when entering and leaving lakes.
While there is little defense to stop zebra mussels from increasing once they get in a lake, so far zebra mussels have not been found in any other lakes in Kandiyohi County.
Meanwhile, Coahran said the DNR is keeping its eye out for another new culprit – the starry stonewort. The invasive grass-like form of algae has been found in nearby Lake Koronis.
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