Habitat Evaluation and Threat Assessment


Vermilion’s water chemistry sets us apart from most Minnesota lakes. Our low calcium and low pH make us low risk for zebra mussels. Our risk for Eurasian and hybrid watermilfoil and starry stonewort also appears to be low. However, until those risks are fully evaluated by researchers, both stay at the top of our Vermilion threat table.

While our soft water protects us from many game-changing invasives that plague central Minnesota and much of Wisconsin and Michigan, it can also expose us to other invaders no one is talking about. We are looking toward the Canadian Shield lakes to our north for information about AIS that prefer a soft water habitat. We don’t know what bad guys are lurking up there.

Our threat table – unchanged in the last year – looks like this:



Research is underway on hybrids between invasive Eurasian watermilfoil and our native northern watermilfoil. Anecdotal reports suggest increased invasiveness and evidence of herbicide resistance. In Lake Vermilion, native watermilfoil co-exists with other native vegetation. Invasive Eurasian watermilfoil has been in Lake Minnetonka for over 30 years, yet we know of none in Lake Vermilion despite considerable boat traffic between these two popular lakes – an indication our habitat and water chemistry may not be suitable. However, at this point, no one knows whether a specific hybrid genotype may find our habitat suitable and overwhelm our native vegetation.

The DNR’s 2019 discovery of zebra mussel veligers (larvae) at Lake of the Woods has important implications for Lake Vermilion. Both lakes have generally low calcium levels, well below the levels thought suitable for zebra mussel reproduction.

However, the Lake of the Woods discovery re-opens the question on whether zebras might conceivably get a foothold along East Two River before it enters Pike Bay. East Two River has relatively high calcium levels at certain times of the year when rainfall is low. As a precaution, volunteers resumed a comprehensive adult and veliger early detection plan on East Two River during 2020.