The freshwater algae, officially called didymo, lives in low nutrient, low temperature environments that are common in North Shore streams and Lake Superior, the Minnesota Department of Natural Resources reported Thursday.

Under the right conditions, didymo can form dense mats of brown slime that smother stream beds and may affect stream invertebrates that are food for fish, birds and other animals.

In other regions of the U.S., and as far away as New Zealand, didymo has been devastating to local trout populations, and anglers are being warned to avoid spreading the algae to other Northland waters. In South Dakota's Rapid Creek, for example, didymo was discovered in 2005 and has since been blamed for a major reduction in the stream's brown trout population.

Didymo was confirmed in Lake Superior at very low levels in 2015 but had never before been seen upstream in rivers. At first thought to be an invasive species, didymo is now believed to be a native species always present in lower levels.

To read more from the original article follow this link to the Duluth News Tribune.  http://www.duluthnewstribune.com/news/4519220-trout-snuffing-rock-snot-confirmed-north-shore-stream