Rock snot is the not-so-sexy name of a slimy goop that can be found clinging to rocks in streams of the Northeast.

And until recently, it was treated as an invasive species, which led the state Department of Environmental Conservation to recommend that anglers not use felt-soled waders. Anglers could also bleach or freeze the felt to help prevent the spread of the algae.

While many know it as rock snot, Didymosphenia geminata is a microscopic algae, or diatom, that can form thick brown mats on stream bottoms. Several recent studies have determined that the algae is native to the waters of the North America, and has been found on every continent except Antarctica, Africa and Australia. A study published in 2014 in the journal Bioscience found that didymo is native to New York, Pennsylvania and Quebec.

Another study published that same year in Canada showed that the algae is native to eastern Canada, an area that the Adirondacks has much in common with, ecologically speaking. That study, which was published in Canadian Journal of Fisheries and Aquatic Sciences, found that didymo had been present in Canada since at least the 1970s, and that recent large blooms had less to do with the algae being invasive, and more to do with a changing climate.

The findings of these studies are already having a practical impact on fishermen and policy.

“Didymo was once thought to be a recently introduced invasive algae species, but recent research has revealed that it is actually native to Vermont and other regions of North America,” a statement on the Vermont Fish and Wildlife website says. Vermont announced last month that it would lift its ban on felt-soled waders, effective July 1.

“Although felt-soled waders and boots can once again be used in state waters, the Vermont Fish & Wildlife Department is asking anglers and other water recreationists to thoroughly clean and dry all of their equipment after leaving any water body before going to another,” the statement goes on to say.

Shawn Good, a state fisheries biologist for Vermont, said the felt-soled waders can still transport invasive species, and angles should be careful to treat the felt properly.

“While some invasives are easy to see such as Eurasian milfoil stuck on a boat trailer,” Good said, “others are too small to be noticed, such as spiny waterflea, larval zebra mussels, or viruses and bacteria that cause fish diseases.”

The New York State DEC did not implement an outright ban on felt-soled waders, but does ask anglers to avoid using them.

“Didymo is currently listed as a prohibited invasive species in New York State,” DEC spokesperson Benning DeLaMater said in an email this week. “As future revisions to the list of prohibited invasive species are undertaken, we will consider any changes to the state’s regulation of this species at that time.”

“The primary way for didymo to be spread is by anglers, kayakers, canoeists, tubers, boaters and others engaging in water-based recreation can unknowingly spread didymo,” the DEC website says. “The microscopic algae can cling – unseen – to waders, boots, boats, clothing, lures, hooks, fishing line and other equipment and remain viable for several weeks under even in seemingly dry conditions.”

Although didymo has been found in several streams and rivers in the southern and central parts of the state, there have been no blooms locally. But DEC warns that there is no way to control or eradicate didymo once it has become established.

Didymo can have a negative impact on streams, even though it is a native species. The DEC says that it can harm fish habitat, and can even cause difficulty for anglers if it gets thick enough.

“Unlike many other aquatic invasive plants, didymo grows on the bottom of both flowing and still waters. It is characterized by the development of thick mat-like growths (blooms), which can last for months, even in fast flowing streams,” the DEC says. “During blooms, these mats may completely cover long stretches of stream beds, altering stream conditions and choking out many of the organisms that live on the stream bottom, which can affect trout and other fish by limiting their food. For the recreational user, footing can become very difficult due to the heavy growths.”

While the algae may be native to the state historically speaking, the algae is “snot” something to mess around with.