"It might go all the way to Trenton," said National Park Service biologist Rich Evans.

This expanded range of rock snot was only confirmed in the past couple of weeks, and Evans said it's because of a change either in the environment or in the organism itself.

Didymo covers rocks like a sort of shag carpet, but has thrived best in colder waters than the stretch of the Delaware where it has now taken up residence.

It is that carpet-like growth, according to Evans, that keeps some fish species from laying their egg sacs on underwater rocks, and prevents caddisfly eggs from attaching to those same rocks as well.