Yes, there is such a thing – and grab a big tissue, because it is spreading!
An invasive single-celled algae, affectionately known as Rock Snot, more politely known as Didymo, and scientifically known as Didymosphenia geminata, is spreading into cold water streams and rivers in North America and New Zealand. Until the last two decades, it was only found in N. American and European mountain streams, but now it is moving into lower elevations. And nobody knows how to get rid of it.
Like a true invasive, rock snot is very successful in its new environments. Big problem for fishermen who get rock snot tangled in their lines and equipment. Also a nuisance for swimmers. Rock snot changes the types of macroinvertebrates (bugs) found in a stream and is a potential problem for fish that lay eggs on stream bottoms.
Rock Snot is easily spread by humans that don’t wash their boats or completely dry out waders, fishing or recreational equipment when they move waterways. Don’t be a snot spreader! Wash and dry your stuff.
See these recent news stories about Rock Snot: