Have you seen this "rock"?

Didymosphenia geminata

Rock Snot or Didymo

Didymo is a species of diatom that grows in warm and shallow water. If it overgrows, it can form large mats on the bottom of lakes, rivers and streams. It is not considered a significant human health risk, but it can affect stream habitats and sources of food for fish and make recreational activities unpleasant. It is considered a nuisance organism or invasive species. The microscopic alga can be spread in a single drop of water.

Rock snot is a type of slimy, yellow-brown, freshwater diatomatious algae that, like a cold, has spread quickly from a small area on Vancouver Island.

t's now a "global invasive species," scientists say, spreading rapidly within B.C. and to locations such as Iceland, New Zealand and across North America including Alberta, Quebec and New Brunswick.

It looks like a shag carpet basically rolled out on the bottom. It's only when it's removed from the water that it looks "snotty"

While obnoxious looking, didymo isn't a threat to human health, but it can potentially alter food webs in rivers and could impact the fish. It usually invades pristine rivers and watersheds and is hard to miss under the water. Didymo needs a stable rocky bottom and stable water flows to do well.

There's also an economic and recreational impact. Didymo can slough off the bottom of the river during high water flow. When it dries on the river banks it often looks like dried-up toilet paper, causing people to think there's a sewage problem in the river. It greatly degrades the recreational experience.

Anything that moves water or microbes can spread didymo,.but

Experts agree the most common cause of the spread of didymo is on the bottom of the felt-soled hip waders of recreational fishermen.