Didymosphenia geminata (Didymo for short) is a single-celled alga that grows at an alarming rate. As it grows, it kills fish; threatens rivers and streams; sprouts tendrils; and, ends up looking like an environmental nightmare (which it is!).
Fishermen and biologists around the world have nicknamed this algae “rock snot”. Disgusting name for a disgusting alga.
Didymo was first confirmed in New York two years ago, according to the NY Times, but it's already made its way to some crucial streams and waterways. Unfortunately, this alga is very robust and easily transportable. All it takes is one cell on a fisherman’s waders to pollute an entire stream. Didymo seems to travel extremely well on the felt-soled waders that are so popular with fishermen everywhere. Fishermen are being encouraged to switch to rubber-soled waders and to clean their waders with bleach after every fishing expedition or stream change. Boaters are being requested to keep their hulls as clean as possible so Didymo cells don’t hitch a ride. In a warm damp environment, cells can live for 90 days!
Treehugger says this about the 2004 Didymo invasion in New Zealand:
Since being found there, it has spread to more than 120 rivers and streams on South Island. Blooms there have severely reduced fish populations and turned wild streams into sludge pits. Scientists believe that a fisherman from North America who packed his damp waders in a bag might have flown to a remote stream in New Zealand with the tenacious Didymo piggybacking on his boots. Once back in water, it made itself at home.
Now it’s a mere 180 miles from New York City. If the city cannot stop it, it is capable of doing more damage than just decimating fish populations. It is capable of clogging water intakes and pipes with the potential to meddle with plumbing and water transportation.
The stuff is such a menace that if you knowingly transport Didymo in New Zealand, you could face up to 5 years in prison.
The US Environmental Protection Agency has labeled Didymo an invasive species. Similar to most invasive algae, Didymo has the potential to bloom in thick masses and fully blanket the bottoms of streams — threatening the ability of other aquatic species to survive by smothering all possible food sources.
According to biologists who've studied it, there are no easy ways to eliminate it: the only solution is hindering its spread. This will be no easy task considering a single cell is enough to eventually choke out an entire river and the cells can live up to 90 days out of their original environment.
Of great concern to scientists also is the fact that Didymo was once a rare species; but, its numbers have grown exponentially over the last few decades. Traditionally a resident of high-altitude, low-nutrient rivers, the algae has now become ubiquitous in rivers in Missouri and Arkansas, leading many to wonder what factors have helped spark its spread. Some suspect drought, dammed rivers and changes in sunlight may play a significant role.
The following information and video has been taken from YouTube.com in its entirety:
In autumn 2006 ASF (Atlantic Salmon Federation) researchers discovered another risk for salmon rivers - the diatom Didymosphenia that creates a thick oxygen-reducing mat on the floors of streams. There is still no evidence whether or not it jeopardizes the nests and later growth of juvenile Atlantic salmon in the river. By 2009 there was "cautiously" less concern, and more of a "wait-and-see" approach - monitoring its presence and impact. But it has not, to date, overwhelmed any of our Atlantic salmon rivers.