Invasive algae native to Nanaimo finds way to foreign waters
By Larissa Johnston, Postmedia NewsAugust 16, 2011
Didymo, invading algae from the Nanaimo area, has spread to foreign waters, thanks to felt-soled waders worn by travelling fishermen.
And even though the freshwater algae travels via soles, not the nose, it's better known as "rock snot." The species is native to Vancouver Island. It started to spread in the early 1990s, shortly after the introduction and widespread use of felt-bottom waders, said Matthias Herborg, a local aquatic invasive species expert with the B.C. Ministry of Environment.
Any gear used in different watersheds can carry the algae, but feltsoled waders that can retain moisture for several days and thus are especially prone to spreading species.
In 2008, felt-bottomed waders were banned in New Zealand, where rock snot is being carried because of a fishing tourism industry similar to Vancouver Island's.
When in the water, the so-called "snot" looks more like dog hair or shag carpet, Herborg said. The algae features thin, five-centimetre yellowish-brown strands.
It's not until the plant is out of the water that it resembles mucous.
That's a turnoff for recreational users expecting "nice, clean, fast-flowing rivers where people go to experience nature," Herborg said.
Instead, they find "these unsightly blooms" in what are traditionally flyfishing streams.
"It really decreases the natural experience," said Herborg.
That's the socio-economic impact.
But researchers don't have much information on the environmental impacts, he said.
"At the moment, there's a lot of uncertainty around didymo." The green algae cover rocks, affecting insects important to the ecosystem.
Large blooms could affect a stream's fish and food web, said Max Bothwell, a local research scientist and rock snot expert.
"However, the evidence for this is mixed and the effects of didymo on trout seem to depend on the species and the particular circumstances. There is no evidence that didymo blooms have harmed salmon populations anywhere in the world," he said. It poses no threat to human health.
There are museum records from the 1880s that show rock snot's presence on Vancouver Island.
"It was always there but it was never reported to be some sort of nuisance," said Herborg.
In the 1990s, scientists noticed thick blooms of the species suddenly popping up in various rivers around the Island.
Something, like water quality, must have changed to create these big blooms, but research showed no change in nutrient numbers, Herborg said.
"It's a big mystery." Over the next five to 10 years, scientists started seeing densities that hadn't been seen before.
From there it spread across the world, beginning in Iceland.
"The big thing was when it reached New Zealand in the mid-2000s - and from there it spread really rapidly," said Herborg.
A new finding in B.C.'s Kootenays region, where the species had never been reported before, created the recent uproar, said Herborg.
"And it has a catchy name: rock snot. People like that."
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