|
Diaspora of once-rare algae may threaten fish survival
Prolific diatom can carpet many kilometres of river bottom
|
Hanneke Brooymans |
The Edmonton Journal |
EDMONTON - It can't be good when something nicknamed "rock snot" is multiplying in Alberta.
Andrea Kirkwood doesn't have anything positive to say about the algae that is spreading through the province's rivers. Not only does it look gross, it could threaten the survival of fish and other aquatic life.
The University of Calgary algal ecologist first noticed what she describes
as an unfamiliar, disgusting-looking growth on rocks in the summer of 2005 while participating in a major survey of the headwater rivers of the South Saskatchewan River basin.
When she put it under the microscope, she saw a type of single-celled algae called a diatom. She set it aside.
But then it started popping up in other areas of the northwest. And most astonishingly, it showed up in New Zealand, where it had never been found before.
Kirkwood looked at Didymosphenia geminata -- didymo for short -- with renewed, more focused interest.
What she discovered, and with colleagues recently published in the Canadian Journal of Fisheries and Aquatic Sciences, is a cosy relationship between didymo and dams.
The dam connection and the algae's unusual preference for clear water has caught the attention of governments.
"It's really on the national radar now because it does so well in pristine systems, which is such an unusual characteristic for algae," Kirkwood says.
"Usually you think of lakes that are pea-soup green because there's so much nutrients in the water the algae grow like gangbusters. But this particular organism actually likes clear, clean, low-
nutrient conditions."
Kirkwood says it seems to thrive when water flow is regulated, which is why it's often found below dams. The algae blooms so well it sometimes covers kilometres of river bottom.
This could be a problem for trout, which like clean, clear, cobble-bottomed rivers.
"When didymo blooms ... rather than seeing nice clean rocks, you're seeing shag carpeting."
The insects the trout eat hide under the rocks and gnaw on the algae growing on the rocks. If didymo covers their food and habitat it could have a domino
effect on the fish, she says.
She hopes to get research money to study the impact didymo might be having on fish in Alberta.
There is some urgency in establishing the nuts and bolts of the algae's biology, because in 2006 it was suddenly discovered far east of Alberta in Quebec and New Brunswick.
Jet-setting fly fishermen are inadvertently moving the microscopic material around on the bottom of their boots or other gear, she says.
Although scientists think this is how the algae moved as far afield as New Zealand, they remain puzzled about why the bumper crop is happening now.
When taxonomists -- scientists who classify organisms into groups -- first arrived in North America about 150 years ago, didymo was already here.
Back then its range was widespread, but there was little of it.
"In fact, for people who are real geeks and love to collect specimens, didymo was a prize because it was so hard to find," Kirkwood says.
"But now that's not the case. So something has happened to change its growth behaviour from being rare to one that completely inundates kilometres and kilometres of river bottom."
Didymo first started doing this on Vancouver Island 20 years ago, while the European variety has been behaving this way for at least 100 years, she says.
"It's suggested that perhaps there was a genetic event that occurred that changed the behaviour of the North American specimen."
Now it blooms in huge mats.
"I've always joked that if we could turn it into some kind of resource we can maybe make sweaters or something, because it really does feel like wet wool when you're handling it."
Kirkwood says when it dies, sloughs off rocks and builds up along riverbanks, it looks like used toilet paper.
That's how Alberta Environment first found out about it, she says. People were asking if there was something wrong with nearby sewage treatment systems.
The full range of the algae in Alberta has not been scientifically established. Other researchers have reported seeing didymo in the upper reaches of the North Saskatchewan River, she says.
Scott Millar, a professional biologist with Alberta Sustainable Resource Development, confirms this and adds it has also been reported in the Athabasca River and it may be even in the Yukon.
There will be a collaborative effort among academic and government
scientists to document these locations, he says. Alberta Environment collects river samples for various tests and will be asked to look for didymo as well.
Anglers can help stop it spreading farther by cleaning their boats and gear, Millar says.
hbrooymans@thejournal.canwest.com
|
