Have you been concerned about didymo (a.k.a. "rock
snot"), the algae that seems to be slowly taking over waterways
throughout the northeast? A study from the University of New Brunswick,
recently published in the Canadian Journal of Fisheries and Aquatic Sciences,
offers both good news and bad news about didymo’s spread.
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| Didymosphenia geminata (www.mdinvasivesp.org) |
Didymo is an algae (technically, a diatom) that forms a
dense mat on the bottom of swiftly flowing freshwater rivers and streams. As its nickname implies, it looks a bit like a thick, gooey layer of mucous covering the bottom of streams and rivers. It
can smother other aquatic vegetation, reducing habitat for the aquatic
macroinvertebrates that fish feed on. In the past two decades it has been
identified in the waters of the U.S., Canada, New Zealand and Europe.
First, the good news. Especially for anglers and boaters. Up
until now, the conventional wisdom was that didymo was an exotic invasive algae
species that was hitchhiking between watersheds on anglers’ gear, especially
felt-soled wading boots, and on boats. State environmental agencies have
launched intensive educational campaigns urging anglers and boaters to wash their gear and let it dry thoroughly to prevent further spread of didymo.
Washing gear with a bleach solution was recommended. But according to the
University of New Brunswick study, anglers and boaters are not spreading
anything that was not already in their local ecosystems. So if anglers and
boaters are not to blame for the ooze of algae popping up in more and more
watersheds, what is going on? Sit tight for the bad news.
The didymo study looked at archival samples of lake sediment
from several regions in Canada, and they found that didymo has been in these
ecosystems for quite some time. Evidence of didymo can be found in the sediment
record back to the beginning of the 20th century and possibly even
the last decade of the 19th century. The researchers found that even
in ecosystems which did not necessarily have evidence of didymo, there were
increases in other algae species at approximately the same rate that didymo was
increasing in lakes where it was present. The researchers found that increases
in didymo and other algaes appeared to correlate with the warming climate. The
study leader, Michelle Lavery, said, "We can't make any solid claims as to
what the mechanism is that is favoring didymo, but we strongly suspect it has
to do with climate." So although anglers and boaters seem to be off the
hook for spreading didymo, the awakening of dormant didymo in bodies of water
potentially throughout North America by a gradually warming mean global
temperature would mean that we have little hope of preventing didymo from
appearing in a river near you. That’s the bad news.
So does this new view of didymo mean that anglers and
boaters don’t need to sweat about washing down their gear between destinations?
No. There are other aquatic nuisance species that are much better understood
than didymo that can hitchhike on our gear. Zebra mussels are one prominent
example. So keep scrubbing down between trips.
I think the take-away message from this study is that didymo
is still going to be a concern for those of us who rely on healthy and diverse
waterways for our outdoor recreational fix. Although the indication is that
anglers and boaters are not spreading it, this new study suggests that didymo may continue to appear throughout the waterways of the traditionally cooler
regions of North America as long as the mean global temperature continues to
inch up. I suspect that these findings mean that researchers can now focus
their future didymo studies looking for ways to minimize inevitable didymo
blooms under the assumption that it is already present but dormant in most aquatic
ecosystems. And for anglers who will have to adapt to wading through dense
patches of slippery rock snot? Maybe it’s time to invest in a wading staff.
Sources:
http://phys.org/news/2014-02-debunk-argument-invasive-algal-species.html
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