Max Bothwell, a research scientist for Environment Canada, who wrote an influential article that linked angler's felt soled boots to dydimo spread has now reversed himself and said that anglers are not responsible.
Here is his original article, On the Boots of Fishermen:
He now believes that dydimo has been in North American waters and that it is a change in water chemistry, specifically lower phosphorus levels that has caused dydimo blooms.
Read the article in the current issue of American Angler, July-August, 2013, pp 8-9.
"'I no longer believe the problem is North American streams is the result of it (dydimo) being moved around.' …. Scientists are now convinced that dydimo lives in many streams, but blooms only when the water has far less than the normal amount of phosphorus…… The most damaging dydimo episode in the US seems to have been on Rapid Creek in South dakota, where a six-mile bloom dramatically impacted a blue ribbon brown trout fishery. In 2007 and 2008, Bothwell and other scientists added phosphorus to sections of Rapid Creek. Sure enough, the dydimo mats shrank."