WTF? The article is about algae, but it sounds like you're talking about leeches.
I believe I was speaking of most any kind of invasive species that travel or are carried to a place that is foreign to them.
Fresh water lakes are undergoing all kind of threats from pollution to foreign critters with no natural enemies.
It is not just for fisherman to fight to keep our natural beauty pure, the cycle of life depends on clean lakes and streams.
Example---If an invasive species came in and destroyed the underwater plants and natural algae to our wild rice, we would have allot of starving Moose up here. All our wild life would be in trouble from the fish to the birds.
Few really take this seriously until the process cannot be stopped. Check out our great lakes that now have a problem with this foreign fish that grows to 3-4 feet long and has no natural enemy. FOX News tried to gather some top notch Chiefs that are known to make a SEA GULL tasty and challenged them to make this fish palatable. Very difficult, they fried them, steamed them, boiled them roasted them but the results were very mixed. This fish will never become a staple on anyones plate here in the USA, perhaps they can be sold in Asia as that is where I believe they came from in the first place.