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Eurasion Watermilfoil

Originating from Europe, the Eurasion watermilfoil has become the number one burden of lakes across Québec and Canada. Nearly uncontrollable, it can attack virtually any lake.

Once introduced in a lake, this plant has the capacity to spread to virtually all surfaces of the water. In effect, its mode of propagation is such that the plant spreads at incredible speeds. Since the plant can easily reach 3 to 4 metres in length, it can rapidly displace other submerged native aquatic plant species.

Since this plant has a well-developed leaf system around the stem, it can become extremely dense. By growing in densely packed colonies, watermilfoil creates a zone of stagnation to the point where the natural turbulence of the water becomes practically non-existent. As such suspended particles present in the lake water get trapped within the milfoil clusters and in turn create new sediments rich in nutrition. This phenomenon is evident by a significant drop in oxygen at the sediment level. The impacts from watermilfoil infestation are numerous. Heading the list is a loss in biodiversity and the nuisance to residents around the lake. Fishing becomes almost impractical. With an increased risk of drowning, water skiing and swimming need to be avoided in the affected areas. Among the inconveniences is the difficulty in boating both motorized and by sail for evident reasons.

Eurasion watermilfoil can also cause major physical-chemical changes. During winter, decomposing plants cause a partial de-oxygenation of the surrounding water which can cause the disappearance of numerous species of fish.

During summer, plants reach again for the surface thereby physically blocking the natural water circulation. As a result water becomes stagnant resulting in high levels of coliforms and other bacteria.

During photosynthesis of a large number of aquatic plants, the ph level has a tendency to increase. We can therefore attain ph levels of 10 to 15 during the summer which can in turn negatively affect the entire aquatic ecosystem.

Taking into account all these factors, we begin to understand why this plant has become a real menace and a significant burden fro our lakes.

There exist a number of methods or products for controlling watermilfoil including chemical, physical, biological and even mechanical. Most of these techniques need to be managed by consultants with expertise in the restoration of lakes.

Current techniques and products include:

  • Manual cultivating
  • Mechanical cutting and retrieval
  • Aquatic harvesting
  • Bottom tarps
  • Aquatic herbicides
  • Lowering water levels
  • Impeller-driven water circulation to re-oxygenate the water
With the exception of the re-oxygenation approach, these techniques have had little success to date.



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