Tuesday, January 17, 2012

Invasive Species: Eurasian water-milfoil

This invasive was suggested to me recently by the author of The Spotting Ghost, who has made numerous suggestions and contributions before.

Water-milfoil (Myriophyllum spicatum) in Ontario coating the bottom of a body of water.
A detailed illustration
This plant is native to much of the Easter hemisphere and has become invasive in North America. The first plants were believed to be in 1942 to Washington D.C. It reproduces rapidly, using an asexual "vegetative" method, namely it just keeps growing and growing, but bits may break off and settle down to grow, allowing it to spread to more areas more quickly. It is generally only found in still water, but when it takes over it competes with other plants for light, shading them out. It is also not as effective a food source for the various animals in the water, including when it comes to the amount of invertebrates that live on the aquatic plants. Crowding also isn't good for fish, making it more difficult for them to find food. In addition, when the plant grows out of control and then decays, it causes the water's oxygen supply to drop.

Managing this plant has proven to be difficult, as it always is when dealing with an invasive species. Herbicides have been tried with little success, but more success has been seen using physical methods. Blocking light from the plants and also removing them or chopping them to bits have had at least some success. There has also been a biological control that has been proposed in the form of a species of weevil.

I don't honestly know what else to talk about. There is a lot more reading to be done on this species, especially if your are interested in the structure, distribution, reproductive methods, and so on. Aquatic plants are quite intriguing due to their only distant relationships with algae. Some of the sources I found most informative are the Wisconsin Department of Natural Resources, United States Geological Survey, and University of Florida.

Source is the Global Invasive Species Database. Images are from Wikimedia Commons and are copyright free or under a Creative Commons license: one, two.

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