What are the Dangers of Milfoil?
by William deLorraine, President of the Sylvia Lake Association
The negative impacts on wildlife and fish populations in water bodies with high densities of Eurasian watermilfoil and the difficulty of motor boating and swimming in infested areas result in recreation-oriented financial losses and the depreciation of shoreline property values (accompanied by a loss of real estate taxes to local economies).
Ecologic damage. Introduction of Eurasian watermilfoil can result in native macrophyte diversity and abundance declines. Eurasian watermilfoil beds form dense canopies at the water surface thereby reducing light penetration early in the season before native macrophytes have reached their full growth, shading them out and slowing/reducing growth potential. Eurasian watermilfoil beds, as a result of the reduction in native plants, have been found to contain significantly fewer macroinvertebrates (including benthic invertebrates) and a concomitantly lower abundance of native fish species. Milfoil-infested lakes tend to have reduced fish spawning areas and lowered fish growth rates. Native waterfowl in the Great Lakes have been found to avoid foraging for food in beds of Eurasian watermilfoil.
Why is milfoil a nuisance in North America?
Eurasian Milfoil is an exotic plant, introduced to the U.S. by the aquarium industry. It is rapidly becoming a major nuisance throughout North America. It is capable of rapid dispersion, principally by fragmentation of plant parts. Each fragment is capable of growing roots and developing into a new plant.
Eurasian watermilfoil plants spread naturally through stem fragments and underground runners. Accidental cutting of the plants can start new plants when the fragments are transported by watercraft or on waves and currents to new areas where they can root and grow.
Similarly, why is Eurasian milfoil a problem?
Eurasian watermilfoil spreads easily and grows quickly. Eurasian watermilfoil crowds out native plants, reducing biodiversity, diminishes fish habitat and negatively impacts wetland habitats. Dense mats form near the surface. As a result, Eurasian watermilfoil can adversely affect our local tourist-dependent economy.
Myriophyllum heterophyllum, commonly referred to as variable milfoil, is an invasive aquatic plant that has been contaminating lakes throughout the Northeastern United States since the 1960s. It looks harmless enough, resembling a green squirrel tail with the occasional small, reddish flower. Yet, variable milfoil can grow up to 15 feet long, forming dense mats of vegetation that choke out native species. These mats block sunlight from reaching other submerged plants, killing them, and can deplete oxygen levels in the water while decaying, which hurts fish and other aquatic animals. The plant not only destroys ecosystems but also inhibits recreational water activities, as the dense mats of milfoil make boating or swimming impossible. Furthermore, these large clusters of plant matter are the perfect breeding grounds for mosquitoes, more bad news for those who visit lakes.
Eurasian milfoil aggressively out-competes native plant species, such as native milfoil. This reduces biodiversity and water quality. The plant grows quickly and forms a thick mass of tangled stems underwater and mats of vegetation on the surface of water bodies. Dense mats of Eurasian milfoil on the water’s surface block light from penetrating the water, which shades out native aquatic vegetation. Stands of the plant results in stagnant water and can create ideal breeding grounds for mosquitoes.
Fish populations are also negatively impacted. Fish can’t swim through dense mats of Eurasian milfoil, and when the plants begin to rot it can reduce oxygen levels. The plant also poses a problem to human recreational activities, such as swimming, fishing and boating. Stems of the weed often get entangled in rudders and boat propellers.
The main problem with such an invasive species is the fact that they consume practically every resource in a water source, preventing other forms of life from flourishing. Since the plants can mat the surface of the water, this can prevent sunlight from penetrating the water and allowing other forms of a plant to grow.
This can also help to drastically decrease the amount of oxygen in the water that can starve both plants and animals alike. Over quite a surprisingly short amount of time, this can completely destroy an ecosystem which can be catastrophic for the water source, and inhabitants who live by or enjoy the water source and the life it brings.
This always affects humans in plenty of different ways. For example, the large dense mats of these plants are ideal breeding grounds for bugs such as mosquitoes. During the summer months, you can expect thousands, even millions, more bugs that you would have to deal with originally, which can be incredibly dangerous for everyone in that area.