Invisible Travellers: Aquatic Invasive Species Threaten Many Waterways

They never even noticed it. When the boat was put into a new water body, the tiny strand of Eurasian watermilfoil (Myriophyllum spicatum) that had attached to the bottom went with it. Whether it is a small motor boat, a ship, or a plane, this is the manner in which plants and animals have been getting moved for decades. While invasive species are a threat at any time of year, with many boats on lakes now, this is the time that is particularly ripe for aquatic invasives. These species, which include plants, fish, mollusks, crustaceans, and insects, can be introduced on purpose or accidentally. However, in new environments, they have no natural predators and thus populations can frequently explode in a very short time period often wreaking havoc on native wildlife.

Both the National Wildlife Federation and the EPA cite invasive species as the second biggest threat to biodiversity after habitat loss. Kimberly Jensen, Environmental Scientist with the VT Department of Environmental Conservation, said invasives can outcompete native wildlife for both space and food. She said boats were the most common way for aquatic plants and animals to be introduced to new places.

Jensen said that species of particular concern are the Eurasian watermilfoil, referenced above, hydrilla (Hydrilla verticillata), and zebra mussels (Dreissena polymorpha). The Eurasian watermilfoil is native to Europe, Asia, and Africa. It is a submersed perennial plant with featherlike leaves and stems that branch when they approach the suface. It can tolerate brackish water and low temperatures. It is agressive, can replace native plants, and forms canopies that block sunlight. Zebra mussels are native to the Black and Caspian Seas. They are extremely small mussels usually not exceeding five cetimeters in length. They attach to any hard surface and can clog pipes. Hydrilla is a submerged aquatic plant, which can grow to 23 feet. It can clog power plant valves and also impacts biodiversity. Jensen stated that it appears zebra mussels have been successfully removed from Lake Dunmore in western Vermont. However, once a species is introduced, it is generally very difficult to get rid of, and Jensen said the best control is prevention in the first place. If an invasive species is confirmed, though, she said there would first be efforts for eradication and then containment. The U.S. Fish and Wildlife ( also stated that eradication would be the first goal and if that was not longer possible, preventing the spread would be the next option.

Boats are the most common way for species to get moved and Jensen said it is important to thoroughly clean and dry boats in between uses. The Vermont Invasives ( recommends draining all water from boats and equipment and drying boats for at least five days before putting them in a different water body. In addition, Jensen recommended the VT Invasive Patrollers who assist in identifying and removing invasive species and stated there was more information about them on the VT Invasives website. It is true that invasives can cause a huge number of problems. However, taking some precautions as well as being on the lookout for exotics can go a long way to preventing their spread and in some cases, successfully eradicating them altogether.