Water chestnut (Trapa natans) is a floating-leaved aquatic annual plant from Eurasia that forms dense, continuous mats over the water surface of lakes and slow moving waters. One seed can give rise to ten to fifteen rosettes, and each rosette may produce as many as twenty seeds. With high rates of germination, growth can be explosive.
Didymo (Didymosphenia geminata), commonly known as rock snot, is a species of diatom that blooms in freshwater rivers and streams, with consistently cold water temperatures. In late winter it can form large mats on the bottom of rivers and streams. It is not considered a significant human health risk, but it can affect stream habitats and sources of food for fish and make recreational activities unpleasant. It is considered a nuisance organism or invasive species. The microscopic alga can be spread in a single drop of water.
Zebra mussel (Dreissena polymorpha) is an AIS species of small freshwater mussel from the Black and Caspian Sea. These mussels are usually about the size of a fingernail, but can grow to a maximum length of approximately two inches.
Eurasian Watermilfoil (Myriophyllum spicatum) is a species native to Europe, Asia, and Northern Africa. Milfoil is believed to have been introduced to America in the 1940’s. It is a submerged aquatic plant, and grows in still or slow-moving water. It has been known to crowd out native plants and create dense mats that interfere with recreational activity.
Purple loosestrife (Lythrum salicari) is an invasive plant of European origin which infests wetlands, wet meadows, shorelines, and roadsides. Large monotypic stands of L. salicaria jeopardize various threatened and endangered native wetland plants and wildlife by eliminating the native food and cover. A single plant can produce over 2.5 million seeds from its multiple purple spikes that bloom in late summer. These seeds are easily dispersed by water and in mud adhered to aquatic wildlife, livestock and people.
Aquatic Invasive Species
Aquatic Invasive Species (AIS) are aquatic and terrestrial organisms and plants that have been introduced into new ecosystems throughout the world and cause harm to the natural resources in these ecosystems. Invasive aquatic plants are introduced plants that have adapted to living in, on, or next to water, and that can grow either submerged or partially submerged in water. Invasive aquatic animals require a watery habitat, but do not necessarily have to live entirely in water. AIS are also considered to be "nuisance" species or "exotic" species and the terms are often used interchangeably.
Many of the AIS species that occupy the United Stated today arrived via human means (i.e. from ballast water of oceangoing ships; released aquaculture species, aquarium specimens, and bait, and other means. The introduction of these foreign invaders results in displaced native species, and diminished biodiversity, resulting in huge economic impacts and fundamental disruptions of wetland, riparian, river, lake, and coastal ecosystems.