Aquatic invasive species both plant and animal pose a serious threat to the biological diversity of coastal waters the world over. With improvements in travel technology, the rate of introductions of nonnative species has increased dramatically.
It is important to remember that humans have carried plants, animals, and disease with them since they first began to travel. Most of the plants and animals were considered necessary or beneficial. This includes everything from food crops like soybeans and wheat, cattle, horses, pigs, fish and shellfish, to pets and decorative garden plants.
Many other organisms have been spread to various parts of the world unintentionally. They arrive in the ballast water of ships, packing materials, wood used for pallets, soil, or as hitchhikers on other plants and animals.
Once nonnative species become established in a new environment where natural enemies, pests, or disease that kept them in check in their native environment are missing, they may spread rapidly and cause unanticipated negative biological and economic impacts. There are numerous examples of the impacts of aquatic invasive species in both marine and freshwater environments. One of the most well known species is the zebra mussel (Dreissena polymorpha). The zebra mussel has caused extensive economic and ecological damage since arriving in the Great Lakes, and is rapidly spreading throughout North America. The Quagga mussel, a sister species, is now present in Lake Mead (NV, AZ) and Lake Havasu, CA., which greatly increases the risk of introduction into Washington State. Readily observed examples of aquatic invasive species in the inland marine waters of Puget Sound and the Georgia Basin include cordgrasses (Spartina spp.), Japanese eelgrass, (Zostera japonica), Oyster drill (Ceratostoma inornatum), varnish or dark mahogany clam (Nuttalia obscurata), and the European Green crab (Carcinus maenas). In the past two years three species of non-native tunicates have developed rapidly expanding populations in Puget Sound and Hood Canal. Freshwater invasive species in Washington include Eurasian Water Milfoil (Myriophyllum spicatum), the Asian clam (corbicula fluminea) and the New Zealand mudsnail (Potamopyrgus antipodarum).
Questions or comments regarding the state’s Ballast Water Management Program may be directed to: