What is ballast water?
Ballast water, not to be confused with bilge water, is water taken up or released by a vessel to alter the draft, change the trim or regulate stability. Ballast water can be sea water (salt water) or river/lake water (freshwater) depending on the location of a vessel when ballasting. Ballast water is generally taken up when little or no cargo is on board. The weight of the ballast water is what helps provide stability for vessels during ocean transit. Ballast water is then generally discharged when cargo is taken on board. Ballast water includes associated sediments that are found either in the water column or settle out in tanks. The majority of modern vessels have tanks that are specifically used to carry/hold ballast water when necessary.
Are aquatic invasive species (AIS) the same as exotic species or introduced species?
Yes. Many names exist to describe the large number of species that have been moved, by human activities, to locations where they do not originally occur. AIS refers specifically to aquatic species, but in general, non-native species may be referred to as exotic, invasive, introduced, nuisance, or alien species. Alternatively, a native species is one that is found naturally in a given habitat or region.
Are all AIS harmful?
No, but this is a bit of a tricky question. Some AIS species such as the Zebra mussel (Dreissena polymorpha) in the Great Lakes cause both significant economic and ecological impacts in a region. Some AIS may not have any economic impacts to humans, but they may pose a significant threat to ecological systems. An AIS may not appear to cause any observable economic or ecological impact, however, scientists must investigate many types of organisms at many levels within a food web (trophic levels) to make sure that simply because we cannot see an obvious impact does not mean that there is not an impact occuring.
How do AIS move from one region to another?
In the aquatic world, the majority of non-native species are transported by ballast water in the hulls of ships or as fouling organisms attached to the submerged outer surfaces of ships. When ballast water is drawn into a vessel, that water may contain a great variety of species that were living in the surrounding water including: plankton (microscopic animals and plants), larval or juvenile fish, spores of various seaweeds and bacteria, to name a few. When ballast water is discharged in port regions, those organisms that were living in the ballast water, and able to survive the journey from port to port, may be released into the surrounding environment. These released organisms are considered invasive when they are able to survive, thrive and reproduce in the new region.
Fouling organisms are species that attach or cling to a vessel's hull, water intake valves and associated piping, or to anchors and other equipment. Fouling organisms may attach to vessel hard surfaces at almost any time, but they are most likely to attach when vessels are not moving, such as when they are in port. Many fouling organisms, particularly those that attach in small nooks and crannies of the vessel (around the rudder or propeller for example) are most likely to be able to survive the forces associated with crossing oceans at relatively high speeds. When the vessel reaches its next port of call, those fouling organisms may fall off of vessel hulls and associated equipment and begin to grow and reproduce in the new environment. Alternatively, some fouling organisms may remain attached to a vessel surface, but they may spawn or reproduce in the new port region. The fouling organisms (whether adult or juvenile) that are able to survive, thrive, and reproduce in the new habitat are considered invasive species.
AIS may also be moved by mechanisms or vectors other than ballast water or vessel fouling. AIS may be introduced accidentally through aquaculture, through the aquarium or pet industry, or by the live seafood and bait trade. Organisms that were intentionally released historically for food or ornamental purposes are also considered invasive species.
What can be done to prevent species introductions from ballast water and vessel fouling?
State, federal, and international regulations are in place to attempt to limit the introduction of new species from ballast water release (see the Ballast Management: Laws and Regulations section in this website). These laws and regulations require ships to exchange their coastal ballast water with mid-ocean ballast water at some point during their trip, or if ballast exchange is not possible during a voyage, ships may hold on to (retain) their ballast water when they enter a port. In general, organisms found in coastal zones, near ports, are unable to survive in the harsh environment of the open ocean and vice versa. Thus when ships exchange their coastal ballast water with mid-ocean ballast water, the coastal organisms should be flushed out and exchanged by mid-ocean organisms. These mid-ocean organisms are then unable to survive when they are released into coastal habitats when a vessel reaches its next port of call. While this system of exchange can be very effective, it is not 100% effective. Because ballast water exchange cannot totally eliminate the risk of species introduction, ballast water managers are moving towards ballast water treatment (such as through ozonation, heating, UV, or chlorination) to kill organisms within the ballast tanks before they are released into the surrounding environment. While many types of treatment are currently being developed and tested, no treatment technology is currently approved by the United States Coast Guard. For more information on ballast water treatment, see the Ballast Management: Treatment Technology section of this website.
Who do I contact if I find an organism that I think may be invasive?
All states have some department that deals with the health of the environment in that state. The department or agency that may be most familiar with the species in any given area is likely some branch of the United States Fish and Wildlife Service: in California it is the Department of Fish and Game, in Oregon it is the Department of Fish and Wildlife, and in Washington it is the Department of Fish and Wildlife. However, you may know of a local nature center or college, univeristy, or educational program that exists near your location that may be able to answer your question quickly and accurately. If it is a question that needs more attention, they can often refer you to the appropriate resources. Remember, there are not enough scientists to examine all habitats at all times for the presence of new invasive species. The public is one of our best resources in the early detection of new species.