Organisms living in coastal waters may be pumped into ballast tanks along with the water. If a ship takes on ballast water in a shallow area, sediments and any associated organisms may be pumped into ballast tanks. When ballast water is released, these organisms may also be released.
The release of ballast water may introduce non-native organisms into the port of discharge. These introduced species, or bioinvaders, are also referred to as exotic species, alien species, nonindigenous aquatic species and aquatic invasive species (AIS). Typically, very few organisms are able to survive in new surroundings because temperature, food, and salinity are less than optimal; however, the few that do survive and establish a population have the potential to cause ecological and economic harm. Populations of bioinvaders, or invasive species, may grow very quickly in the absence of natural predators. In turn invasive species may displace native organisms by preying on them or outcompeting native species for food and habitat space.
Economic damage may occur when an invasive species displaces native species that are harvested for food or other goods, or when damage structures, e.g. intake/discharge pipes. These organisms grow on almost any structure, forming large clumps of mussels which can clog water intake pipes and damage or impair other structures. Periodically these organisms need to be removed from pipes and other structures which requires time, money, and possibly specialized equipment.
