• What are exotic species?
• How are they able to cross oceans?
• What enables them to colonize foreign environments?
• Do they represent a threat to coastal ecosystems?
• What can policy makers do to protect estuaries from non-native species?

NEWS FLASH!
In September 1999, U.S. President Bill Clinton issued an executive order that directed the Departments of Agriculture, Interior, and Commerce, the Environmental Protection Agency, and the U.S. Coast Guard to develop an alien species management plan within 18 months to blunt the economic, ecological, and health impacts of invasive species.

Agriculture Secretary Dan Glickman promised "a unified, all-out battle against unwanted plants and animal pests." But senior administration officials acknowledged that the task poses difficulties and may succeed only through greater international cooperation.

Officials acknowledge that the United States also has species that cause adverse impacts when they are carried to other countries. Interior Secretary Bruce Babbitt said the long-term answer is to resolve these issues through international agreements that would benefit all countries.

Environmentalists, meanwhile, complain that the Clinton Administration has been slow in regulating ballast discharges from freighters — one of the major pathways for exotic aquatic organisms such as the Chinese mitten crab (annual economic cost unknown); green crab (annual economic cost $44 million); and Asian clam (annual economic cost, $1 billion), which are threatening native marine life in San Francisco Bay and as far north as Washington state. Another such animal is the veined rapana whelk, which has been recently discovered in Chesapeake Bay.

Since the issue involves interstate and international commerce, individual states and counties cannot, under the U.S. Constitution, regulate ballast water. "The West Coast invaders," says Linda Sheehan of the Center for Marine Conservation in San Francisco, "are driving out native crabs and clams and threatening local oysters—even burrowing into and weakening flood control levees, which could potentially result in huge losses from property damage during floods."

A coalition of environmental groups and the Association of California Water Agencies asked the EPA to regulate freighter ballast water discharges under the Clean Water Act.

Introduction
Silently, almost imperceptibly, the planet’s oceans, seas, estuaries, and lakes are being invaded by plants, animals, bacteria, and even viruses from distant climes. These organisms are called alien, exotic, or invasive species. Sometimes their impact is negligible, rarely is it beneficial, and often it borders on the disastrous. At a January 1999 meeting of the American Association for the Advancement of Science, Cornell University ecologist David Pimentel estimated the total cost of invasive species at $123 billion a year.

Instead of remaining in an ecosystem in which all members have evolved and interacted over time, in the relative blink of an eye invasive species may be transported beyond their natural range into the presence of other organisms with which they will immediately begin to interact, and perhaps compete.

Once thrust into a new environment, an organism faces a whole new set of conditions. To survive, all living organisms must live long enough to bear offspring and thus ensure the future of their gene pool. The ‘aim’ of exotic species is not to take over an estuary or clog a factory’s water pipes, but rather to simply survive and reproduce.

Scientists believe that most non-native organisms fail to survive in their new environment long enough to become established. And that’s a very good thing. But occasionally, the introduced organism finds its new home completely livable, sometimes even ideal. Successful invasive species usually share a similar set of characteristics, according to the U.S. Coast Guard:

• They are hardy, indicated by their surviving a trip inside a ship for perhaps thousands of miles.
• They are aggressive, with the capacity to outcompete native species.
• They are prolific breeders, and can take quick advantage of any new opportunity.
• They disperse rapidly.

Rapid dispersal is facilitated by having a planktonic larval stage, which allows the juveniles to be carried far and wide by currents. Such an introduced species often spreads rapidly, especially when predators and pathogens normally encountered in its home range are absent from the new environment, or when they are better able to feed than their new neighbors, or if they find their new neighbors especially tasty.

In the preceding scenario, alien species flourish and potentially can reach astonishingly high population levels. Often, native species are displaced, or 'outcompeted' by the invaders. Then the situation is often called an invasion.

Invasive species can inflict damage on ecosystems by:

• outcompeting native species,
• introducing parasites and/or diseases,
• preying on native species, and/or
• dramatically altering habitat, e.g., rearranging the spatial structure of an ecosystem.

Most invasive species are brought to new shores in the ballast water of ships, but animals dumped into an estuary from aquariums or accidental releases from aquaculture facilities may also contribute.

What is ballast water? Ballast water is carried by ships in special tanks to provide stability, optimal steering, and efficient propulsion. According to the U. S. Coast Guard, the use of ballast water varies among vessel types, among port systems, and with cargo and sea conditions.

How much ballast water is involved? The National Oceanographic and Atmospheric Administration (NOAA) has calculated that 40,000 gallons (150,000 liters) of foreign ballast water are dumped into U.S. harbors each minute.

The problem with ballast water is very simply stated: ballast water is taken up by a ship in ports and other coastal regions, in which the waters may be usually rich in planktonic (small, floating, or weakly swimming) organisms. It may be released at sea, in a lake or a river, or in the open ocean along coastlines—wherever the ship reaches a new port. As a result, a myriad of organisms is transported and released around the world within the ballast water of ships. Here are two examples.

Scientists studying an Oregon bay counted 367 types of organisms released from ballast water of ships arriving from Japan over a four-hour period! Another study documented a total of 103 aquatic species introduced to or within the United States by ballast water and/or other mechanisms, including 74 foreign species.

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