IS A MARINE BIOINVASION?
In its native waters, a hungry green crab feeds on marine animals that its ancestors may have been feeding on there for millions of years. Together, those animals help make a balanced ecological system. But when that same green crab travels to a new locale, it suddenly can become a party crasher and the party it crashes can be an entire marine ecosystem.
On land or in water, an ecosystem is a complex community of organisms that functions as a whole. The introduction of a non-native species (also known as an exotic or bioinvader) does not necessarily spell doom for a habitat, but it can easily disrupt a delicate balance. In a marine environment, for instance, an exotic fish or invertebrate may find few or no natural predators. This allows it to swiftly multiply, monopolize food sources, crowd out native inhabitants, and potentially spread disease to local species.
Green crabs are just one example. Since making their way from Europe to the Eastern Coast of the United States in the 18th century, and more recently to the West Coast, they have caused widespread problems.
In the Northeast, marine invaders include the Japanese shore crab (Hemigrapsus sanguineus), the common periwinkle (Littorina littorea), several species of sea squirts, an algae known as green fleece (Codium fragile tomentosoides), the green crab (Carcinus maenus), and mute swans.
HOW AND WHY
In the United States, the most notorious freshwater invader to arrive in ballast water is the zebra mussel. Since its introduction to the Great Lakes in the mid-1980s, it has caused immense environmental woes, with a price tag of billions of dollars.
Hitchhikers in marine ballast water include plants such as algae and animals such as snails, sea squirts, comb jellies, crabs, and fish.
And Baits and
CLOSE UP: IMPORTING
THE JAPANESE SHORE CRAB
The Japanese shore crab measures 2 to 3 inches across and has a square-shaped shell with three spines on each side. Its claws have red spots, and its legs have alternating light and dark bands. Depending on its location, this crab can range from a mottled, deep brown to purple, orange, green, and pink.
CLOSE UP: EXPORTING
THE COMB JELLY
WHAT CAN YOU
If you boat, be sure to remove any plants or animals from your boat, trailer and other equipment. Drain all the water from the motor, livewell, bilge and transom well away from the water. Wash your boat, tackle, trailer and other equipment with 104° water, a high-pressure spray, or at the very least, with tap water. Then dry everything for at least five days to make sure that none of the exotics have survived.
If you have an aquarium, don't dump fish or plants into a waterway. Dispose of them in the trash.
Scientists can't map new range expansions or new discoveries until new finds are verified. If you see a plant or marine creature that looks like a new invader, you can help out by contacting the Sea Grant program in your state, the local natural history museum, a University field station or a local U.S. Fish & Wildlife Office. If you're concerned about ballast water invasions, contact your state and federal regulators and find out how they are addressing this problem.
species information from the United States Geological Survey
Sea Grant nonindigenous
Northeast Sea Grant's
Feature on Marine Bioinvasion