Invasive species advance on US

Could the US coastline be hit with its own "killer algae?"

Marine experts say US shores are already being inundated with transoceanic hitchhikers that squeeze out native critters.

In just one waterway, San Francisco Bay, scientists estimate there is a successful invasion of some kind of marine species - slug, barnacle, crab, fish, worm, or mollusk - every 14 weeks. They arrive in the holds of ships, which carry ballast water from distant ports and then discharge it into local waters.

All told, there are 7,000 invasive marine and terrestrial species that have taken root in the United States, roughly 15 percent of which cause some kind of ecological or economic damage.

"The door is wide open," says James Carlton, professor of marine science at Williams College-Mystic Seaport in Mystic, Conn., and an expert on invasive marine species. "The challenge is can we do something about it?"

The biggest and most costly invader so far has been the zebra mussel, a black-and-white striped bivalve from Central Europe that appeared in the Great Lakes in 1988.

Since then, it has spread to 19 midwestern states and two Canadian provinces. The zebra mussel covers river bottoms, destroys other bottom-dwelling or benthic species, prevents fish from laying eggs, damages intake pipes at power plants, and destroys jetties. The electric power industry estimated zebra mussel damage to its plants at $3.1 billion.

Despite the best efforts of scientist, nothing so far has stopped it.

Other regions are also facing threats:

*On Long Island Sound, the Japanese shore crab arrived in 1994 and has driven out all other native species.

*In Chesapeake Bay, the rapa whelk, a 6-by-4-inch carnivorous marine snail threatens commercial clam and oyster populations.

*In the Gulf of Mexico, Perna, a mussel from the southern hemisphere is now causing major damage on buoys, reefs, and jetties.

*In Southern California, the diminutive sea squirt is replacing other small marine invertebrates, although its long-term impact isn't known.

(c) Copyright 2000. The Christian Science Publishing Society