Invasion of the Zebra Mussels

Communities around the U.S. are in a panic over the creeping invasion of a native Caspian Sea mollusk called the Zebra Mussel.

This tiny, shelled creature – less than two inches long – has installed itself into hundreds of bodies of water around the country, from California to New York. In all, they are in at least 23 states. And along the way they are eating up life-giving phytoplankton, thus starving other organisms, and clogging the pipes and drains in dams, power plants and factories.

Federal, state and local agencies are extremely unhappy about this shellfish. As the U.S. Geological Service puts it, “They colonize pipes, constricting flow, therefore reducing the intake in heat exchangers, condensers, fire fighting equipment, and air conditioning and cooling systems.” The agency says that the mussels colonize so densely that they were found to be congregating in numbers of 700,000 per square meter in a single Michigan power plant.

The Zebra Mussel was first described in the eighteenth century by a visitor to the mouth of the Ural River in the northeastern Caspian near present-day Kazakhstan. It was then found as well in the Azov and Black seas. In the nineteenth century it spread into Europe through canals, and in 1988 it was discovered for the first time in the U.S.

But how did they reach the U.S.? For that answer, I e-mailed Zebra Mussel expert Thomas Horvath, director of the environmental sciences program at the State University of New York at Oneonta. "The Ponto-Caspian region is home to zebra mussels," Horvath replied a little while ago.

As for how they got from there to here, Horvath said, "Caspian ships can make their way out to the Baltic via various canals. The Great Lakes's zebra mussels may very well have come from a number of places -- European ports, Black Sea areas, and even the Baltic ports."

In writings elsewhere, experts have suggested that a tanker traveled from someplace between the Caspian and Europe, went through the St. Lawrence Seaway and on to the Great Lakes, where it dumped ballast containing Zebra Mussel larvae.

With no native enemies, the mussel spread.

A problem is that there’s been no proven way to eradicate them because poisons tend to hurt other organisms. But there is hope. In England, scientists are testing something called the bio-bullet, which is a small capsule of potassium chloride, coated in vegetable fat. In the States, according to Encyclopedia Britannica, scientists are testing something a bit more afield – anti-depressants. This is a spinoff of an experiment showing that pregnant zebra mussels that ingest serotonin produce nonviable larvae.

Image: California Department of Water Resources