Portfolio VI: Exotic Species

The Issue

Research undertaken during the last decade has demonstrated that nonindigenous species can pose significant threats to estuarine and coastal ecosystems like the Chesapeake Bay. This is a worldwide problem, and researchers in the Chesapeake Bay region continue to serve as internationally respected experts on the subject, tracking the movement of nonnative species to all corners of the globe. In the Black Sea, to take one famous example, the comb jelly Mnemiopsis leidyi is thought to have traveled from the Chesapeake Bay via ballast water. The result has been a major impact on the Black Sea's food web and a resultant crash in the commercially valuable anchovy population.

In the Chesapeake Bay, while citizens are becoming more aware of the damage caused by nonnative animals such as the mute swan and the South American nutria in tidal marshlands, there is less understanding of the constant and often insidious threat posed by other, less easily observed organisms. Mounting genetic evidence suggests, for example, that MSX, a haplosporidian parasite that has at times virtually decimated the Bay's oyster stocks, most likely originated in Asia, and traveled to the Bay either with nonnative oysters planted in the estuary or in ships arriving from the Far East.

Other examples of problematic intruders include plants such as Eurasian milfoil and hydrilla. Of special interest to researchers in the Chesapeake Bay area are potentially invasive mollusks, such as the zebra mussel, the quagga mussel and the Rapa whelk. Also of particular interest is the vector by which such species can enter the Chesapeake - most especially the ballast water of large ships, which can dump huge amounts of organisms, including microorganisms, carried from abroad to local harbors.