Ballast Water

A foreign vessel headed for Baltimore Harbor with cars from Asia or sugar from South America could offload a very different commodity into the Chesapeake Bay — organisms from its native port.

To give a ship stability while traveling across the ocean, captains often add seawater to ballast tanks before the voyage. But when more goods come aboard, the ship will need to lose the extra weight. In preparation for the return trip, the crew dumps the ballast water — and whatever lives in it. Microbes. Plankton. Fish larvae from far away.

These hitchhikers may be non-native to the Bay and its environs and, if established, could disrupt the dynamics of the ecosystem. Most of the more than 150 invasive species in the Chesapeake are believed to have found their way to the Bay via ballast water, including perhaps MSX, the disease that has decimated native oyster populations.

Recognizing the threat of harmful introductions to ports across the nation, the Coast Guard now requires large ships entering or operating in the U.S. to follow a mandatory ballast water management program. For many ships this may include undergoing a ballast water exchange in the open ocean. The idea is that species from a coastal port would have difficulty surviving in the open ocean, and species adapted to the ocean would not thrive in the next port.

This method is not foolproof, though, and scientists are at work to find better ways to treat ballast water and to avoid invasions. A new initiative by the Maryland Port Administration and the University of Maryland Center for Environmental Science hopes to buoy these efforts. In July 2008 the two groups partnered to open the Maritime Environmental Resource Center (MERC), an institution geared toward addressing issues facing the shipping industry, especially ballast water. Housed at the Chesapeake Biological Laboratory in Solomons, Maryland, MERC will focus on the scientific, engineering, and economic challenges of ballast water treatment systems.

Useful Links

Maritime Environmental Resource Center

Coast Guard ballast water regulations

Current and past Maryland Sea Grant-funded research on aquatic invasive species, including ballast water treatment

Alien Ocean DVD

Chesapeake Quarterly, Vol. 5 No. 2, The MSX Files