[Alaska Sea Grant]

Unwanted Hitchhikers May Catch Ride in Ships' Ballast

Date: May 23, 1996
Contact: Leann Ferry, RCAC, 907-835-5957; Rick Steiner, UAF, 907-274-9691; and Andy Cohen, U-Cal Berkeley, 510-848-1029

VALDEZ, Alaska--Tankers that will soon carry Alaska crude oil to foreign ports may bring back exotic plants, animals, pollution, and even disease to the state's waters. That has scientists and environmentalists worried.

At issue is sea water pumped into the ships from foreign ports. The water acts as ballast, stabilizing ships during their return voyages. But along with the sea water, the ships also may bring aboard species not native to Alaska. Once back in Alaska the ships dump the ballast--and anything in it--overboard.

"We're concerned that non-indigenous species could end up in Prince William Sound and upset the ecosystem," says Leann Ferry, project manager with the Prince William Sound Regional Citizen's Advisory Council, a watchdog group formed after the 1989 Exxon Valdez oil spill. "There is that potential and it's happened in other places."

One of those places is the Great Lakes, where in the 1980s European zebra mussels made their way to the lakes in the ballast tanks of cargo ships. The mussels found the Great Lakes to their liking, reproduced rapidly, and now cause millions of dollars in damage each year to ships, power plant cooling pipes, and city water supplies. Non-native species also have shown up in California's San Francisco Bay, where they compete with native species, often driving them out of their habitats and dramatically altering the ecosystem.

"We found 231 species of introduced organisms in the San Francisco Bay system," says Andy Cohen, a marine scientist at the University of California Berkeley, who recently completed a study of the bay's changing ecosystem.

"We now have a new organism show up and become established in the bay every 15 weeks. We think the increase in the rate of invasion is largely due to organisms arriving in ships' ballast water."

One solution is to require that ships flush their ballast tanks while still far at sea, where--in theory at least--any non-native species would not likely survive. Likewise, any deep-water species brought into the ship during the exchange would not fare well in the nearshore environment. It's a solution Congress included in recent legislation allowing the foreign export of Alaska crude oil. But while the requirement is expected to reduce the risks, it won't eliminate them.

"As tankers exchange their ballast water in the Gulf of Alaska or on the high sea, the ocean currents might carry these non-indigenous species right back into Prince William Sound," says Ferry. "So we're worried about that as well."

Ferry also is concerned that marine organisms may not be flushed out in the ballast exchange. Instead, they may cling to the sides of the hull or remain in sediments at the bottom of the tanker. And then there is the problem of what to do with ballast water carried in tanks that also contain oil. This water cannot be dumped at sea, but must be treated at the Alaska pipeline terminal in Valdez.

"The ballast water pumped into compartments that also have oil in them could potentially have non-indigenous species in it," says Ferry. "But that treatment facility is not set up to treat organisms. It is only set up to remove oil. So we don't know whether that is also a pathway for non-indigenous species to get into Prince William Sound."

Finally, the ballast exchange rule applies only to vessels coming from foreign ports. Rick Steiner, a marine advisory agent at the University of Alaska Fairbanks, points out that ships coming from U.S. ports have never been required to exchange their ballast water.

"The potential for introduction of exotic species was never considered an issue," says Steiner. "I'm not sure we've introduced foreign species into the sound this way, but probably."

Further restrictions, such as requiring all tankers coming to Alaska to exchange their ballast at sea, are being debated as Congress considers the Invasive Species Act. The proposed legislation also calls for the study of technologies that could kill organisms in the ballast and a monitoring program to track the introduction of non-native species.

Alaska Sea Grant 1996 News Releases | Alaska Sea Grant In the News
Alaska Sea Grant Homepage