Look at what the cargo ship dragged in
With invasive aquatic species costing billions yearly, lawmakers seek to stop their spread by clamping down on the discharge of ballast water from cargo ships.
In June, a Chesapeake Bay crabber made an unusual – and possibly ominous – catch. John Delp hauled up a trap holding a crab with what appeared to be fur on its pincers.Skip to next paragraph
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The Maryland Department of Natural Resources (DNR) caught wind of Mr. Delp's find and, after an examination, concluded it was a Chinese mitten crab, an exotic species native to East Asia and well established in San Francisco Bay, but never before seen on the East Coast. Immediately, the DNR issued an alert. One male crab wasn't proof of a breeding population, but it was cause for vigilance.
In August a second animal, caught years earlier and preserved in a waterman's freezer, came to light. Exactly how two Chinese mitten crabs – both male and both a continent away from the nearest known population – found their way to Chesapeake Bay is a mystery, but scientists suspect an old villain: ballast water.
Before setting sail, cargo ships take in vast amounts of water for stabilization, and then discharge the water at their destination. Only nominally filtered on uptake, this water, known as ballast, inevitably contains a host of organisms, ranging from algae to the larvae of various mollusk species to (at least in one case) an entire school of fish.
"Considering that there are over 30,000 ships at sea this morning," writes James Carlton, director of the Williams College-Mystic Seaport Maritime Studies Program, in an e-mail, "the total number of organisms and species in this global 'bioflow' on the morning your readers read your piece could be staggering – billions of individuals, and thousands of species."
Indeed, scientists have long considered ballast water the primary way invasive aquatic organisms are introduced. From the zebra mussel's arrival in the Great Lakes, to an American jellyfish severely disrupting Black Sea fisheries, the potential costs of accidental introduction of a species to new homes can be tremendous. Aquatic invasives cost the US $9 billion yearly, according to estimates by David Pimentel, professor emeritus of ecology and evolutionary biology at Cornell University in Ithaca, N.Y. Zebra and quagga mussels (a cousin to the zebra) alone cost the $1 billion annually.
As the cost of invasive species has become increasingly apparent, the adoption of – and technology for – ballast water management has become more pressing. California passed tough ballast-water standards in September, and last week the International Maritime Organization (IMO), the UN body charged with formulating international standards, met in London to discuss the issue. Meanwhile, companies worldwide are rushing to provide solutions for what may become a billion-dollar industry: the shipboard sterilization of large amounts of water.
Currently, the Coast Guard requires all ships entering US waters to exchange their ballast at least 200 nautical miles from shore where the ocean is at least a mile deep, or face a fine of up to $27,500 per day. Adapted to the lower salinity of coastal waters, organisms found in ballast water theoretically won't survive the higher salinity of the open ocean.
Enforcement of these measures since they became mandatory in 2004 – previously, they were voluntary – has reduced the number of organisms carried in ballast by 90 percent, says Gregory Ruiz, a marine ecologist at the Smithsonian Environmental Research Center in Edgewater, Md., who works with the Coast Guard on ballast water management. "Ships have radically changed the way they behave."
But others emphasize that ballast water exchange was meant to be an interim fix on the way to a more effective solution. Studies conducted in the Great Lakes, where mandatory ballast exchange has been in effect since 1996, indicate no slowdown in the introduction of exotic species, says Edward Mills, director of the Cornell Biological Field Station in Bridgeport, N.Y.
The problem, he says, are NOBOBs, an acronym for ships with No Ballast on Board, which are exempt from current regulations. Although their tanks don't contain water, they carry a layer of sediment that may harbor an array of organisms. When ships do take up ballast, after they have delivered their cargo, they inevitably "dribble the sediment throughout the lakes."
For this reason, environmental groups have long pressed for national guidelines specifying what discharged ballast water can and cannot contain. "We're not trying to dictate what kind of technologies they use," says Jennifer Nalbone, campaign director of Great Lakes United, a coalition of organizations dedicated to preserving and restoring the Great Lakes. "The standard is most important."