After decades of delay, US government officials are beginning to crack down on cargo ships that allow foreign invasive species to hitch-hike to US waters, where they have turned ecosystems upside down and caused billions of dollars in economic losses.
Organisms as large as adult fish and as small as bacteria lurk in ship ballast tanks, which hold millions of gallons of water and sediments that keep vessels upright in rough seas.
When the soupy mixtures are dumped in harbours as freight is taken on, the stowaways often find hospitable surroundings and no natural predators. They spread rapidly, usurping native species and spreading diseases in aquatic life.
Since arriving in the Great Lakes in the mid-1980s, the zebra mussel and its cousin the quagga mussel have clogged municipal and power plant water intake pipes. They are blamed for a salmon collapse at Lake Huron and botulism that has killed thousands of birds. Japanese shore crabs are threatening native clams and mussels from Maine to Chesapeake Bay, which is infested with 150-plus exotic species. Another invader, the spotted jellyfish, became so abundant in the Gulf of Mexico a decade ago they ripped apart fishing nets and caused a temporary halt to commercial shrimping.
“Larvae of almost every major group of invertebrates can be found in ballast water,” said Tom Shirley, specialist with Texas A&M University-Corpus Christi. “Protozoa and bacteria thrive there, too.”
Ballast is the biggest means of transport for the aquatic aliens, scientists say. Yet regulators have been slow to demand accountability from the shipping industry, which has long insisted there isn’t adequate technology to make ballast tanks invader-free.
Now, agencies are turning up the heat as companies report progress toward developing effective sterilisation systems. The US Coast Guard says it will release final regulations by April limiting the number of live organisms in ballast water and let shippers decide how to comply.
The Environmental Protection Agency (EPA) also has begun regulating discharges of ballast and other waste water from vessels, although shippers and environmentalists have sued. EPA is discussing settlements while creating an updated discharge permit effective in 2013. And at least a dozen states also have ballast policies, leaving shippers increasingly worried about having to navigate a patchwork of requirements.
Jim Tierney, an executive in the New York Department of Environmental Conservation, said the agency was considering shippers’ pleas for a grace period. Environmental groups want the department to stand its ground, pointing to findings by the National Oceanic and Atmospheric Administration that about 75 species are prime candidates to invade the Great Lakes, mostly through ballast water.
“Most clean-water laws assume it’s OK to have a little pollution because it will dilute, evaporate, degrade,” said Andy Buchsbaum, director of the National Wildlife Federation’s office in Ann Arbor. “But invasive species are not like normal pollution. They reproduce and multiply. You have to keep the numbers as low as you possibly can to avoid reaching that critical mass where an entire water body will be colonised.”