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In the dank bowels of the ship, a million microbes squirm and writhe. Their watery cradle — the ballast — plays a central role in balancing the weight of giant cargo ships that regularly shuttle back and forth between the world’s oceans.
Invisibly ferried from port to port, the hitchhiking larvae, phytoplankton and bacteria pose a costly threat. If flushed into the wrong environment, these aliens could very well take over ecosystems.
“Invasions happen all the time,” said Mario Tamburri, a marine ecologist at the University of Maryland’s Center for Environmental Science and the director of the Maritime Environmental Resource Center, or MERC, in the Chesapeake Bay. “Some are benign, but some cause enormous damage.”
Dr. Tamburri and his colleagues spend much of their time aboard one of the newest research vessels in American waters, trying to find solutions to the ballast problem.
The challenge is not trivial: of the 59 invasive species known to have colonized the Great Lakes since the 1950s, for example, about half are likely to have arrived in the ballast discharges of border-crossing vessels. Annually, invasive species introduced by ballast cost an estimated $130 million in damage in the Great Lakes alone.
New rules aim to alleviate the problem. Under the Coast Guard’s new regulations, which reflect those issued by the United Nations International Maritime Organization and the Environmental Protection Agency, most ships built after December 2013 that enter United States waters will have to contain an approved onboard ballast treatment system.
The number of live organisms allowed in discharged ballast has been reduced by several orders of magnitude, to fewer than 10 living cells per cubic meter of water.
But how to abide by those regulations when ships pump millions of liters of organism-ridden ballast in and out of their hulls, and many of these creatures cannot be seen by the naked eye?
Along with two other research centers, the Golden Bear Facility in California and the Great Ships Initiative in the Great Lakes Dr. Tamburri and his colleagues at MERC are seeking o figure out the best ballast-sterilizing techniques. As described in an article in the journal Science, their options range from erecting barriers like mesh screens to exclude larger animals to direct kills like applying toxic chlorine, bombarding animals with damaging ultraviolet rays or depriving the creatures of oxygen to suffocate them.
To figure out how effective their methods are, the researchers must quantify the fate of the tiny organisms in samples of treated ballast. While control water samples will teem with thousands of squirming copepods and rotifers, treated samples will contain only a couple of creatures that are still kicking.
Determining whether the minuscule animals are still alive requires prodding each one with a tiny ice pick-like tool to see if it moves when coaxed. And that’s the easy part. Figuring out whether phytoplankton is alive proves more challenging because those organisms do not move.
The researchers are looking into staining techniques that pick up on chlorophyll present in still-living phytoplankton to try and ease the task. Determining the survival rate for bacteria like E. coli, on the other hand, is relatively straightforward since testing kits are available from the E.P.A.
Each potential ballast-sterilizing solution presents a unique set of challenges. “We want to kill most organisms, but also, when we release the ballast into the water, we want to make sure it’s safe for the environment,” Dr. Tamburri said.
Chlorine, for example, might need to be neutralized with another chemical before it is discharged into the water. The ship itself may also be harmed by some techniques: for example, oxidizing compounds may corrode its hull. And for all treatments, crew safety has to be taken into account. “There’s no perfect solution — all have their strengths and weaknesses,” Dr. Tamburri said.
Ballast-sterilizing techniques may need to be customized for different types of ships plying different routes. In the Chesapeake Bay, MERC researchers test the methods on water gradients of varying salinity, from fresh to brackish to very salty. Initial trials suggest that a broad suite of solutions may ultimately be adopted.
Dr. Tamburri is quick to point out that ballast is only part of the problem. Creatures like barnacles and mussels hitch rides on the outside of ships, causing damage and also posing an invasive risk. MERC is trying to find ways to quantify these ship-fouling communities and to quantify the threat they pose.
Once the team figures out which types of ships and which areas of a ship are most at risk of introducing invasive species, they hope to fashion solutions like incorporating nonstick surfaces and improving cleaning techniques.
For now, Dr. Tamburri and his colleagues are scrambling to pull together the best technologies possible in time to meet the new regulations for the approximately 90,000 annual big cargo ship visits that unload nearly 200 million tons of ballast in United States waters each year.
“We don’t know when the next zebra mussel will be coming,” he said, citing one of the most prominent invaders of the last few decades. But he is optimistic that the new techniques, once perfected, will at least minimize that risk.
“We can’t have zero risk on invasive species from ships,” he added. “The key is to make them as safe as feasibly possible.”
Can be found at:
http://green.blogs.nytimes.com/2012/05/17/sterilizing-that-blasted-ballast/
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