INTRO: Ships plying the world's oceans sometimes have unwanted hitchhikers lurking inside their ballast tanks. When the tanks are emptied at distant ports, the marine hitchhikers can displace local marine species. Earlier this year, the federal government mandated that each state begin to deal with the problem. Recently, an Alaska oil tanker became a test-bed for a new technology aimed at killing these invasive species before they can cause harm. Doug Schneider has more, in this week's Arctic Science Journeys Radio.
STORY: The oil supertanker Tonsina is an imposing 869 feet long. When full, it carries more than 807,000 barrels of Alaska crude oil within its double hull to ports along the United States West Coast. The ship also has massive seawater ballast tanks that help stabilize the ship in rough seas. When the ship reaches its destination, the seawater is emptied into local waters.
But all too often, it's not just seawater that's pumped back into the ocean. Bacteria, viruses, and non-native crabs, mussels and fish are also released. When these foreign species end up in local waters, they can wreak havoc on the marine environment.
Killing these invasive species before they do harm is the goal of an ambitious collaboration between the Tonsina's owner, British Petroleum, and university scientists at the Washington Sea Grant Program. Recently, while the Tonsina was in Seattle, Washington, scientists conducted experiments to see if ozone, a naturally occurring chemical, could be used to kill marine organisms in the ship's ballast tanks. Russ Herwig is a Washington Sea Grant ballast water specialist at the University of Washington School of Aquatic and Fishery Sciences.
HERWIG: "Today we're aboard the S/T Tonsina. We're conducting an ozone treatment experiment. This is a real shipboard experiment, using real ballast water and using a technology known as ozone treatment. As many people realize, ballast water is transported all over the world from one port to another, and this may result in the introduction of organisms that are not desirable."
BP volunteered the Tonsina for the experiment, and then paid nearly $3 million to fit the tanker with miles of pipes, pumps and ozone generators to inject ozone into the ship's ballast tanks.
HERWIG: "On the Tonsina, the ozone is introduced into the ballast tanks through a system of pipes and diffusers. There's approximately 2,000 diffusers installed on the Tonsina. The ballast tanks are monstrous. There are approximately 900,000 gallons of seawater in a ballast tank, so in order to treat it, you have to diffuse the ozone evenly throughout."
The ozone itself is a gas commonly used in wastewater treatment plants and swimming pools. More recently, the technology has made its way into home spas and hot tubs.
But here on the Tonsina, ozone will be used to kill harmful marine life. Before turning on the ship's ozone generators, Jeff Cordell, a senior research biologist at the University of Washington, examines the critters lurking inside the tanks.
CORDELL: "What we're looking at is a plankton net haul taken in one of the ballast tanks before the ozone treatment. It was a vertical haul taken from the bottom of the tank all the way up to the top. So this is a fraction of what was in the tank. I put it under the microscope on the television screen and you can see that it is really quite prolifically full of life."
To be effective, scientists have to figure out just how much ozone is needed to kill everything from the tiniest plankton to the largest fish and crab that may have hitched a ride aboard the ship. Russ Herwig.
HERWIG: "Our real challenge, though, is the vast diversity of biota that is present in seawater, and finding a technology that's effective for the microorganisms through the macro organisms. Many organisms also have resistant stages called cysts that can resist chemical treatments. They then emerge from the cysts stage and can cause devastation."
In an earlier test conducted in Alaska, the ozone treatment successfully killed most of the bacteria and plankton. Other species, like crabs, proved resistant to the ozone, so tests will continue. But it's likely that the system designed for the Tonsina won't be the only solution to deal with invasive species. Researchers elsewhere are experimenting with other chemical treatments and the use of ultraviolet light to sterilize ballast-water critters.
This is Arctic Science Journeys Radio, a production of the Alaska Sea Grant Program at the University of Alaska Fairbanks School of Fisheries and Ocean Sciences. I'm Doug Schneider.
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Arctic Science Journeys is a radio service highlighting science, culture, and the environment of the circumpolar north. Produced by the Alaska Sea Grant College Program and the University of Alaska Fairbanks. The shortcut to our ASJ news home page is www.asjnews.org.
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For more information
Ozone, Seawater and Aquatic Non-indigenous Species: Testing a Full-Scale Ozone Ballast Water Treatment System on an American Oil Tanker (11th International Conference on Aquatic Invasive Species)
Ozone holds hope for treating tanker ballast water (Anchorage Daily News)
BP gets tough on tanker ballast creatures (Kenai Clarion)
BP gets tough on tanker ballast creatures (Alaska Journal of Commerce)
Related ASJ stories
Unwanted Ballast Hitchhikers (1996)
Ballast Aliens (1997)