Deoxygenating ship ballast tanks to reduce corrosion may also prevent the introduction of non-native aquatic species, report Mario Tamburri of the Monterey Bay Aquarium Research Institute and colleagues.

Ballast water is considered to be one of the most important ways that non-native aquatic species are transported and introduced to new locations. Although several promising techniques are available for treating ballast water to prevent the transport of aquatic organisms, such as filtration, UV radiation, heat treatment, and the use of biocides, such processes impose significant costs on the shipping industry, are often dangerous to ship crew members, and can have a negative impact on areas where ballast water is discharged.

The new anticorrosion technique, which was developed by researchers at Sumitomo Heavy Industries in Japan, is a cost-effective way to prevent rust in ballast tanks. The process, which involves purging oxygen from ballast water with nitrogen, could save approximately $70,000 a year for each ship that uses the technology instead of paint to prevent rust, according to the researchers.

To determine whether the process can also limit invasions, the researchers performed oxygen tolerance experiments on the larvae of three aquatic invasive species—an Australian tubeworm, European green crab, and European zebra mussel. After 2 days of exposure to low levels of oxygen (< 0.8 mg/L), 79% of the tubeworm and 97% of the green crab larvae were killed, and after 3 days, 82% of the zebra mussel larvae were killed. Thus, the new rust-prevention technique appears to extend ship life and, at the same time, dramatically reduce the numbers of live organisms found in ballast water. (Biol. Conserv. 2002, 103, 331–341). —BRITT ERICKSON