A seaweed soaks up TNT - and may help clean oceans

One of seaweed's more unusual traits is its ability to survive in intertidal zones, where it lives sometimes in salt water, sometimes in fresh. Now, Ira Levine, a University of Southern Maine researcher, is using chemicals to flip the porphyra's internal physiological switch. His idea is to create a full-time freshwater seaweed for upstream salmon hatcheries to absorb excess nitrogen and fish waste that can foul streams.

"It's only one cell thick, like a sheet of paper, but it grows fast," says Dr. Levine. "That's why it can absorb nutrients so quickly." It also gives hatcheries another crop they can harvest for the valuable pigments and fatty acids in porphyra. If successful, the technique could be used in salmon aquaculture around the world. It might also be used to detoxify more widespread pollutants like polychlorinated biphenyls (PCBs).

The US coastline could use a cleanup. River estuaries "are like a sink," Cheney notes, since they receive society's waste, which then becomes buried in sediments. Instead of staying put, though, the toxins often begin working their way into plant life and on up the food chain, as has happened with mercury in fish tissues.

Overall, the nation's estuaries are rated "fair" - with about 8 percent of estuary sediments in the Northeast rated toxic and in "poor condition," according to the 2005 report from the US Environmental Protection Agency. Major pollutants in those sediments include PCBs, mercury, and other heavy metals.

Right now, one of the few techniques for dealing with sediment pollution like this is costly dredging. But that still leaves a mountain of toxic waste to be removed and disposed of. "We are hopeful we might discover or select a native seaweed that can remediate or detoxify PCBs buried in sediments in river basins around the world," Cheney says.

Ironically, Cheney's TNT-sopping seaweed can't be tested in the wild because it might spread out of control or have some other unintended effect. So the professor and his students are now using natural selection instead of genetic engineering. They've already bred a natural version that is nearly as effective as the genetically engineered variety, he says.

"The professor is wise to think about the ecological considerations with the engineered organism," says Jane Rissler, senior scientist with the Union of Concerned Scientists in Washington. "It's a good idea to keep the genetically engineered version in a bottle if a naturally selected seaweed can do the same thing."

For his part, Cheney harbors hope that he might return one day to studying the nutritional benefits of porphyra. But in the meantime, he's pleased that the seaweed's potential environmental benefits have made the task of attracting top graduate students into his classroom easier.

"These students are eating sushi in the cafeteria - and growing the same seaweed species up here in the lab," he says. "Now they're finding out that nori is the super seaweed that's good for you - and the environment."

Page: 1 | 2