195 



while Americans get their information from 

 TV, they don't necessarily trust that me- 

 dium: They place the highest tnjst m doc- 

 tors, articles hy scientists, and reports from 

 the National Institutes of Health, and de- 

 scending levels of trust in newsmagazines. 

 TV news, newspapers, and TV talk shows. 



Not surprisingly, the single most powerful 

 influence on scientific literacy was educa- 

 tion. Ranking second was regular reading of 

 magazines and newspapers. Age showed up 

 as an independent influence: People over 65 

 had a poorer grasp of biomedicine than 

 younger people, even when other factors 

 such as education were held cot\stant. That is 

 "problematic." says Pifer, since older people 

 are more likely to need biomedical knowl- 

 edge to deal with their own health problems. 



The overwhelming message of the study, 

 says Miller, is that "education drives the sys- 

 tem" of understanding science. He adds that 

 "in order to change... the proportion of Am- 

 ericans who understand scientific inquiry, 

 we must do it in our schools. If we miss that 

 boat, we aren't going to change very much." 

 -M.B. 



Flood Flexes Its Mussels ^^^m 



A new and unlikely item has been added to 

 the list of problems stemming from the Great 

 Rood of 1993, which soaked the midwcstem 

 United States: zebra mussels. As climatolo- 

 oist Stanley Changnon of the Illinois State 

 Water Survey explained at the AAAS meet- 

 ing, the flood moved great numbers of these 

 destructive mollusks down the Illinois River 

 almost to the point where it joins the Missis- 

 sippi. And while the impact of the mus- 

 sel migration may pale in comparison 

 to 30 lives lost, 17 million acres sub- 

 merged, and trar^sportation systems 

 cnppled. Changnon warned that the 

 spread of the zebras isn't a trivial prob- 

 lem. "This may turn out to be truly an 

 ecological disaster." he said. 



This disaster is one aquatic biolo- 

 gists have feared, though they didn't 

 expect It so soon. The tiny, stnped Eu- 

 ropean Zebra mussels {Dreissena poly- 

 morpha) were first found on U.S. shores 

 in 1988. probably hitchhiking into 

 Lake St. Claire on a ship from Europe. Water 

 The problem with the invaders is that spread 

 they breed quickly and live in dense 

 clumps, clogging pipes that carry water to 

 cool ship engines and power plant condens- 

 ers. In addition, they glom onto and destroy 

 native mussels, clams, and snails — -and de- 

 plete water oxygen levels, threatening all the 

 marine life in areas they infest 



Until recently, the zebra invasion hadn't 

 advanced alt that far The zebras have largely 

 been confined to the Great Lakes and been 

 found mostly in baseball-sized clumps. But 

 in August 1993, divers for the Illinois Nat- 



1226 



ural History Survey (INHS), a state-run sis- 

 ter agency of Changnon's Water Survey, 

 found them carpeting the Illinois River 300 

 miles downstream of Chicago. 5 miles from 

 where the river merges with the Missis- 

 sippi. T^e carpet was 2 inches thick and 

 contained an estimated 94,000 mussels per 

 square meter — in a spot where fewer than 

 1000 per square meter had been found the 

 year before. "There hasn't been an explosion 

 like this yet. even upstream." says INHS's 

 Richard Sparks, an aquatic ecologtst. This 

 means that the critters are now poised to 

 overrun the Mississippi itself. 



A few lines of evidence lead Changnon 

 and Sparks to believe that the masses of for- 

 eign shellfish were washed dowiistream by 

 the flood. For one thing, populations found 

 in the Illinois River closer to Chicago's Lake 

 Michigan, the likely source, were not as 

 der\se as the populations downstream near 

 the confluence of the Illinois and the Missis- 

 sippi. This suggests that heavy rains carried a 

 "pulse of larvae" downstream, where they 

 settled on the bottom. In keeping with this 

 theory, the mussels found downstream were 

 smaller than the ones found upstream. 



Preliminary evidence gathered by INHS 

 suggests the zebras may already be depleting 

 oxygen levels in the Illinois River. Sparks 

 says aquatic life is stressed when oxygen lev- 

 els fall to less than 5 parts per million, and 

 already levels as low as 3.2 have been found 

 in areas heavily infested with zebras. "One of 

 the most dramatic effects is they could wipe 

 out native species of mussels and snails," says 

 Sparks. The oxygen depletion. Sparks argues, 

 could also have "drastic" effects on sewage 



s^n. The Great Rood ol 1993 seems to have 

 the zebra mussels downsiream. 



treatment plants that are permitted to dump 

 oxygen -depleting organic wastes into the riv- 

 er- If these plants are forced to cut back on the 

 wastes they can discard, he reasons, the in- 

 creased coses will be passed on to consumers. 

 To prevent such consequences. INHS has 

 proposed a scheme to slow zebra mussel mi- 

 gration. If larvae do not float dowrutream 

 and repopulate the mats of mussels now in 

 the Illinois Rivet, chey will naturally die out 

 in 4 to 5 years. One way larvae could be 



SCIENCE • VOL, 263 • 4 MARCH 1994 



exterminated upstream is by warming the 

 water in the canal system that links the 

 Great Lakes to the Illinois River at Chicago. 

 INHS proposes heating the water tn the ca- 

 nal system with waste heat from municipal 

 and industrial sources. Though this strategy 

 will not prevent existing populations from 

 sending larvae further downstream in the Il- 

 linois and into the Mississippi, INHS be- 

 lieves the overall damage could be signifi- 

 cantly lowered by breaking the chain. 



If nothing is done to slow the zebra mussel 

 migration, INHS predicts hordes of larvae 

 will float downstream in the next 2 years, 

 carpeting much of the Illinois River and 

 some of the Mississippi. And if that happens, 

 the Great Flood of 1993 will become greater 

 still, as It continues to wreak havoc in the 

 unlikely form of a striped freshwater invader 

 that displaces everything in its path. 



-Jon Cohen 



Quantum Baseball With Lasers ■ 



Physical chemist Kent Wilson of the Univer- 

 sity of California. San Diego, refers to his 

 work as "controlling the future of matter. "In 

 his talk at the AAAS meeting, he used a 

 photoof Babe Ruth to explain this enigmatic 

 phrase, saying that when the baseball star 

 wanted to control the future of the base- 

 ball — say, to make it clear the right field 

 fence at Yankee Stadium — he applied just 

 the right driving force with the bat. Wilson is 

 trying to do something simitar, not with 

 baseballs but with the denizens of the 

 microworld: atoms and molecules. And his 

 tool IS nothing as crude as 36 ounces of hick- 

 ory or ash — it's a laser system producing pre- 

 cisely crafred pulses. 



Ever since the invention of lasers. 30 

 years ago, researchers have wanted to use 

 them to control chemistry. But all attempts 

 so far have failed, because energy applied to a 

 particular bond would leak to other bonds in 

 a molecule, explains Wilson's Princeton col- 

 league, chemical physicist Warren Warren. 

 It didn't matter how finely tuned the laser 

 pulses were, says Warren, "we couldn't do 

 anything that can't be done with an ordinary 

 bunsen burner " As a result, many people still 

 consider laser-controlled chemiscrv a pipe 

 dream or a joke, he adds. 



But several recent advances have made 

 this idea seem less whimsical. The first came 

 in the mid-1980s, when scientists learned to 

 create laser pulses short enough to deal with 

 chemical reactions on their own time 

 scale — a quadrillionth of a second or less. But 

 since then, people have only used laser pulses 

 to observe — not to control chemistry. Now, 

 says Wilson, he is learning to use high-speed 

 computers to calculate a laser pulse with just 

 the right frequency-versus-iime profile to 

 achieve a specific goal, such "as stretching a 

 bond or controlling an electron's position. 



