To measure pollution in tainted waters, scientists use the aquatic equivalent of a miner's canary. In standard tests, they measure pollution by how fast small crustaceans or fish die, or by changes in their reproductive rate. This approach beats measuring each of hundreds of chemicals, but it can still cost more than $1,000 a test and take a week.
Scientists at the Georgia Institute of Technology have devised a new test that sharply cuts both time and cost. The secret is using a tiny creature called a rotifer. As pollution rises, the pinhead-size animals eat more slowly. So researchers concocted a diet of microscopic glowing rubber balls. By feeding the balls to the rotifers, then measuring how much the creatures glow, it's possible to ascertain pollution levels in one hour, at a cost of about $20. Eventually, the rotifers could be genetically engineered with a gene for bioluminescence, says Georgia Tech's Terry Snell. That way, they would glow on their own in clean water and dim as pollution increases.