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Despite its resistance to water, DDT is easily soluble in fats and highly susceptible to "biological magnification" as it makes its way up the food chain. A typical case of this kind of metabolic mayhem occurred in Long Island Sound. After some mosquito-infested marshes were sprayed, the DDT was found in the nearby water in a "safe" concentration of .000003 parts per million. Nonetheless, the DDT quickly accumulated in more concentrated form in the
Sound's tiny Zooplankton (.04 ppm), then built up further in the fatty tissue of plankton-eating fish (.5 ppm). These small fish, in turn, were devoured by larger fish with yet another increase in DDT concentration (2.0 ppm). By the time the chemical had passed into the bodies of such fish-eating birds as cormorants, mergansers and ospreys its concentration (25 ppm) had increased an astounding 10 million times over the original amount (see diagram).
DDT also interferes with the reproductive cycle. Adult fish, for example, are able to tolerate relatively high levels of DDT. The fish embryo, on the other hand, dies almost immediately when it begins to absorb the pesticide through the fatty yolk sac. In birds, DDT kills off the young by interfering with the female's egg-laying process. Though the exact chemistry is still obscure, the pesticide apparently sends the mother bird's liver into a frenzy of enzyme production. The excess enzymes break down such steroids as estrogen that are essential to the manufacture of calcium. Lacking adequate calcium, the bird's eggs emerge thin-shelled and flaky, offering scant protection for the embryo. In at least one instance, reports the National Audubon Society, which has just joined the public crusade against DDT, a bald-eagle egg was found on the shores of Lake Superior with no shell at all—just a fragile membrane. According to University of Wisconsin Ecologist Joseph Hickey, DDT has caused a disastrous decline in the population of the bald eagle, which is the U.S. national symbol—and the emblem of next week's Apollo 11 flight. Other predators, such as the osprey and peregrine falcon, are gradually vanishing, as are the brown pelican and the extremely rare Bermuda petrel.
Airborne Cats. Beyond the danger to fish and birds lies DDT's threat to the whole ecological system. Concentrations of DDT no larger than a few parts per billion in plankton, says Biologist Charles F. Wurster Jr., chief scientific adviser to a New York conservationist group called the Environmental Defense Fund, can substantially hinder the photosynthesis process. On a larger scale, such interference could have a devastating effect, since phytoplankton produces 70% of the earth's oxygen.
A bizarre case of ecological damage from DDT occurred in Borneo after the World Health Organization sprayed huge amounts of the pesticide. The area's geckos, or lizards, feasted on the houseflies that had been killed by DDT. The geckos, in turn, were devoured by local cats. Unhappily, the cats perished in such large numbers from DDT poisoning that the rats they once kept in check began overrunning whole villages. Alarmed by the threat of plague, WHO officials were forced to replenish Borneo's supply of cats by parachute.