Glacial warming's pollutant threat.

Every summer, certain lakes in the northern Rockies receive a rich input of long-banned air pollutants. A tiny crustacean has just pointed scientists to an unexpected source--glaciers.

Oily, semivolatile pollutants can spend years leapfrogging around the globe, by repeatedly evaporating and settling, until they reach cold climes and can't re-evaporate (SN: 3/16/96, p. 174). Once in the water there, the pollutants slowly move up the food chain. Plankton pick up only a little of the substances, but oily, predatory fish and marine mammals accumulate plenty.

In Bow Lake in Alberta, however, researchers from the University of Alberta in Edmonton stumbled upon a striking anomaly. Despite being near the bottom of the food chain, the lake's carrot-hued copepods, Hesperodiaptomus arcticus, turned out to be the most highly contaminated organisms, notes David W. Schindler. Like "swimming bags of fat," these 3-millimeter-long critters absorb pollutants "straight through the body wall," he explains. In probing what makes this lake different from others in the region, his group traced up to 80 percent of the gamma-hexachlorocyclohexane and other banned pollutants entering Bow Lake to meltwater from the Wapta Icefield.

Large amounts of bomb-test fallout in this water suggest that this group of pollutants arrived in the 1950s or 1960s and remained entombed until a recent spate of warm summers increased melting. If the climate continues to warm, Schindler says, the glacier may free even more pollution.