National Geographic : 2010 May
. down a scary, slopeside jeep trail into the re- stricted area. At the edge of the Pumice Plain we began the two-and-a-half-mile walk that the lean 52-year-old has taken thousands of times. His ponytail swung with each step. He talked ecology almost nonstop, his New York accent still discernible after 30 years in the blast zone. Behind us was the volcano, snowless and gray, its northern wall collapsed, its crater exposed. In front was the lake, its surface calm and two- hs covered by the "log ra ," a shi - ing mass of thousands of oating logs. Along the trail were r saplings, lupines, and Indian paintbrush, 15-foot-tall thickets of willow and alder, and, near a stream, hordes of toads and tree frogs. At the lake's edge, we got into warm eece overalls that Crisafulli called bunny suits, into dry suits and masks and snorkels, and into a Zodiac ra , which motored into Duck Bay. And then into the frigid water. The first surprise was the colors: brilliant yellows and greens, electric in the sunlight, a world apart from the drab Pumice Plain. ey belonged to aquatic plants, thick, vine- like macrophytes stretching ten feet from lake bed to surface. Mossy clumps were suspended above the silt. Everywhere I turned were sh, hook-jawed and fat, all of them 20 or more inches. I swam a er them. ey didn't spook. e sunken jungle, I noticed, was only in the shallows. In deeper water it was gone---and so were the sh. Before the eruption Spirit Lake was, like many subalpine lakes, unproductive and nutrient-poor, with clear water and few shallow spots. When the volcano top slid into it at 150 miles an hour, it became choked with what Crisafulli terms "pyrolyzed forest constituents"---organic mate- rial burned in the blast. e water was warmed to body temperature, lled with dissolved car- bon, manganese, iron, and lead. Visibility went from 30 feet to six inches. Bacteria ourished. e rst scientists to take water samples came down with unexplained ailments. ere was a rapid succession of microbes: aerobes, which quickly used up all the oxygen; anaerobes, which require none; then nitrogen-consuming bacteria; and then forms that fed on methane and heavy metals. For 18 months Spirit Lake was ruled by chemistry, home to "hundreds of mil- lions of bacteria per milliliter," Crisafulli says. Finally, the microbes had consumed so much that they began to die o , and streams and snow- melt came in, and the water cleared. Once light penetrated Spirit Lake, algae and other phytoplankton colonized, followed by zooplankton, which fed on the phytoplankton, followed by aquatic insects and amphibians. By the early 1990s, macrophytes grew in shal- low shoals---ideal trout habitat that didn't exist before the eruption. Gorging on tiny midges and freshwater snails, the rainbows were reaching a record four or ve pounds in two or three years. e post-eruption lake followed a pattern Cri- safulli would see many times in the blast zone. New organisms colonize the virgin environment with dramatic success, only to burn themselves out or be checked by predators, parasites, or competitors. is was the second revelation of St. Helens: When there's a blank slate, ecological succession is a cycle of boom and bust. Spirit Lake's richness is spilling over. When a tadpole dies as a frog on the Pumice Plain, when an insect hatched in the lake is deposited in the ash, their nutrients are transferred to land. Slowly this process undoes what the eruption wrought. "Before the eruption, the terrestrial environment was superproductive," Crisafulli says, with "lots of nutrients and carbon tied up in the old-growth forest. In comparison, the lake was impoverished. A er the eruption they Some hear tales of two-foot trout and ask why Spirit Lake is off-limits. Others grumble that it is time to open the restricted zone.