In a Pennsylvania Rainforest

salamander

It's mid August here in central Pennsylvania, and the land is gripped by drought. But two miles north of Penn State's main campus, the forest is a tangle of verdant health. This is where biology graduate student Matt Laposata spends much of his summer hours. Today he's inspecting temporary homes for Jefferson salamanders.

These are no ordinary woods. Once a week, for 12 hours straight, they get sprayed with water from high-pressure, revolving lawn sprinklers set 50 feet apart. In the dappled, misty sunlight, the streams splash off oak, poplar, and birch in shimmering rainbows, adding two inches of water a week, plus rainfall. The appropriate word here is lush. No wonder; the water comes from Penn State's treatment plant, an experimental water disposal and fertilization system set up here 15 years ago. The outflow is filled with all the myriad chemicals you'd expect to find in the treated effluent of a small city. What better place to see what effect society's runoff might have on amphibians?

Scattered through the irrigated woods are ten plastic flower pots with their bottoms cut out, sunk into the ground. Wire-screen tops have been snapped snugly across their 14-inch rims. Ten more pots sit in adjacent areas—similar, but sprayless.

In each pot lives a single Jefferson salamander, spending most of its time in a short, muddy, artificial burrow. The animals are deep brown, almost black, the size of a child's pinky. They feel like satin.

"What we're trying to do," Laposata explains, "is to see if their physiological balance can be upset through exposure to adverse soil conditions." Soil chemicals can pass right through their permeable skin.

Today he's measuring soil temperature, collecting a little dirt for analysis, and dumping a vial of redworms into each pot. Later, he'll gather the 20 Jeffersons, compare them for physical anomalies, then (after a quick death by freezing), analyze them to see if their sodium-potassium-calcium-magnesium ratio is out of balance.

The findings may help Laposata solve questions resulting from a series of tests earlier this year. In April, he selected six ponds, half in the treated area, half outside it. Then he fashioned 30 amphibian nurseries the size of cleanser cans from plastic tubing with ends of screening. Into each he dropped 15 eggs (three each of Jefferson salamanders, wood frogs, and spotted salamanders), and slid them into the ponds.

The sample was too small to produce solid figures. "But at first glance," says Laposata, "the results are really interesting. In every case we found higher mortality in the sprayed-area ponds than in those outside it. We're not sure why."

Is there something in the treated water that is killing salamanders? No, Laposata will conclude three months later. The ponds hold no mysterious toxin. It's simply that the effluent is so nutrient-rich that plant life—mostly duckweed—has covered the pond almost completely. The result: little surface area available for air absorption, and because of blocked light, few underwater plants producing oxygen. No tadpole can live in an oxygen-less world.

Matthew Laposata (mml146@psu.edu) is a graduate student in the Intercollege Graduate Degree Program in Ecology, 208 Mueller Lab, University Park, PA 16802; 814-863-0278. His adviser is William Dunson, Ph.D., professor emeritus of biology in the Eberly College of Science, 208 Mueller; 865-2461; wad4@psu.edu. This project is funded by the Pennsylvania Cooperative Fish and Wildlife Research Unit and the University. Robert Gannon teaches science writing at the University.

Last Updated May 01, 1998