Salamanders May One Day Monitor Degradation In Small Streams

"In general, amphibians, are thought to be good ecological indicators and frogs and toads are often used for this purpose," says Gian L. Rocco, Ph.D. candidate in wildlife and fisheries science. "Stream dwelling salamander populations are considered generally more stable than temporary pool breeding amphibians and may offer another biological tool to assess stream habitat quality, especially where fish and bugs are absent."

While wildlife experts monitor streams for acidity, temperature and pollutants directly, these factors say little about how environmental degradation affects animal populations. Because these salamanders are lungless, breathing through their skin and the linings of their mouths, they can be very sensitive to changes in their aquatic and terrestrial environments. Also, some species lay eggs on land while others lay eggs in the water. These differences, among others, may make some species more sensitive to waterborne pollutants than others.

Lungless salamanders are abundant and widespread; serve as both predators and prey; and lead both aquatic and terrestrial lives. With so many different habitat and breeding requirements and possibly varying tolerances for levels and types of pollution, lungless salamanders are choice amphibians to monitor stream community health.

"Four species of lungless salamander appear to be sufficiently abundant and widespread in Pennsylvania to qualify as potential bioindicators," Rocco told attendees today (June 25) at the 1999 joint annual meeting of the American Society of Ichthyologists and Herpetologists, American Elasmobranch Society, Herpetologist's League and the Society for the Study of Amphibians and Reptiles held at Penn State's University Park campus.

The researchers, who also include Dr. Robert P. Brooks, professor of wildlife and wetlands and Cynthia J. Condliff, undergraduate in wildlife and fisheries, looked at the populations of seven species of salamanders in 14 streams in the central Appalachians of Pennsylvania in 1997 and 1998.

The streams fell into four categories. Minimally disturbed or degraded streams were those that are unaffected by acidity or other pollutants. Episodically acidified streams experience temporary episodes of high acidity and high aluminum in the spring when rains and melting snow greatly increase stream flow. In the summer and fall, these same streams are not as acidic.

Streams suffering from acid mine drainage (AMD) are abundant in Pennsylvania and the Appalachians and occur when coal-bearing rock is exposed to water and air. This produces sulfuric acid and releases a number of metals such as iron, aluminum and manganese into streams.

AMD streams are always acidic and contain metals that are toxic to many aquatic animals, including amphibians. The fourth stream type is not acidic but flows through a watershed fragmented by urbanization or agriculture. The researchers sampled each study stream by searching 4 square meter plots that included both wet and dry bank area. "Three of the seven species were very rare in the samples, but this is probably due to our sampling techniques," says Rocco. "The northern red salamander prefers slow areas of streams and we sampled faster moving water; the longtail salamander ranges farther from the stream and our terrestrial area may not have been large enough; and the seal salamander needs to have very rocky banks, which we did not have."

However, the researchers found the remaining four species abundant enough for stream quality monitoring.

"The mountain dusky salamander was found in most of the study streams and appears fairly insensitive to environmental changes," says Rocco. "We even found them in one stream with very high levels of aluminum."

Another species, the northern dusky, was not found in most acidic streams and appears to be much more sensitive than its close relative, the mountain dusky. The northern dusky is larger than the mountain dusky, and in areas where it is absent, the mountain dusky may become more widespread since it can move into areas generally occupied by the northern dusky.

Lungless salamanders in aquatic life stages were generally scarce in degraded streams. When salamanders were found, these were usually juveniles or adults. The absence of larval stages suggests that reproduction was not possible on site and the salamanders had dispersed from nearby unpolluted seeps and springs.

The other two salamander species are the two-lined and spring salamander. The two-lined, based on field sampling only, appears to be acid intolerant and in most cases was not found in acidic streams. It also seemed to thrive in the warmer streams flowing through the lesser forested watersheds. The spring salamander, based on field sampling only, appears to be relatively acid tolerant and was found in most of the episodically acidified streams and in the lesser contaminated sections of acid mine drainage impacted streams. However, it was rarely found in warmer streams associated with fragmented watersheds.

Counting salamanders, however, does not tell the whole story. The researchers looked at the distribution of life stages -- larvae and juveniles, show how degradation alters reproduction and community assemblages. Relatively unpolluted and fragmented streams had lots of larvae and juveniles. AMD streams had no larvae at all and the episodic streams had few larvae. Areas without larvae did have adult populations.

"Stream conditions may prevent reproduction, but adults and juveniles migrate in from cleaner areas such as seeps," says Rocco. With this variety of environmental tolerances, field surveys of these four species may tell researchers a great deal about water quality in small streams.