UGA study reveals ecosystem-level consequences of frog e...( Athens Ga. Streams that once sang w...)

Athens, Ga. Streams that once sang with the croaks, chirps and ribbits of dozens of frog species have gone silent. They're victims of a fungus that's decimating amphibian populations worldwide.

Such catastrophic declines have been documented for more than a decade, but until recently scientists knew little about how the loss of frogs alters the larger ecosystem. A University of Georgia study that is the first to comprehensively examine an ecosystem before and after an amphibian population decline has found that tadpoles play a key role keeping the algae at the base of the food chain productive.

"Many things that live in the stream depend on algae as a base food resource," said lead author Scott Connelly, a doctoral student who will graduate in December from the UGA Odum School of Ecology. "And we found that the system was more productive when the tadpoles were there."

The results, which appear in the early online edition of the journal Ecosystems, demonstrate how the grazing activities of tadpoles help keep a stream healthy. The researchers found that while the amount of algae in the stream was more than 250 percent greater after the amphibian population decline, the algae were less productive at turning sunlight and nutrients into food for other members of the ecosystem. Without tadpoles swimming along the streambed and stirring up the bottom, the amount of sediment in the stream increased by nearly 150 percent, blocking out sunlight that algae need to grow.

The study is part of a larger effort known as the Tropical Amphibian Declines in Streams (TADS) project, which also involves researchers from Southern Illinois University, Drexel University and the University of Alabama. The project is now in its third round of funding by the National Science Foundation and was initiated by Catherine Pringle (UGA Odum School of Ecology) and Karen Lips (Southern Illinois University) in 2000 through a Small Grant for Ex
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