USGS scientist collecting a water-quality sample from the Okefenokee Swamp, GA (circa 2002) that will be analyzed for nutrients and alkalinity.

Preparing a water-quality meter to measure field parameters (pH, temperature, dissolved oxygen, and specific conductance) of waters in the Okefenokee Swamp, GA (circa 2002).

USGS technicians installing a pressure transducer in a pond in the Saint Marks National Wildlife Refuge, FL (circa 2004). Hydraulic data provides the framework for the analysis of amphibian population data.

USGS scientists checking under a cover board for amphibians and collecting a water sample to analyze the acid-neutralizing capacity (ANC) of the water from the adjacent vernal pool, Rock Creek National Park, Washington, DC (circa 2002).

USGS scientist collecting a water sample from a pond in Rocky Mountain National Park, CO (circa 2000) to answer questions about the effect of contaminants on amphibian populations.

USGS biologists preparing to collect amphibian samples at Kettle Tarn in Rocky Mountain National Park, CO (circa 2001). Hydrologists and biologists are working together to understand the reasons for recent amphibian declines.

USGS biologist with an amphibian (boreal toad) that will be weighed, measured, and released after being fitted with a small magnetic tag for later reidentification (circa 2001).

USGS scientist measuring the pH of Paine Run in Shenandoah National Park, VA (circa 2002). Water-quality data is being used to help provide the context for the analysis of amphibian population data.

USGS scientist collecting a water-quality sample from Paine Run in Shenandoah National Park, a site that is part of the Amphibian Research and Monitoring Initiative network.