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Phycology Section, Patrick Center for Environmental Research

USGS and the Patrick Center:
Using Diatoms and Other Freshwater Algae to Assess Water Quality

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Algae Research with the USGS National Water-Quality Assessment (NAWQA) Program

The NAWQA program is the largest federal effort to date to monitor and assess the conditions of rivers and streams throughout the United States. Fifty-one major watersheds and aquifers (referred to as “study units”) are being evaluated, representing 60% of the nation's drinking water. The goal of NAWQA is to provide continuous water quality assessments that identify and describe major water quality issues. The results of the program will serve as the basis for understanding watershed ecosystems nationwide, and for solving serious water quality problems. To this end, the USGS research staff is measuring a wide variety of water chemistry parameters and physical habitat characteristics, in addition to identifying fish, benthic invertebrates and algae. Data are analyzed on the watershed scale and also on a national scale. At the watershed scale, the focus is on water quality issues pertaining to a particular watershed. National scale syntheses address broader issues such as the distribution and concentration of pesticides and nutrients among watersheds.

The USGS and the Patrick Center for Environmental Research have established a four-year cooperative agreement. Patrick Center scientists in the Phycology Section analyze algal samples collected by USGS biologists; this information is integrated with chemistry, fish, insect, and geomorphologic data collected by NAWQA scientists. The Patrick Center effort will contribute significantly to understanding water quality issues nationwide, while emphasizing the importance of algal distribution and ecology.

Patrick Center scientists have been analyzing NAWQA algal samples since 1994. Under the four-year cooperative agreement which began in 1999, the PCER role was expanded to include data synthesis and interpretation, as well as the preparation and analysis of about 500 samples per year. The Patrick Center subcontracts the analyses of some of these samples to other phycology centers, primarily Dr. Jan Stevenson's lab at Michigan State University.

All samples are collected from the surface of rocks and other natural substrates, then preserved and shipped to Philadelphia. Subsamples of soft-algae, which include green, red, and blue-green forms, and diatoms are analyzed. Accurate identification of algae is rigorously documented with photographs taken through state-of-the art microscopes. After the samples are analyzed, they are stored at the Academy for future reference. The diatom slides are a major addition to the Academy's Diatom Herbarium, already the largest in North America and a major resource for the scientific community.