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AQUATIC-ECOLOGICAL INVESTIGATION IN THE YELLOWSTONE RIVER BASIN David A. PetersonU.S. Geological Survey Cheyenne, Wyoming The Yellowstone River Basin is one of more than 50 river basins nationwide selected for study by the U.S. Geological Survey (USGS) under the National Water Quality Assessment (NAWQA) program. The overall goals of the NAWQA program are to (1) describe current water-quality conditions for a large part of the of the Nation's freshwater streams and aquifers, (2) describe how water quality is changing over time, and (3) improve our understanding of the primary natural and human factors affecting water quality. An ecological investigation is planned throughout the 70,100 square mile basin in Wyoming, Montana, and North Dakota. Sampling sites have been selected on the basis of an environmental stratification including factors such as ecoregion, geology, and land use. The approach is intended to provide insight into ecological variability over time, the role that water quality plays in community structure and stability, differences with respect to various environmental settings, and an overview of the ecological status of the study unit. Biological and related components of the investigation include fish community, bed-sediment and fish-tissue analyses, aquatic invertebrates, algae, and habitat. Retrospective analysis of available reports and data for these components began in 1997 and is ongoing. Fish community assessment began in 1998 at 10 fixed stations, which will also be sampled for water quality and other biological components. Four integrator stations are located on the main stem of the Yellowstone River, three integrator stations are located on the Clarks Fork Yellowstone River, the Bighorn River and the Powder River, and three indicator stations are located on Soda Butte Creek, the Tongue River, and the Little Powder River. Fish communities at each site were sampled using techniques such as electrofishing, seining, and netting. All of the fish captured were weighed and measured, examined for external anomalies, and released, except for those fish retained as voucher specimens for later taxonomic identification. Fish community assessments will be repeated for three years and three reaches at a subset of the sites. Bed-sediment and fish-tissue samples were collected at 24 sites during the late summer and fall of 1998. Samples of both media were preserved and sent to a laboratory for analysis of selected organic compounds and trace elements. Target taxa for the fish-tissue samples were brown trout and carp. White sucker was sampled at several sites as the preferred alternate species when the target taxa were absent or rare. Five to eight fish were composited for each sample; whole bodies were sampled for organic analyses and livers were sampled for trace element analyses. Assessment of aquatic invertebrates, algae, and habitat are planned during the high intensity phase of the project, 1999-2001. Quantitative and qualitative samples of invertebrates and algae will be collected at the 10 fixed stations where fish communities were sampled. Analyses of chlorophyll in algae also are planned. Stream habitat will be characterized on a hierarchical framework that incorporates data at basin, segment, reach, and microhabitat scales. At the reach scale, eleven transects are established to collect information on channel, bank, and riparian characteristics. Examples of data collected at transects are stream gradient, bankfull-channel width, riparian-canopy closure, and substrate size and embeddedness. Sampling methods and protocols used in this study and in other NAWQA studies have been published as a series of USGS reports. Related work conducted in 1998, in cooperation with the National Park Service, included sampling of bed sediment and fish tissue in the Yellowstone River at Yellowstone Lake outlet and the Shoshone River at the mouth to Bighorn Lake. Samples of water, bed sediment, and fish tissue were collected at five sites for a national study of mercury speciation and distribution, in cooperation with the NAWQA national-trace element synthesis planning team and the USGS National Mercury Project. The results of this investigation will be released as part of multiple USGS reports that describe various aspects of the investigation and relate the biological communities to the water quality and habitat characteristics. |
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U.S. Department of
the Interior, U.S. Geological Survey |