Stream Ecology

Streams are home to countless species, some of which we’re familiar with, and some less so. The aquatic organisms in streams include fish, of course, but go far beyond that.  Molluscs, like clams and mussels. Amphibians, like salamanders and frogs. The larvae of many insects, like dragonflies, damselflies, and mayflies. Algae and bacteria.

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Stream ecology encompasses the study of these aquatic organisms, but also the study of the riparian zone, sediment transport, the movement of energy and nutrients within the stream, and a host of other aspects of stream ecosystems.  USGS National Water-Quality Program studies of stream ecology seek to:

• Assess the status and trends of aquatic ecological conditions (invertebrates, fish, algae and habitat) in rivers and wadeable streams.
• Relate ecological conditions to chemical stressors (such as nutrients and pesticides) and physical disturbances (such as habitat and hydrologic alterations) in the context of different environmental settings and land uses.
• Enhance understanding of factors that influence the biological integrity of streams and how stream ecosystems may respond to diverse natural and human factors.
• Develop key ecological indicators of aquatic health.

How Healthy Are Our Streams?

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Healthy functioning stream ecosystems provide society with many benefits, including water purification, flood control, nutrient recycling, waste decomposition, fisheries, and aesthetics. Access a national assessment of the ecological health of our nation’s streams.

Water Quality and Ecology of Small Streams (RSQA)

The Regional Stream Quality Assessment (RSQA) is studying the relations between stressors (chemical and physical) and stream ecology (fish, algae, and aquatic invertebrates) at hundreds of small streams across five major regions of the United States.  Users can access an online mapping tool to see scorecards that summarize stream health at each stream site and to compare water quality at small streams across a region. Users also can download data for hundreds of chemical compounds measured in streams.

Streamflow Alteration

Humans, just like aquatic organisms, need water, but flood control, urban infrastructure, irrigation of agriculture, and myriad other ways we manage water affect the natural flow of streams and rivers.  Learn how the ways we manage land and water affects the natural patterns of streamflow and the ecosystems that depend on them.

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Nutrients and Stream Ecosystems

Intensive studies by the USGS National Water Quality Program in agricultural areas provide insight into how nutrients associated with agricultural activities have affected algal and invertebrates communities in agricultural streams.

Effects of Urban Development on Stream Ecosystems

Nowhere are the environmental changes associated with urban development more evident than in urban streams. Contaminants, habitat destruction, and increasing streamflow flashiness resulting from urban development have been associated with the disruption of biological communities, particularly the loss of sensitive aquatic species. Read about a comprehensive study of effects of urban development on stream ecosystems in nine major metropolitan areas of the U.S.