Ecological Indicators | Region 10 | US EPA

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Ecological Indicators

Indicators are types of data that detect and track changes in integrity and sustainability of ecological condition. Core indicators are those that have known utility for describing the ecological condition of rivers and streams. Additional indicators will be collected from the western pilot focus areas.

Core Indicators

Water Quality
Physiochemical water quality characteristics affect the ability of species to persist in a given lotic habitat. Water quality data are collected to determine the acid-base status, trophic condition (nutrient enrichment), and chemical stressors. Physical parameters include light penetration (e.g., turbidity, suspended solids), temperature and ionic strength (e.g., conductivity). Chemical parameters include the concentrations of dissolved gases, major cations, anions, and nutrients (i.e., nitrogen, phosphorus).

Physical Habitat Structure
Stream physical habitat structure includes all those structural attributes that influence or sustain organisms within the stream. Habitat assessments generally provide a critical understanding of a stream's ecology. Some common physical habitat attributes are stream size, channel gradient, channel substrate size and type, habitat complexity and cover, and riparian vegetation cover and structure. The understanding of the physical habitat of an area allows for better assessments of the stream ecosystem and human caused effects.

Aquatic Macroinvertebrate Assemblage
Aquatic macroinvertebrates play important functional roles in lotic ecosystems and are good indicators of stream quality. Aquatic macroinvertebrates represent a fundamental link in the food web between organic matter resources (e.g., leaf litter, periphyton, detritus) and fishes. Within specific biogeographical regions, aquatic macroinvertebrate assemblages respond in predictable ways to changes in stream environmental variables. Because many aquatic macroinvertebrates have limited migration patterns or a sessile mode of life, they are particularly well suited for assessing site-specific effects.

Fish and Aquatic Vertebrate Assemblage
The fish and other aquatic vertebrates can indicate stream and riparian quality. Extensive life history information is available for many species, and because many are high order consumers, they often reflect the responses of the entire trophic structure to environmental stress. Also, fish provide a more publicly understandable indicator of environmental degradation. Fish generally have long life histories and integrate pollution effects over longer time periods and large spatial scales.

Periphyton are algae, fungi, bacteria, protozoa, and associated organic matter associated with channel substrates. Periphyton are useful indicators of environmental condition because they respond rapidly and are sensitive to a number of anthropogenic disturbances, including habitat degradation, contamination by nutrients, metals, herbicides, hydrocarbons, and acidification.

Data Collection
Methods of data collection have been developed for each of the core indicators. In-depth explanation of data collection methods used for the EMAP Western Pilot are available in the Surface Waters Field Operations and Methods Manual for Measuring Ecological Condition of Wadeable Streams (1998). To obtain a copy contact:

1. Lillian Herger

2. Click here for a copy of the Surface Waters Manual (PDF) (295 pp. 38MB) It is recommended that this PDF not be downloaded unless using a broadband connection.

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