Preliminary Classification of Ecosystems under Consideration and
the Selection of Reference Sites
The classification entails the division of the aquatic ecosystems
into classes or groups based on physical and geographic characteristics
not subject to human perturbation. The intent of classification
is to identify the smallest number of classes which, under ideal
conditions, would represent comparable biological communities.
These classes are usually developed for specific waterbody types,
such as rivers and streams, lakes, estuaries and wetlands. The classes
are often further subdivided where necessary to provide further
ecosystem specificity within a group. Subclassification is often
done based on ecoregions and/or waterbody size.
A set of multiple reference sites are then selected from within
each ecosystem class. The reference sites are those least impaired
by human influence and are characteristic of the biological community
represented by that particular class. For better statistical power,
each class should have a minimum of 5 to 10 reference sites from
which the biocriteria are to be developed for that particular class.
For further information, go to EPA classification and reference
site selection guidance for: (1) Streams and Small Rivers, (2) Lakes,
and (3) Estuaries.
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