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Biological assessments and criteria can be an important component
of State and Tribal watershed management programs by assisting in
prioritization and targeting of actions, setting restoration goals
and performance standards, and documenting results.
Biological assessments provide integrated evaluations of water
quality. They can identify impairments of aquatic life from contamination
of the water column and sediments from unknown or unregulated chemicals,
non_chemical impacts, and altered physical habitat. Resident biota
function as continual monitors of environmental quality, increasing
the likelihood of detecting the effects of episodic events (e.g.,
spills, dumping, treatment plant malfunctions, nutrient enrichment),
toxic nonpoint source pollution (e.g., agricultural pesticides),
cumulative pollution (i.e., multiple impacts over time or continuous
low-level stress), or other impacts that periodic chemical sampling
is unlikely to detect. Impacts on the physical habitat such as sedimentation
from stormwater runoff and the effects of physical or structural
habitat alterations (e.g., dredging, filling, channelization) can
also be detected.
Biological criteria, derived form data collected from bioassessments,
provide an effective tool for addressing water quality problems
by providing regulatory mechanisms to assess the biological resources
at risk from chemical, physical or biological impacts. A primary
strength of biological criteria is the detection of water quality
problems that other methods may miss or underestimate. Biological
criteria can be used to determine to what extent current regulations
are protecting designated and/or existing aquatic life uses.
Biological Assessments and
Criteria: Crucial Components of Water Quality Programs (EPA
822-F-02-006) (PDF, 1MB)
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