Environmental Engineering Reference
In-Depth Information
Similarly, the advantages of periphyton are that they
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Have a naturally high number of species
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Have a rapid response time to both exposure and recovery
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May be identiied to a species level by experienced biologists
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Are easily sampled, requiring few people
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Have a tolerance for or a sensitivity to speciic changes in environmental conditions that is,
for many species, well known.
7.5.3 I
nVertebrateS
Perhaps one of the more common groups of indicators is the invertebrates, particularly the bottom-
living or benthic macroinvertebrates, as discussed in the preceding chapter. For example, taxa such
as the EPT are generally intolerant, so a high number of EPT taxa is usually an indication of an
undisturbed condition.
Generally, invertebrates are good indicators of aquatic health since they (available at: http://
www.epa.gov/bioiweb1/html/indicator.html):
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Live in the water for all or most of their life
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Stay in areas suitable for their survival
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Are easy to collect
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Differ in their tolerance to the amount and type of pollution
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Are easy to identify in a laboratory
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Often live for more than 1 year
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Have limited mobility
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Are integrators of environmental conditions
7.6 RAPID BIOASSESSMENTS
Rapid bioassessments were initially developed in the 1980s to reduce the time (ield, laboratory,
and analytical costs) associated with bioassessments. The advantage of the rapid bioassessment is,
as the name implies, that it can be conducted rapidly with minimal time and cost. Basically, a rapid
bioassessment compares the biota, habitat, and chemistry of selected sites to those of a similar but
undisturbed (or relatively undisturbed) site, the reference condition. Indices are then developed to
quantitate the characteristics of the study sites and compare them to the reference condition. The
study sites are then classiied based on the deviation from the reference or acceptable condition
(such as nonimpaired, moderately impaired, or severely impaired). To keep the method “rapid,”
visual inspections, simple chemical analysis (such as using probes), and a relatively coarse taxo-
nomic classiication of biota (such as insect family) are largely relied upon. Detailed guidance on
conducting rapid bioassessments is provided by Barbour et al. (1999) and Hughes et al. (2009).
One of the irst steps in applying a rapid bioassessment is the selection of the reference condition.
Ideally, the reference condition would be an undisturbed (unimpaired) stream or river. However,
since completely undisturbed systems are rare, some acceptable condition may be deined. Examples
of criteria that are useful in the selection of a reference condition are provided in Table 7.1.
An assessment of the habitat is a key component of a rapid bioassessment. For rapid bioassess-
ment, a visually based approach is used (rather than a rigorous survey method), where speciic
parameters are deined that represent the habitat. Some of the parameters that may be used are indi-
cated in a survey sheet provided as part of the U.S. EPA's rapid bioassessment protocols (Barbour
et al. 1999), as summarized in Table 7.2. Each of the categories could be checked in terms of
general habitat limitation or speciically as limiting to biota (such as periphyton, ish, or macroin-
vertebrates). For a more detailed assessment, examples of rating sheets for habitats are provided in
Figures 7.5 and 7.6.
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