River Ecology and Restoration - River Dynamics and Integrated River Management - page 678

3) Uses of the IBI
IBIs provide a valuable framework for assessing the status and evaluating the restoration of aquatic
communities. IBIs encompass the structure, composition, and functional organization of the biological
community. IBIs can be viewed as quantitative empirical models for rating the health of an aquatic
ecosystem, providing a single, defensible, easily understood measure of the overall health of a river reach
in question (Lyons et al., 2001). For example, IBIs can be used to quickly identify both high-quality reaches
for protection and degraded sites for rehabilitation.
While total IBI scores can provide the user with an indication that a stream fish community is
potentially degraded by environmental stressors, the total score cannot provide the ability to identify
which individual stressors are causing the response. The same total IBI score can be reached by an
infinite combination of individual metric scores, each with its own environmental stressor. Thus, several
researchers have focused not on the final IBI score, but rather on how the individual metrics can be used
to describe the effects of anthropogenic stresses on the fish community (e.g., Manolakos et al., 2007;
O'Reilly, 2007; Novotny et al., 2008; Bedoya et al., 2009). If relations between stresses and the fish
community can be found ways to reduce these stresses and efficiently improve the fish community can
be derived.
10.3.3 Bioassessment
10.3.3.1 Rapid Bioassessment
Rapid bioassessment techniques are most appropriate when restoration goals are nonspecific and broad,
such as improving the overall aquatic community or establishing a more balanced and diverse
community in the river ecosystem (FISRWG, 1997). Bioassessment often refers to use of biotic indices or
composite analyses, such as those used by the Ohio Environmental Protection Agency (Ohio EPA, 1990),
and rapid bioassessment protocols (RBP), such as those documented by Plafkin et al. (1989). The Ohio
EPA evaluates biotic integrity by using an invertebrate community index that emphasizes structural
attributes of invertebrate communities and compares the sample community with a reference or control
community. The invertebrate community index is based on 10 metrics that describe different taxonomic
and pollution tolerance relations within the macro-invertebrate community. The rapid bioassessment
protocols established by the U.S. Environmental Protection Agency were developed to provide states
with the technical information necessary for conducting cost-effective biological assessments (Plafkin et
al., 1989). The RBP are divided into five sets of protocols, three for macroinvertebrates and two for fish,
as shown in Table 10.6.
The rapid bioassessment protocols RBP Ē to RBP Ĕ are for macroinvertebrates. RBP Ē is a
“screening” or reconnaissance-level analysis used to discriminate obviously impaired and unimpaired
sites from potentially affected areas requiring further investigation. RBP ē and Ĕ use a set of metrics
based on taxon tolerance and community structure similar to the invertebrate community index used by
the State of Ohio. Both are more labor-intensive than RBP Ē and incorporate field sampling. RBP II uses
family-level taxonomy to determine the following set of metrics used in describing the biotic integrity of
a stream: (1) Species richness, (2) Hilsenhoff biotic index (Hilsenhoff, 1982), (3) Ratio of scrapers to
filtering collectors, (4) Ratio of Ephemeroptera/ Plecoptera/Trichoptera (EPT) and chironomid abundances,
(5) Percent contribution of dominant taxa, (6) EPT index, (7) Community similarity index, and (8) Ratio
of shredders to total number of individuals. RBP Ĕ further defines the level of biotic impairment and is
essentially an intensified version of RBP ē that uses species-level taxonomy. As with the invertebrate
community index, the RBP metrics for a site are compared to metrics from a control or reference site.