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Biological Integrity and B-IBI
The following are brief descriptions of Biological Integrity, Biomonitoring, and the Index of Biological
Integrity. For more in-depth information, see http://www.cbr.washington.edu/salmonweb/.
Biological Integrity and Biomonitoring what is it, why is it important, and how is it influenced by human
activity?
The federal Clean Water Act (1972) states a clear and broad goal: "The objective of this Act
is to restore and maintain the chemical, physical, and biological integrity of the nation's waters" - Clean
Water Act (CWA) Section 101(a).
Integrity refers to an unimpaired condition, a state of being complete or undivided. Biological
integrity has been defined as "[t]he ability to support and maintain a balanced, integrated adaptive
assemblage of organisms having species composition, diversity, and functional organization comparable
to that of natural habitat of the region" (Karr and Dudley 1981, Karr et al. 1986). As a result of
evolution, each organism is adapted to the environmental conditions in its native biogeographic region.
An environment that supports an assemblage of organisms similar to that produced by long-term
evolutionary processes has high biological integrity. Changes that result from human activities cause a
divergence from biological integrity, that is, a decline in biological condition.
A Word about Chemical vs. Biological Monitoring
The Clean Water Act stipulates that the chemical, physical and biological integrity of our waters
are of value. Most monitoring activity over the past 25 years has focused on chemical monitoring with
an emphasis on meeting human health goals. Unfortunately, the emphasis on chemical monitoring has
not led to clean water or to healthy streams (Karr and Chu 1997). Chemical monitoring only provides a
slice of the stream integrity picture - water quality as a value to humans.
Chemical monitoring can underestimate degradation in living systems. When biological
condition is measured, the number of impaired river miles doubles from 25% as indicated by chemical
monitoring to 50% (Karr and Chu 1998). As this statistic indicates, biological monitoring provides
insight to a stream's ability to provide a healthy place to live for aquatic organisms.
Biological integrity, although specified in the Clean Water Act has been, until recently, largely
ignored. Measuring the stream biota provides a direct assessment of resource condition because the
characteristics of the biota reflect the influence of human activity in the surrounding watershed. If the
biota is not present at the level expected, we have direct confirmation that human influences are
degrading steams and the environments that they drain. Biological monitoring is a method for measuring
biological condition. In aquatic environments, biological monitoring can be focused on a variety of
assemblages (e.g., algae, invertebrates, fish, macroinvertebrates).
Measuring Human Influences
Biological monitoring allows us to understand more of the processes occurring in our watersheds
by determining what organisms are found in a stream and comparing it to what organisms are expected
to be present. Biological integrity of streams is directly influenced by human activity (forestry,
agriculture, urban development, recreation, grazing, etc.). Measuring biological integrity provides an
insight to the human impacts upon stream systems and provides clues regarding where we need to
protect streams or where we can start helping to restore their integrity.
A biological integrity monitoring approach consists of five steps: 1) defining biological
condition in a minimally disturbed area - what the natural condition in the area should be, 2) defining
biological attributes that change along the gradient of human influence, 3) associating those changes
with specific human impacts, 4) identifying management practices for improving biological integrity,
and 5) communicating results to citizens and policy makers.
Biological Integrity and the Decline of Salmon
The loss of biological integrity within salmon spawning grounds equates to a loss of salmon. If a
stream's biological condition is degraded (as reflected by the condition of the benthic macroinvertebrate
population), it is safe to conclude that the stream will not support healthy salmon or other fish
populations. The decline of healthy salmon spawning and rearing habitat has been identified as one
major cause of the decline of wild salmon populations.
SalmonWeb focuses on monitoring the integrity of salmon habitat by monitoring benthic (bottom
dwelling) macroinvertebrates (large organisms without backbones). These critters may consist of mayfly
larvae, stonefly larvae, caddisfly larvae, worms, beetles, snails, dragonfly larvae, and many others.
SalmonWeb has chosen to measure benthic macroinvertebrates because they are long-term inhabitants
of streams, relatively immobile, easy to collect, and represent an assemblage that responds predictably to
human induced stress. Conversely, salmon are harder to collect, are highly mobile, and migrate out of
their spawning grounds.
Furthermore, a benthic macroinvertebrate monitoring program can provide insight to the
biological integrity of a stream even if it has never carried a salmon within its banks. Using benthic
macroinvertebrates has the additional advantage of being able to detect human influence upstream of
any sampling site. In other words, what happens upstream is reflected in the biotic communities
downstream - benthic macroinvertebrates are historical markers for upstream impacts.
Measuring Integrity: The Benthic Index of Biological Integrity
(B-IBI)
"Our ability to protect biological resources depends on our ability to identify and predict the
effects of human actions on biological systems, especially our ability to distinguish between natural and
human-induced variability in biological condition" (Karr and Chu 1998).
An Index of Biological Integrity (IBI) is a synthesis of diverse biological information which
numerically depicts associations between human influence and biological attributes. It is composed of
several biological attributes or 'metrics' that are sensitive to changes in biological integrity caused by
human activities. The multi-metric (a compilation of metrics) approach compares what is found at a
monitoring site to what is expected using a regional baseline condition that reflects little or no human
impact (Karr 1996b). Just as doctors use data from a check-up (e.g., blood samples, temperature, weight,
blood pressure, etc.) to compare against what is considered healthy in humans, multimetric indexes
utilize a variety of measurements to assess the biological condition, or health, of streams.
Multi-metric biological indexes include the following benthic macroinvertebrate information:

Pollution tolerance/intolerance taxa;

Taxonomic composition (number and abundance of taxa); and

Population attributes (e.g., number of predators).
Measuring Human Influence with the Index of Biological Integrity
As human influence and impact increase along a gradient from high to low, indices of biological
integrity mirror this gradient. One method for measuring the gradient of human influence is the percent
of impervious surface (e.g., roads, parking lots, sidewalks, houses etc). As humans pave roads, develop
rural areas into suburbs and cities, the impacts upon streams increase. These impacts create noticeable
and measurable changes in the biotic community.
Graph showing taxa richness vs. degree of human disturbance
(http://www.cbr.washington.edu/salmonweb/)
An Index of Biological Integrity monitoring approach provides the following four types of stream
condition descriptors of the condition of a stream as reflected by the biota:

Quantitative description (the monitoring data set),

Verbal description (number and types of species present or absent),

Graphical description (mapping the resulting IBI on a graph), and

Qualitative description (relative integrity description).
Furthermore, monitors can understand the processes driving the final IBI score by analyzing how each
metric contributed to the final score.
How IBI’s Work
Indices of Biological Integrity are developed for specific geographic areas and for specific
sampling methodologies. It is important to use an IBI calibrated for your sampling region and for your
sampling methodology.
The Benthic Index of Biological Integrity (B-IBI) for the Puget Sound Lowlands is one such
benthic macroinvertebrate multimetric index. Each of the metrics have been chosen because of their
consistency in responding to several types of human disturbance: urbanization, forestry, agriculture,
grazing, and recreation. The metrics are listed below with predicted response to human impact.
Metric
Predicted Response due
to Human Impact
 Total number of taxa;
Decrease
 Number of Mayfly taxa;
Decrease
 Number of Stonefly taxa;
Decrease
 Number of Caddisfly taxa;
Decrease
 Number of long-lived taxa;
Decrease
 Number of intolerant taxa*
Decrease
 % of tolerant individuals*
Increase
 % of predator individuals
Decrease
 Number of clinger taxa
Decrease
 % dominance (3 taxa)
Increase
* Refers to organic pollution tolerances
Level of Identification
Macroinvertebrate identification is a key component of the benthic index of biological integrity
(B-IBI) calculation. Identification may be completed to the taxonomic level of family or may be taken
further to the genus or even species level for many aquatic insects. Volunteers may complete
identification to family using pictorial keys. More specific identification to genus or species is
completed by professionals using dichotomous keys. Dichotomous keys have not been created for all
aquatic organisms to the species level because scientists are still learning how to distinguish among
those that are very similar. The phrase "lowest practical taxonomic level" is typically used to indicate
that organisms have been keyed as specifically as possible, given the present body of knowledge. Nearly
all insects can be keyed down to at least the genus level, and most can be keyed to species. However,
some non-insect macroinvertebrates, such as roundworms, leeches, and freshwater sponges, are typically
keyed only to phylum, order, class, or sub-class level.
A B-IBI can be calculated whether aquatic insects are identified to the family, genus, or lowest
practical taxonomic level. Decisions about the appropriate level of macroinvertebrate identification
typically depend on the purpose of the study, other potential uses for the data, the expertise of the
taxonomist, and the funding available for the study. When samples are identified to genus or the lowest
practical taxonomic level, a ten metric scoring system is used. When samples are identified to the family
level, a five metric scoring system is used.
B-IBI scores calculated from samples identified to the genus or lowest practical taxonomic level
will reflect the ecological condition of a site with more statistical precision than samples identified to the
family level only. In other words, smaller differences in site condition will be detected with genus or
species level scoring than with family level scoring. The statistical precision improves because more
metrics are included in the final scoring calculation and because more information is obtained for each
metric at more specific levels of identification. Family level scoring is a useful tool for a "first cut" at
site condition. Scientists completing research or resource managers who need to make land-use
decisions often identify samples to genus or lowest practical taxonomic level. It has not yet been
determined whether B-IBI scores calculated from lowest practical taxonomic level data are more
statistically precise than B-IBI scores calculated from genus-level information.
One group of aquatic insects that is particularly difficult to identify is Chironomidae, or midges,
a family of the true flies. These flies have tiny heads and few easily identifiable characteristics, making
their identification to lowest practical taxonomic level rather time consuming, even for professionals.
For the genus-level B-IBI, Chironomidae are only identified to family.
No matter what level the identification goes to, the B-IBI uses the same ten metrics. The values
assigned to the metrics are adjusted for each taxonomic level so that the final scores will still fall within
the same ranges identifying the relative health of the stream.
References
Fore, L. S., K. Paulsen, & K. O'Laughlin. (In press) Assessing the performance of volunteers in
monitoring streams. Freshwater Biology.
Karr, J.R. 1996a. Ecological integrity and ecological health are not the same. Pp. 97-109 in P.C.
Schulze, ed. Engineering Within Ecological Constraints. National Academy Press, Washington,
DC.
Karr, J.R. 1996b. Rivers as Sentinels: Using the biology of rivers to guide landscape management. Pp in
RJ. Naiman and R.E. Bilby, eds. The Ecology and Management of Streams and Rivers in the
Pacific Northwest Coastal Ecoregion. Springer-Verlag, New York.
Karr, J.R., and E.W. Chu. 1997. Biological Monitoring and Assessment: Using Multimetric Indexes
Effectively. EPA 235-R97-001. Seattle: University of Washington.
Karr, J.R. 1999. Defining and measuring river health. Freshwater Biology, 41:221-234.
Karr, J.R. and E.W. Chu. 1998. Restoring Life in Running Waters: Better Biological Monitoring. Island
Press, Washington, DC.
Karr, J.R. and D.R. Dudley. 1981. Ecological perspective on water quality goals. Environmental
Management, 5:55-68.
Karr, J.R., K.D. Fausch, P.L. Angermeier, P.R. Yant, and I.J. Schlosser. 1986. Assessing biological
integrity in running waters, a method and its rational. Illinois Natural History Survey, Special
Publication 5.
Morley, S.A. (2000) Effects of urbanization on the biological integity of Puget Sound lowland streams:
Restoration with a biological focus, Washington, USA. Thesis, University of Washington,
Seattle, WA.
Rossano, E.M. 1996. Diagnosis of Stream Environments with Index of Biological Integrity. Sankaido,
Tokyo, Japan