Biological Integrity and the Index of
Biological Integrity (from www.salmonweb.org)
The
following are brief descriptions of Biological Integrity, Biomonitoring, and
the Index of Biological Integrity. For more in-depth information, please refer to
specific articles in the “Publications” section of www.salmonweb.org.
Biological Integrity and Biomonitoring -
what is it, why is it important, and how is it influenced by human activity?
Clean Water Act: "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 of meeting human health goals.
Unfortunately, the emphasis of chemical monitoring has not lead 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.
Still from the Fresh
Waters Flowing Video of gradient of human disturbance.
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.
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) is one such benthic macroinvertebrate
multimetric index designed and calibrated for use in Puget Sound Lowlands using
the SalmonWeb monitoring protocol. 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 |
|
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. Therefore some
organizations may choose to have most of the organisms in their samples keyed
to the genus level or lowest practical taxonomic level, but will leave
Chironomidae only identified to family.
B-IBI metric scores can be
entered into the Salmonweb website at three taxonomic levels:
- Lowest practical taxonomic level identification for all
macroinvertebrates
- Lowest practical taxonomic level identification for most
macroinvertebrates, Chironomidae identified to family
- Genus level identification for most macroinvertebrates, Chironomidae
identified to family
These three methods all use 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. Scoring criteria for
family-level identification, which uses five metrics, has different scoring
ranges identifying the relative health of the stream. Family-level metric
scoring cannot be entered onto the website at this time.
Generating B-IBI Summary Metrics from Raw Data
Ten summary metrics are used to
calculate the B-IBI value of a stream. Each metric described below must be
calculated for your field sample for submission to the SalmonWeb web site.
The descriptions below assume
that all taxa have been sorted, identified, and counted. Use the specie list
designation (search the Northwest Taxa Database to find designations) to determine the
metric scores (e.g., whether the taxa are long-lived, clingers, pollution
tolerant, etc). Taxon means a single taxonomic group such as family, genus, or
species. Taxa is plural.
Species
Level Summary Metrics
The following species level
metric descriptions are used for both the Species and Species/Family
taxonomic identification methods.
Criteria are for species-level
identification of most insects, rhyacophilids to subgroup, and chironomids to
genus. See Species
Level 10 Metric B-IBI for details and the Scoring Criteria for this level of
taxonomic identification.
Species/Family
Level 10 Metric B-IBI
Adjustments to are made to the species-level scoring
criteria when chironomids are identified at the family rather than genus level.
Criteria require species level identification for most insects. See Species/Family Level 10 Metric B-IBI for details and the
Scoring Criteria for this level of taxonomic identification.
Total
Taxa Richness
The total number of unique taxa identified in each
replicate. The numbers from the three replicates are then averaged for this
metric.
Ephemeroptera
Taxa Richness
The total number of unique mayfly (Ephemeroptera) taxa
identified in each replicate. The numbers from the three replicates are then
averaged for this metric.
Plecoptera
Taxa Richness
The total number of unique stonefly (Plecoptera) taxa
identified in each replicate. The numbers from the three replicates are then
averaged for this metric.
Trichoptera
Taxa Richness
The total number of unique caddisfly (Tricoptera) taxa
identified in each replicate. The numbers from the three replicates are then
averaged for this metric.
Number
of Long-Lived Taxa
The total number of unique long-lived taxa identified in
each replicate. The numbers from the three replicates are then averaged for
this metric.
Number
of Intolerant Taxa
The total number of unique intolerant taxa identified in
each replicate. Chironomids
are not included in this metric. The numbers from the three replicates are then averaged for
this metric.
Percent
Tolerant Individuals
The total number of tolerant individuals counted in each
replicate, divided by the total number of individuals in that replicate, multiplied
by 100. Chironomids
are not included in this metric. The numbers from the three replicates are then averaged for
this metric.
Number
of Clinger Taxa
The total number of unique clinger taxa identified in
each replicate. The numbers from the three replicates are then averaged for
this metric.
Percent
Predator Individuals
The total number of predator individuals counted in each
replicate, divided by the total number of individuals in that replicate, multiplied
by 100. The numbers from the three replicates are then averaged for this
metric.
Percent
Dominance
The sum of individuals in the three (3) most abundant
taxa in each replicate, divided by the total number of individuals in that
replicate, multiplied by 100. The numbers from the three replicates are
then averaged for this metric.
Genus
Level Summary Metrics
The following genus level
metric descriptions are used for both the Genus and Genus (pre 1999)
taxonomic identification methods.
Genus Level 10 Metric B-IBI Criteria
For genus level scoring, aquatic insects are
identified to the genus level, with the exception of chironomids, which are
identified to the family level. Non-insects are identified to the order or
family level. See Genus
Level 10 Metric B-IBI for details and the Scoring Criteria for this level
of taxonomic identification.
Genus Level (pre 1999) 10 Metric B-IBI Criteria
Criteria for genus level scoring used prior to 1999. For genus
level scoring, aquatic insects are identified to the genus level, with the
exception of chironomids, which are identified to the family level. Non-insects
are identified to the order or family level. See Genus Level (pre 1999) 10 Metric B-IBI for details and the
Scoring Criteria for this level of taxonomic identification.
Total
Taxa Richness
The total number of unique taxa is identified in each
replicate. The numbers from the three replicates are then averaged for this
metric.
Ephemeroptera
Taxa Richness
The total number of unique mayfly (Ephemeroptera) taxa is
identified in each replicate. The numbers from the three replicates are then
averaged for this metric.
Plecoptera
Taxa Richness
The total number of unique stonefly (Plecoptera) taxa is
identified in each replicate. The numbers from the three replicates are then averaged
for this metric.
Trichoptera
Taxa Richness
The total number of unique caddisfly (Tricoptera) taxa is
identified in each replicate. The numbers from the three replicates are then
averaged for this metric.
Number
of Long-Lived Taxa
The cumulative number of unique long-lived taxa identified across all three
replicates.
Number
of Intolerant Taxa
The cumulative number of unique intolerant taxa identified across all three
replicates.
Percent
Tolerant Individuals
The total number of tolerant individuals counted in each
replicate, divided by the total number of individuals in that replicate, multiplied
by 100. The percentages from the three replicates are then averaged for
this metric.
Number
of Clinger Taxa
The total number of unique clinger taxa is identified in
each replicate. The numbers from the three replicates are then averaged for
this metric.
Percent
Predator Individuals
The total number of predator individuals counted in each
replicate, divided by the total number of individuals in that replicate, multiplied
by 100. The percentages from the three replicates are then averaged for
this metric.
Percent
Dominance
The sum of individuals in the three (3) most abundant
taxa in each replicate, divided by the total number of individuals in that
replicate, multiplied by 100. The percentages from the three replicates
are then averaged for this metric.
Family
Level Summary Metrics
The 5-metric Family B-IBI will
not give you as much qualitative information as the 10-metric B-IBI, but it
will provide you with a relative integrity score. Researchers continue to
evaluate the effectiveness of the 5 metric B-IBI.
Family Level 5 Metric B-IBI Criteria
Criteria are for family-level identification of all taxa.
See Family Level 5 Metric B-IBI for details and the Scoring
Criteria for this level of taxonomic identification.
Total
Taxa Richness
The total number of unique taxa identified in each replicate.
The numbers from the three replicates are then averaged for this metric.
Ephemeroptera
Taxa Richness
The total number of unique mayfly (Ephemeroptera) taxa
identified in each replicate. The numbers from the three replicates are then
averaged for this metric.
Plecoptera
Taxa Richness
The total number of unique stonefly (Plecoptera) taxa
identified in each replicate. The numbers from the three replicates are then
averaged for this metric.
Trichoptera
Taxa Richness
The total number of unique caddisfly (Tricoptera) taxa
identified in each replicate. The numbers from the three replicates are then
averaged for this metric.
Percent
Dominance
The sum of individuals in the single most abundant taxa
in each replicate, divided by the total number of individuals in that
replicate, multiplied by 100. The numbers from the three replicates are
then averaged for this metric.
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.
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
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,
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.
Rossano, E.M. 1996. Diagnosis of Stream Environments with Index of
Biological Integrity. Sankaido,