Worksh
Abstracts
2000/2001 Aquatic Ecosystem
Classification and Reference
editions STAR Progress
Review Workshop
September 24,2002
Denver, CO
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Aquatic Ecosystem Classification and Reference Conditions STAR Progress Review Workshop
Table of Contents
Introduction iii
Hierarchical Physical Classification of Western Streams: Predicting Biological Condition
in Terms of Key Environmental Processes Bridging Local to Ecoregional Scales 1
Brian P. Bledsoe, N. LeRoy Poff, Ellen E. Wohl
Assessing an HGM-Based Wetland Classification and Assessment Scheme Along a 1,000 km
Gradient of the Appalachian Mountains: Hydrology, Soils, and Wetland Function 3
Charles A. Cole, Denice Heller Wardrop, Robert P. Brooks, Christopher P. Cirmo
An Empirical Evaluation of the Performance of Different Approaches To Classifying Reference
Conditions in Streams 5
Charles P. Hawkins, R. Jan Stevenson, David W. Roberts
A Biologically Driven National Classification Scheme for U.S. Streams and Rivers 7
Alan Herlihy, Yangdong Pan, Bob Hughes
Development and Implementation of a Comprehensive Lake and Reservoir Strategy for Nebraska
as a Model for Agricultural Dominated Ecosystems 9
John C. Holt, James W. Merchant, Anatoly A. Gitelson, Sherilyn C. Fritz,
Kyle D. Hoagland, Istvan Bogardi, Donald C. Rundquist
Protocols for Selection of Classification Systems and Reference Conditions:
A Comparison of Methods 11
Lucinda Johnson, Jeffrey Schuldt, George Host, Jan Ciborowski, Carl Richards
Index of Authors 13
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Introduction
The mission of the U.S. Environmental Protection Agency (EPA) is to protect public health and safeguard and
improve the natural environment—air, water, and land upon which life depends. Achievement of this mission requires
the application of sound science to the assessment of environmental problems and to the evaluation of possible
solutions. The National Center for Environmental Research (NCER) at EPA is committed to providing the best
products in high-priority areas of scientific research through significant support for long-term research.
The Office of Research and Development's (ORD) Environmental Monitoring and Assessment Program's (EMAP)
goal is to build the scientific basis, and the local, state, and tribal capacity, to monitor for status and trends in the
condition of the Nation's aquatic ecosystems. Research into the development of new and better classification sys-
tems has been identified by EMAP as essential to improving the current EMAP approach. The research presented at
this progress review represents some of the extramural component of EMAP. You may find extensive information
about the EMAP program at http://www.epa.gov/emap.
In 2000 and 2001, NCER issued a Request for Applications (RFA) on the Development of Aquatic Ecosystem
Classifications and Reference Conditions. The purpose of these solicitations was to support research that led to the
development of functional, defensible classification schemes and associated reference conditions for use in the
application of biocriteria to one or more of the following aquatic resources: wetlands, large rivers, ephemeral sys-
tems, reservoirs, lakes, streams, estuaries, near-shore coastal environments, and coral reef communities. A total of 6
grants have been funded under this program.
Annual progress reviews such as this one will allow investigators to interact with one another and to discuss
progress and findings with EPA and other interested parties. Although the research described in this report has been
funded wholly or in part by the EPA, it has not been subjected to the Agency's required peer and policy review and
therefore does not necessarily reflect the views of the Agency and no official endorsement should be inferred. Any
opinions, findings, conclusions, or recommendations expressed in this report are those of the investigators who
participated in the research. If you have any questions regarding the program, please contact the program manager,
Barbara Levinson, at 202-564-6911 or levinson.barbara@epa.gov.
To learn more about EPA's STAR Program, visit NCER's Web Site at: http://www.epa.gov/ncer.
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Aquatic Ecosystem Classification and Reference Conditions STAR Progress Review Workshop
Hierarchical Physical Classification of Western Streams:
Predicting Biological Condition in Terms of Key Environmental
Processes Bridging Local to Ecoregional Scales
Brian P. Bledsoe, N. LeRoy Poff, and Ellen E. Wohl
Colorado State University, Fort Collins, CO
A hierarchical classification framework is being de-
veloped for stream environments in the western United
States that identifies the relative importance of key envi-
ronmental characteristics at multiple spatial scales. Spe-
cific objectives of this research project are to: (1) develop
an exhaustive, multiscaled physical habitat classification
of western U.S. streams to derive predictive statistical
models relating biotic condition to multiscaled environ-
mental variables; (2) demonstrate the explanatory power
and flexibility of the classification within and across di-
verse western U.S. ecoregions; (3) explicitly assess how
well a classification that includes intermediate scale pro-
cesses can predict biotic condition at localities without
requiring extensive local (reach scale) habitat data; and
(4) develop a systematic approach for objectively identi-
fying and stratifying reference sites.
Regional Environmental Monitoring and Assessment
Program (REMAP) data are being used on first through
fourth order streams from six ecoregions in Colorado,
Oregon, and Washington and new data as available from
the EMAPWestern Pilot Study to link a multiscale physi-
cal classification with expectations of taxa distribution
and categorical abundance in western U.S. streams and
rivers. Given the current emphasis on ecoregional and
local scales in biomonitoring protocols, this approach
will provide essential information on how environmen-
tal factors measured at intermediate scales can be used
to further understand and predict biotic condition at in-
dividual sites distributed across the landscape.
In the Cascades Ecoregion in Oregon, up to 72 per-
cent of the variation in macroinvertebrate genus rich-
ness at a site can be explained using no more than four
environmental descriptors, at both the local and water-
shed scales. The model for macroinvertebrate richness
for sites dispersed throughout the State of Oregon also
performed well (R2 = 0.59) using watershed scale factors
such as land cover and disturbance indicators (e.g., road
crossings). Over a geographic range comparable to a Level
III Ecoregion (Omernik 1987), local scale metrics such
as bed substrate descriptors best predict macroinvertebrate
richness. Preliminary results also indicate that using com-
bined watershed and local scale metrics results in better
prediction of macroinvertebrate communities than using
either scale independently (see Table 1).
By examining how much additional variation in com-
munity organization is explained by characterizing envi-
ronmental factors at scales other than ecoregions and lo-
cal habitat, this work provides essential information for
weighing the costs and benefits associated with different
levels of spatial resolution in monitoring. Thus, it directly
supports the EMAP initiative.
The physical classification and the metrics describ-
ing the physiochemical environment at multiple scales
across Oregon, Washington, and Colorado REMAP and
EMAP sites will be further refined by developing inter-
mediate-scale environmental descriptors prior to test-
ing with biological data. Once a comprehensive matrix
of multiscale hydrogeomorphic descriptors is developed,
statistical analyses (e.g., multiple regression, CCA,
CDA, Stochastic CART analysis, and other approaches)
will be used to elucidate the key physical controls on
biological communities. Last, the classification will be
applied in collaboration with state-level water quality
managers to further generalize the classification, im-
prove user-friendliness, and demonstrate practical ap-
plications.
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Table 1. Summary of key environmental descriptors for macroinvertebrate response variables ranked in order
of importance, and R2 explained by associated regression models for five geographic areas.
Colorado
Landcover
Water
Quality
Watershed
Disturbance
0.370'
CO
(Screened
for mine
drainage)
Reach
Descriptor
Substrate
Watershed
Disturbance
0.509*
Oregon
Local Basin
Descriptor
Watershed
Disturbance
Substrate
0.496+
Cascades
Substrate
Reach
Descriptor
Local Basin
Descriptor
Geology
0.715*
Colorado
(Screened) +
Oregon
Landcover
Precipitation
Substrate
Watershed
Disturbance
0.432*
* = p<0.01
= p< 0.001
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Aquatic Ecosystem Classification and Reference Conditions STAR Progress Review Workshop
Assessing an HGM-Based Wetland Classification and Assessment
Scheme Along a 1,000 km Gradient of the Appalachian
Mountains: Hydrology, Soils, and Wetland Function
Charles A. Cole', Denice Heller Wardrop', Robert P. Brooks', and Christopher P. Cirmo2
'Pennsylvania State University, University Park, PA; 2State University
of New York, Cortland, NY
The objectives of this project are to expand a recently
developed wetland classification and functional assess-
ment protocol, created in Pennsylvania, to regions north
and south within the Appalachian mountains and to de-
termine if: (1) similar wetland types occur along a broad
latitudinal gradient, and (2) wetland structure and func-
tion are similar (see Figure 1). The objective of the project
is to test the ability of these tools to provide useful sci-
entific and management information outside of their re-
gion of development.
Alarge reference wetland data set, developed in Penn-
sylvania over the past 10 years, will be expanded. Stan-
dard assessment protocols designed to measure a wide
variety of structural variables for input into wetland func-
tional assessment models will be used. Up to 20 extant
reference wetland sites in Pennsylvania will be revisited
to obtain updated information. Approximately 20 new ref-
erence sites will be developed in New York and 20 in
Virginia to test the applicability of these models along a
broad latitudinal gradient. All study sites will be instru-
mented with continuous water level recorders to develop
comprehensive hydrologic data for site assessment. These
data will be used in the assessment models and serve as a
check on the classification of each wetland.
Site selection began in the summer of 2002 in New
York and Virginia. To date, eight sites have been lo-
cated in the Adirondacks and several more potential sites
have been identified in the Catskills. Sites will be lo-
cated in the George Washington and Jefferson national
forests in Virginia, the southern assessment area. Train-
ing of personnel, including Principal Investigators and
graduate students, has commenced to provide all per-
sonnel with a unified understanding of the study's pro-
tocol. Water level recorders have been installed in many
of the Adirondack wetlands and will be placed in some
Pennsylvania sites before winter. The Virginia sites are
expected to be instrumented by early spring. Data col-
lection for the functional assessment models has begun
both in New York and Pennsylvania.
There are no preliminary findings to date. The selec-
tion of all sites will be finalized by the end of fall 2002,
and as much information as possible will be collected
before winter limits site accessibility. This will provide
the first real test of the transferability of the classification
scheme throughout the study region. The classification
key will be adjusted if it proves to be inadequate. In addi-
tion, the bulk of the model data will be collected during
the summers of 2003 and 2004.
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Figure 1. Wetland functional assessment across a 1,000 km gradient of the Appalachian Mountains.
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Aquatic Ecosystem Classification and Reference Conditions STAR Progress Review Workshop
An Empirical Evaluation of the Performance of Different
Approaches To Classifying Reference Conditions in Streams
Charles P. Hawkins', R. Jan Stevenson2, and David W. Roberts'
'Utah State University, Logan, UT; Michigan State University, East Lansing, MI
The goal of this project is to identify the type and level
of classification that is optimal for bioassessment purposes.
Two primary questions are being explored: (1) How is the
sensitivity of assessments aifected by the approach used to
classify sites (regionalization versus predictive discriminant
model), the type of assemblage examined, and the spatial
scale of classification? and (2) Are approaches to site clas-
sification transferable among regions? It is hypothesized
that the classifications that most closely approximate local
environmental conditions affecting individual organisms
will be the best predictors of expected conditions.
All analyses are being conducted on two biological
assemblages: algae and invertebrates. A combination of
existing and new data are being used to evaluate perfor-
mance of different classifications (e.g., ecoregions, catch-
ment, type of stream reach, thermal strata) in terms of
their accuracy and precision as well as their effect on the
sensitivity of detecting impairment. The study area in-
cludes a 13-state region (CA, OR, WA, ID, NV, AZ, MM,
UT, CO, WY, MT, SD, ND).
During the first year of the project, field sampling was
completed at 324 sites located in 10 different states (OR,
ID, MT, ND, WY, NV, UT, CO, AZ, NM). During this
same time period, collaboration occurred with personnel
from the U.S. Environmental Protection Agency (EPA)
Region 8, the U.S. Department of Agriculture Forest Ser-
vice, Oregon Department of Environmental Quality, and
Washington State Department of Ecology to obtain data
from approximately 200 additional sites in SD, ID, WY,
OR, WA, and MT. Together with data collected previously
from CA, OR, and WA, data from more than 1,000 poten-
tial reference sites have been collected for use in testing
the hypotheses (see Figure 1). All of the invertebrate
samples (excluding chironomid midges) have been pro-
cessed and identified, and initial analyses have been started
for the invertebrate data. The chironomid midge data will
be available in about 6 months for the 324 sites that were
sampled, once all samples have been mounted and identi-
fied. Approximately 50 percent of the diatom samples have
been permanently mounted onto slides, and rapid counts
(100 or 200 valves) have been completed for 115 slides.
All field data have been entered into a computer database
and initial quality assurance/quality control has been con-
ducted on the database. In addition, compilation of land-
scape-level data has begun from which additional infor-
mation will be extracted to characterize the environmen-
tal setting of each site. The following coverages are being
produced within a Geographic Information System: digi-
tal elevation models (DEMs), bedrock geology, stream net-
work, climate (temperature and precipitation), and land
use. Approximately 340 water chemistry samples have
been analyzed to date for NO3, NH,, TN, SRP, CL, and Si.
Analysis for cations is underway. Much of the effort dur-
ing the first year has been focused on several quality as-
surance issues. These issues include development of con-
sistent criteria for defining reference sites (with EPAORD
Corvallis and EPA Region 8), development of a consistent
taxonomy to be applied to periphyton, and analyses to
quantify sources of error in the estimation of different bio-
logical indicators. Work is being done with both Forest
Service personnel and EPA ORD scientists involved in
similar large-scale monitoring and assessment projects to
document and devise ways of controlling sources of error.
It is still too early in the analyses to comment on the
significance of the findings, but the level of cooperation
and collaboration developed with different states, many
of which view this project as directly relevant to their
bioassessment needs, has been beneficial.
The majority of data analyses will be conducted dur-
ing the upcoming project period. Only a modest amount
of field activity has been planned for this year to fill in
gaps in the developing database. The main activity will
be associated with building predictive models for both
invertebrate and diatom assemblages and creating the a
priori classifications based on landscape attributes that
will be compared with the predictive modeling results.
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Aquatic Ecosystem Classification and Reference Conditions STAR Progress Review Workshop
Figure 1. Distribution of 1,064 reference sites in the western United Slates that are being used to test hypotheses
regarding useful approaches to classifying streams for hioassessment purposes. Filled symbols are
locations of sites that were sampled during the summers of 2002 and 2003. Open symbols arc locations
of sites that either we or our collaborators sampled previously.
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Aquatic Ecosystem Classification and Reference Conditions STAR Progress Review Workshop
A Biologically Driven National Classification Scheme
for U.S. Streams and Rivers
Alan Herlihy, Yangdong Pan, and Bob Hughes
Oregon State University, Corvallis, OR
Analyzing stream biological assemblage data at a
national scale is extremely difficult and rarely attempted
due to the problems of compiling the necessary database.
The goal of this research project is to assemble a na-
tional database for the conterminous 48 U.S. states of
stream/river fish, macroinvertebrate, and periphyton as-
semblages derived from regional scale synoptic surveys.
The objectives of this project are to: (1) use our national
database to develop 10-30 biologically driven national
"classes" of stream systems; (2) within each class, sepa-
rate natural from anthropogenic effects on stream eco-
logical condition; and (3) establish quantitative relation-
ships between catchment and riparian condition and water
body condition (structure and function).
As a first cut, all publically available stream ecologi-
cal data from the U.S. Environmental Protection Agency's
(EPA) Environmental Monitoring and Assessment Pro-
gram (EMAP) and Regional Environmental Monitoring
and Assessment Program (REMAP) projects will be com-
piled, formatted, and validated into an approximately
3,600-site national database. These data were all collected
with the same field protocol, and sites were picked in a
randomized, systematic fashion so they are representa-
tive of the study area. The national database will be aug-
mented with high-quality state databases that were col-
lected with similar methods. A set of least disturbed ref-
erence sites will be screened from the combined national
database using available water quality and habitat data.
A multivariate cluster analysis of the reference sites will
identify 10-30 clusters, and a discriminant function analy-
sis will be conducted to identify the environmental fac-
tors that best predict class membership. Within each new
biologically derived class in the entire database, ordina-
tion analyses will be used to identify the major gradients
in the assemblage data and relate them to the measured
physical and chemical habitat. This will help separate
natural from anthropogenic effects and establish the major
functional relationships between stream biota and stream
condition for each class. For 2-4 of the classes, catch-
ment land cover data from remote sensing will be gath-
ered to determine the scale and types of land use most
related to the biological ordination in that class.
Most of the existing EMAP and REMAP data have
been collected, and construction of the national database
has begun. The status of the data collection efforts on a
state-by-state basis are shown in Figure 1. Complete
EMAP/REMAP statewide probability survey data have
been obtained for 20 states, representing about one-half
the area of the 48 states. REMAP data exist for portions of
another 9 states. To fill in spatial gaps in the databases, a
number of different state agencies have been queried for
any existing data that will meet the study's needs. If these
queries are successful, data from most of the country will
be obtained (see Figure 1).
Analyzing a combined national EMAP database pro-
vides a unique opportunity to study classification, ecologi-
cal gradients, relationships, and reference conditions at a
national scale. At the end of the study, it will be possible to
demonstrate patterns in stream biota and biological condi-
tion across the United States. Such a demonstration will
aid in justifying a national stream assessment if the U.S.
EPA and states choose to embark on one.
Available databases will be collected during the rest
of 2002. All data will be formatted into a common format,
and inconsistencies and differences in taxonomic names
across datasets will be resolved. Also, differences in taxo-
nomic resolution (i.e., family, genus, species levels) need
to be resolved and coded in the data for future data analy-
ses. The goal is to have a final national database ready by
January 2003. The first half of 2003 will be spent on con-
ducting the multivariate analyses of the national database
and identifying preliminary national clusters.
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Aquatic Ecosystem Classification and Reference Conditions STAR Progress Review Workshop
Data Status
I Complete EM A P Coverage
[ | Partial EMAP Coverage
| | Stale Agency Queried
i ~~| No Data
Figure 1. Status of the national stream biological assemblage database by U.S. state.
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Aquatic Ecosystem Classification and Reference Conditions STAR Progress Review Workshop
Development and Implementation of a Comprehensive Lake and
Reservoir Strategy for Nebraska as a Model for Agricultural
Dominated Ecosystems
John C. Holz, James W. Merchant, Anatoly A. Gitelson, Sherilyn C. Fritz,
Kyle D. Hoagland, Istvan Bogardi, and Donald C. Rundquist
University of Nebraska, Lincoln, NE
In agriculturally dominated regions, land use prac-
tices have an unusually large impact on water bodies and,
therefore, land use may reduce the utility of current
ecoregion-based approaches to lake classification by
dampening the signals that underlie the ecoregion frame-
work. A team of water quality researchers has been as-
sembled to develop a comprehensive classification
scheme for agriculturally dominated ecosystems, using
Nebraska as a highly representative model. Three objec-
tives critical to achieving this goal are to establish: (1) a
protocol for aggregating water bodies in agricultural eco-
systems into classification strata and identifying refer-
ence conditions for these classes; (2) the role of remote
sensing and the Geographic Information System in a clas-
sification strategy; and (3) a technology transfer link be-
tween the proposed classification system and end-users.
A water quality database for nearly 325 Nebraska lakes
and reservoirs was established by sampling an additional
181 water bodies during the first 2 years of this project.
All water bodies were sampled monthly from May through
September for common limnological parameters (e.g., nu-
trients, clarity, chlorophyll). From this database, lakes and
reservoirs are being classified hierarchically using a com-
bination of rule-based and data-based approaches. For ex-
ample, in the Sand Hills region of Nebraska, lake classes
were defined by performing a factor analysis on the lim-
nological data and plotting the significant factors to iden-
tify five groups of lakes with similar water quality charac-
teristics. The factor analysis revealed that three significant
factors explained more than 73 percent of the variability
of the data, with alkalinity, conductivity, chlorophyll,
nitrate+nitrite, Secchi depth, total suspended solids, or-
thophosphate, and total phosphorus loading significantly
into the three factors. Interestingly, the Level IV Ecoregions
based on soil type, native vegetation cover, topography,
and geology do not accurately represent water quality in
this region. Limited surface water inputs, combined with
local hydrology, reduce the utility of landscape classifica-
tion approaches in the Sand Hills region.
Improved methods also are being developed for inte-
grating field data, data collected via airborne and close
range remote sensing, data collected via operational and
near future satellite remote sensing systems, and ancillary
geospatial data in a multistage approach to lake classifica-
tion. Biological indicators that integrate the lake condi-
tions of each stratum will be developed from summerphy-
toplankton and zooplankton collections, and special em-
phasis has been placed on developing methods to remotely
sense biological indicators of water quality based on the
optical phytoplankton pigment structures of lakes. Algo-
rithms for remote estimation of chlorophyll were devel-
oped and tested in close range remote sensing measure-
ments in water bodies with different trophic status. The
developed technique was very sensitive to even slight varia-
tion in chlorophyll concentration as well as in turbidity
and Secchi depth. Standard error of chlorophyll concen-
tration prediction was less than 5 mg/m3 in the range of
chlorophyll concentration from 10 to more than 194 mg/
m3 (see Figure 1). The technique also allows indication of
presence of blue-green algae in water, although at this stage
quantitative accuracy of the technique in phycocyanin es-
timation was not assessed. Measurements from aircraft
(non-imaging) also showed high sensitivity of algorithms
to chlorophyll and other optically active constituents.
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S
TJ
Aquatic Ecosystem Classification and Reference Conditions STAR Progress Review Workshop
3.0
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JC 55T
° » 1 5
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0) QC
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O
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oc
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150
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Figure 1. Actual chlorophyll concentrations versus an index of close-range, remotely-sensed chlorophyll
concentrations in Nebraska lakes and reservoirs.
10
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Aquatic Ecosystem Classification and Reference Conditions STAR Progress Review Workshop
Protocols for Selection of Classification Systems and Reference
Conditions: A Comparison of Methods
Lucinda Johnson', Jeffrey Schuldf, George Host1, Jan Ciborowski3, and Carl Richards4
'Natural Resources Research Institute, University of Minnesota, Duluth, MN; University of Wisconsin,
Superior, WI; 3University of Windsor, Ontario, Canada; 'Minnesota Sea Grant,
University of Minnesota, Duluth, MN
The specific goals of this research project are to:
(1) apply an a priori classification system to Great Lakes
coastal ecosystems; (2) quantitatively identify reference
sites within classification units using widely available
spatial databases; (3) define reference biological condi-
tions for classification units; (4) use biological data to
test the efficacy of reference classifications; and (5) de-
termine whether degraded biological conditions differ
from reference conditions in a subset of classification
units.
A hierarchically structured classification system will
be implemented over a large region in the central United
States to test a statistically based protocol for identifying
reference conditions in a region. A combination of exist-
ing and newly collected data will be used to apply an a
priori classification system to Great Lakes coastal eco-
systems and identify regional reference conditions (see
Figure 1). This classification will identify homogeneous
units representing underlying abiotic conditions that con-
trol the structure and function of coastal ecosystems. A
variety of existing national and statewide databases will
be used to identify the number and type of pressure indi-
cators within each unique classification unit. Pressure
indicators will be used to assess the degree of anthropo-
genic influence on individual ecosystems and, conse-
quently, identify candidate reference ecosystems. The
biotic (macrobenthos and fish) communities and habitat
structure will be characterized within these reference
ecosystems. Several statistical methods will be used to
test whether the biotic communities within each refer-
ence site are unique to a given classification unit. The
same level of stratification will not be required to uniquely
identify reference sites for all coastal ecosystem types;
therefore, the classification system will be refined using
agglomerative or divisive approaches.
A comprehensive inventory has been completed of the
coastal wetlands for the entire Great Lakes coastal region
within the United States, excluding connecting channels.
The Great Lakes coastal ecosystems were classified on a
regional basis using the scheme of Keys et al.1 at the
EcoProvince level, and Omernik et al.2 at the Ecoregion
level. Five geomorphic units along the shoreline were iden-
tified: high energy zones, bays, coastal marshes, riverine
wetlands, and protected wetlands. Land use, road density,
point sources, and population density data were summa-
rized for unique topographic receiving areas for each shore-
line unit. Within classification units, reference ecosystems
have been defined as those sites with the least amount of
anthropogenic influence. Sampling of biotic (macrobenthos
and fish) conditions in 100-120 reference ecosystems is
underway.
A novel method of defining the bounds of the refer-
ence condition based on the joint influence of multiple
stressors has been developed, and a significant contribu-
tion has been made to the research and management com-
munity in the Great Lakes by assembling a comprehen-
sive inventory of coastal wetlands. Results from the field
data collections are not available yet.
Sampling of high energy shorelines, protected wet-
lands, and riverine wetlands is underway. Quantifying
stressors for coastal marshes and embayments, to be
sampled next year, will continue.
'Keys Jr. J., Carpenter C., Hooks S., Koenig F., McNab W.H., Russell W., Smith M.L. Ecological units of the eastern United
States—first approximation. Atlanta, GA: U.S. Department of Agriculture, Forest Service, 1995.
2Omernik J.M. Ecoregions of the conterminous United States. Annals Assoc Am Geographers 1987;77:118-125.
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Aquatic Ecosystem Classification and Reference Conditions STAR Progress Review Workshop
Refine Classification
* Apply Classification Scheme
Quantify Pressure Indicators
Identif
Reference
Units
Sample Fish & Invertebrates
Define Reference Condition
Evaluate"
Reference
Classifies-^
tior
Test Site Comparisons
Figure 1. Conceptual model of reference area identification.
12
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Aquatic Ecosystem Classification and Reference Conditions STAR Progress Review Workshop
Index of Authors
Bledsoe, B.P., 1
Cole, C.A., 3
Hawkins, C.R, 5
Herlihy,A.,7
Holz,J.C.,9
Johnson, L., 11
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