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Use of Biological
Information to Better Define
Designated Aquatic Life
Uses in State and Tribal
Water Quality Standards:
Tiered Aquatic Life Uses
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DISCLAIMER
The discussion in this draft document is intended solely to provide information on advancements in the
field of bioassessments and on current State and Tribal practices using bioassessments to define their
designated aquatic life uses. The statutory provisions and U.S. EPA regulations described in this
document contain legally binding requirements. This document is not a regulation itself, nor does not it
change or substitute for those provisions and regulations. Thus, it does not impose legally binding
requirements on U.S. EPA, States, or the regulated community. This document does not confer legal
rights or impose legal obligations upon any member of the public.
While U.S. EPA has made every effort to ensure the accuracy of the discussion in this document, the
obligations of the regulated community are determined by statutes, regulations, or other legally binding
requirements. In the event of a conflict between the discussion in this document and any statute or
regulation, this document would not be controlling.
The general description provided here may not apply to a particular situation based upon the
circumstances. Interested parties are free to raise questions and objections about the substance of this
document and the appropriateness of the application of the information presented to a particular situation.
U.S. EPA and other decision-makers retain the discretion to adopt approaches on a case-by-case basis that
differ from those described in this document where appropriate.
Mention of trade names or commercial products does not constitute endorsement or recommendation for
their use.
This.is a living document and may be revised periodically. U.S. EPA welcomes public input on this
document at any time. ;
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Preface
Our Nation's waters are a valuable ecological resource. Protecting them begins with State and authorized
Tribal adoption of water quality standards. This draft document, the Use of Biological Information to
Better Define Designated Aquatic Life Uses in State and Tribal Water Quality Standards: Tiered Aquatic
Life Uses, provides up-to-date information on practical, defensible approaches to help States and Tribes
more precisely define designated aquatic life uses in their water quality standards. Biologically-based
tiered aquatic life uses, based on the scientific model presented in this document, can help States and
Tribes develop aquatic life uses that more precisely describe the existing and potential uses of a
waterbody and then use bioassessments to help measure attainment of the uses.
Biologically-based tiered aquatic life uses coupled with numeric biological criteria provide a direct
measure of the aquatic resource that is being protected. The condition of the biota reflects the cumulative
response of the aquatic community to individual or multiple sources of stress - an environmental outcome
measure. The technical approaches described in this document support U.S. EPA's Environmental
Indicators Initiative to move the Agency closer to a performance-based rather than process-based
environmental protection system (http://www.epa.gov/indicators). Launched in November 2001, the
Environmental Indicators Initiative responds to the President's call to have agencies and departments
manage for results by measuring environmental outcomes.
This document is a compilation of the tools, practices, and experiences of State and Tribal scientists who
have used biological information to more precisely define their aquatic life uses. The presented model
brings biological condition and stressor information together to inform decisions on use designation. The
document fulfills a commitment in the U.S. EPA Water Quality Standards Strategy to provide technical
support, outreach, training, and workshops to assist States and Tribes with designated uses, including use
attainability analyses and tiered aquatic life uses (EPA-823-R-03-010, Strategic Action #7, Milestone #2).
U.S. EPA encourages States and Tribes to incorporate biological information into their decisions. U.S.
EPA believes the use of bioassessments will help improve water quality protection. The information in
this document can help States and Tribes use bioassessments to more precisely define their aquatic life
uses and communicate this information to the public. U.S. EPA is making this document available so
States and Tribes can pilot a bioassessment-based tiered approach to defining their designated aquatic life
uses. If you choose to undertake a pilot, U.S. EPA would appreciate hearing about your experience. We
are interested in feedback on the following questions:
• Is this document helpful in addressing current issues in your program?
• Does this document address the technical challenges in your Region, State, or Tribe?
• How can this document be improved to help you develop tiered aquatic life uses in your
program?
• What additional information would be helpful to you?
Should you have any questions or wish to provide feedback, please contact Susan K. Jackson via email at
Jackson.Susank@epa.gov or at the following address:
Tiered Aquatic Life Uses Document
Attn: Susan K. Jackson
Health and Ecological Criteria Division (4304T)
Office of Science and Technology
U.S. EPA, Office of Water
1200 Pennsylvania Avenue
Washington, DC 20460
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Executive Summary
This document provides up-to-date information on how States and Tribes can use biological information to more
precisely define designated aquatic life uses for their waters. Thirty years ago, under the Clean Water Act (CWA),
States and Tribes were required to adopt in their water quality standards, where attainable, designated uses that
included the protection and propagation offish, shellfish, and wildlife. During the 1970s, the biological goals
adopted into State or Tribal water quality standards as designated aquatic life uses may have been appropriately
general (e.g., "aquatic life as naturally occurs") given the limited data available and the state of the science.
However, while such general use classifications meet the requirements of the Clean Water Act and the implementing
federal regulations, they may constitute the beginning, rather than the end, of appropriate use designations.
Improved precision may result in more efficient and effective evaluation of attainment of condition and utilization of
restoration resources. Finally, improved precision in uses can enhance demonstrating progress towards management
goals. In the years since the CWA was passed, considerable advancements have been made in the science of aquatic
ecology and in biological monitoring and assessment methods. This document summarizes these advancements and
provides a scientific model that States and Tribes can use to refine their designated uses in a manner that can
improve their water quality assessment and management.
This document was developed based on the technical expertise and practical experience of State and Tribal
scientists. In 2000, the U.S. EPA convened a technical expert workgroup, including State and Tribal scientists, to
identify scientifically sound and practical approaches to help States and Tribes provide more specificity in their
designated aquatic life uses. The workgroup developed a scientific model, the Biological Condition Gradient (BCG),
which describes biological response to increasing levels of stressors. The model describes how ten attributes of
aquatic ecosystems change in response to increasing levels of stressors. The attributes include several aspects of
community structure, organism condition, ecosystem function, and spatial and temporal attributes of stream size and
connectivity. The gradient can be considered analogous to a field-based dose-response curve where dose (x-axis) =
increasing levels of stressors and response (y-axis) = biological condition. The BCG differs from the standard dose-
response curve, in that the BCG does not represent the laboratory response of a single species to a specified dose of
a known chemical, but rather the in situ response of the biota to the sum of stresses it is exposed to. The BCG is
divided into six tiers of biological condition along the stressor-response curve, ranging from observable biological
conditions found at no or low levels of stress to those found at high levels of stressors. The model provides a
common framework for interpreting biological information regardless of methodology or geography. When
calibrated to a regional or state scale, States and Tribes can use this model to more precisely evaluate the current and
potential biological condition of their waters and use that information to inform their decisions on aquatic life
designations. Additionally, States and Tribes can use this interpretative model to more clearly and consistently
communicate these decisions to the public.
Maine and Ohio have adopted biologically-based tiered aquatic life uses in their WQS and have over twenty years
experience implementing this type of use designation approach. Both Maine and Ohio developed and adopted tiered
aquatic life uses for similar reasons: 1) to incorporate ecologically relevant endpoints into decisions; 2) to inform
water quality management decisions; 3) to quantify water quality improvements; and 4) to merge the design and
practice of monitoring and assessment with the development and implementation of their water quality standards.
Maine and Ohio scientists have identified a sequence of steps and milestones that U.S. EPA has compiled as a
template that other States and Tribes may use to develop biologically-based tiered uses. Examples from Maine and
Ohio are included in this document to illustrate how they used biological data to establish tiered uses and the
programmatic gains from having done so.
The U.S. EPA encourages States and Tribes to incorporate biological information into their decisions. The U.S.
EPA believes that the use of biological information can help improve water quality protection. Currently, States and
Tribes that use biological data as part of their assessment program apply some type of tiered aquatic life use to guide
their interpretation of their biological data. States and Tribes have either explicitly adopted tiers directly into their
water quality standards as designated uses, or used tiers in monitoring and assessment of their surface waters. This
document provides examples of practical and scientifically sound approaches to using biological information to tier
designated aquatic life uses.
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FOREWORD
Why is U.S. EPA publishing this document?
In the more than 30 years since the Clean Water Act (CWA) wax passed, there has been considerable progress in the
science of aquatic ecology and in the development of biological monitoring and assessment techniques. During the
1970s, the biological goals adopted into State or Tribal water quality standards as designated aquatic life uses may
have been appropriately general (e.g., ."aquatic life as naturally occurs") given the limited data available and the
state of the science. However, while such general use classifications meet the requirements of the Clean-Water Act
and the implementing federal regulations, they may constitute the beginning, rather than the end, of appropriate use
designations. Improved precision may result in more efficient and effective evaluation of attainment of condition
and utilization of restoration resources. Finally, improved precision in uses can enhance demonstrating progress
towards management goals. Tiered aquatic life uses, hosed on the biological condition gradient model presented in
this document, can help States and Tribes to better define and develop more precise, scientifically defensible aquatic
life uses that account for the natural differences between waterbodies and should result in more appropriate levels
of protection for specific waterbodies.
States and Tribes have created different use classification systems ranging from a straightforward replication of the
general uses identified in the CWA (e.g., protection and propagation of fish, shellfish, and wildlife; recreation;
agriculture; industrial and other purposes, including navigation) to more complex systems that express designated
uses in more specific terms or establish classifications which identify different levels of protection. For example,
some States designate general "aquatic life" uses, while others subcategorize waters based on the expected
biological assemblage. Some have established tiers representing different levels of biological condition (e.g.,
excellent, good, fair). Although a variety of defensible approaches have evolved and become established in State
and Tribal programs, current U'.S. EPA regulations are not specific about the level of precision States or Tribes must
achieve in designating uses. This document is designed to help inform States and Tribes how to better define and
improve the precision of their designated uses.
Over the past thirty years, both the state of aquatic science and the application of the science in State and Tribal
water programs have advanced. Major areas of uncertainty in water management, such as distinguishing between
natural variability and effects of stressors on aquatic systems as well as determining the appropriate level of
protection for individual waterbodies, are being addressed. Many States and Tribes now use biological information
to directly assess the biological condition of their aquatic resources (U.S. EPA 2002a). Three States have formally
adopted biologically-based tiered aquatic life uses in their water quality standards. "Lessons learned" from two of
these States indicate that implementation of tiered aquatic life uses supports more appropriate levels of protection
for individual waters by promoting uses and criteria that are neither over- nor under-protective. U.S. EPA now
recognizes that the States having implemented tiered aquatic life uses have significantly benefited from the
approach. The use designation process needs to clearly articulate and differentiate intended levels of protection with
enough specificity so that 1) decision makers can appropriately develop and implement their water quality standards
on a site, reach, or watershed specific basis and 2) the public can understand, identify with, and influence the goals
set for waters.
In 2001, the National Research Council (NRC) published its report on. Assessing the TMDL Approach to Water
Quality Management (NRC 2001). In the report, the NRC recommended tiering designated uses as an essential step
in setting water quality standards and improving decision-making. The NRC, finding that the Clean Water Act's
goals (i.e., "fishable," "swimmable") are too broad to serve as operational statements of designated use,
recommended greater specificity in defining such uses. For example, rather than stating that a waterbody needs to
be "fishable," the designated use would ideally describe the expected fish assemblage or population (e.g., cold water
fishery, warm water fishery, or salmon, trout, bass, etc.) as well as the other biological assemblages necessary to
support that fish population.
Additionally, the NRC recommended that biological criteria should be used in conjunction with physical and
chemical criteria to determine whether a waterbody is meeting its designated use. The NRC described a "position of
the criterion" framework, which reflects how representative a criterion is of a designated use according to its
position along a conceptual causal pathway (Figure F-l). This alignment is comparable to that of performance
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(indicators of point source quality) versus impact standards (indicators of resource condition) (Courtemanch et al.
1989), or of stressor and exposure (effluent, chemical, and physical parameters) in contrast to response indicators
(biological) (Yoder and Rankin 1998). In Figure F-l, stressor indicators correspond to box 1 and were termed
effluent standards by the NRC. Pollutant-specific indicators that function as indicators of exposure and stress
correspond to box 2. Biological indicators show responses to stress and exposure and correspond to box 3. Because
designated uses are written in qualitative, narrative terminology, the challenge is to relate a criterion to the
designated use. Establishing this relationship is easier as the criterion is positioned closer to the designated use, thus
the NRC recommendation on the use of biological information to help determine more appropriate aquatic life uses
and to couple the narrative use statements with quantitative methods. The "position of criterion" concept provides a
useful construct for considering the relationship of water quality criteria (biological, chemical, and physical) to the
designated uses they are intended to protect.
1. Pollutant load from
each source
4. Land use, characteristics of the
channel and riparian zone, flow
regime, species harvest condition
(pollution)
2. Ambient pollutant
concentration in waterbody
3. Human health and
biological condition
Appropriate designated use
for the waterbody
FIGURE F-l. Types of water quality
criteria and their position relative
to designated uses (after NRC
2001).
To help States and Tribes more precisely define use descriptions, there is a need to incorporate current scientific
understanding of aquatic ecology and the appropriate use of monitoring data. To this end, the U.S. EPA convened a
technical expert workgroup to identify scientifically sound and practical approaches that would help States and
Tribes provide more specificity in their designated aquatic life uses. The workgroup met four times between 2000
and 2003. The workgroup, composed primarily of U.S. EPA, State, and Tribal scientists, also included research
scientists from the U.S Geological Survey (USGS), the academic community, and the private sector. The
workgroup was asked to base their recommendations on "lessons learned" from State and Tribal water programs in
the development and the application of biologically-based aquatic life uses, bioassessments, and biocriteria. The
workgroup developed a scientific model, the Biological Condition Gradient (BCG), which describes graduated tiers
of biological response to increasing levels of stressors. This model was developed and tested through a series of
data exercises using a diverse array of data sets. States and Tribes can use the BCG to more precisely define and set
appropriate designated aquatic life uses for their waters.
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During the final workgroup meeting in 2003, State and Tribal members discussed their current thinking on how
using biological information to tier designated aquatic life uses could benefit their water quality management
programs. The main reasons discussed included biologically-based tiered uses could help:
• set ecologically-based aquatic life goals for waterbodies;
• establish a consistent approach for identifying attainable, incremental restoration goals that are
grounded in the concept of biological integrity;
• provide a framework that better relates traditional water quality criteria (stressor and exposure
variables) and biological criteria (response variables) in determining use attainment, thus strengthening
stressor/response models implicit in designated uses and criteria in water quality standards;
• better link monitoring and assessment with water quality standards; and
• prioritize management actions that result in the more effective use of resources.
When asked about the significant value-added outcomes of these benefits to their water programs, States and Tribes
workgroup members anticipated being able to make more scientifically defensible listings of impaired waters as well
as enhance identifying and protecting high quality waters. For several States, biologically-based tiered uses may
help in the transition from reliance on current conditions in developing designated uses to being able to better
consider the potential for improvement Another important added value anticipated by all State and Tribal
representatives was the ability to communicate more effectively with program managers, the public, and key
stakeholders. Workgroup members expressed the opinion that biologically-based aquatic life uses could help
maximize the return on their monitoring and assessment efforts by eliminating a major source of uncertainty in
water quality management by 1) accounting for natural variability in aquatic systems and 2) helping to specify an
appropriate level of protection for a waterbody that includes consideration of the system's potential for
improvement.
Biologically-based aquatic life uses, as described in this document, are a natural evolution that reflects an improved
understanding of surface waters resulting from more than 20 years of assessment data. The proposed approach will
help better integrate the science of aquatic ecology into Water Quality Standards. This document represents the
culmination of four years of workgroup deliberations, including four workgroup meetings and two workshops to
"road test" the BCG model. Based on the collective experience of the workgroup members, the science and
methods in the fields of biological assessments and criteria have progressed sufficiently over the past thirty-five
years to support the use of biological information to tier designated aquatic life uses in State and Tribal water quality
standards.
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Acknowledgments
U.S. EPA PROJECT LEAD
Susan Jackson, U.S. EPA Office of Science and Technology
WRITING & EDITING TEAM
David Allan, University of Michigan; Margo Andrews, Tetra Tech, Inc.; Michael Barbour, Tetra Tech, Inc.; Jan
Cibrowski, University of Windsor; Maggie Craig, Tetra Tech, Inc.; Susan Da vies, Maine Department of
Environmental Protection; Tom Gardner, U.S. EPA; Jeroen Gerritsen, Tetra Tech, Inc.; Charles Hawkins, Utah State
University; Robert Hughes, Oregon State University; Susan Jackson, U.S. EPA; Lucinda Johnson, Natural
Resources Research Institute, University of Minnesota - Duluth; Phil Larsen, U.S. EPA; JoAnna Lessard, Tetra
Tech, Inc.; Abby Markowitz, Tetra Tech, Inc.; Dennis Mclntyre, Great Lakes Environmental Center; Jerry Niemi,
Natural Resources Research Institute, University of Minnesota - Duluth; Dave Pfeifer, U.S. EPA; Ed Rankin,
Center for Applied Reassessment and Biocriteria; Tom Wilton, Iowa Department of Natural Resources; Chris
Yoder, Midwest Biodiversity Institute
TIERED AQUATIC LIFE USES WORKGROUP
U.S. EPA Chair: Susan Jackson, U.S. EPA Office of Science and Technology
State Chair: Susan Davies, Maine Department of Environmental Protection
STATE AND TRIBAL WORKGROUP MEMBERS
Arizona Department of Environmental Quality - Patti Spindler
California Department of Fish and Game - Jim Harrington
Colorado Department of Public Health and Environment - Robert McConnell, Paul Welsh
Florida Department of Environmental Protection - Leska Fore, Russ Frydenborg, Ellen McCarron, Nancy Ross
Idaho Department of Environmental Quality - Mike Edmondson, Cy ndi Grafe*
Kansas Department of Health and Environment - Bob Angelo, Steve Haslouer, Brett Holman
Kentucky Department for Environmental Protection - Greg Pond*, Tom VanArsdall
Maine Department of Environmental Protection - David Courtemanch, Susan Davies
Maryland Department of the Environment - Joseph Beaman, Richard Eskin, George Harmon
Minnesota Pollution Control Agency - Greg Gross
Mississippi Department of Environmental Quality - Leslie Barkley, Natalie Guedon
Montana Department of Environmental Quality - Randy Apfelbeck, Rosie Sada
Nevada Division of Environmental Protection- Karen Vargas
North Carolina Department of Environment and Natural Resources - David Lenat, Trish MacPherson
Ohio Environmental Protection Agency - Jeff DeShon, Dan Dudley
Ohio River Valley Water Sanitation Commission - Erich Emery
Oregon Department of Environmental Quality - Doug Drake, Rick Hafele
Pyramid Lake Paiute Tribe - Dan Mosley
Texas Commission on Environmental Quality - Charles Bayer
Vermont Department of Environmental Conservation - Doug Burnham, Steve Fiske
Virginia Department of Environmental Quality - Alexander Barren, Larry Willis
Washington State Department of Ecology - Robert Plotnikoff
Wisconsin Department of Natural Resources - Joe Ball, Ed Emmons, Robert Masnado, Greg Searle, Michael
Talbot, Lizhu Wang**
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U.S. EPA
Office of Water: Chris Faulkner, Thomas Gardner, Susan Holdsworth, Susan Jackson, Kellie Kubena, Douglas
Norton, Christine Ruff, Robert Shippen, Treda Smith, William Swietlik
Regional Offices:
Region 1: Peter Nolan
Region 2: Jim Kurtenbach
Region 3: Maggie Passmore
Region 4: Ed Decker, Jim Harrison, Eve Zimmerman
Region 5: Ed Hammer, David Pfeifer
Region 6: Philip Crocker, Charlie Howell
Region 7: Gary Welker
Region 8: Tina Laidlaw, Jill Minter «
Region 9: Gary Wolinsky
Region 10: Gretchea Hayslip
Office of Environmental Information: Wayne Davis
Office of Research and Development: Karen Blocksom, Susan Cormier, Phil Larsen, Frank McCormick, Susan
Norton, Danielle Tillman, Lester Yuan
USGS
Evan Hornig*, Ken Lubinski
SCIENTIFIC COMMUNITY
David Allan, University of Michigan
Michael Barbour, Tetra Tech, Inc.
David Braun, The Nature Conservancy
Jeroen Gerritsen, Tetra Tech, Inc.
Richard Hauer, University of Montana
Charles Hawkins, Utah State University
Robert Hughes, Oregon State University
James Karr, University of Washington
Dennis Mclntyre, Great Lakes Environmental Center
Ed Rankin, Center for Applied Bioassessment and Biocriteria
Jan Stevenson, Michigan State University
Denice Wardrop, Pennsylvania State University
Chris Yoder, Midwest Biodiversity Institute
BCG STEERING COMMITTEE
Michael Barbour, Susan Davies, Robert Hughes, Susan Jackson, Phil Larsen, Dennis Mclntyre, Susan Norton,
Maggie Passmore, Jan Stevenson, Chris Yoder, Lester Yuan
STRESSOR GRADIENT STEERING COMMITTEE
David Allan, Michael Barbour, Jan Cibirowski, Jim Harrison, Robert Hughes, Luanda Johnson, JoAnna Lessard,
Jerry Niemi, Doug Norton, Ed Rankin, Tom Wilton
*Now with U.S. EPA
**Now with Michigan Department of Natural Resources
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Use of Biological Information to Better Define Designated
Aquatic Life Uses in State and Tribal Water Quality
Standards: Tiered Aquatic Life Uses
TABLE OF CONTENTS
Preface i
Executive Summary iii
Foreword.. v
Acknowledgments ix
Table of Contents xi
Tables, Figures, and Case Examples xiii
INTRODUCTION 1
CHAPTER 1: What are Tiered Aquatic Life Uses? 1
1.1 The CWA goals and objectives for aquatic life 2
1.2 WQS statutory and regulatory background 3
1.3 The role of designated aquatic life uses in Water Quality Standards 4
1.4 State and Tribal experiences with tiered aquatic life uses 5
1.5 The Biological Condition Gradient: A tool for better defining and developing more precise
aquatic life uses 8
1.6 Conceptual basis for the Biological Condition Gradient 10
1.7 Key points from Chapter 1 11
1.8 Organization of the document 12
THE BIOLOGICAL CONDITION GRADIENT IS
CHAPTER 2: What is the scientific basis of the Biological Condition Gradient? 16
2.1 What the BCG model looks like 17
2.2 How the BCG was developed, tested, and evaluated 27
2.3 The relationship between the BCG and designated uses 30
2.4 Key points from Chapter 2 31
CHAPTER 3: How do you develop and calibrate a Biological Condition Gradient? 39
3.1 Conceptual foundation of a regional BCG model 40
3.2 Data needs: Assess and modify technical program 45
3.3 Calibrate a regional BCG model 46
3.4 Key points from Chapter 3 55
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CHAPTER 4: Thex-axis: A Generalized Stressor Gradient 71
4.1 The scientific foundation for the stressor gradient 71
4.2 The conceptual model for a Generalized Stressor Gradient 72
4.3 How the BCG model and management actions are linked 76
4.4 How a GSG can be developed and calibrated 85
4.5 Key points from Chapter 4 89
INCORPORATING TIERED AQUATIC LIFE USES INTO STATE AND
TRIBAL WQS: CASE EXAMPLES 91
CHAPTER 5: Key concepts and milestones in the development of Tiered Aquatic Life Uses...93
5.1 Key concepts for developing tiered aquatic life uses 93
5.2 Key milestones for developing tiered aquatic life uses 94
5.3 Using TALUs to support water quality management 97
5.4 Key points from Chapter 5 98
CHAPTER 6: How have States and Tribes used TALUs in Water Quality Standards and
management? ......99
References & Additional Resources 115
Glossary 135
Acronyms 141
Appendix A: Maine TALU Implementation Case History 143
Appendix B: Ohio TALU Implementation Case History 155
Appendix C: Technical Guidelines: Technical Elements of a Bioassessment Program
(Summary of Draft Document) 181
Appendix D: The Role of Reference Condition in Biological Assessment and Criteria
(Introduction to Draft Document) 185
Appendix E: Statistical Guidance for Developing Indicators for Rivers and Streams: A Guide
for Constructing Multimetric and Multivariate Predictive Bioassessment Models
(Summary of Draft Document) 187
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Tables, Figures, and Case Examples
Tables
Table 1-1. Aquatic Life Subcategories in Texas WQS 6
Table 1-2. The benefits and WQS regulation context for TALUs 7
Table 2-1. Biological Condition Gradient matrix 18
Table 2-2. Evidence in support of the depicted changes in ecological attributes in the BCG 21
Table 2-3. Biological Condition Gradient: Maine example scenario for a cold-water stream catchment.. 32
Table 3-1. Kansas stream biological integrity categories 56
Table 3-2.'Summary attribute matrix for New Jersey high gradient streams 58
Table 3-3. Relative findings chart 60
Table 3-4. Definitions of six biological grades, developed by regional biologists of the Environment
Agency in England and Wales (Helmsley-FIint 2000) 65
Table 3-5. Maine water quality classification system for rivers and streams, with associated biological
standards (Davies et al. 1995) 66
Table 3-6. Proposed decision rules for New Jersey high gradient streams 68
Table 4-1. Example scenarios for humid-temperate (A) and arid (B) regions of the US under three levels
of stressors 74
Table 4-2. Fundamental environmental processes typically altered by disturbances that ultimately
generate stressors 79
Table 4-3. Percent variance in biological response (R2) explained by catchment and riparian land use, and
percent land use producing poor IBI scores (modified from Hughes et al. unpublished manuscript) 86
Table 5-1. Expertise and tasks for key TALU milestones 96
Table 6-1. Statewide total phosphorus targets (mg/L) for Ohio rivers and streams 101
Table 6-2. Numeric targets for biological, habitat, and water quality parameters for the Stillwater River
in western Ohio 102
Table 6-3, A matrix of stressor, exposure, and response indicators for the Ottawa River mainstem based
on data collected in 1996 (after Ohio EPA 1998) 109
Table A-l. Maine's narrative aquatic life and habitat standards for rivers and streams (M.R.S.A Title 38
Article 4-A § 464-465) 146
Table A-2. Definitions of terms used in Maine's water classification law 146
Table A-3. Maine tiered uses based on measurable ecological values 147
Table A-4. Examples of how numeric biocriteria results determine whether or not a waterbody attains
designated aquatic life uses in Maine 152
Table A-5. Chronology of Maine's biocriteria development 154
Table B-l. Biological criteria (fish) for determining aquatic life use designations and attainment of Clean
Water Act goals (November, 1980; after Ohio EPA 1981) 160
Table B-2. Biological criteria (macroinvertebrates) for determining aquatic life use designations and
attainment of Clean Water Act goals (November, 1980; after Ohio EPA 1981) 160
Table B-3. Example of individual stream and/or segment use designations in the Ohio water quality
standards showing aquatic life, water supply, and recreational use designations 162
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Table B-4. Key features associated with tiered aquatic life uses in the Ohio WQS (OAC 3745-1-07)... 166
Table B-5. Important timelines and milestones in the planning and execution of the rotating basin
approach conducted annually and since 1990 by Ohio EPA 170
Table B-6. Summary of recommendations for use designations in the Big Darby Creek watershed
based on a biological and water quality assessment completed in 2000 172
Table B-7. The tangible products that are symptomatic of aquatic ecosystem health and the measurable
biological, chemical, and physical indicators of healthy and degraded aquatic systems 178
Table B-8. Key events and milestones that occurred in the evolutionary development, adoption, and
implementation of biological assessments, numeric biocriteria, and tiered aquatic life uses in Ohio
between 1974 and the present 179
Figures
Figure F-l. Types of water quality criteria and their position relative to designated uses (after NRC
2001) vi
Figure 1-1. Conceptual model of the Biological Condition Gradient 8
Figure 1-2. The causal sequence from stressors and their sources through the five major water resource
features to the biological responses, i.e., the biological endpoints 9
Figure 1-3. The five major factors that determine the biological condition of aquatic resources (modified
from Karr et al. 1986) 10
Figure 1-4. Modification of the NRC "position of the criterion" concept (Fig. F-l) showing the causal
sequence from indicators of stress, exposure, and response in relation to point and nonpoint source
impacts, specific types of criteria, and designated uses that define the endpoints of interest to society
(after Karr and Yoder 2004) • .-. 11
Figure 1-5. Roadmap to the document : 12
Figure 2-1. Conceptual model of the Biological Condition Gradient 25
Figure 2-2. Response of mayfly density to enrichment in Maine streams as indicated by a gradient of
increasing conductivity 26
Figure 3-1. Technical components of the Biological Condition Gradient 39
Figure 3-2. Conceptual model of the response of Fish and macroinvertebrate assemblages to a gradient of
impacts in warmwater rivers and streams throughout Ohio (modified from Ohio EPA 1987 and Yoder and
Rankinl995b) 43
Figure 3-3. Ohio BCG tiers and copper concentration 50
Figure 3-4. Hypothetical example of biotic index scores of sites assigned to BCG tiers, where the index
is able to discriminate tiers most of the time ....52
Figure 3-5. Hypothetical example of biotic index scores of sites assigned to BCG tiers, where the index
is not able to discriminate tiers 52
Figure 3-6. Decline in geographical distribution of black sandshell mussel in Kansas 57
Figure 3-7. Cumulative frequency distribution for Kansas streams with minimum three-year period-of-
record and five or more species historically 57
Figure 3-8. Vermont's designated aquatic life uses as differentiated by biological threshold criteria 62
Figure 3-9. Series of four linear discriminant models 67
Figure 4-1. Conceptual model illustrating the linkages between pressure and biological condition 72
Figure 4-2. Relationship between pressure, stressors, and biological response 77
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Figure 4-3. Perspective of scale for pressure-stressor-response variables (modified from Richards, C. and
L.B.Johnson. 1998) : 84
Figure 4-4. The first principal component of the agricultural variables for the U.S. Great Lakes basin.... 87
Figure 4-5. Flow diagram detailing the steps used by GLEI researchers in quantifying their stressor
gradient (modified from Danz et al. 2005) '. 88
Figure 5-1. U.S. EPA Water Quality Based Approach to Pollution Control based on Chapter 7, Water
Quality Standards Handbook 91
Figure 5-2. TALU and biocriteria program development tasks: Timeline and key milestones 97
Figure 6-1..Dissolved oxygen concentrations (individual grab samples) vs. Index of Biotic Integrity (IBI)
values in the HELP and ECBP ecbregions of Ohio 100
Figure 6-2. Box plots of minimum dissolved oxygen concentrations by IBI ranges for continuous
monitoring data at all locations monitored in 1998 and 1994.„ 100
Figure 6-3. 1986 photograph of Hurford Run near Canton, Ohio looking upstream at the reach that is
classified as a Limited Resource Water 103
Figure 6-4. Map of Hurford Run near Canton, Ohio showing Ohio EPA IBI (solid circles) and habitat
(QHEI, triangles) sampling stations 103
Figure 6-5. Box and whisker plots of IBI (left) and QHEI (right) by stream segment in Hurford Run near
Canton, Ohio 104
, Figure 6-6. Scatter plots showing values for two biological community variables, generic richness (left)
and generic diversity (right), from Sta. 129, the Penobscot River below Lincoln Pulp and Paper,
between 1974 and 1996 105
Figure 6-7. Map of the Ottawa River with magnification of two reaches in the Lima, Ohio area (after
Ohio EPA 1998) 108
Figure 6-8. Results for two key fish assemblage measures (%DELT anomalies, upper left panel and IB I,
lower left panel) showing the thresholds for toxic responses in the Ottawa River study area between
1985 and 1996 :. 110
Figure 6-9. Six leading causes of aquatic life impairment in Ohio up to the year 2000 (from Ohio EPA
2000) Ill
Figure 6-10. Examples of habitat stressor gradients vs. IBI for Ohio wadeable streams in the ECBP and
HELP ecoregions 112
Figure A-l. Differences in numbers and types of organisms that are associated with different levels of
disturbance can be evident even to the untrained eye 144
Figure A-2a. Subsidy-stress gradient: The ecological theory basis for Maine's aquatic life use
descriptions (Odum et al. 1979) 144
Figure A-2b. Empirically observed subsidy-stress gradient in Maine streams, documented by changes
in benthic macroinvertebrate density 145
Figure A-3. Relation between Maine TALUs and other water quality standards and criteria 147
Figure A-4. Maine TALUs in relation to the BCG tiers 148
Figure A-5. Macroinvertebrate sampling stations in Maine 150
Figure A-6. Maine five-year rotating basin sampling schedule 151
Figure A-7. Increased designation of Class A A and Class A uses on major Maine rivers (as shown by
river miles) between 1970 and 2004, as a result of water quality improvements and public support for
the Class AA/A goal in the Triennial Review Process 153
Figure A-8. Percent of linear miles of all rivers and streams in each of Maine's designated use classes
(year 2000) 154
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Figure B-l. Evolutionary development of TALK and allied tools, criteria and assessments from the
baseline of the 1974 WQS based on general uses and few specific water quality criteria to refined
TALUs and specific chemical, physical, and biological criteria implemented via an integrated
monitoring and assessment framework 157
Figure B-2. Numeric biological criteria adopted by Ohio EPA in 1990, showing stratification of
biocriteria by biological assemblage, index, site type, ecoregion for the warmwater habitat (WWH)
and exceptional warmwater habitat (EWH) use designations ....: 163
Figure B-3. The relationship of Ohio's tiered designated uses and numerical biological criteria to the
Biological Condition Gradient 166
Figure B-4, Five-year basin approach for determining annual watershed monitoring and assessment
activities and correspondence to support major water quality management programs 170
Figure B-5. Strategic support provided over time by systematic monitoring and assessment; functions
related to the implementation of TALUs are italicized and underlined '. 171
Figure B-6. The number of individual stream and river segments in which aquatic life use designations
were revised during 1978-1992 and 1992-2001 174
Figure B-7. The major steps of the Ohio EPA numeric biological criteria calibration and derivation
process leading to their application in biological and water quality assessments; this example is for the
Index of Biotic Integrity (IBI) for wading sites 177
Figure B-8. Box-and-whisker plots of Invertebrate Community Index (ICI) results in the mainstem of
the Cuyahoga River between Akron and Cleveland between 1984 and 2000 180
Figure C-L Conceptual illustration of confidence in detecting different stress levels as a function of
assessment rigor 182
Figure C-2. Conceptual illustration of the capability of increasingly comprehensive bioassessments
to detect and discriminate along the biological condition gradient 183
Case Examples
Case Example 3-1. Using Historical Information to Identify Reference Streams in Kansas 56
Case Example 3-2. New Jersey Tier Description -. 58
Case Example 3-3. Maine Biologists' Assignment of Sites to Classes (Tiers) 60
Case Example 3-4. Vermont's Use of Existing Biological Information for the BCG 62
Case Example 3-5. Developing Biological Condition Tiers in Great Britain 64
Case Example 3-6. Maine's Use of Linear Discriminant Models to Assess Aquatic Life Use Tiers 66
Case Example 3-7. New Jersey Quantitative Rule Development 68
Case Example 6-1. Refining Water Quality Criteria in Ohio 99
Case Example 6-2. Development of More Precise Targets for Restoration in Ohio 101
Case Example 6-3. Determining Appropriate Levels of Protection in Ohio 102
Case Example 6-4. Long-term Monitoring and Use Re-establishment in Maine 105
Case Example 6-5. Development of Limits for NPDES Permits in Maine 106
Case Example 6-6. NPDES Permitting and Use Attainability Analysis in Ohio 107
Case Example 6-7. Support for Dredge and Fill Permitting in Ohio Ill
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Introduction
This chapter provides the background and rationale for using biological information to tier designated
aquatic life uses and better define them in State and Tribal water quality standards. Ideally, the use
designation process clearly articulates and differentiates intended levels of protection with enough
specificity so that 1) decision makers can appropriately develop and implement their water quality
standards on a reach or watershed specific basis; and 2) the public can understand, identify with, and
influence the goals set for waters. In 2000, the U.S. EPA convened a technical expert workgroup,
including State and Tribal scientists, to identify existing scientifically sound and practical approaches
using biological information to better define aquatic life uses. The workgroup produced a scientific
model, the Biological Condition Gradient (BCG), for interpreting biological response to increasing levels
of stressors. The workgroup's findings are consistent with The National Research Council's call for
greater specificity in water quality standards that can result in improved decision-making (NRC 2001).
The BCG is intended to help States and Tribes develop more precise aquatic life uses that should result in
more appropriate levels of protection for their surface waters.
CHAPTER 1. WHAT ARE TIERED AQUATIC LIFE USES?
Designated aquatic life uses are State or Tribal descriptions of the biological goals for their waterbodies.
Tiered aquatic life uses (TALUs) use biological information to more precisely define these goals relative
to natural conditions. Bioassessments can then be used to measure attainment of the goals. U.S. EPA's
current thinking is that a system of tiered uses could:
• accommodate observable differences in expected biological condition in waterbodies in different
ecological regions;
• provide an objective means of describing the biological potential for a specific waterbody;
• recognize and accommodate observable differences in biological potential among waters with
different types and levels of stressors;
• reflect an understanding of the relationship between stressors and biological community response;
• guide selection of environmental indicators for monitoring and assessment and make full use of
available biological data; and
• articulate a stressor-response model that maximizes the likelihood of success of water quality
management actions based on water quality standards (assessment, 303(d) listings/TMDLS,
NPDES permits).
Tiered aquatic life uses are based on general observations about aquatic communities that have become
central to aquatic ecology and consistent with 30 years of empirical observations. These are:
• surface waters and the biological communities they support are predictably and consistently
different in different parts of the country (classification along a natural gradient, ecological
region concept)',
• within the same ecological regions, different types of waterbodies (e.g., headwaters, streams,
rivers, wetlands) support predictably and consistently different biological communities
(waterbody classification);
• within a given class of waterbodies, observed biological condition in a specific waterbody is a
function of the level of stress (natural and anthropogenic) that the waterbody has experienced (the
biological condition gradient discussed in this document);
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• similar stressors at similar intensities produce predictable and consistent biological responses in
waters within a class, and those responses can be detected and quantified in terms of deviation
from an expected condition (reference condition); and
• waterbodies exposed to higher levels of stressors will have lower biological performance
compared to the reference condition than those waters experiencing lower levels of stress (the
biological condition and stressor gradients discussed in this document).
The first three sections of this chapter provide the statutory and regulatory background of water quality
standards, emphasizing the role of designated aquatic life uses. Section 1.4 explores how tiered
biologically-based definitions can help set more appropriate and precise designated aquatic life uses in
State and Tribal water quality standards. The next two sections discuss the primary products of the
technical workgroup charged with identifying existing scientifically sound and practical approaches to
help States and Tribes to better define and provide more precision in their designated aquatic life uses.
Chapter 1 concludes with a summary of key points, organization of the document, and related technical
support documents.
1.1 The CWA goals and objectives for aquatic life
One objective of the 1972 Clean Water Act (CWA) is to restore and maintain the chemical, physical, and
biological integrity of the Nation's waters (CWA sec lOla). In the scientific literature, an aquatic system
with chemical, physical, and biological integrity has been described as being capable of "supporting and
maintaining a balanced, integrated, adaptive community of organisms having a composition and diversity
comparable to that of the natural habitats of the region" (Frey 1977). Over the intervening years, our
understanding of how to define and measure the integrity of aquatic systems has advanced. The term
integrity has been further refined in the literature to mean a balanced, integrated, adaptive system having a
full range of ecosystem elements (genes, species, assemblages) and processes (mutation, demographics,
biotic interactions, nutrient and energy dynamics, metapopulation dynamics) expected in areas with no or
minimal human influence (Karr 2000). The aquatic biota residing in a waterbody are the result of
complex and interrelated chemical, physical, and biological processes that act over time and on multiple
scales (e.g., instream, riparian, landscape) (Karr et al. 1986, Yoder 1995). By directly measuring the
condition of the aquatic biota, we are able to more accurately define the aquatic community that is the
outcome of all these factors.
To help achieve the integrity objective, the CWA also established an interim goal for the protection and .
propagation of fish, shellfish, and wildlife and recreation in and on the water. The protection and
propagation interim goal for aquatic life has been interpreted by U.S. EPA to include the protection of the
full complement of aquatic organisms residing in or migrating through a waterbody. As explained in U.S.
EPA's Questions and Answers on Antidegradation, the protection afforded by water quality standards
includes the representative aquatic community (e.g., fish, benthic macroinvertebrates, and periphyton):
"The fact that sport or commercial fish are not present does not mean that the water may not be
supporting an aquatic life protection function. An existing aquatic community composed entirely
of invertebrates and plants, such as may be found in a pristine tributary alpine stream, should be
protected whether or not such a stream supports a fishery. Even though the shorthand expression
'fishable/swimmable' is often used, the actual objective of the Act is to restore the chemical,
physical and biological integrity of our Nation's waters (Section 101(a)). The term 'aquatic life'
would more accurately reflect the protection of the aquatic community that was intended in
Section 101(a)(2) of the Act." (Appendix G, EPA-823-B-94-005)
i
The representative community of aquatic organisms residing in, or migrating through, a waterbody will
vary depending on the waterbody type. For example, fish, benthic macroinvertebrates, and, increasingly,
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periphyton are aquatic assemblages typically measured by States and Tribes when assessing streams and
rivers. In headwater streams and many wetlands, amphibians are an important component of the biotic
community and fish may be absent.
1.2 WQS statutory and regulatory background
Section 101 (a) of the CWA establishes broad national goals and objectives such as the chemical, physical,
and biological integrity objective. Other sections of the CWA establish the programs and authorities for
implementation of those goals and objectives. Section 303(c) sets up the basis of the current water quality
standards program. Water quality standards (WQS) are parts of State (or, in certain instances, federal)
law that define the water quality goals of a waterbody, or parts of a waterbody, by designating the use or
uses of the waterbody and by setting criteria necessary to protect the uses. The standards also include an
antidegradation policy consistent with 40 CFR Part 131.12.
Although the CWA gives the U.S. EPA an important role in determining appropriate minimum levels of
protection and providing national oversight, it also gives considerable flexibility and discretion to States
and Tribes to design their own programs and establish levels of protection beyond the national
minimums. Section 303 directs States and authorized Tribes to adopt water quality standards to protect
public health or welfare, enhance the quality of water, and serve the purposes of the Clean Water Act.
"Serve the purposes of the Act" (as defined in Sections 101(a), 101(a)(2), and 303(c) of the CWA) means
that water quality standards should 1) include provisions for restoring and maintaining chemical, physical,
and biological integrity of State and Tribal waters, 2) provide, wherever attainable, water quality for the
protection and propagation offish, shellfish, and wildlife and recreation in and on the water (i.e.,
"fishable/swimmable"), and 3) consider the use and value of State and Tribal waters for public water
supplies, propagation of fish and wildlife, recreation, agricultural and industrial purposes, and navigation.
Further requirements for water quality standards are at 40 CFR Part 131.
State WQS provide the foundation for water quality-based pollution control programs. With the public
participating in their adoption (see 40 CFR 131.20), such standards serve the dual purposes of
establishing the water quality goals for a specific waterbody, and serving as the regulatory basis for the
establishment of water quality-based treatment controls and strategies beyond the technology-based levels
of treatment required by Sections 301(b) and 306 of the CWA.
A waterbody's designated use(s) are those uses specified in water quality standards, whether or not they
are being attained (40 CFR 131.3(f)). The "use" of a waterbody is the most fundamental description of its
role in the aquatic and human environments. All of the water quality protections established by the CWA
follow from the waterbody's designated use. As designated uses are critical in determining the water
quality criteria that apply to a given waterbody, determining the appropriate designated use is of
paramount importance in establishing criteria that are appropriately protective of that designated use.
Section 131.10 of the regulation describes States' and authorized Tribes' responsibilities for designating
and protecting uses. The regulation:
• requires that States and Tribes specify the water uses to be achieved and protected,
• requires protection of downstream uses,
• allows for sub-category and seasonal uses,
• sets out minimum attainability criteria,
• lists six factors of, which at least one must be satisfied to justify removal of designated uses that
are not existing uses,
• prohibits removal of existing uses, '
• requires upgrading of uses that are presently being attained but not designated, and
• establishes conditions and requirements for conducting use attainability analyses.
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In addition, the regulations effectively establish a "rebuttable presumption" that the uses of protection and
propagation of fish, shellfish, and wildlife and recreation in and on the water are attainable and should
apply to a waterbody, unless it has been affirmatively demonstrated that such uses are not attainable.
40 CFR 131.10(a) requires that States specify appropriate water uses to be achieved and protected. The
classification of the waters of the State must take into consideration the use and value of water for public
water supplies, protection and propagation offish, shellfish, and wildlife, recreation in and on the water,
and agricultural, industrial, and other purposes, including navigation. Changing designated uses for a
specific waterbody requires a change in the water quality standards. Like all new and revised State and
Tribal water quality standards, these changes are subject to U.S. EPA review and approval (see 40 CFR
131.21).
Where appropriate, a State may subcategorize or refine the aquatic life use designations for the receiving
water. States may adopt subcategories of a use and set the appropriate criteria to reflect varying needs of
such subcategories of uses, for instance, to differentiate between coldwater and warmwater fisheries (see
40 CFR 131.10(c)). States may also adopt seasonal uses (40 CFR 131.10(f)). If seasonal uses are
adopted, water quality criteria should reflect the seasonal uses; however, such criteria shall not preclude
the attainment and maintenance of a more protective use in another season.
Water quality criteria are elements of State WQS expressed as constituent concentrations, levels, or
narrative statements representing a quality of water that supports a particular use. When criteria are met,
water quality will generally protect the designated use (40 CFR 131.3). While some States have adopted
a variety of criteria expressed as constituent concentration levels (or numeric criteria) for various
pollutants for the protection of aquatic life, all States have adopted criteria expressed as narrative
statements (or narrative criteria). Once adopted into standards, criteria can serve as the basis for 1)
regulatory controls on point sources, 2) measuring attainment of standards and the effectiveness or
programs, and 3) watershed planning.
Section 304(a) criteria are developed by the U.S. EPA under authority of section 304(a) of the CWA
based on the latest scientific information on the relationship that a constituent concentration, level, or
measure has on a particular aquatic species and/or human health. This information is issued periodically
to the States as guidance for use in developing criteria. In adopting criteria to protect their designated
uses, States may establish criteria based on 1) section 304(a) guidance, 2) section 304(a) guidance
modified to reflect site-specific conditions, or 3) other scientifically defensible methods.
1.3 The role of designated aquatic life uses in Water Quality Standards
It is in designating uses that States and Tribes establish the environmental goals for their water resources
and then measure attainment of these goals. In designating uses, a State or Tribe weighs the
environmental, social, and economic consequences of its decisions. The regulation allows the State or
Tribe, with public participation, some flexibility in weighing these considerations and adjusting these
goals over time. However, reaching a conclusion on the uses that appropriately reflect the current and
potential future uses for a waterbody, determining the attainability of those goals, and appropriately
evaluating the consequences of a designation can be a difficult and controversial task.
A principal function of designated uses in water quality standards is to communicate the desired state of
surface waters to water quality managers, the regulated community, and the interested public. An
effective designated use system is one that translates readily into indicators (e.g., numeric water quality
criteria, biological indexes) that respond in predictable ways to stress and can be evaluated using data
collected from the waterbody. Experience with implementation of various State designated use systems
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suggests that, regardless of the system selected, States that use biological data as part of their assessment
program apply some type of refined, or tiered, aquatic life use approach to guide interpretation of their
biological data. States have either made this explicit by adopting the tiers directly into their water quality
standards as designated uses or implicit by using tiers in their monitoring and assessment protocols.
Although the benefits of more specificity may apply to any of the designated uses described in CWA
section 303, it may be most relevant for aquatic life uses. Aquatic communities can vary significantly
from waterbody to waterbody. One major challenge in assigning designated uses for aquatic life to
surface waters is separating the natural variability that is a function of stream type (e.g., naturally
coldwater vs. warmwater stream) and location (ecoregion) from the variability that results from exposure
to stressors. By accounting for natural variability in aquatic systems, biologically-based tiered aquatic life
uses eliminate a major source of uncertainty and error in water quality management efforts.
1.4 State and Tribal experiences with tiered aquatic life uses
Over the years, States and Tribes have created many different use classification systems ranging from a
straightforward replication of the uses specifically listed in section 303 of the CWA, to more complex
systems that express designated uses in very specific terms or that establish subclassifications identifying
different levels of protection. Some States designate general "aquatic life" uses while others list a variety
of subcategories based on a range of aquatic community types, including descriptions of core aquatic
species representative of each subcategory (e.g., coldwater and warmwater fisheries). Many States also
have narrative biological criteria, which is often a general statement such as "aquatic life communities
shall be maintained similar to aquatic life as naturally occurs." Single thresholds for attainment of these
general uses and narrative biological criteria are established with numeric biological criteria. For
example, many State water quality agencies interpret narrative general use statements using an index
(e.g., Index of Biotic Integrity (IBI)) (Karr et al. 1987, Karr 1990, Gibson et al. 1996, U.S. EPA 2002a).
The index is standardized to regional reference conditions, and the biological criteria threshold is often
established as a percentile of the distribution of reference site scores. The index is the basis for numeric
biological criteria in many States and Tribes (U.S. EPA 2002a).
The alternative to a single broad use is to divide the continuum of biological condition (the BCG) into
several tiers for more precise management As mentioned earlier, tiered aquatic life uses couple narrative
descriptions of the use with criteria for measuring attainment of the use. Ideally, the narrative
descriptions should incorporate biologically meaningful differences among tiers. The BCG provides an
interpretative framework for defining reference conditions and articulating the biological condition that is
being protected or restored in the water of interest.
Several States and Tribes have adopted tiered aquatic life use statements in their water quality standards
and some are developing the technical program and further tightening the linkage between their narrative
use statements and numeric biological criteria (U.S. EPA 2002a). For example, Texas has had tiered
aquatic life uses identified in their water quality standards for surface waters since 1984 (Table 1-1).
Texas' current WQS identify numeric dissolved oxygen criteria and include narrative aquatic life
attributes. Numeric biological criteria have been developed for assessing both fish and benthic
macroinvertebrate communities in wadeable streams. If site-specific conditions do not meet criteria for
"High" use category as determined by receiving water assessment, a use attainability analysis will be
conducted. Texas continues to evaluate the application of biological criteria for other aquatic systems,
but at this point does not have a specific action plan to adopt numeric biological criteria for those systems.
Other States cited elsewhere in this document, e.g., Maine, New Jersey, Ohio, and Vermont, have either
developed or are considering developing tiered aquatic life uses. Though these approaches for tiering
aquatic life uses may differ in detail and assessment methods, their uses share the same core elements:
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• Biological information is the basis for the use designations.
• Numeric biological indicators or biocriteria are developed for each use.
• Development of tiers based on data from comprehensive, robust monitoring program.
TABLE 1-1. Aquatic Life Subcategories in Texas WQS (Figure; 30 TAG §307.7(b)(3)(A)(i)).
Aquatic Life
Use
Subcategoiy
Exceptional
High
Intermediate
Limited
Dissolved Oxygen Criteria, mg/L
Freshwater
mean/
minimum
6.0/4.0
5.0/3.0
4.0/3.0
3.0/2.0
Freshwater
in Spring
mean/
minimum
6.0/5.0
5.5/4.5
5.0/4.0
4.0/3.0
Saltwater
mean/
minimum
5.0/4.0
4.0/3.0
3.0/2.0
Aquatic Life Attributes
Habitat
Character-
istics .
Outstanding
natural
variability
Highly
diverse
Moderately
diverse
Uniform
Species
Assemblage
Exceptional
or unusual
Usual asso-
ciation of
regionally
expected
species
Some
expected
species
Most
regionally
expected
species
absent
Sensitive
species
Abundant
Present
Very low
in
abundance
Absent
Diversity
Exceptionally
high
High
Moderate
Low
Species
Richness
Exceptionally
high
High
Moderate
Low
Trophic
Structure
Balanced
Balanced
to slightly •
unbalanced
Moderately
imbalanced
Severely
imbalanced
Dissolved oxygen means are applied as a minimum average over a 24-hour period.
Daily minima are not to extend beyond 8 hours per 24-hour day. Lower dissolved oxygen minima may apply on a site-specific basis, when natural daily
fluctuations below the mean are greater than die difference between the mean and minima of the appropriate criteria.
Spring criteria to protect fish spawning periods are applied during that portion of ihe first half of the year when water temperatures are 63.0"F to 73.0"F.
Quantitative criteria to support aquatic life attributes are described in the standards implementation procedures.
Dissolved oxygen analyses and computer models to establish effluent limits for permitted discharges will normally be applied to mean criteria at steady-
state, critical conditions.
Determination of standards attainment for dissolved oxygen criteria is specified in §307.9(d)(6) (relating to Determination of Standards Attainment).
The insights and experiences from States and Tribes that have adopted tiered aquatic life uses and
numeric.biocriteria in their water quality standards, as well as from those currently developing biological
assessment and criteria programs, reveal the values of tiered aquatic life uses implemented in State and
Tribal WQS (Table 1-2)..
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TABLE 1-2. The benefits and WQS regulation context for TALUs.
Value-added
Explanation
Supporting WQS Regulation
Set more appropriate designated
ALUs
Define ALUs in a more precise
way that is neither under-
protective of existing high-quality
resources nor overprotective for
waters that have been extensively
and irretrievably altered
40CFR131.10
40CFR131.12 (Protect High
Quality Waters)
40CFR130.23 (Support
attainment decisions and
diagnose causes)
Strengthen the linkage between
designated ALUs and how
attainment is assessed
TALUs help to clarify and refine
water quality goal statements so
numeric biological, chemical and
physical criteria can be adopted
to protect the use
40CFRI31.10(c)
40CFR131.12 (Protect High
Quality Waters)
40CFR130.23 (Support
attainment decisions and
diagnose causes)
Enhance public understanding
and participation in setting water
quality goals
TALUs provide a common frame
of reference or generic yardstick
to more clearly recognize
common ground and differences
in desired environmental goals of
various stakeholders as
designated uses are adopted
40CFR131.20(a)(b)
Building on these "lessons learned," the U.S. EPA convened a technical workgroup in 2000 to identify
existing scientifically sound and practical approaches that would help States and Tribes provide more
precision, or specificity, in their designated aquatic life uses. The workgroup included biologists and
aquatic ecologists from States, Tribes, U.S. EPA, USGS, the academic research community, and the
private sector. The workgroup was asked to address the following questions:
• What are effective technical approaches using biological information to provide more specificity
in their designated aquatic life uses?
• What are the "lessons learned" that can be capitalized on and shared with other States and Tribes?
The workgroup was charged with developing a scientific framework using biological information to
better define designated aquatic life uses, enabling more precise use descriptions. Their product is a
narrative model describing graduated tiers of biological response to increasing levels of stressors, the
Biological Condition Gradient (BCG). The model is founded on peer-reviewed work in the field of
bioassessments over the past thirty years (Fausch et al. 1984, Karr et al. 1986, Cairns and Pratt 1993,
Barbour et al. 1999) and on the experiences and empirical observations of States and Tribes that have
developed tiered aquatic life uses and biological criteria for use in their water programs (Courtemanch et
al. 1989, Courtemanch 1995, Yoder 1995, Yoder and Rankin 1995b).
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1.5 The Biological Condition Gradient: A tool for better defining and developing more
precise aquatic life uses
The Biological Condition Gradient (BCG) is a scientific model for interpreting biological response'to
increasing effects of stressors on aquatic'ecosystems (Figure 1-1). The model describes how ten
attributes of aquatic ecosystems change in response to the increasing levels of stressors. The attributes
include several aspects of community structure, organism condition, ecosystem function, and spatial and
temporal attributes of stream size and connectivity. The gradient can be considered analogous to a field-
based dose-response curve where dose (x-axis) = increasing levels of stressors and response (y-axis) =
biological condition (see figure below). The BCG differs from the standard dose-response curve, in that
the BCG does not represent the laboratory.response of a single species to a specified dose of a known
chemical, but rather the in-situ response of the biota to the sum of stresses it is exposed to. The BCG is
divided into six tiers of biological condition along the stressor-response curve, ranging from observable
biological conditions found at no or low levels (Tier 1) to those found at high levels of stressors (Tier 6).
The BCG model was developed to provide a common framework for interpreting biological information
regardless of methodology and geography. When calibrated to a regional or state scale, States and Tribes
can use the model to more precisely evaluate the current and potential biological condition of their waters
and use that information to better define their aquatic life uses. Additionally, States and Tribes can use
this interpretative model to more clearly communicate the condition of their aquatic resources to the
public.
2
E
E "a?
O Q.
O £,
O O
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O Ul
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8
I
Natural structural, functional, and taxonomic integrity is preserved
StruCAire and function similar to natural community with some additional
taxa &i}ft)mass; no or Incidental anomalies; sensitive non-native taxa maybe
present; ecosystem level functions are fully maintained
Evitfatit changes in structure due to toss of some rare native
taxa} Hftifis In relative abundance; ecosystem level functions fully
maintained through redundant attributes of the system.
Modfer&te changes in structure due to replacement of
sensing ubiquitous taxa by more tolerant taxa; overall
balancB&ttistr&ution of all expected taxa; ecosystem
functions largely maintained.
Sensitive taxa markedly diminished;
conspicuously unbalanced distribution
of major groups from that expected;
organism
sondltlon shows signs of physiological
stress; ecosystem function shows reduced
comffaxity and redundancy; Increased build
up or export of unused materials.
Extreme changes In structure; wholesale changes In
taxonomic composition; extreme alterations from
normal densities; organism condition Is often poor;
anomalies may be frequent;'
eco$yiit£m functions are
extremely atfeted'
LOW Level of Stressors >• HIGH
FIGURE 1-1. Conceptual model of the Biological Condition Gradient.
The BCG model was developed based on common patterns of biological response to stressors observed
empirically by aquatic biologists and ecologists from different geographic areas of the U.S. Once a draft
model was constructed, it was tested at a workgroup meeting and then at two regional workshops. The
model was tested by determining how consistently the scientists assigned samples of macroinvertebrates
or fish to the different tiers of biological condition. Workgroup members identified similar sequences of
biological response to increasing levels of stressors regardless of geographic area. These results support
the use of the BCG as a nationally applicable model for interpreting the biological condition of aquatic
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systems. Chapter 2 discusses the development and makeup of the conceptual BCO and Chapter 3
explores strategies for regionally modifying, or calibrating, the conceptual model. Chapter 4 describes
how the x-axis of the BCG model, the stressor gradient, can be characterized and explains how the effects
of stressors on biological condition play a role in constructing and using a BCG. Chapter 5 discusses the
underlying principles and processes States have learned in using biological information to develop tiered
aquatic life uses, and examples of how States have applied tiered uses in water quality management are
presented in Chapter 6.
Integral to the development of the BCG is characterizing the model's x-axis, the stressor gradient (Figure
1 -1). Stressors are physical, chemical or biological factors that induce an adverse response from aquatic
biota (U.S. EPA 2000b; EPA/822/B-00/025). For example, high concentrations of certain metals,
nutrients, or sediment can adversely impact aquatic biota. Loss of aquatic habitat or presence of aquatic
invasive species can also adversely impact, or stress, the aquatic biota expected for a specific waterbody.
These stressors can cause aquatic ecosystems to change from natural conditions, exhibiting altered
compositional, structural, and functional characteristics. The degree to which stressors affect the biota
depends on the magnitude, frequency, and duration of the exposure of the biota to the stressors.
Developing a BCG for a given system characterizes the general relationship between its stressors in total
(the model's x-axis) and its.overall biological condition (the y-axis). Multiple stressors are usually
present, and thus the stressor x-axis of the BCG seeks to represent their cumulative influence as a
Generalized Stressor Gradient (GSG), much as the y-axis generalizes biological condition.
Understanding the links between stressors and their sources and the response of the aquatic biota will help
to more accurately determine the existing and potential condition of the aquatic biota (Figure 1-2). There
are different approaches and emerging science to define and quantify the causal sequence between
stressors and their .sources and biological responses. Building on current State and Tribal approaches, a
framework for characterizing stressors, the processes and mechanisms that generate them, and the
resulting biological response is presented. This framework may not only help State and Tribal managers
more precisely define designated uses, including potential future uses, but may support diagnosis of use
impairment and help prioritize management decision making.
FIGURE 1-2. The causal sequence from
stressors and their sources through the
five major water resource features to the
biological responses, i.e., the biological
endpoints. This model illustrates the
multiple pathways that stressors and
their sources can affect aquatic biota.
Insert illustrates the relationship
between stressor dose and the gradient
of biological responses (after Karr and
Yoder 2004; used by permission of J.D.
Allan, originally presented at the 2002
TALU Workgroup Meeting).
Processes and
mechanisms that
generate stressors
Altered water
resource features
Biological
endpolnt
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1.6 Conceptual basis for the Biological Condition Gradient
The five factors that determine the integrity of a water resource, which were originally described by Karr
and Dudley (1981; Figure 1-3), have been consistently used as the conceptual basis for biological
assessment and tiered aquatic life uses. In the context of the TALU approach, consideration of the five ,
factors in Figure 1 -3 are components of the stressor axis of the BCG model, while the condition of the
water resource is accounted for by the response of the biological community to the stressors, the
Biological Condition Gradient (BCG). The health and well-being of the aquatic biota is an important
barometer to measure progress towards achieving Clean Water Act goals. Biological integrity has been
defined as the combined result of chemical, physical, and biological processes in the aquatic environment
(Karr and Dudley 1981, Karr et al. 1986). Biological criteria help reconcile the mosaic of factors and
interactions that exist, parts of which may be characterized and measured using chemical and physical
indicators.
BIOLOGICAL CONDITION OF
THE WATER RESOURCE
WMWDepth
Bank Stability
Channel
Morphology
Substrate
Canopy
(Modified from Karr et aL 1986).
FIGURE 1-3. The five major factors that determine the biological condition of aquatic
resources (modified from Karr et al. 1986).
An important conceptual foundation of tiered aquatic life uses is the "position of the standard" that was
described by the National Research Council Committee on Science in TMDLs (NRC 2001; Figure F-l).
This concept describes the "position" of different types of criteria with respect to their position along a
causal chain of indicators beginning with sources (stressor indicators), to changes in pollutant
contributions or attributes of landscape and/or hydrology that emanate from those sources (exposure
indicators), to instream exposures (pollutants, attributes of habitat), to indicators of biological condition
(response indicators) that directly assess the designated use. Because designated uses are written in
qualitative, narrative terminology, the challenge is to relate a criterion to the designated use. In general,
establishing this relationship becomes easier as the criterion is positioned closer to the designated use,
hence the NRC recommendation on the use of biological information to help determine more appropriate
aquatic life uses and to couple the narrative use statements with quantitative methods. Thus biological
criteria can fill a gap along this position spectrum and serve a useful role in the expression and
implementation of water quality standards.
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Karr and Yoder (2004) further elaborated upon this concept by adding the interactive relationships
between pollution and pollutants from both point and nonpoint sources (Figure 1-4). It also relates
different types of indicators in the causal sequence of events and exemplifies the appropriate roles of
chemical, physical, and biological parameters as stressor, exposure, and response indicators (Yoder and
Rankin 1998). In this scheme, attainment of a designated use is the desired result of the management of
stressors (chemical, biological, physical) and is explained by how stressors influence and change the five
factors that determine the integrity of an aquatic resource (Karr and Yoder 2004). In each of these
process descriptions, the end outcome of water quality management is reflected in the status of a
designated use. Attainment of the designated use confirms the effectiveness of the sequence of
management actions; non-attainment is evidence of an incomplete process and a prompt to re-examine the
management strategy. Each provides important feedback about the effectiveness of management
strategies. Therefore, how designated uses are developed, assigned, and measured is key to the outcomes
derived from water quality management.
Pollution (specific
human activities)
Pollutant loading
for all sources
(source specific)
Ecological health
(cumulative effects on
biological condition)
Source
Exposure
(landscape)
Response
Endpoint
FIGURE 1-4. Modification of the NRC
"position of the criterion" concept
(Figure F-l) showing the causal sequence
from indicators of stress, exposure, and
response in relation to point and
nonpoint source impacts, specific types of
criteria, and designated uses that define
the endpoints of interest to society (after
Karr and Yoder 2004).
1.7 Key points from Chapter 1
1. Section 101(a) of the CWA establishes broad national goals and objectives such as the chemical,
physical, and biological integrity objective. To help achieve the integrity objective, the CWA
also established, among other things, an interim goal for the protection and propagation of fish,
shellfish, and wildlife. The protection and propagation interim goal has been interpreted by U.S.
EPA to include the protection of the full complement of aquatic organisms residing or migrating
through a waterbody. The health and well-being,.or condition, of the aquatic biota is an
important barometer to measure progress towards achieving Clean Water Act goals and
objectives.
2. State water quality standards provide the foundation for water quality-based pollution control
programs. With the public participating in their adoption (see 40 CFR 131.20), such standards
serve the dual purposes of establishing.the water quality goals for a specific waterbody
(designated uses) and serve as the regulatory basis for the establishment of water quality-based
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treatment controls and strategies beyond the technology-based levels of treatment required by
Sections 301(b) and 306 of the CWA.
3. A waterbody's designated use(s) are those uses specified in water quality standards, whether or
not ihey are being attained (40 CFR 131.3(f)). The "use" of a waterbody is the most fundamental
articulation of its role in the aquatic and human environments. All of the water quality
protections established by the CWA follow from the waterbody's designated use.
4. Tiered aquatic life uses are bioassessment-based statements of expected.biological condition in
specific waterbodies. Tiered uses allow more precise and measurable definitions of designated
aquatic life uses.
5. Several States and Tribes have adopted tiered aquatic life uses in their water quality standards.
This document is based on the "lessons learned" from their experiences and the recommendations
from a technical workgroup charged with integrating existing scientifically sound and practical
approaches to 1) tier designated aquatic life uses using biological information, and 2) incorporate
information on sources of stress as drivers of biological condition.
1.8 Organization of the document
This chapter provided the background and rationale for using biological information to designate aquatic
life uses in tiers that more specifically differentiate the characteristics of the biological community
currently present or desired in-a waterbody. The following chapters are based on the recommendations of
the TALU technical workgroup tasked with identifying existing scientifically sound and practical
approaches that would help States and Tribes provide more precision, or specificity, in their designated
aquatic life uses (Figure 1-5). Chapters 2 and 3 discuss the Biological Condition Gradient (BCG) - what
it is, how the national conceptual model was developed and tested, and how to calibrate the conceptual
model to a region. Chapter 4 describes how the x-axis of the BCG model, the stressor gradient, can be
characterized and explains how the effects of stressors on biological condition play a role in constructing
and using a BCG. Chapter 5 provides examples on how States have developed tiered aquatic life uses.
The experiences of Maine and Ohio, two States that have completed this process, serve as comprehensive
case histories that are found in Appendixes A and B. Chapter 6 details how Maine and Ohio have used
tiered aquatic life uses in assessment and management as examples that might guide future
implementation guidance.
FIGURE 1-5. Roadmap to the
document.
Introduction
1. What are Tiered Aquatic Life Uses
(TALUs)?
The Biological Condition
Gradient (BCG)
2. What Is the scientific basis of the
ace?
3. How do you develop and calibrate
a BCG?
4. The x-axis: A Generalized
Stressor Gradient (GSG)
Incorporating TALUs Into State
and Tribal WQS: Case Examples
5. Key concepts and milestones in the
development of TALUs
6. How have states and tribes used
TALUs in WQS and management?
References,
Glossary & Acronyms
Appendixes A-E
Maine TALU Implementation
Case History (A)
Ohio TALU Implementation
Case History (B)
Summary of draft documents
addressing technical elements
of reassessment programs (C),
reference condition (D), and
statistical guidance for
developing Indicators (E)
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12
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fr'* .
IV
Related Technical Support Documents:
Appendixes C, D & E contain summaries of three "companion" documents that are under development.
Each contains detailed information relevant to developing tiered aquatic life uses, including components
of State and Tribal bioassessment programs, statistical methods that use biological data, and best practices
for developing reference conditions. Following is a brief description of each document.
Technical Guidelines: Technical Elements of a Bioassessment Program - DRAFT
This document is intended primarily for use by State and Tribal program managers and staff who are
responsible for monitoring and assessment and water quality standards programs. The document
describes the technical attributes of biological assessment programs, and can thus be used by States
and Tribes to I) determine where they are in the biological assessment and criteria development
processes, and 2) develop, structure, and, if necessary, modify their programs and refine designated
aquatic life uses.
U.S. EPA project leads: Susan Jackson, Office of Water; Ed Hammer, Region 5; Tina Laidlaw, Region 8;
and Gretchen Hayslip, Region 10
The Role of Reference Condition in Biological Assessment and Criteria - DRAFT DOCUMENT ON
DEVELOPMENT AND APPLICATION OF THE REFERENCE CONDITION CONCEPT
This document will provide States, Tribes, and other practitioners with guidelines on using reference
conditions in their water management programs, particularly for ecological assessments. The
guidelines described are intended to facilitate greater implementation of best practices for reference
condition, thereby improving the success of individual programs and leading to greater consistency
among States and Tribes.
U.S. EPA project leads: Evan Hornig, Office of Water; Phil Larsen, Office of Research and Development;
and Wayne Davis, Office of Environmental Information
Statistical Guidance for Developing Indicators for Rivers and Streams: A Guide for Constructing
Multimetric and Multivariate Predictive Bioassessment Models - DRAFT
This document will provide methods and outlines the steps required to complete multimelric and
multivariate predictive assessment models, two methods for analyzing and assessing waterbody
condition from assemblage and community-level biological information.
U.S. EPA project lead: Florence Fulk, Office of Research and Development
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The Biological Condition Gradient
The Biological Condition Gradient (BCG) is a scientific model that allows consistent interpretation of
biological condition although assessment approaches may differ. The BCG combines scientific
knowledge with the practical experience and needs of resource managers and can assist environmental
practitioners in the U.S. to better:
define aquatic resources
establish direct relationships between biological condition
and stressors
communicate clearly to the public both the existing and
potential uses of a waterbody
Chapter 2 outlines the development and makeup of the BCG model.
The BCG describes changes in ten ecological attributes across a
gradient of biological condition caused by increasing stressors (Table
2-1). It is divided into six condition tiers, Tier 1 representing natural,
or undisturbed, conditions through Tier 6 representing severely altered
conditions.
77w BCG is eonsfeteftf w.8ft
ecological theory and is & means
for standardizing MBipietatians
to&tre$$ot$. ft® model shew®
, managers, and the
on the current conditions
specific wst&tuxii&s.
TALU Workgroup biologists from across the U.S. agreed that a similar sequence of biological alterations
occur in streams in response to stressors, strengthening the feasibility of using the BCG as a common
framework to guide management decisions that protect and restore aquatic systems in the U.S. (Davies
and Jackson in press). The model is consistent with ecological theory and can be adapted or calibrated to
reflect specific geographic regions. Scientific knowledge can be reviewed and consolidated and research
needs can be expressed in a context relevant to management. Thus, the model also serves as a framework
that 1) synthesizes what has been observed into testable hypotheses, and 2) identifies knowledge gaps in
need of further research.
Chapter 3 explores strategies for regionally modifying, or calibrating, the BCG including approaches for
recalibrating existing indexes. Three States (Maine, Ohio, and Vermont) have incorporated a BCG into
their water quality standards as well as numeric criteria. Several other States (e.g., New Jersey, Texas, and
a consortium of New England states) have begun the process of evaluating the potential use of a BCG.
Each of these States is following basically the same approach used by the national TALU Workgroup to
develop the BCG model, reaching consensus among regional biological experts familiar with natural
aquatic communities and their responses to stress.
Chapter 4 describes the model's x-axis, the stressor gradient that illustrates alteration in biological
condition. The degree to which stressors affect the biota depends on the magnitude, frequency, and
duration of the exposure of the biota to the stressors. Developing a BCG for a given system characterizes
the general relationship between its stressors in total (the model's x-axis) and its overall biological
condition (the y-axis). Multiple stressors are usually present, and thus the stressor x-axis of the BCG
seeks to represent their cumulative influence as a Generalized Stressor Gradient (GSG), much as the y-
axis generalizes biological condition. Chapter 4 explains how stressors can be characterized and
describes how the influence of stressors on biological condition plays a role in constructing and using a
BCG.
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CHAPTER 2. WHAT is THE SCIENTIFIC BASIS OF THE BIOLOGICAL ,
CONDITION GRADIENT?
The Biological Condition Gradient (BCG) extends the empirical work of earlier researchers and .
practitioners to create a nationally consistent model that links management goals for resource condition
with the quantitative measures used in biological assessments. The BCG was designed to describe
ecological response to stressors in sufficient detail so that a site can be placed into a tier along the BCG
continuum through use of the core data elements collected by most State or Tribal monitoring programs.
The practice of using biological indicators to assess water quality is over a century old. The Saprobien
System, a concept proposed by Lauterborn in 190land further developed the following year by Kolkwitz
and Marsson (Davis 1995), uses benthic macroinvertebrates and planktonic plants and animals as
indicators of organic loading and low dissolved oxygen, and has been updated and is currently used in
several European countries. Concurrently, the limnologists Thienemann and Naumann developed the
concept of trophic state classification for lakes in the 1920s (Carlson 1992, Cairns and Pratt 1993). These
early indexes described a response gradient (or response classes for lakes) to enrichment. The Saprobien
System was explicitly developed to assess human pollution in rivers, but the trophic state concept was
originally developed to describe natural conditions in lakes and only later became a concept to describe
pollution-caused eutrophication (e.g., Vollenweider 1968). The 1950s marked the development of
Beck's biotic index in the U.S. and Pantle and Buck's Saprobic Index in Europe, which were directly
based on the Saprobien System (cited in Davis 1995). The Saprobic Index, which led to the development
of the widely used Hilsenhoff Index (e.g., Hilsenhoff 1987) in the U.S., could be considered the
predecessor of today's biotic indexes (Davis 1995).
The conceptual foundation of the BCG is based on many decades of biologists' accumulated experience
with biological assessment and monitoring. Biological information from monitoring programs has been
frequently synthesized by constructing biotic indexes, such as the Index of Biotic Integrity (IBI) (Karr
1981, Karr et al. 1986). The IBI integrated the concept of anchoring the measurement system in
undisturbed reference conditions with the measurement of several indicators intended to reflect ecological
components of composition, diversity, and ecosystem processes. It thus combined a conceptual model of
ecosystem change in response to increasing levels of stressors with a practical measurement system for
fish. The BCG is also grounded in the concepts in Cairns et al. (1993) describing "natural" conditions
and the change in biological condition caused by stressors. To achieve maximum potential application
nationwide, the BCG tiers were developed based on States' various experiences designing and
implementing tiered aquatic life use and management goals as well as the practical experience of aquatic
scientists from different bio-geographic areas, each of whom had fifteen to thirty years of experience in
the field. The BCG:
1. Describes a complete scale of condition from natural (Tier 1) to severely altered (Tier 6);
2. Synthesizes existing field observations and generally accepted interpretations of patterns of
biological change within a common framework; and
3.. Helps determine the degree to which a system may have departed from natural condition,
based on measurable, ecologically important attributes.
At present, the description of biological attributes that make up the model applies best to permanent, hard-
bottom streams that are exposed to increases in temperature, nutrients, and fine sediments because this is
the stream-type and stressor regime originally described by the model. The model has been further tested
with States and Tribes in different parts of the country (e.g., arid west and great plains) to evaluate the
national applicability of the model. Results have been successful with some necessary refinement of the
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16
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model attributes to accommodate regional differences. For example, during a workshop in Texas where
the BCG was being evaluated using Texas data, Attribute II (sensitive-rare taxa) was redefined as highly
sensitive taxa because rarity of a taxon in the region was not deemed to be associated with sensitivity to
stress. In arid streams, many rare, native taxa are highly tolerant to stressors such as low dissolved
oxygen and high temperature. Thus, the BCG can be applicable to other aquatic ecosystems and stressors
with appropriate modifications. The BCG should be viewed as an evolving model that must be
responsive to changes in scientific understanding resulting from the analysis of empirical data.
The value of a heuristic model such as the BCG is not only that it documents experimentally established
knowledge, but also that it promotes a more rigorous testing of empirical observations by clearly stating
them in a provisional model. Conceptual models formalize the state of knowledge and guide research.
Empirically based generalizations have led to conceptual models that describe the behavior of biological
systems under stress (Brinkhurst 1993; Margalef 1963, 1981; Odum, et al. 1979; Rapport et al. 1985;
Schindler 1987; Fausch et al. 1990; Karr and Dudley 1981). For example, Brinkhurst observed that
"Everyone knew [in 1929] that increases in numbers and species could be related to mild pollution, that
moderate pollution could produce changes in taxa so that diversity remained similar but species
composition shifted, and that eventually species richness declined abruptly and numbers of some tolerant
forms increased dramatically." Such ecosystem responses to stressor gradients have been portrayed as a
progression of stages that-occur in a generally consistent pattern (Odum et al. 1979, Odum 1985, Rapport
et al. 1985, Cakns and Pratt 1993). Establishing and validating quantifiable thresholds along that
progression with empirical data is a priority need for resource managers (Cairns 1981).
2.1 What the BCG model looks like
The BCG model depicts ecological condition in terms of ten system attributes expressed at different
spatial scales (Table 2-1). In biological assessments, most information is collected at the spatial scale of a
site or reach and the temporal scale of a single^ampling event. Many of the attributes that make up the
BCG are based on these scales. Site scale attributes include aspects of taxonomic composition and
community structure (Attributes I-VI) and organism and system performance (Attributes VII and VIII).
At larger temporal and spatial scales, physical-biotic interactions (Attributes IX and X) were also
included because of their importance in evaluating the longer term impacts, restoration potential and
recoveries.
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TABLE 2-1. Biological Condition Gradient matrix.
Ecological
Attributes
1
Historically
documented.
sensitive.
long-lived or
regionally
endemic
taxa
II
Sensitive-
rare taxa
III
taxa
IV
intermediate
tolerance
V
Tolerant
taxa
Biological Condition Gradient Tiers
1
Natural or native
condition
Native structural,
functional and
taxonomic
integrity is
preserved;
ecosystem
function is
preserved within
the range of
natural variability
As predicted for
natural
occurrence
except for global
extinctions
As predicted for
natural
occurrence, with
at most minor
changes from
natural densities
As predicted for
natural
occurrence, with
at most minor
changes from
natural densities
As predicted for
natural
occurrence, with
at most minor
changes from
natural densities
As naturally
occur, with at
most minor
changes from
natural densities
2
Minimal chanoes
in the structure of
community and
minimal chanaes
in ecosystem
function
Virtually all native
taxa are
maintained with
some changes in
biomass and/or
abundance;
ecosystem
functions are fully
maintained within
the range of
natural variability
As predicted for
natural
occurrence
except for global
extinctions
Virtually all are
maintained with
some changes in
densities
Present and may
be increasingly
abundant
As naturally
present with slight
increases in
abundance
As naturally
present with slight
increases in
abundance
3
Evident chanaes
in structure of the
biotic cornmunitv
and minimal
changes in
ecosystem
function
Some changes in
structure due to
toss of some rare
native taxa; shifts
in relative
abundance of
taxa but
Sensitive-
ubiquitous taxa
are common and
abundant;
ecosystem
functions are fully
maintained
through
redundant
attributes of the
system
Some may be
absent due to
global extinction
or local
extirpation
Some loss, with
replacement by
functionally
equivalent
Sensitive-
ubiquitous taxa
Common and
abundant; relative
abundance
greater than
Sensitive-rare,
taxa
Often evident
increases in
abundance
May be increases
in abundance of
functionally
diverse tolerant
taxa
- 4
structure of the
biotic community
and minimal
chanaes in
ecosystem
function
Moderate
changes in
structure due to
replacement of
some Sensitive-
ubiquitous taxa
by more tolerant
taxa, but
reproducing
populations of
some Sensitive
taxa are
maintained;
overall balanced
• distribution of all
expected major
groups;
ecosystem
functions largely
maintained
through
redundant
attributes
Some may be
absent due to
global, regional or
local extirpation
May be markedly
diminished
Present with
reproducing
populations
maintained; some
replacement by
functionally
equivalent taxa of
intermediate
tolerance.
Common and
often abundant;
relative
abundance may
be greater than
Sensitive-
ubiquitous taxa
May be common
but do not exhibit
significant
dominance
5
Maior chanaes in
structure of the
biotic cornmunitv
and moderate
• chanaes in
ecosystem
function
Sensitive taxa are
markedly
diminished;
conspicuously
unbalanced
distribution of
major groups
from that
expected;
organism
condition shows
signs of
physiological
stress; system
function shows
reduced
complexity and
redundancy; .
increased build- '•
up or export of
unused materials
Usually absent
Absent
Frequently absent
or markedly
diminished
Often exhibit
excessive
dominance
Often occur in
high densities
and may be
dominant
6
Severe chanaes
in s' ructure of the
bio ic cornmunitv
and maior loss of
ecosystem
Extreme changes
in structure;
wholesale
changes in
taxonomic
composition; •
extreme
alterations from
normal densities
and distributions;
organism
condition is often
poor; ecosystem
functions are
severely altered
Absent
Absent
Absent
May occur in
extremely high
OR extremely low
densities;
richness of all
taxa is low
Usually comprise
the majority of the
assemblage;
often extreme
departures from
normal densities
(high or low)
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TABLE 2-1. Biological Condition Gradient matrix.
V!
Non-native
0£
intentionally
Introduced
taxa
VII
(esoec allv
of long- ived
oraanismsl
VIII
Ecosystem
Functions
IX
Soatialand
temporal
extent of
detrimental
effects
X
Ecosystem
connectance
V-
Biological Condition Gradient Tiers
1
Natural or native
condition
Non-native taxa, if
present, do not
displace native
taxa or alter
native structural
or functional
Integrity
Any anomalies
are consistent
with naturally
occurring
incidence and
characteristics
All are maintained
within the natural
range of
variability
N/A
A natural
disturbance
regime is
maintained
System is highly
connected in
space and time,
at least annually
2
Minimal chanaes
in the structure of
the biotic
communtvand
minimal c nanges
in ecosystem
function
Non-native.taxa
may be present,
but occurrence
has a non-
detrimental effect
on native taxa
Any anomalies
are consistent
with naturally
occurring
incidence and
characteristics
All are maintained
within the natural
range of
variability
Limited to small
pockets and short
duration
Ecosystem
connectance is
not impacted
3
Evident chanaes
in structure of the
biotic community
and minimal
changes in
ecosystem
function
Sensitive or
intentionally
introduced non-
native taxa may
dominate some
assemblages
(e.g. fish or
macrophytes)
Anomalies are
infrequent
Virtually all are
maintained
through
functionally
redundant system
attributes;
minimal increase
in export except
at high storm
flows
Limited to the
reach scale
and/or limited to
within a season
Slight loss of
connectance but
there are
adequate local
recolonization
sources
4
Moderate
chanaes in
structure of the
biotic community
and minimal
chanaes in
ecosystem
function
Some .
replacement of
sensitive non-
native taxa with
functionally
diverse '
assemblage of
non-native taxa of
intermediate
tolerance
Incidence of
anomalies may
be slightly higher
than expected
Virtually all are
maintained
through
functionally
redundant system
attributes though
there is evidence
of loss of
efficiency (e.g.,
increased export
or decreased
import)
Mild detrimental
effects may be
detectable
beyond the reach
scale and may
include more than
one season
Some loss of
connectance but
colonization
sources and
refugia exist
within the
catchment
5
Maior qhanqes in
structure of the
biotic community
and moderate
changes in
ec9§ysjerrj
function
Some
assemblages
(e.g., fish or
macrophytes) are
dominated by
tolerant non-
native taxa
Biomass may be
reduced;
anomalies
increasingly
common
There is apparent
loss of some
ecosystem
functions
manifested as
increased export
or decreased
import of some
resources, and
changes in
energy exchange
rates (e.g., P/R;
decomposition)
Detrimental
effects extend far
beyond the reach.
scale leaving only
a few islands of
adequate
conditions; effect
extends across
multiple seasons
Significant loss of
ecosystem
connectance is
evident;
recolonization
sources do not
exist for some
taxa
6
Severe chanqes
in structure of the
biotic community
and maior loss of
ecosystem
teto
Often dominant;
may be the only
representative of
some
assemblages
(e.g., plants, fish,
bivalves)
Long-lived taxa
may be absent;
Biomass reduced;
anomalies
common and
serious; minimal
reproduction
except for
extremely tolerant
tjroups
Most functions
show extensive
and persistent
disruption
Detrimental
effects may
eliminate all
refugia and
colonization
sources within the
catchment and
affect multiple
seasons
Complete loss of
ecosystem
connectance in at
least one
dimension (i.e.,
longitudinal,
lateral, vertical, or
temporal) lowers
reproductive
success of most
groups; frequent
failures in
reproduction &
recruitment
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2.1.1 The BCG Attributes
Taxonomic Composition and Structure: Attributes I - VI
Attribute I: Historically documented, sensitive, long-lived or regionally endemic taxa.
"Historically documented" refers to taxa known to have been supported in a waterbody or region prior
to enactment of the 1972 Clean Water Act, according to historical records compiled by State or federal
agencies or published scientific literature.
"Sensitive or regionally endemic taxa " have restricted, geographically isolated distribution patterns
(occurring only in a locale as opposed to a region), often due to unique life history requirements. They
' may be long-lived, late maturing, low fecundity, limited mobility, or require a mutualist relation with
other species. They may be among listed Endangered or Threatened (E/T) or special concern species.
Predictability of occurrence is often low, and therefore requires documented observation. Recorded
occurrence may be highly dependent on sample methods, site selection, and level of effort.
Attribute II: Sensitive-rare taxa. .
These are taxa that naturally occur in low numbers relative to total population density but may make up a
large relative proportion of richness. They may be ubiquitous in occurrence or restricted to certain
micro-habitats, but because of low density, recorded occurrence is dependent on sample effort. Often
stenothermic (having a narrow range of thermal tolerance) or cold-water obligates; commonly k-
strategists (populations maintained at a fairly constant level; slower development; longer life-span). May
have specialized food resource needs or feeding strategies. Generally intolerant to significant alteration
of the physical or chemical environment; are often the first taxa observed to be tost from a community.
Attribute III: Sensitive ubiquitous taxa.
"Sensitive" taxa from Attributes Hand III are taxa that are intolerant to a given stress; they are the first
species affected by the specific stressor to which they are "sensitive" and the last to recover following-
restoration. Sensitive ubiquitous taxa are ordinarily common and abundant in natural communities when
conventional sampling methods are used. They often have a broader range of thermal tolerance than
Sensitive-rare taxa and comprise a substantial portion of natural communities and often exhibit negative
response (loss of population, richness) at mild pollution loads or habitat alteration.
Attribute IV: Taxa of intermediate tolerance.
Taxa that comprise a substantial portion of natural communities; may be r-strategists (early colonizers
with rapid turn-over times; e.g.," boom/bust population characteristics). May be eurythermal (having a
broad thermal tolerance range). May have generalist or facultative feeding strategies enabling
utilization of relatively more diversified food types. Readily collected with conventional sample methods.
May increase in number in waters with moderately increased organic resources and reduced competition
but are intolerant of excessive pollution loads or habitat alteration.
Attribute V: Tolerant taxa.
Taxa that comprise a low proportion of natural communities. Taxa often are tolerant of a broader range
of environmental conditions and are thus resistant to a variety of pollution or habitat induced stress.
They may increase in number (sometimes greatly) in the absence of competition. Commonly r-strategists
(early colonizers with rapid turn-over times: e.g., "boom/bust" population characteristics), able to
capitalize when stress conditions occur. These taxa are the last survivors in highly disturbed systems.
Taxa tolerance to stressors (ATTRIBUTES I-V).
Taxa differ in their sensitivities to stressors. Changes in the numbers, kinds and relative
abundance of taxa across stressor gradients are important and useful indicators of adverse
DRAFT: Use of Biological Information to Better Define Designated Aquatic Life Uses in State
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effects (Cairns 1977, Karr 1981). Sensitivity of taxa to stress can vary among species, as well
as with stressor. Shifts in taxa as a function of differing sensitivities to aquatic and riparian
disturbance are well documented (Table 2-2). For perennial streams in temperate zones,
disturbance tends to select for short-lived, tolerant species and against longer-lived, less
tolerant species (Pianka 1970, Odum 1985, Rapport et al. 1985). In the highest quality tiers of
the BCG, locally endemic taxa that are long-lived and ecologically specialized are well
represented. With increasing stress, assemblage composition shifts towards tolerant species or
short-lived taxa that can rapidly colonize disturbed environments. Assemblages in the lower
tiers are dominated by eurytopic taxa (those with wide environmental ranges) with generalist
or facultative feeding strategies.
TABLE 2-2. Evidence in support of the depicted changes in ecological attributes in the BCG.
BCG Attribute
I-V
Response
Shifts in the numbers
and kinds of species
present, and in the
number of individuals
per species, as a
function of varying
tolerances to different
kinds of aquatic and
riparian disturbance.
Shifts from K-selected
strategists to r-selected
strategists following
disturbance or in
response to pollution
Regional and national
species attribute lists
and taxonomic tolerance
values
Case-specific documentation
changes in lake diatom species composition in response to
intentional fertilization
loss of sculpins downstream of metal mines
changes in algal species across a nutrient gradient in the
Florida Everglades
changes in diatom assemblages with increased acidification
and eutrophication of lakes
shifts in species composition along a gradient of pulp and
paper mill effluent concentration in a Maine river
shifts in damselfly species from specialist species to
generalist species along a gradient of organic pollution in an
Italian river
variable sensitivities of benthic macroinvertebrate species to
acidic conditions
changes in fish species composition in an Oregon river with
increased nutrients and temperature
differentially tolerant fish species in response to heavy metal
and dissolved oxygen gradients in two Indian rivers
decline in darters, sunfish, and suckers as well as other intolerant
fishes and increase In tolerant fishes in the Midwest
variable responses of stream amphibians to severe siltation
shifts from fragmentation-sensitive to fragmentation-tolerant
bird species in relation to disturbed riparian habitats
higher proportion of r-selected species in a flow regulated
river as compared to a natural flow regime river
shittto r-selected, generalist damselfly species along a
gradient of increasing pollution
water-level fluctuation in a mesocosm resulted in increased
proportion of r-strategist species
high pollutional stress correlated with increase in r-selected
strategists in the same river 21 years apart
compendium of pollution tolerance, habitat preferences,
feeding guilds for fish species of the northeastern U.S.
compendium of pollution tolerance, habitat preferences,
feeding guilds for fish species of the Pacific northwest, U.S.
organic pollution tolerance ranks for Wisconsin stream insect
taxa
compendium of pollution tolerance, habitat preferences,
feeding guilds of North American fish and aquatic
macroinvertebrate taxa
Reference
Zeebetal. 1974;
Yang etal. 1996
Mebane et al. 2003
Stevenson et al. 2002
Dixit etal. 1999
Rabeni etal. 1988
Solimini etal. 1997
Courtney and
Clements 2000
Hughes and Gammon
1987
Ganasan and Hughes
1998
Karr et all 986; Yoder
and DeShon 2003
Welsh and Ollivier
1998
Croonquist and
Brooks 1993; Allen
and O'Connor 2000;
Bryce etal. 2002
Nilsson etal. 1991
Solimini et al. 1997
Troelstrup and
Hengenrader1990
Richardson et al. 2000
Haliiwell etal. 1998
Zaroban et a). 1999
Hilsenhoff 1987
Barbour et al. 1999
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TABLE 2-2. Evidence in support of the depicted changes in ecological attributes in the BCG.
BCG Attribute
VI
VII
VIII
IX
X
Response
Detrimental effects of
non-native taxa
Changes in organism
condition or increase in
anomalies in response to
pollution gradients
ecosystem-level
disruptions of functional
integrity
influence of spatial and
temporal scale of
pressures on biological
effects and recovery
potential
ecosystem connectance
Case-specific documentation
loss of 150-200 endemic species in Lake Victoria following
intentional introduction of Nile perch (Lales niloticus) and Nile
tilapia (Oreochromis niloticus)
dominance of many lowland rivers in the western USA by
non-native fishes and invertebrates
food web disruption and loss of native mussels from zebra
mussel invasion
detrimental changes in non-native taxa in TVA rivers where
Corbicula is present
loss of small, soft-finned fish species from Northeast USA
lakes following predator introductions
mid-twentieth century collapse of native salmonid fisheries
following colonization of the Laurentian Great Lakes by sea
lamprey (Petromyzon marinus) and alewife (Alosa
pseudoharengus)
increased fish anomalies in the vicinity of toxic outfalls
altered blood chemistry and mortality in fish associated with
wetlands that received oil sands effluent
changes in growth, organism condition, fecundity, and feeding
strategies for creek chub (Semotilus atromaculatus) across a
variety of pressure gradients (urbanization, agriculture,
temperature)
the presence of tumors, deformities, lesions, etc. in the fish
from highly disturbed streams
extinction and succession of littoral lake invertebrate species
secondary to lake acidification; Initially detected by temporal
changes in taxonomic and density measures but followed by
top-down and bottom up effects at all trophic levels, caused
by reduced nutrient cycling. A trophic cascade ultimately
involved loss of fish and increased biomass of primary
producers.
simplification of global coastal ocean ecosystems to microbial
domination due to combined effects of historical and current
overfishing and pollution
large-scale, multi-state status and trends assessments of
Pacific salmon influenced the listing of the species under the
Endangered Species Act
environmental factors operating at different temporal and
spatial scales influence the production and survivorship of
juvenile Atlantic salmon
past land use activity has long-term effects on aquatic bio-
diversity
assessments of stream fish and benthic macroinvertebrate
assemblages at state and regional scales reveal serious
alterations in indicators of biological integrity
Ocean-wide ecological extinction of large predators from
historical and current overfishing
replacement of 4 native freshwater fish species by 37 marine
species in the lower Rio Grande following flow diversions that
caused the lower river to cease flowing and become tidal salt
water
decreased fish species and guilds with decreased riverine
connectivity with ftoodplain water bodies
5 federally listed headwater fish species have had their
ranges restricted and isolated by mainstem impoundments,
increasing their susceptibility to local physical and chemical
habitat degradation
Reference
WitteetaLl992
Moyle1986, Karretal
1986, Miller etal.
1989
Whittier etal. 1995
Kerans and Karr 1994
Whittier and Kincaid
1999
Smith 1972
Hughes and Gammon
1987,Yoderand
Rankin 1995b
Bendellyoung et al.
2000
Fitzgerald etal. 1999
Karretal. 1986,
Yoder and DeShon
2003
Appelberg etal. 1993
Jackson et al. 2001
Nehlsenetal. 1991
Poff and Huryn 1998
Harding et al. 1998
U.S. EPA 2000a
Myers and Worm
2003
Contreras-Balderas et
al. 2002
Aarts etal. 2004
Freeman et al. 2005
DRAFT: Use of Biological Information to Better Define Designated Aquatic Life Uses in State
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TABLE 2-2. Evidence in support of the depicted changes in ecological attributes in the BCG.
BCG Attribute
Response
Case-specific documentation
alteration of natural flow regimes result in changes in
biological assemblage structure
extirpation of Pacific Northwest salmon following construction
of impassable dams
extirpation of Colorado River fishes following dam
construction
Reference
Poll et al. 1997, Bunn
and Arthington 2002
FrisselM993
Holden and Stalnaker
1975
Attribute VI: Non-native or intentionally introduced taxa.
With respect to a particular ecosystem, any species that is not found in that ecosystem. Species
introduced or spread from one,region of the U.S. to another outside their normal range are non-native or
non-indigenous, as are species introduced from other countries.
This attribute represents both an effect of human activities and a slressor in the form of
. biological pollution. Although some intentionally introduced species are valued by large
segments of society (e.g., gamefish), these species may be just as disruptive to native species
as undesirable opportunistic invaders (e.g., zebra mussels). Many rivers in the U.S. are now
dominated by non-native fishes and invertebrates (Moyle 1986), and introductions of alien
species are the second most important factor contributing to fish extinctions in North America
(Miller et al. 1989). The BCG identifies maintenance of native taxa as an essential
characteristic of Tier 1 and 2 conditions. The model only allows for the occurrence of non-
native taxa in these tiers if those taxa do not displace native taxa and do not have a detrimental
effect on native structure and function. Tiers 3 and 4 depict increasing occurrence of non-
native taxa. Extensive replacement of native taxa by tolerant or invasive, non-native taxa can
occur in Tiers 5 and 6.
Organism Condition and System Performance: Attributes VII and VIII
Attribute VII: Organism condition.
Organism condition is an element of ecosystem function, expressed at the level of anatomical or
physiological characteristics of individual organisms.
Organism condition includes direct and indirect indicators such as fecundity, morbidity,
mortality, growth rates, and anomalies such as lesions, tumors, and deformities and for
purposes of the BCG, primarily applies to fish and amphibians. Some of these indicators are
readily observed in the field and laboratory, whereas the assessment of others requires
specialized expertise and much greater effort. The most common approach for State and
Tribal programs is to forego complex and demanding direct measures of organism condition
(e.g., fecundity, morbidity, mortality, growth rates) in favor of indirect or surrogate measures
(e.g., % of organisms with anomalies, age or size class distributions) (Simon (ed.) 2003).
Organism anomalies in the BCG vary from naturally occurring incidence in Tiers 1 and 2 to
higher than expected incidence in Tiers 3 and 4. In Tiers 5 and 6, biomass is reduced, the age
structure of populations indicates premature mortality or unsuccessful reproduction, and the
incidence of serious anomalies is high.
Attribute VIII: Ecosystem function.
"Function" refers to any processes required for normal performance of a biological system. The term
may be applied to any level of biological organization. Immigration and emigration are functional
processes at the population level. Examples of ecosystem functional processes are primary and
secondary production, respiration, nutrient cycling, and decomposition.
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The "functional integrity" of an ecosystem refers to the aggregate performance of dynamic
interactions among an ecosystem's biological parts (Cairns 1977). The term "ecosystem
function" includes measures of both the interactions among taxa (food web dynamics) and
energy and nutrient processing rates (energy and nutrient dynamics). These attributes are
included in the BCG because ecologists universally recognize their fundamental importance.
At this time, the level of effort required to directly assess ecosystem function is beyond the
means of most State and Tribal monitoring programs. Instead, most programs rely on
taxonomic and structural indicators to make inferences about functional status (Karr et al.
1986). For example, shifts in the primary source of food may cause changes in trophic guild
indexes or indicator species. Although direct measures of ecosystem function are currently
difficult or time consuming, they may become practical in the future (Gessner and Chauvet
2002).
Attribute VIII also includes aspects of individual, population, and community condition.
Altered interactions between individual organisms and their abiotic and biotic environments
may generate changes in growth rates, reproductive success, movement, or mortality. These
altered interactions are ultimately expressed at ecosystem-levels of organization (e.g., shifts
from heterotrophy to autotrophy, onset of eutrophic conditions) and as changes in ecosystem
process rates (e.g., photosynthesis, respiration, production, decomposition). Maine's example
scenario (Table 2-3, located at the end of this chapter) describes a progression of functional
changes. It depicts a naturally oligotrophic and heterotrophic system with P/R <1 in Tiers 1
and 2. Tiers 3 ^and 4 depict functional changes commonly associated with the effects of
increased temperature and nutrient enrichment (P/R > 1, diurnal sags in dissolved oxygen,
changes in taxonomic composition and relative abundance" increased algal biomass). Tier 5
depicts an autotrophic system impacted by excessive algal biomass.
Scale-dependent Factors: Attributes IX and X
Attribute IX: Spatial and temporal extent of stressor effects.
The spatial and temporal extent of stressor effects includes the near-field to far-field range of observable
effects of the stressor. Patchy islands or periods of unsuitable conditions, within a generally intact
system, give way to patchy islands or periods of suitable conditions, within a substantially degraded
system.
Attribute X: Ecosystem connectance.
Access or linkage (in space/time) to materials, locations, and conditions required for maintenance of
interacting populations of aquatic life; the opposite of fragmentation; necessary for metapopulation
maintenance and natural flows of energy and nutrients across ecosystem boundaries.
Scale-dependent factors (ATTRIBUTES IX AND X).
These attributes relate to interactions between the physical environment in all its aspects
(spatial, temporal, structural, chemical, etc.), and the biota. Attributes DC and X are
interpreted at different spatial and even temporal scales than the rest of the attributes, i.e., the
reach, or sampled community perspective has been expanded to consider alterations occurring
within entire catchments, basins, and regions, or within seasonal and annual cycles. These
attributes were included in the BCG because the extent of ecosystem alteration has important
environmental implications in terms of an individual waterbody's vulnerability to further
effects from stressors as well as potential for mitigation. For example, ecosystem connectivity
is 'fundamental to the successful recruitment and maintenance of organisms into any
environment. A single impacted stream reach in an otherwise intact watershed has far more -
DRAFT: Use of Biological Information to Better Define Designated Aquatic Life Uses in State
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24
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restoration potential than a similar site in a basin that has undergone extensive land-scape
alteration (Table 2-2). Tiers 1 and 2 depict a naturally connected or isolated system in which a
natural disturbance regime, e.g. natural variability, is maintained. Detrimental effects in Tiers
3 and 4 are limited to the reach or seasonal scale. The two lowest tiers depict a system with
detrimental effects extending to the catchment scale and affecting multiple seasons. A few
"islands" of adequate physical/chemical conditions may serve as refugia in Tier 5, but
extensive loss of connectance and refugia occur in Tier 6.
2.1.2 The BCG Tiers
t&ttmt structural, functional, and taxonomlc Integrity Is preserved.
' StfUftfyre and function similar to natural community with some additional
2 MX* ft&ffnass; no or Incidental anomalies; sensitive normative taxa may be
item level lunations are Kitty maintained
changes In structure due to loss of some rare native
In relative abundance; ecosystem level functions tally
through redundant attributes ot the system.
Although the BCG is continuous in concept, it has been divided into six tiers to provide as much
discrimination of different levels of condition as workgroup members deemed discernable, given current
assessment methods and robust monitoring information (Figure 2-1). Defining the tiers between 3 and 5
was a challenge to the' workgroup and entailed considerable discussion. The workgroup ultimately agreed
some States and Tribes may only
be capable of discriminating 3-4
tiers, while others might be
capable of discerning 6 tiers based
on characteristics of their database
and monitoring program.
However the workgroup agreed
that the important role of the BCG
model is to be a starting point for
a State or Tribe to think about
how to use information to better
define their designated aquatic life
uses and to communicate more
clearly about biological condition.
There is no expectation that States
and Tribes establish six tiers of
use classes. The ultimate number
of the tiers is a State or Tribal
determination.
funci
changes In structure due to replacement ol
iblqultous taxa by more tolerant faxa; overall
ol alt expected taxa; ecosystem
maintained.
Sensitive taxa markedly diminished;
conspicuously unbalanced distribution
ot major groups from that expected;
organism
upc
shows signs ot physiological
ecosystem function shows reduced
tty and redundancy; Increased build
ol unused materials.
Extreme changes In structure; wholesale changes In
taxonomlc composition; extreme alterations from
normal densities; organism condition la often poor;
may be frequent;
tuacypnsare
''
LOW
Level of Stressors
HIGH
FIGURE 2-1. Conceptual model of the Biological Condition Gradient.
Tier 1: Natural or native condition.
Native structural, functional, and taxonomic integrity is preserved; ecosystem function is preserved
within the range of natural variability.
Tier 1 represents biological conditions as they existed (or still exist) in the absence of measurable
effects of stressors. The Tier 1 biological assemblages that occur in a given biogeophysical setting
are the result of adaptive evolutionary processes and biogeography that selects in favor of survival
of the observed species..For this reason, the expected Tier 1 assemblage of a stream from the arid
southwest will be very different from that of a stream in the northern temperate forest. The
maintenance of native species populations and the expected natural diversity of species are essential
for Tiers 1 and 2. Non-native taxa (Attribute VI) may be present in Tier 1 if they cause no
displacement of native taxa, although the practical uncertainties of this provision are acknowledged
(discussed in Section 2.2).
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25
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Attributes I and II (e.g., historically documented and sensitive taxa) can be used to help assess the
status of native taxa and could be a surrogate measure to identify threatened or endangered species
when classifying a site or assessing its condition.
Tier 2: Minimal changes in structure of the biotic community and minimal changes in ecosystem
function.
Virtually all native taxa are maintained with some changes in biomass and/or abundance; ecosystem
functions are fully maintained within the range of natural variability.
Tier 2 represents the earliest changes in densities, species composition, and biomass that occur
as a result of slight elevation in stressors (such as increased temperature regime or nutrient
enrichment). There may be some reduction of a small fraction of highly sensitive or
specialized taxa (Attribute II) or loss of some endemic or rare taxa as a result. Tier 2 can be
characterized as the first change in condition from natural and it is most often manifested in
nutrient enriched waters as slightly increased richness and density of sensitive ubiquitous taxa
and taxa of intermediate tolerance (Attributes III and IV). These early response signals have
been observed in many State programs as illustrated in Figure 2-2, showing slight to moderate
increases in conductivity in Maine streams.
DUU
SOO
3
L
j
J
'
•
Y
J
gbi I5?! ""r5
^r^ . »*^
(?S
*
|
1
i |:pj£i|
FIGURE 2-2. ¥
enrichment in
a gradient of
•
HI Non-Outlier Max
Non-Outlier Min
E23 75%
25%
o Median
O Outliers
0-30 30-60 60-100 100-200 >200 » Extra™.
Conductivity
Tier 3: Evident changes in structure of the biotic community and minimal changes in ecosystem
function.
Evident changes in structure due to loss of some rare native taxa; shifts in relative abundance of taxa but
sensitive-ubiquitous taxa are common and abundant; ecosystem functions are fully maintained through
redundant attributes of the system.
Tier 3 represents readily observable changes that, for example, can occur in response to
organic enrichment or increased temperature. The "evident" change in structure for Tier 3 is
interpreted to be perceptible and detectable decreases in sensitive-rare or highly sensitive taxa
(Attribute II) and increases in sensitive-ubiquitous-taxa or opportunist organisms (Attributes
III and IV). Attribute IV taxa (intermediate tolerants) may increase in abundance as an
opportunistic response to nutrient inputs.
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Tier 4: Moderate changes in structure of the biotic community with minimal changes in ecosystem
function.
Moderate changes in structure due to replacement of some sensitive-ubiquitous taxa by more tolerant
taxa, but reproducing populations of some sensitive taxa are maintained; overall balanced distribution of
all expected major groups; ecosystem functions largely maintained through redundant attributes.
Moderate changes of structure occur as stressor effects increase in Tier 4. A substantial
reduction of the two sensitive attribute groups (II and III) and replacement by more tolerant
taxa (Attributes IV and V) may be observed. A key consideration is that some Attribute III
sensitive taxa are maintained at a reduced level but are still an important functional part of the
system (function maintained).
Tier 5: Major changes in structure of the biotic community and moderate changes in ecosystem
function.
Sensitive taxa are markedly diminished; conspicuously unbalanced distribution of major groups from
those expected; organism condition shows signs of physiological stress; ecosystem function shows
reduced complexity and redundancy; increased build-up or export of unused materials.
Changes in ecosystem function (as indicated by marked changes in food-web structure and
guilds) are critical in distinguishing between Tiers 4 and 5. This could include the loss of
functionally important sensitive taxa and keystone taxa (Attribute I, II and III taxa) such that
they are no longer important players in the system, though a few individuals may be present.
Keystone taxa control species composition and trophic interactions, and are often, but not
always, top predators. As an example, removal of keystone taxa by overfishing has greatly
altered the structure and function of many coastal ocean ecosystems (Jackson et al. 2001).
Additionally, tolerant non-native taxa (Attribute VI) may dominate some assemblages and
changes in organism condition (Attribute VII) may include significantly increased mortality,
depressed fecundity, and/or increased frequency of lesions, tumors and deformities.
Tier 6: Severe changes in structure of the biotic community and major loss of ecosystem function.
Extreme changes in structure; wholesale changes in taxonomic composition; extreme alterations from
normal densities and distributions; organism condition is often poor; ecosystem functions are severely
altered.
Tier 6 systems are taxonomically depauperate (low diversity and/or reduced number of
organisms) compared to the other tiers. For example, extremely high or low densities of
organisms caused by excessive organic enrichment or severe toxicity may characterize Tier 6
systems.
2.2 How the BCG was developed, tested, and evaluated
The BCG model was developed and tested by the TALU fo ttevefcp^tfje BCG, &&
Workgroup. Based on recommendations from the full workgroup, a workgroup believed ft was
steering committee created a matrix that summarized biologists' fmoortant fftatthe moefeffee
experience and knowledge about how biological attributes change in
response to stress in aquatic ecosystems (Table 2-1). In developing Bounded^sauodthsorf, easy
the BCG, the workgroup believed it was important that the model be to sppfyt andimtflto flewfe of ..
grounded in sound theory as well as actual empirical observations, practitioners around #ie&>t#tffi
easy to apply, and meet the needs of users around the country. In
building the model, the workgroup followed an iterative, inductive approach, similar to means-end
analysis (Martinez 1998). The model was tested by determining how consistently workgroup members
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assigned samples of macroinvertebrates or fish to the six tiers, the results of which support the contention
that the BCG represents aspects of biological condition common to all existing assessment methods.
The workgroup began by testing whether biologists from different parts of the country would draw
similar conclusions regarding the condition of a waterbody using simple lists of organisms and their
counts. This approach was based on Maine's experience, in which expert biologists independently
assigned samples of macroinvertebrates to a priori defined classes of biological condition defined by
differences in assemblage attributes (Davies et al. 1995). Decision instructions were provided to
biologists in the form of a matrix, which outlined expected trajectories of quantifiable aspects of
invertebrates (See Case Example 3-3 in the next chapter). These corresponded with biological
expectations for four water quality classes (A, B, C and Non-Attainment; See Appendix A, Tables A-1 and
A-2). The high level of majority and unanimous agreement (98% and 64% respectively) among experts in
placing samples into the different classes allowed Maine to develop a predictive statistical model that is
now used to assess the biological condition of new sites (Courtemanch 1995) (See Case Example 3-3).
To provide a functional framework for practitioners, the TALU Workgroup described how each of the ten
attributes varies across six tiers of biological alteration (Table 2-1). The general model was then
described in terms of the biota of a specific region (Maine). Based on 20 years of biomonitoring data, the
Maine example describes how the relative densities of specific taxa with varying sensitivities to stressors
change across the BCG tiers (Table 2-3, located at the end of this chapter).
To test the general applicability of the BCG to sampling data taken from real ecosystems, the workgroup
evaluated how consistently individual biologists classified samples of aquatic biota based on the attributes
incorporated into the BCG. Governmental and research biologists from 23 States and one Tribe
participated in the data exercise. The full workgroup was divided into breakout groups according to
regional (Northeast, South-Central, Northwest, Arid Southwest/Great Plains) or assemblage (fish,
invertebrates) expertise. Samples were selected from invertebrate and fish data sets to span as many of the
BCG tiers as possible. The invertebrate samples and fish samples used in the tests were collected from six
different regions within the U.S. (Northeast, Mid-Atlantic, Southeast, Northwest, Southwest, Central) and
included only basic descriptors of stream physical characteristics (substrate, velocity, width, depth, etc.),
taxonomic names, densities, and in some cases, metric values. These data represent the basic core
elements common to nearly all biological monitoring programs. Participants were asked to place each
sample into one of the six condition tiers, though they were cautioned not to apply a simple relative
quality ranking since all six tiers did not necessarily occur within the data sets. Biologists relied primarily
on differences in relative abundances and sensitivities of taxa (i.e., Attributes I-VI) to make tier
assignments because information needed to evaluate the status of the other Attributes was not available.
Percent concurrence among the individuals was calculated to assess the level of agreement among
biologists when applying the BCG to raw data. Perfect concurrence was set to equal the product of the
number of raters by the number of streams. Case Examples 3-2, 3-3, and 3-7, at the end of Chapter 3,
outline how Maine and New Jersey biologists described tiers and assigned sites.
In the first stage of the data exercise, between-biologist differences were evaluated by asking workgroup
participants to rate a single data set of 6-8 samples. The breakout groups were then asked to classify
samples from larger and more variable datasets. The groups were also instructed to summarize their
interpretations and to identify biological responses to changes in conditions not captured by the BCG.
Finally, the groups identified which tiers corresponded to how they currently assess biological integrity
and the CWA interim goal for protection and propagation of aquatic life.
Workgroup members placed 82% of the benthic macroinvertebrate samples and 74% of the fish samples
into the same BCG tiers. The range of variation among individuals was within one tier's distance in
either direction. Tiers were revised following full workgroup discussion so that transitions were more
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distinct. Each of the breakout groups independently reported that the ecological characteristics
approximately described by Tiers 4 and above were compatible with how they currently assess the
CWA's interim goal for protection and propagation of aquatic life. These groups also identified the
characteristics described by Tiers 1 and 2 as indicative of biological integrity.
Workgroup members reported that key concepts were important with respect to classifying samples into
tiers and identifying the boundaries in between. For Tiers I and 2, biologists identified the maintenance
of native species populations as essential to their understanding of biological integrity. Although many
participants noted that criteria for distinguishing differences between tiers in Attribute VIII (ecosystem
function) were poorly defined, most nevertheless identified ecosystem function changes (as indicated by
marked changes in food-web structure and guilds) as critical in distinguishing between Tiers 4 and 5.
Discussion following the BCG exercise revealed that participants readily agreed on some of the condition
attributes, but not others. For example, participants indicated they mostly used Attributes I-V (taxonomic
composition and tolerance), Attribute VI (non-native taxa, for Tiers 2-6 only) and Attribute VII (organism
condition) to evaluate biological conditions. In contrast, because Attributes VIII - X (ecosystem function
and scale-dependent features) are rarely directly assessed by biologists, the evaluation of these attributes
was accompanied by relatively high uncertainty. Even so, workgroup members strongly advocated
retaining these attributes in the BCG because of the importance of this information in making restoration
decisions.
The presence of non-native taxa in Tier 1 was also the subject of considerable discussion. Knowledge of
the extensive occurrence of some non-native taxa in otherwise near-pristine systems conflicted with the >
desire by many to maintain a conceptually pure and natural tier. Further discussion resulted in agreement
that the presence of non-native taxa in Tier 1 is permissible only if they cause no displacement of native
taxa, although the practical uncertainties of this provision were acknowledged. The resulting tier
descriptions, which allow for non-native species in the highest tiers as long as there is no detrimental
effect on the native populations, has practical management implications. For example, introduced
European brown trout (Salmo trutta) have replaced native brook trout (Salvelinusfontinalis) in many
eastern U.S. streams. In some catchments, brook trout only persist in stream reaches above waterfalls that
are barriers to brown trout. The downstream reaches are nearly pristine except for the presence of brown
trout (D. Lenat, North Carolina Department of Natural Resources, personal communication). In these
places, if society decided to remove the introduced brown trout and if stream habitat is preserved
throughout the catchment, brook trout can potentially repopulate downstream reaches. In the use
designation process, recognizing that the entire catchment has the potential to attain Tier 1 conditions will
inform the public that a very high quality resource exists.
Critical gaps in knowledge were uhcovered'during the development of the BCG. For example, the
workgroup identified the need for regional evaluations of species tolerance to stressors associated with
pressure. Tolerance information presented in the current version of the BCG tends to be based on
generalized taxa responses to a non-specific stressor gradient. At this time, tolerance information is not
available for most taxa and for many common stressors (temperature, nutrients, sediments). In some
cases, tolerance values are based on data collected in other geographic regions or for other purposes (e.g.,
van Dam's European diatom tolerances are used for North American taxa) (van Dam et al. 1994).
Improved tolerance value information is needed to refine the BCG and improve its precision.
Additionally, taxa that are considered tolerant to stressors in one region of the country may not be
similarly classified in another region. For example, long-lived taxa have generally been characterized as
sensitive to increasing pressure and tend to be replaced by short-lived taxa in stressed systems. As such,
the presence of long-lived taxa in a waterbody has been used to indicate high quality conditions, whereas
the predominance of short-lived taxa indicates degradation. However, in small streams in the arid
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western U.S., extreme changes in hydrology'define the natural regime for some systems and an opposite
trend has been observed: short-lived taxa can dominate the biological community in natural settings. In
these systems, a shift to long-lived taxa may be an indicator of altered, less variable flow regimes.
2.3 The relationship between the BCG and designated uses
The BCG is a model that provides a rational and consistent way to identify and communicate waterbody
condition. It can thus be used to establish appropriate ALUs in State water quality standards and to assess
attainment. The ecological condition to support an ALU for a specific waterbody can be described in
terms of the BCG tiers and can be related to specific use categories such as fishery-based uses. For
example, the ecological condition needed to support salmon spawning is an exceptional, high-quality
natural stream and will likely be either a Tier 1 or 2 on the BCG. The ecological attributes that
characterize the BCG tiers can be measured with methods used by each State, and these condition
assessments can be directly linked to a State's ALUs.
Maine and Ohio are examples of States that have adopted uses based on a biological condition gradient
into water quality standards (Courtemanch et al. 1989, Yoder and Rankin 1995a). Both of these States
have incorporated multiple tiers of resource quality in their water quality standards (State of Maine 1985,
2003; Davies et al. 1995; State of Ohio 2003). As discussed above, the tiers in these States' TALUs
describe aquatic-life management goals and attainment criteria for different waterbody types. For
example, in Maine a waterbody is assigned to one of four management tiers by considering both its
existing biological condition and its highest attainable condition as determined by a public and legislative
process. These four tiers of biological quality in Maine's water quality standards are based on Odum's
subsidy stress gradient (Odum et al. 1979, Odum 1985) (See Appendix A, Figure A-2a and Table A-]).
Attainment of standards is assessed by determining to which tier a sample of macroinvertebrates is most
similar (Courtemanch et al. 1989). Site-specific taxonomic composition data and other metrics are used
in a discriminant model to identify the class of a particular waterbody (See Case Examples 3-3 and 3-6 in
Chapter 3). Maine has found multiple tiers to be useful in 5 ways:
1) identifying and preserving the highest quality resources,
2) depicting existing conditions more accurately,
" 3) setting realistic and attainable management goals,
4) preserving incremental improvements, and
5) determining appropriate management action when conditions decline.
Over the past thirty years, States have independently developed technical approaches to assess condition
and set ALUs specific to the biology of the State and its regulatory and political settings (U.S. EPA
2002a). Although these different approaches have fostered innovative technical approaches, they have
also complicated the development of a nationally consistent approach to interpreting the condition of
aquatic resources. Assessment results are often difficult to compare when quantitative outcomes (i.e.,
index or indicator values) represent different qualitative conditions. Additionally, without a common
interpretative framework, use of different methods can hinder collaboration among natural resource
agencies that have complementary missions. A consistent approach to interpreting biological condition
will allow scientists and the public to more effectively evaluate the current and potential conditions of
specific waters and watersheds and use that information to set appropriate ALUs.
The BCG can help promote consistent interpretation of scientific data by applying a common framework
to diverse conditions and different assessment methods at national, regional, state, or watershed levels.
By providing a means for managers and the public to identify outstanding resources, recognize
incremental improvements, more appropriately allocate resources and prioritize management actions,
aquatic and natural resource agencies will be able to coordinate and target resources more effectively.
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2.4 Key points from Chapter 2
1. The biological condition gradient is a descriptive model predicting biological response to
increasing levels of stressors. The biological gradient can be thought of a field-based dose-
response curve where dose (x-axis) is level of stressors and response (y-axis) is biological
condition.
2. The purpose of the Biological Condition Gradient is to provide an ecologically-based model •
about biological condition and to promote clearer understanding of current conditions
relative to natural conditions. This should result in more meaningful engagement of the public
in the designation of aquatic life uses in State and Tribal water quality standards programs.
3. The model must be validated with data. The BCG model does not reduce the necessity of
developing robust methods for the quantitative and statistical validation of biological conditions.
The list of attributes is intended to organize how we interpret biological information concerning a
given aquatic community response to increasing levels of stressors. The approach should be
thought of as seeking to identify a "best fit" tier, which consists of weighing the importance and
signal-strength of the different attributes as they pertain to a specific waterbody or as used to
describe a designated use class.
4. The conceptual framework is not defined by any one method. As presented in Chapter 3, the
attributes have a quantifiable aspect that can potentially be assessed and validated in many
different ways. The BCG has been designed to be independent of different assessment
methodologies (i.e. Rapid Biological Assessment, Index of Biological Integrity; RIVPACS,
multivariate analyses, etc.). The intent is for the ecological premises that support the model to
reflect the same basis that underlies all successful methods used to quantify biological response to
increasing levels of stressors.
5. The number of useful tiers is flexible. The purpose of the number of tiers is to provide a highly
resolved biological condition gradient. There is no expectation that State or Tribal programs
adopt six tiers, or categories, of designated uses. While step-wise progress toward refinement of
designated aquatic life uses in State and Tribal water quality standards programs is desired over
the long term, the ultimate number and type of tiers of uses is a State or Tribal determination.
6. The BCG was designed to facilitate communication of the current biological condition of a
waterbody compared to natural conditions. For example, the BCG is grounded in natural
conditions, which can help users and the public understand that current conditions do not
necessarily represent natural conditions. In areas where natural or near-natural conditions exist,
people are generally familiar with what is natural and what is altered. But in extensively altered
regions practitioners and the public alike tend to accept the "best of what is left" as the potential
for a system. In such places, it is difficult to visualize the natural conditions that were once
present and designated uses may end up based on a diminished perspective. Natural conditions
may not be achievable in many places, but an improved understanding of the changes that have
occurred will result in a more scientifically defensible evaluation of current conditions and what
can potentially be restored.
The next chapter provides information on how to adapt the national BCG model to reflect the specific
ecology and stressor gradient characteristics of a particular state or region, and introduces some ways to
quantify a biological condition gradient with monitoring data.
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TABLE 2-3. Biological Condition Gradient: Maine example scenario for a cold-water stream catchment1
Resource
Condition "Tiers"
Biological Condition Characteristics (Effects)
I Historically documented, sensitive, long-lived, or regionally endemic taxa
' •* Long-lived native species of fish-host specialist or long-term brooder mussels such as Brook floater-
Alasmodonta varicosa; Triangle floater- Alasmodonta undulate; Yellow lampmussei- Lampsilis cariosa
' are present in naturally occurring densities
•* Fishes: Brook stickleback, Swamp darter
Natural or native
condition
Native structural,
functional and
taxonomic integrity is
preserved;
ecosystem function is
preserved within the
range of natural
variability
II Sensitive-rare taxa
•» The proportion of total richness represented by rare, specialist and vulnerable taxa is high, for
example, without limitation, the following taxa are representative: Plecoptera: Capniidae,
Taeniopteryx, Isoperla, Perfesfa, Pteronarcys, Leuctra; Ephemeroptera: Cinygmula, Rhithrogena,
Epeorus, Serratella, Leucrocuta; Trichoptera: Glossosoma; Psilotreta; Brachycentnjs; Diptera:
Stempetlina, Hexatoma, Probezzia; Coleoptera: Promoresia; Fishes: Slimy sculpin, Longnose sucker;
Longnose dace
HI Sensitive-ubiquitous taxa
•* Densities of Sensitive-ubiquitous taxa are as naturally occur. The following taxa are representative of
this group for Maine: Plecoptera: Acroneuria; Ephemeroptera: Stenonema, Baetis, Ephemerelta,
Pseudocloeon; Fishes: Brook trout, Burbot, Lake chub
IV Taxa of intermediate tolerance
•* Densities of intermediate tolerance taxa are as naturally occur. The following taxa are representative
of this category: Trichoptera: Hydropsychidae, Chimarra, Neuredipsis, Polycentropus; Diptera:
Tvetenia, Micmtendipes, Rheocricotopus, Simulium; Fishes: Common shiner, Fallfish
V Tolerant taxa
•* Occurrence and densities of Tolerant taxa are as naturally occur. The following taxa are
representative of this category: Diptera: Dicrotendipes, Tribelos, Chironomus, Parachironomus; Non-
Insects: Caecidotea, Isopoda, Physa, Helobdetla; Rshes: White sucker, Blacknose dace, Creek chub
VI Non native or Intentionally Introduced taxa
•* Non native taxa such as Brown trout, Rainbow trout, Yellow perch, are absent or, if they occur, their
presence does not displace native biota or after native structure and function
VII Physiological condition of long-lived organisms
-» Anomalies are absent or rare; any that occur are consistent with naturally occurring incidence and
characteristics
VIII Ecosystem Function
•* Rates and characteristics of life history (e.g., reproduction, immigration, mortality, etc.), and materials
exchange processes (e.g., production, respiration, nutrient exchange, decomposition, etc.) are
comparable to that of "natural" systems
-» The system is predominantly heterotrophic, sustained by leaf litter inputs from intact riparian areas,
with low algal biomass; P/R<1 (Photosynthesis: Respiration ratio)
IX Spatial and temporal extent of detrimental effects
•» Not applicable- disturbance is limited to natural events such as storms, droughts, fire, earth-Hows. A
natural flow regime is maintained.
X Ecosystem connectance
•* Reach is highly connected with groundwater, its floodplain, and riparian zone, and other reaches in the
basin, at least annually. Allows for access to habitats and maintenance of seasonal cycles that are
necessary for life history requirements, colonization sources and refugia for extreme events.
' This scenario presents Maine biologists' summary of the ecological characteristics of the six tiers in the Biological
Condition Gradient model as observed in Maine (see Appendix A, Sections II arid III). It is based on analysis of
genus/species level benthic macroinvertebrate data (400 samples from rivers and streams spanning conditions from
near-natural to severely altered) (Davies et al. 1999).
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I Historically documented, sensitive, long-lived, regionally endemic taxa
•» Some regionally endemic, long-lived species (e.g., some mussel species such as the Dwarf
wedgernussel- Alasmidonta heterodon, and/or fish species, such as the Brook stickleback are absent
due extirpation from Maine prior to the enactment of the CWA; some mussel species of Special
Concern in Maine are present (e.g., Brook floater- Atasmodonta varicosa; Triangle floater-
Alasmodonta undulata; Yellow lampmussel- Lampsil/s cariosa)
II Sensitive-rare laxa
•* Richness of rare and/or specialist invertebrate taxa is high though densities may be low (e.g., for
Maine- Plecoptera: Capniidae, Taeniopteryx, Isoperia, Agnetina, Perlesta, Pteronarcys, Leuctra',
Ephemeroptera: Cinygmula, Rhithrogena, Epeorus, Serrate/la, Leucrocuta; Trichoptera:
Gtossosoma, Psilotreta, Brachycentrus; Diptera: Stempel/ina, Rheopelopia, Hexatoma, Probezzia;
Coleoptera: Promoresia). Densities of scrapers such as Glossosoma are increased •
•* Fish assemblage is predominantly native including such sensitive fish as Slimy sculpin, Longnose
sucker, Longnose dace.
Ill Sensitive- ubiquitous taxa
•* Superficial scraper-grazers and collector-gathers are favored due to slightly increased periphyton
biomass on hard substrates, which results in higher relative abundance of these groups (e.g.,
Ephemeroptera: Stenonema, Stenacron, Baetis, Ephemerella, Pseudocloeon). Predatory stoneflies
are common (e.g., Acroneuria, Agnetina). Populations of such native fish taxa as Brook trout, Lake
chub, Burbot are common.
IV Taxa of Intermediate tolerance
-» Increased biomass of diatom species that respond positively to increased nutrients and temperatures,
but sensitive diatom species are maintained. Diatom richness is increased; filamentous forms are rare
or as naturally occur
•* May be slight increases in densities of macroinvertebrate taxa such as Trichoptera: Hydropsychidae,
Philopotamidae, Neuredipsis; Diptera: Ftheotanytarsus, Microtendipes, Rheocricotopus, Simulium
•* Common shiner and Falllish are in good condition
V Tolerant taxa
•» May be slight increases in occurrence of tolerant taxa such as Diptera: Potypedilum, Tvetenia, Non-
Insects: Isopoda, Physa', Fishes: White sucker; Creek chub, Blacknose dace
VI Non-native or Intentionally introduced taxa
-> Any intentionally introduced fish species (e.g., Brown trout- Salmo trutta, Rainbow trout-
Oncorhynchus mykiss) occupy non-detrimental niche space
VII Physiological condition of long-lived organisms
•* Any anomalies on fish are consistent with naturally occurring incidences and characteristics such as
rare occurrence of gill or anchor parasites, blackspot, etc.
•* Spawning areas of native fishes are evident during spawning season
Minimal changes In
structure of the
blotic community
and minimal
changes In
ecosystem function
Virtually ail native
taxa are maintained
with some changes in
biomass and/or
abundance;
ecosystem functions
are fully maintained
within the range of
natural variability
VIII ecosystem Function
•» Rates and characteristics of life history (e.g., reproduction; immigration; mortality etc.), and materials
exchange processes (e.g., production; respiration; nutrient exchange; decomposition etc.) are
unimpaired and not significantly different from the range of natural variability.
* The system is predominantly heterotrophic, sustained by leaf titter inputs from intact riparian areas;
P/R/ is<1
IX Spatial and temporal extent of detrimental effects
•* Extent is limited to small pockets or brief periods
X Ecosystem connectance
-» Unimpaired access to habitats and maintenance of seasonal cycles that are necessary to fulfill life
history requirements, and to provide colonization sources and refugia for extreme events.
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Evident changes In
structure of the
biotlc community
and minimal
changes in
ecosystem function
Some changes in
structure due to loss
of some rare native
taxa; shifts in relative
abundance of taxa
but sensitive-
ubiauitous taxa are
common and
abundant; ecosystem
functions are fully
maintained through
redundant attributes
of the system
\ Historically documented, sensitive, long-lived, or regionally endemic taxa
•* Brook floater- Atasmodonta varicosa; Triangle floater- Alasmodonta undulata; Yellow lampmussel-
1 Lampsi/is cariosa; are uncommon; Dwarf wedgemussel- Alasmidonta heterodon (and/ or a fish
species) absent due to extirpation from Maine prior to CWA -
1II Sensitive- rare taxa
•» Some replacement of taxa having narrow or specialized environmental requirements, with functionally
equivalent sensitive-ubiquitoustaxa; coldwater obligate taxa are disadvantaged. Taxa such as
Plecoptera: Capniidae, Taeniopteryx, Isoperla, Pertesta, Pteronarcys, Leuctra, Agnetina;
Ephemeroptera: Cinygmula, Rhithrogena, Epeorus, Serratella, Leucrocuta; Trichoptera:
Glossosoma, Psilotreta, Brachycentrus', Diptera: Stempellina, Rheopelopia; Hexatoma, Probezzia;
Coleoptera: Promoresia; Fishes: Brook stickleback, Longnose sucker, Longnose dace are
uncommonly encountered or absent
III Sensitive- ubiquitous or generalist taxa
•* Sensitive- ubiquitous or generalist taxa are common and abundant; taxa with broader temperature-
tolerance range are favored (e.g., Plecoptera: Acroneuria; Ephemeroptera: Stenonema, Baetis,
Ephemerella, Pseudodoeon)
•* Overall mayfly taxonomic richness is reduced relative to the Tier 2 condition, with the preponderance
of richness represented by sensitive- ubiquitous taxa; densities of remaining taxa are high and are
• sufficient to indicate healthy, reproducing populations
•* Native Brook trout are significantly reduced due to the introduction of non-native Brown trout and the
increased temperature regime
IV Opportunist or facultative taxa of intermediate tolerance
•» Filter-feeding blackflies (Simulium) and net-spinning caddisllies (e.g., Hydropsyche, Cheumatopsyche,
Polycentropus, Neureclipsis) show increased densities in response to nutrient enrichment, but relative
abundance of all expected major groups is well-distributed
-> Increased temperature and increased available nutrients result in increased algal productivity causing
an increase in the thickness of the diatom mat. This results in a "slimy" covering on hard substrates.
•* Fish assemblage exhibits increased occurrence of Common shiner and Fallfish
V Tolerant taxa
•» Richness of Diptera: Chironomidae is increased; relative abundance of Diptera and Non-insects is
somewhat increased but overall relative abundance is well-distributed among taxa from Groups ill, IV
and V, with the majority of taxa represented from Groups III and IV. Blacknose dace and white sucker
are more common.
VI Non-native or Intentionally introduced taxa
•» Brown trout have largely replaced native brook trout
Vll Physiological condition of long-lived organisms
•» Incidence of anomalies such as gill parasites, anchor parasites, blackspot, etc., is low; serious
anomalies such as tumors or deformities are essentially absent
-> Environmental quality is sufficient to fully support reproduction of most long-lived species
VIII Ecosystem Function
•» Increased temperature and algal metabolism causes small diurnal sags in dissolved oxygen,
compensated by adequate aeration from turbulence over riffle areas
•* Algal biomass somewhat exceeds what can be utilized by resident grazers, resulting in evidence of
die-back and slight downstream export of sloughed material.
-» Patchy loss of high food quality riparian vegetation (e.g., oak; maple, beech) and elevated
temperature, results in decreased growth and survival of some specialized shredder taxa
(Pteronarcidae; Taeniopterygidae) with replacement by shredders capable of utilizing lower quality
organic matter (Lepidostomatidae; Limnephilidae; Tipulidae).
IX Spatial and temporal extent of detrimental effects
•* Filamentous green algae occur in small patches within reaches; low dissolved oxygen levels occur
only during the high temperature and low flow summer periods.
•» Interstitial spaces, within the substrate of pools, are filled with fine sediment resulting in localized
losses of interstitial habitats but riffle areas continue to provide adequate water flow and oxygen
through interstitial habitats.
X Ecosystem connectance
•» Some downcutting has resulted in a patchy decrease in connectanceof the stream from its floodplain
except at unusually high flows.
•* Thinning and patchy loss of riparian vegetation has altered the microclimate of the surrounding
landscape causing a decrease in survival and reproductive success of adult mayflies and stoneflies.
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Moderate changes
in structure of the
blotlc community
and minimal
changes in
ecosystem function
Moderate changes in
structure due to
replacement of some
Sensitive-ubiquitous
taxa by more tolerant
taxa, but reproducing
populations of some
Sensitive taxa are
maintained; overall
balanced distribution
of all expected major
groups; ecosystem
functions largely
maintained through
redundant attributes
I Historically documented, sensitive, long-lived, regionally endem/ctaxa
. * Healthy, reproducing populations of generalist mussel species are present (such as Eastern elliptic-
Eliptio complanata; or Eastern lampmussel- Lampsilis radiate radiata or Eastern floater- Pyganodon
cataracta) but Brook floater- Alasmodonta varicosa; Triangle floater- Atasmodonta undulata; Yellow
lampmussel - Lampsilis cariosa are absent.
II Sensitive- rare, specialist, vulnerable taxa with narrow environmental requirements
•» Richness of specialist and vulnerable taxa is notably reduced; if present, densities are low (e.g.,.
Plecoptera: Capniidae, Taeniopteryx, Isoperla, Perlesta, Pteronarcys, Leuctra, Agnetina;
Ephemeroptera: Cinygmula, Rhithrogena, Epeorus, Serratella, Leucrocuta; Trichoptera:
Glossosoma; Psilotreta; Brachycentrus; Diptera: Stempellina, Rheopelopia; Hexatoma, Probezzia;
Coleoptera: Promoresia, Fishes.1 Occurrence of Slimy sculpin, Longnose sucker and Longnosedace
is reduced •
111 Sensitive- ubiquitous or generalist taxa
•* Densities of sensitive- ubiquitous scraper and gatherer insects (e.g., Stenonema, Heptagenia, Baetis,
Ephemerella, Pseudodoeon) are sufficient to indicate that reproducing populations are present but •
relative abundance is reduced due to increased densities of opportunist invertebrate taxa (Group IV);
•> Predatory stoneflies are reduced (e.g., Acroneuria)
IV Opportunist or facultative taxa of Intermediate tolerance
•* Many substrate surfaces are covered by bryophytes and macro-algae responding to increased
nutrients, resulting in displacement of lithophytic (stone-dwelling) micro-algae in favor of epiphytic
(plant-dwelling) and filamentous forms (e.g., Cladophora).
•» Increased loads of suspended particles favor collector-filterer invertebrates resulting in notably
increased densities and relative abundance of fitter-feeding caddisflies and chironomids (e.g.,
Trichoptera: Hydropsychidae, Chimarra, Neureclipsis, Potycentropus; Diptera. Tvetenia,
Microtendipes, Rheocricotopus, Simulium; Fishes: Common shiner and Fallfish are common and
abundant
V Tolerant taxa
* There is an increase in the relative abundance of tolerant generalists (for example, Polypeditum,
Eukeifferiella, Cricoptopus) and/or in numbers of non-insect scrapers and gatherers (e.g., Physa,-
Sphaerium, Asellus, Hyalella) but they do not exhibit significant dominance
•» Overall relative abundance is well distributed among taxa from Groups III, IV and V, with trie majority
of the total abundance represented from Group IV.
•* Native fish such as White sucker, Blacknose dace, Creek chub are common.
VI Non-native or Intentionally introduced taxa
•* Brook trout are absent or transient but such taxa as Smallmouth bass, Golden shiner and
Yellow perch are common.
VII Physiological condition of long-lived organisms
•» Incidence of anomalies such as blackspot and gill and anchor parasites is slightly higher than
expected
•» Occurrence of tumors, lesions and deformities is rare
VIII Ecosystem Function
•» Increased available nutrients increase algal productivity causing increased diatom, macro-algae and
macrophyte biomass, and consequently lowering evening dissolved oxygen levels and increasing
daytime oxygen levels. Invertebrate biomass is nigh but production has shifted to result in greater
biomass of intermediate tolerance organisms than sensitive organisms. For example, filter-feeders
utilizing suspended material shift from mayflies and sensitive mussels and caddisflies (e.g., Isonychia,
Elliptic, Brachycentrus) to facultative types (e.g., Hydropsychidae, Rheotanytarsus, Spnaeriidae,
Musculium, Pisidium); grazers of diatoms shift from sensitive mayflies and caddisflies (e.g.,
Heptagenia, Leucrocuta, Glossosomatidae) to facultative scrapers and collector gatherer organisms
(e.g., Baetis, Callibaetis, Physidae, Leptoceridae). The suspended organic matter load somewhat
exceeds what can be utilized by resident filterers resulting in increased levels of exported material.
Sloughing of excess macro-algae and macrophyte biomass results in increased downstream export of
course participate organic matter.
•* The system is becoming more autotrophic due to algal photosynthesis. The P/R ratio shows a slight
increase.
IX Spatial and temporal extent of detrimental effects
•» Increased macrophyte and algal biomass extends downstream beyond the confluence with the next
tributary; filamentous algae first appears in the stream as temperatures warm in late spring; pools and
deposition^ areas are silt-filled; the interstitial spaces in the substrate of runs is becoming obstructed
by sand and silt
-» Early morning low dissolved oxygen levels occur occasionally during late spring and fall as well as
during the mid summer
X Ecosystem connectance
•» Riling of interstitial spaces obstructs access to hyporheic zone for early instar stonefly nymphs,
eliminating nursery areas and refugia for storm-events and low flows. Adult stoneflies from upstream
reaches continue to oviposit but reproductive success is limited; stonefly nymphs continue to colonize
by drift, with limited success.
* Poorly managed culverts on some tributaries impede fish passage and access to some spawning
areas.
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I Historically documented, sensitive, long-lived, or regionally endemic taxa
• •* Mussel fauna, including commonly occurring, generalist taxa (e.g., Eastern lampmussel- Lampsilis
radiata radiata; Eastern floater- Pyganodon cataracta; Eastern elliptio- Elliptio complanata) is markedly
• diminished due to poor water quality
Major changes in
structure of the
biotic community
and moderate
changes in
ecosystem function
Sens/ft've taxa are
markedly diminished;
conspicuously
unbalanced
distribution of major
groups from that
expected; organism
condition shows
signs of physiological
stress; system
function shows
reduced complexity
and redundancy;
increased build-up or
export of unused
materials
II Sensitive-rare taxa
•* Only the rare occurrence of individual representatives of specialist and vulnerable taxa with no
evidence of successful reproduction
III Sensitive-ubiquitous taxa . .
•* Either absent or present in very low numbers, indicating impaired recruitment and/or reproduction
IV Opportunist or facultative taxa of Intermediate tolerance
•» Filter-feeding invertebrates such as Hydropsychid caddisflies (e.g., Cheumatopsyche) and filter-
feeding midges (e.g., Rheotanytarsus, Microtendipes) occur in very high numbers
V Tolerant taxa
•* Frequent occurrence of tolerant collector-gatherers (e.g., Orthocladiini, Micropsectra,
Pseudochironomus, Dicrotendipes, Isopoda- Caeddotea; Amphipoda- Hyalella, Gammarus);
-» Relative abundance of non-insects often equal to or higher than relative abundance of insects
•» Deposit-feeders such as Oligochaeta are increased
•» Numbers of tolerant predators are increased (Hirudinea, Thienemannimyia, Cryptochironomis}
•* Native fish species are essentially absent with the exception of tolerant taxa like White sucker,
Blacknose dace and Creek chub
VI Non-native or Intentionally Introduced taxa
•* Golden shiner, Smallmouth bass, and Yellow perch are common
VII Physiological condition of long-lived organisms
•» Biomass of young of year age classes is low; overall fish biomass is reduced;
-» Sex ratio of remaining fish does not equal 1
•» Occurrence of parasitic infestations and disease is common
•* Incidence of serious anomalies such as tumors and anatomical deformities is higher than expected
VIII Ecosystem Function
•* High algal photosynthetic activity results in daytime dissolved oxygen supersaturation accompanied by
nighttime dissolved oxygen levels less than 4 ppm. Extremely high algal biomass significantly alters
the habitat structure of the substrate;
•» The P/R ratio is significantly > 1; the system is predominantly autotrophic
•* Loss of coarse participate shredders and alteration of bacterial decomposer community contributes to
build-up and/or export of unused organic matter;
•* Mechanisms for nutrient spiraling are significantly simplified and less efficient resulting in increased
export of nutrients from the system
IX Spatial and temporal extent of detrimental effects
•* Substrate has become armored by increased sediment loading, altered flow regime and altered
channel morphology resulting in compaction of interstitial space habitat, leaving only patches of well-
scoured gravel substrate in high-gradient riffle areas;
•» Armoring is resistant to spring scouring events, preventing annual spring sediment flushing and re-
sorting of substrate;
•* Near complete canopy removal results in all day insolation of stream and surrounding land surface
causing abnormally elevated temperature regime in early spring and late fall. This causes unnaturally
elevated seasonal temperature cues and results in failures of life history requirements.
X Ecosystem connectance
•* Lateral connectance to floodplain areas is eliminated except at peak flows, due to altered channel
morphology caused by human intervention (bank riprapping, dikes) and altered flow regime.
•» All appropriate high quality spawning gravel in upstream areas is destroyed by silt deposition,
preventing spawning of white suckers, leaving only mature adults. Culverting is common, contributing
to impairment of fish passage
•* Lack of riparian vegetation eliminates habitat for adult flying aquatic insects, reducing survival and
reproduction of resident organisms and reducing successful recruitment of immigrating organisms (i.e.,
flight dispersal of ovipositing females).
DRAFT: Use of Biological Information to Better Define Designated Aquatic Life Uses in State
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36
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I Historically documented, sensitive, long-lived, regionally endemic taxa
• •» Poor water quality, compaction of substrate, elevated temperature regime and absence of fish hosts
for reproductive functions preclude the survival of any mussel fauna
II Sensitive-rare taxa
Severe changes In •» These taxa are absent due to poor water quality, elevated temperature regime, alteration of habitat,
structure of the loss of riparian zone, etc.
biotic community
and major loss of '" Sensitive- ubiquitous taxa
ecosvstem function "* Absent due to above listed factors, though an occasional transient individual, usually in poor condition,
1 may be collected.
Extreme changes in ,v Taxa of Intermediate tolerance
structure; wholesale -» Filter-feeding insects and other macroinvertebrate representatives of this group are severely reduced
changes in taxonomic in density and richness, or are absent.
composition; extreme
alterations from V Tolerant taxa
normal densities and "* Low dissolved oxygen conditions preclude survival of most insect taxa except those with special
distributions' adaptations to deficient oxygen conditions (e.g., Chironomus)
' .... „ ,„ * The macroinvertebrate assemblage is dominated by tolerant non-insects (Planariidae, Oligochaeta,
organ>sm condition,s Hirudinea, Sphaeriidae, etc.)
often poor;
ecosystem functions vi Non-native or Intentionally Introduced taxa
are severely altered •» Native species are essentially absent
•* Only very tolerant invasive alien fish taxa are collected (Golden shiner, Yellow perch);
•* Number of individuals collected is abnormally low
Vll Physiological condition of long-lived organisms
•* Fish biomass is very low; individuals that are collected appear to be transients and are in poor
condition
•» Incidence of parasitic infestations and disease is high; anatomical deformities and/or tumors are
common
•* Minimal evidence of recruitment or reproduction except some extremely tolerant groups may have
high production; young of year age classes are absent
VIII Ecosystem Function
•* Water quality has degraded to such an extent that algal photosynthesis is negligible
•* Decomposition of organic matter creates P/R markedly <1; the system is predominantly heterotrophic
as a result of high bacterial respiration and minimal photosynthesis
•» Reproductive success is very low
•* Recruitment of emigrating organisms into upstream and downstream habitats is impaired due to low
fecundity and high mortality rates of resident biota.
IX Spatial and temporal extent of detrimental effects
•* The reach and all tributaries are affected by widespread alteration of within stream conditions as a
result of severely altered land-use and poor water quality.
X Ecosystem connectance
•* l/Vate/s/red-wide land use changes and alteration of stream morphology has affected all tributaries
eliminating sources of recruitment and destroying spawning habitat;
-* Physical and chemical requirements to fulfill life history functions (e.g., seasonal temperature cues for
mating behavior and egg development; intact nursery habitats; optimal levels of dissolved gases, etc.)
are severely disrupted resulting in very low reproductive success and high mortality rates.
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DRAFT: Use of Biological Information to Better Define Designated Aquatic Life Uses in State
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CHAPTER 3. How Do You DEVELOP AND CALIBRATE A BIOLOGICAL
CONDITION GRADIENT?
Figure 3-1 shows the overall approach for calibrating the Biological Condition Gradient, BCG, for a
specific region. This chapter discusses the technical elements and steps for calibrating a regional BCG.
The calibration process includes:
• Identification of defensible biological goals (also see Chapters 1 and 5)
• Development of the conceptual foundation of the regional BCG (Section 3.1)
• Assessment and modification, if necessary, of the State's biological monitoring program to
support quantitative calibration of a regional BCG (Section 3.2)
• Calibration of a regional quantitative BCG model for operational assessment (Section 3.3)
>
a!
•I?
£
Establish Conceptual Foundation of
Regional BCGModd
(Section 3.1)
Describe native aquatic assemblages
Identify regiond stressois
Describe expected biological response to
stresses (the BCG)
Assess Monitoring Program
(Section 3.2)
' Biologic^ assemblages
• Methodology
• Geographic coverage
• Database
Information
sufficient to
support BC
Modify Monitoring Program
Quantify and Calibrate
the Regional BCG
.(Section 3 J)
• Assemble information
Describe quantifiable attributes
Describe BCGtieis; assign sites
Devdop or apply quantitative
assessment method (index or model)
Adopt TALUs into Water
Quality Standards
(Chapters 5 & 6)
FIGURE 3-1. Technical components of the Biological Condition Gradient.
DRAFT: Use of Biological Information to Better Define Designated Aquatic Life Uses in State
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A State's water management program can support development of tiered aquatic life uses if it is flexible
with respect to improvements in scientific knowledge and acknowledges that scientific advances may
support adjustment of biological goals. State and Tribal designated uses form the aquatic life goals and
water quality criteria (biological, chemical and physical) to protect the uses provide the basis for
measuring attainment of the goals.
3.1 Conceptual foundation of a regional BCG model
The first technical component of calibrating a regional BCG is to adapt the national BCG model to
regional conditions. Model development includes three components that, together, provide a complete
ecological description of biological response to stressors that is consistent with ecological theory and
empirical observation:
• Describe the native aquatic assemblages under natural, undisturbed conditions
• Identify the predominate regional stressors
• Describe the BCG, including the theoretical and empirically observed foundation of assemblage
response to stressors
Similar to the national BCG model development process, regional BCG calibration can take place through
technical panels and workshops that bring together aquatic biologists and ecologists knowledgeable about
the waterbodies and assemblages in their regions. The technical experts describe native aquatic
assemblages, regional stressors, and patterns of biological alteration based on both empirical observations
and theoretical foundation to develop a regional biological condition gradient. The technical experts can
include scientists from State and federal water quality agencies and natural resource departments,
interstate river commissions, universities, and the private sector.
Expert participants in the regional model and calibration exercise should be knowledgeable about the
assemblages sampled in the applicable monitoring programs (invertebrate biologists, ichthyologists,
algologists, endangered species experts, etc.). The group should also include scientists involved in
monitoring programs who are familiar with the sites and the organisms, plus other State, federal,
university, and private sector biologists with relevant expertise. In some cases, BCGs have been initially
drafted by a single experienced and knowledgeable individual, followed by a consensus process to
confirm and modify the model.
3.1.1 Describe native aquatic assemblages
The BCG is grounded in natural biological assemblages that are present in ecosystems with no or minimal
disturbance. Developing the BCG entails specific descriptions of the natural aquatic assemblages. The
description of natural conditions requires biological knowledge of the region, classification of the natural
assemblages, and, if available, historical descriptions of the habitats and assemblages.
Existing information - Information on biota in undisturbed or minimally disturbed habitats is required to
develop a regional BCG model. If the State has an extensive monitoring program with undisturbed
reference sites, its existing monitoring data will play an important role in developing the descriptions of
reference biota. In addition to monitoring data, participants should also consult general references on
biota of the region, especially references showing the historical and present-day geographic distribution of
flora and fauna. These references often exist for fish and vascular plants, or may be unpublished reports
and lists for threatened invertebrates such as mussels, snails, and dragonflies. However, such references
are often unavailable for benthic macroinvertebrates or algae.
DRAFT: Use of Biological Information to Better Define Designated Aquatic Life Uses in State
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Classification - Developing a description of the BCG requires that biologists take into account the natural
variability in assemblage structure and composition among sites and explain that variability where
possible. This requires a classification system or model to predict the natural variation among sites (e.g.,
Wright et al. 1984, Barbour et al. 1999, Bailey et al. 2004). In this document, the term "classification"
refers to identifying consistent differences between biological assemblages from undisturbed or
minimally disturbed aquatic systems, if information available, and explaining those differences in terms
of natural environmental gradients. Such natural gradients are encompassed within the regional
descriptions of the undisturbed or minimally disturbed condition of the stressor gradient (Chapter 4).
Distributions of the organisms that make up aquatic communities are controlled by the effects of
temperature, water velocity, light, oxygen, water quantity, dissolved substances (e.g., DOC, alkalinity,
pH), food resources, cover, reproductive habitat, variability of physical and chemical factors, competitors,
and predators. These physical and chemical factors vary geographically enabling biologists to
characterize several community types by geographic location, such as cold water/warm water fish
communities and low gradient/high gradient invertebrate communities. Scientists have also recognized
geographic boundaries characterized by geology or vegetation (ecoregions: Omernik 1987; fish
communities: Hughes and Larsen 1988; macroinvertebrate communities: Gerritsen et al. 2000). Some
variables, notably measures of stream size (e.g., order, catchment area, length, total flow), have a more
continuous effect on biological variables (e.g., increase of fish species richness with stream size; Karr et
al. 1986).
Reference condition - Closely connected with classification of undisturbed or minimally disturbed
systems and communities is the definition and measurement of reference condition. Methods for
establishing reference condition need to be consistent for differing waterbody conditions to be compared
(Hughes 1985, 1994; Hughes et al. 1986; Moss et al. 1987; Bailey et al. 2004; Stoddard et al. in press).
Undisturbed or minimally disturbed conditions are comparable to "natural conditions," e.g. BCG tiers 1
and 2. Therefore, defining "natural" reference conditions is the starting point for development of a
regional BCG. Ideally, empirical data assembled from reference sites with no or minimal levels of
stressors characterize Tiers 1 and 2 of the BCG. This is because Tier 1 biological condition is, by
definition, an assemblage structure, function, and taxonomic composition that is "naturally derived" from
a physical environment not effected by stressors (Angerrneier and Karr 1994).
Minimally disturbed sites (as defined by physical, chemical, and landscape measures) can be slightly
altered from undisturbed condition, but should retain most characteristics of the resident biota in
undisturbed sites. In many regions of the country where Tier 1 and Tier 2 sites may no longer exist, the
reference sites used by agencies are considered "least disturbed." These sites have also been termed as the
"best available," or "best existing," in the region but may be substantially altered from pristine, natural
conditions. In extensively altered regions where undisturbed or minimally disturbed sites are absent, the
best means to accurately characterize Tiers 1 or 2 may be through historical records of the taxonomic
distributions of different assemblages and descriptions of the physical setting of undisturbed conditions
(see below).
Historical descriptions - Historical descriptions help reconstruct undisturbed aquatic habitats and may
help identify present-day sites that approximate historical conditions. This information is especially
critical in areas where the best existing sites are significantly altered. Sources of historical information
include early photographs and taxonomic collections, pre-dam and pre-irrigation physical data (USGS
flow data, BLM data), and the descriptions of pioneers, naturalists, and scientists. Recent compilations
and summaries of historical information have been developed where local or conservation interest is
strong (e.g., Kuzelka et al. 1993, Johnson 1994). See Case Example 3-1 on considering historical stream
characteristics to estimate minimally disturbed conditions and support reference stream selections in
Kansas.
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If no undisturbed or minimally disturbed reference sites exist in a region, the stressor gradient provides a
means for determining the best regional candidates to act as benchmarks for comparison, i.e., "least
disturbed" or "best available conditions." Chapter 4 discusses the stressor gradient and a framework to
organize stressor information derived from measures of the physical, chemical, and landscape variables of
a sampled site. Applying monitoring information that is organized into the stressor gradient framework
will help managers evaluate the status of their waters relative to change, or departure, from reference
condition.
3.1.2 Identify regional stressors
A description of regionally dominant stressors will help define expectations for biological responses that
are likely to occur. This step considers sources of physical and chemical stressors and causes of
landscape or habitat disturbance (the stressor gradient; Chapter 4). For example, if an ecoregion is
primarily mountainous, then stressors from extensive row-crop agriculture will be relatively less frequent
than stressors from other sources. Other examples of regionally important stressors include hydrologic
alteration from urbanization; effluent-created permanent streams in the arid west; and acid mine drainage
and.related metals contamination in coal mining regions of the Appalachians and metal mining regions of
the Rocky Mountains.
Identification of stressors and their sources is the first step in characterizing the stressor gradient (Chapter
4). The stressor gradient is the combination of causal factors that induce an adverse response in the
aquatic biota. A conceptual model of fish and macroinvertebrate assemblage response to a regional
stressor gradient ranging from undisturbed or minimally disturbed conditions to severely altered
conditions was developed based on empirical observations of assemblage responses to multiple sources in
Ohio (Figure 3-2). The graphic represents measured assemblage abundance (y-axis) against an
assemblage index (fish IB I, macroinvertebrate ICI; x-axis) with the generalized response of selected
metrics. Biological descriptions correspond to the six tiers of the BCG model and include descriptions of
assemblage characteristics, chemical water quality conditions, physical habitat and flow regime, and
sources of stress that are typically associated with each. This was modified from an original conceptual
model by Ohio EPA (1987) and Yoder and Rankin (1995b). It demonstrates that understanding the
relationship between assemblage responses and stressors is a fundamental aspect of bioassessments.
3.1.3 Describe the Biological Condition Gradient
In testing the national BCG model, regional experts calibrated it to specific regional sites and
assemblages. Biologists familiar with the regions' natural aquatic communities and their responses to
stress worked collaboratively to calibrate the BCG model to conditions in the following regions: Maine,
Kentucky, the Central Great Plains, and selected areas in the arid west (Arizona and eastern Washington).
Table 2-3 shows the resulting model for Maine.
The equivalent step in developing a regional BCG model is to develop a local counterpart to the national
BCG model. The objective is to ground the BCG in local conditions. The regionally calibrated BCG
describes the undisturbed or minimally disturbed aquatic ecosystems of the region, and the responses of
the biota to the predominate regional stressor gradient. To the extent possible, the regional model should
describe undisturbed or minimally disturbed conditions.
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Substantially
(initial enrichment)
Least Impacted
(best available)
Unlmpacted
(as naturally
occurs)
Condition likely
beyond scope of
current indices
Severely
(acutely toxic
Assemblage index (IBI, ICI)
'tons)
Arrow direction indicates measured value; line thickness indicates strength of signal
Tuna Richness
Intolerant Taxa
%TolerantTaxa
%0mnivores
Specialist Taxa et
%DELTs
' Biological andStressor Gradient Descriptors
"As Naturally ' "Initial "Moderate • , "Gross "Severely
Occurs" "Least Impacted" Enrichment" Enrichment" Enrichment" Altered"
(Pristine) (exceptional) (Good) (Fair) (Poor) (Very Poor)
Assemblage Characteristics
Native
assemblages;
no symptoms of
stress
As natural; no
human-made
compounds
present
Natural habitat
and flow
regime; no
human-made
modifications
No effects oi
human activity
are evident
"Best of what's
left"
assemblages;
high richness;
intolerants,
specialists
predominate
"Typical"
assemblages;
good richness;
emerging
symptoms of
stress in selected
metrics
"Impaired"
assemblages;
tolerants &
generalists
predominate
numbers/bio-
mass; loss of
intolerants
Chemical Water Quality Conditions
"Best reference" "Background "Enriched"
quality; toxics < reference" quality; quality; toxics <
detection; high toxics < chronic; chronic; marginal
D.O., low nutrients adequate D.O., D.O. regime,
nutrients = nutrients >
reference reference
Physical Habitat & Flow Regime
Excellent
quality habitat
& flow regime;
recovered from
human-made
modifications
Good quality
habitat & flow
regime; de
minimis human
modifications
Fair quality
ha Wat & (tow
regime; active
human modifi-
cations;
incomplete
recovery
"Degraded";
highly tolerant
taxa pre-
dominate;
reduced
abundance;
anomalies
increasing
"DegradecT
quality; toxics >
chronic; low
D.O., nutrients
»reference
Poor quality
habitat & flow
regime; active
human modifi-
cations; no
recovery
Examples of Sources and Activities
Point sources
present, do not
dominate flows;
NFS impacts
buffered by
extensive
riparian system
Point sources
may dominate
flows; NPS
impacts
buffered by
good riparian
zones
PS/NPS enrich-
ment impacts;
NPS unbutferd;
channel modifi-
cations; im-
poundments
Gross PS/NPS
enrichment
impacts inc.
CSOs; NPS
unbufferd; chan-
nel modifications;
urbanization
"Severely
degraded"; very
low numbers;
few taxa; very
high %
anomalies; toxic
signatures
"Extremely poor"
quality; toxics >
acute; very low
P.O., nutrients »
reference;
contaminated
sediments
Severe modifi-
cations; ephemeral
flows; active human
modifications; no
recovery potential
Severe PS/NPS
toxic impacts;
extreme channel
modifications;
urbanization; acid
mine drainage,
severe thermal
FIGURE 3-2. Conceptual model of the response of fish and macroinvertebrate
assemblages to a gradient of impacts in warmwater rivers and streams throughout Ohio
(modified from Ohio EPA 1987 and Yoder and Rankin 1995b).
DRAFT: Use of Biological Information to Better Define Designated Aquatic Life Uses in State
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The BCG model may require some example data from sites to empirically ground-truth conclusions. An
example regional BCG was described in Chapter 2, the Maine scenario for cold-water, high gradient
streams (Table 2-3). Ohio also developed a conceptual model of the BCG, shown in Figure 3-2, as part of
its tiered aquatic life use development. In addition to the description of undisturbed, natural assemblages
and the predominate stressor gradient in a region, the regional model also requires a narrative description
of the tiers and their biological attributes.
A narrative description of the tiers of the BCG for the region - The regional model includes description
of individual tiers along the gradient of biological response to stressors, including organisms present and
organisms absent. The descriptions of changes in the attributes corresponding to the different tiers are
derived from the consensus among technical experts as well as agreement on the number of tiers that can
be discriminated across the entire gradient. The regional narrative descriptions refine the national
model's descriptions of changes across the stressor gradient to reflect local conditions, (e.g., see Maine
example, Table 2-3 and Ohio example, Figure 3-2). The description of the Ohio BCG is in the row titled
"Assemblage Characteristics" (Figure 3-2). In Ohio, enrichment occurs at intermediate disturbance
levels for the metrics (numbers or biomass).
The descriptions should account for the natural classification that applies to the region. As noted in
Section 3.1.1, "classification" is defined as the process of stratifying according to natural gradients. It
may be necessary to develop separate narrative descriptions for major classes of natural gradients if the
biological expectations differ widely among classes. For example, the biota of low-gradient streams with
fine, sandy substrates may be dominated by invertebrates adapted to those conditions, such as midges and
worms. These same organisms are often indicators of degraded conditions in fast-flowing streams with
coarse substrate, but may be expected to occur under the best conditions in naturally silty streams.
A narrative description of the ecological attributes that are used to determine the tiers - Ecological
attributes are measurable characteristics of the system (described in Chapter 2). For bioassessment
programs that sample biota of target assemblages, the critical attributes are those most closely related to
taxonomic information contained in the sampled assemblages. Many species can be assigned to an
attribute group, and the change in the attributes is described in the conceptual model. In the Ohio
example (Figure 3-2), attributes include intolerants, generalists, specialists, etc. listed in the descriptions
in the first row (Assemblage Characteristics).
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3.2 Data needs: Assess and modify technical program
Consistent, quality assured and controlled (qa/qc) monitoring information is key to developing a
quantitative'assessment system within a BCG framework. Key elements of a biological monitoring
programs are listed below, correspond to design and data collection elements outlined in Technical
Guidelines: Technical Elements of a Bioassessment Program (see Appendix C) (Barbour and Yoder
unpublished manuscript). Elements of a monitoring program for quantitative calibration of the BCG are
discussed below.
3.2.1 Biological assemblages
Development of a quantitative BCG can include one or more biological assemblages (e.g., benthic
macroinvertebrates, fish, periphyton, phytoplankton). Choice of each of these assemblages, and field
sampling methods, are discussed in Rapid Bioassessment Protocols for Use in Streams and Wadeable
Rivers: Periphyton, Benthic Macroinvertebrates and Fish (EPA/841-B-99-002; Barbour et al. 1999).
3.2.2 Consistent methodology
Consistent and demonstrated methodology is important for calibration of a regional BCG.
Methodological consistency includes sampling methods that obtain representative samples of relevant
biota in the assessment unit, choice and use of sampling equipment, index period, definition of sampling
site (e.g., stream reach), and allocation of sampling and subsampling effort to obtain representative
estimates of composition and structure. Field sampling considerations are discussed in Rapid
Bioassessment Protocols for Use in Streams and Wadeable Rivers: Periphyton, Benthic
Macroinvertebrates and Fish (EPA/841-B-99-002; Barbour et al. 1999), and statistical considerations are
discussed in Statistical Guidance for Developing Indicators for Rivers and Streams (Appendix E).
3.2.3 Geographic coverage
The monitoring program should have sufficient spatial and temporal coverage to provide adequate
quantitative information to describe biological community expected undisturbed/minimally disturbed
conditions (Section 3.1.1). This would include major geographic regions, waterbody types, and
environmental gradients of pressure and stressors.
Natural Classifications -There should be sufficient reference site data in the State's database to classify
natural conditions and account for natural spatial variability among sites. Classification was discussed in
Section 3.1.1.
Stressor gradient - To describe the BCG, examples are used for each of the tiers that occur in the state or
region. Hence, data must span the entire condition gradient from the least disturbed to the most disturbed
sites in a particular region, along the entire stressor gradient.
Geographic information - In addition to routine monitoring data, geographic information helps to
develop natural classification of waterbodies to refine the expected condition. As noted above, one of the
requirements for developing a description of the BCG is to have a natural classification of the resource,
which provides a framework for organizing and interpreting natural variability among sites. Useful
geographic information includes:
• Watershed delineations - catchments of the specific sampling sites
• Physical characteristics of sampling site catchments (catchment area, distance to source, mean
slope, etc.)
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In addition to natural characteristics, geographic information should include information for
characterizing the stressor gradient, the x-axis of the BCG and evaluating whether there are undisturbed
or least disturbed reference sites. This would include information on discharges,.non-point sources of
pollutants, and watershed and landscape characteristics.
Reference condition ~ The no or low stressor end of the stressor gradient, whether undisturbed or least
disturbed condition, should be well represented as reference sites and reference condition in the database.
Considerations for establishing reference condition were discussed in Section 3.1.1.
3.2.4 Database
A comprehensive and complete database is critical to BCG calibration. The database should include all
information collected in the monitoring program, as well as stressor and pressure information that may be
collected on a geographic basis. The data must be organized and made accessible so that expert
participants can easily view and interpret the data.
3.2.5 Modify monitoring program
If the specific data and information from a State monitoring program are not sufficient to support a
quantitative BCG calibration, then the State may need to strengthen its technical program. Monitoring
and sampling program design are not covered here. See Technical Guidelines: Technical Elements of a
Bioassessment Program and Statistical Guidance for Developing Indicators for Rivers and Streams
(Appendixes C and E).
3.3 Calibrate a regional BCG model
The final step in developing an assessment method using the BCG framework is to quantify and calibrate
a model or system for routine assessment of waterbodies. In this step, the conceptual model that was
adjusted for regional conditions is further refined and validated with data and, where possible, with
quantitative relationships. The same expert panel that developed the regional conceptual model is best
suited to calibrate the BCG model with quantitative information.
Regional BCG models have been calibrated for routine use in bioassessment and biocriteria programs.
These calibrations can be used independently as stand-alone assessment methods, or in conjunction with
existing biotic indexes. The earliest operational development took place in Maine and Ohio (Ohio EPA
1987, Courtemanch et al. 1989, Davies et al. 1995, Yoder and Rankin 1995a, Davies et al. 1999) and was
the basis for the development of the national conceptual model. Regional calibration extends beyond
application of the conceptual model and requires consistent operational rules so that sites can be assigned
to tiers in a consistent fashion.
The following sections outline the process of regionally calibrating and developing a BCG model.
3.3.1 Assemble information
The information required to complete these tasks includes the database of consistently collected
biological monitoring data from a subset of sites throughout the region and geographic and historical
information where available (Section 3.2). If the State or agency has a very large data set from a long-
standing monitoring program, then it is not practical to make all of the data available to the regional BCG
workshop participants. Instead, select a subset of sites that represent the entire stressor gradient, from the
minimally or least disturbed to the most stressed sites in the state. The objective of the rating exercise is
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to select a variety of representative sites across the gradient so that all tiers occurring in the region are
represented in the calibration sample of sites. Some reference sites should be included in this set as well
as intermediate and severely stressed sites. The data must be organized arid made accessible so that
expert participants can easily view and interpret the data. The following information should be available:
• A comprehensive species list for each assemblage that is monitored (e.g., macroinvertebrates,
periphyton, fish), which can be sorted by higher taxonomic categories (order and family). To the
extent known, tolerance values (to various stressors), trophic status (functional feeding group),
habit, breeding guild, etc. should be included in each taxa list.
• Counts of abundance, by taxon, for each sample. If necessary, the database program can adjust
for unequal effort among samples.
• Complete habitat data
• Field notes
• Complete field physical and chemistry data (e.g., streamflow, pH, conductivity, temperature,
velocity, etc.)
• Complete laboratory chemistry results
• Landscape and hydrologic alteration of the catchments of the sampling sites, if available;
otherwise land use of the smallest hydrologic accounting unit that contains the sampled
catchments
• Site identification (name, ID, location)
Sites from a comprehensive monitoring program should span the range of water and habitat quality found
in the state, from the best to the worst. At this point, the data will have passed QA checks and will meet
the requirements for developing a BCG, outlined briefly in Section 3.2 and in Appendix C, and in greater
detail in Technical Guidelines: Technical Elements of a Bioassessment Program (Barbour and Yoder
unpublished manuscript).
Rather than expecting the expert group to work with stacks of printed data, it is useful to develop a
spreadsheet that can be manipulated by participants or projected onto a screen for use during group
discussions. The spreadsheet displays data from a single site at a time and calculates taxa and abundances
of attribute groups. One person should be assigned responsibility for assembling all relevant data for the
workshop exercise. If the State data are not well organized (i.e., not housed in a single comprehensive
database), then assembling the data may require substantial time and effort.
Classification - In this stage, it may be necessary to develop, refine, or empirically test classification
schemes proposed in conceptual model development (Section 3.1) if the State does not have a fully tested
classification scheme for aquatic assemblages in natural waterbodies. The purpose of classification for
this document was also explained in Section 3.1. Classification is influenced by the components of a
monitoring design: methods', measured variables, sample size (number of sites), etc. There are several
quantitative approaches to developing a classification system, including categorical models, continuous
models, a priori methods (use of existing models), and a posteriori methods (empirical models using data
in hand). Many references are available to help analysts develop biological classifications of waterbodies
(bioassessment case studies and methods: Barbour et al. 1999, Wright 2000, Gerritsen et al. 2000,
Hawkins et al. 2000, Hawkins and Vinson 2000, Smith et al. 2001, Bailey et al. 2004; textbooks:
Jongman et al. 1987, Ludwig and Reynolds 1988, Legendre and Legendre 1998, Davies et al. unpublished
manuscript).
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3.3.2 Describe attributes
Ecological attributes are measurable characteristics of the system described in Chapter 2. These are the
measures used to determine a waterbody's position along the BCG. As described in Chapter 2, attributes
that are derived from taxonomic composition or organism condition (Attributes I to VII) are routinely
measured and interpreted in State and Tribal water programs. As a practical matter, these are the key
attributes that need to be quantitatively characterized for routine assessment.
The technical expert panel should work through the list of taxa collected in the monitoring program and
assign the taxa to Attributes I through VI. In this process, the specific definitions of the attributes may be
adjusted to reflect local knowledge. For example, New Jersey biologists redefined Attribute II from
"sensitive-rare" taxa to "highly sensitive" taxa because rarity was not considered to be related to
sensitivity to pollution, and sampling methods do not capture rare taxa with any predictable reliability.
See Case Example 3-2 for further discussion of New Jersey's tier descriptions for high and low gradient
streams.
• Attribute I consists of rare and endemic taxa, which are not often encountered by routine
biological sampling methods. Their presence may be known from larger-scale surveys designed
to assess rare species.
• Attributes II through V are taxonomic groupings organized according to tolerance to pollution,
where Attribute II taxa are the most sensitive and Attribute V taxa are the most tolerant. These
four attributes are the quantitative workhorses for assessment on the BCG and must be thoroughly
characterized to calibrate a regional BCG. The tolerances of these attributes can be initially
assigned based on existing tolerance estimates, but the panel should consider whether the existing
tolerance estimates are accurate based on their experience and observations of the organisms.
• Attribute VI consists of introduced taxa.
Due to incomplete information, rarity in the database, or lack of knowledge, not all taxa will be assigned
to an attribute.
3.3.3 Describe tiers and assign sites to tiers
Similar to die national BCG model development process, regional development can occur in workshops
that bring together aquatic biologists and water quality standards experts familiar with streams in their
regions. Workshop participants are asked to develop both the ecological attributes and the rules for
assigning sites to tiers along the gradient. Workshops proceed as follows:
1. Participants consider the conceptual model of the BCG to identify specific biological changes that
can be observed along the stressor gradient in their region. Specific metrics or attributes that can
be measured within the BCG framework are identified.
2. The groups consider data from selected monitoring sites and assign the sites to tiers in the BCG
based on the biological monitoring information from each site. Initially there may be
disagreement among the group members, but as they become familiar with the process, sites are
rated more consistently.
3. From the discussions and decisions, a set of rules is developed for assigning sites to individual
tiers in the BCG.
Using the regionally adapted conceptual model (Section 3.1.3), participants examine data from selected
sites throughout the region. Sites are selected from the preliminary stressor gradient (See Chapter 4) to
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represent the gradient as it occurs in the region. The group should consider the biological condition,
species present and absent, and come to consensus on the tier to which each site should be assigned.
Experience has shown that assemblages are best kept separate at this stage. The group should describe
the tiers and assign sites to tiers separately for macroinvertebrates, fish, periphyton, and other
assemblages.
Groups typically start with several candidate reference sites in the region in an effort to establish a
reference baseline. Depending on the completeness of the database, the best sites in that database may
not reflect undisturbed or minimally disturbed conditions. Additionally, if the ecoregion spans more
than one state, the best sites might be in a different state or tribal land—and may not be part of the
database. Ideally, calibration of the BCG in physiographic or ecological regions that cross state
boundaries should be niulti-state and tribal efforts. The important point here is that the best sites are not
automatically assigned to Tiers 1 or 2. The assemblages from the candidate reference sites should be
compared to the descriptions of Tier 1 and Tier 2 sites developed in the initial theoretical exercise. The
following questions should be addressed:
• Do the candidate reference sites meet the theoretical expectations of Tier 1 or Tier 2? Then, if the
answer is no, first validate the model's Tier 1 and 2 expectations by addressing the following
questions:
o Are these candidate reference sites minimally disturbed, that is, are there no or negligible
effects from stressors?
o Can the level of stressors be documented? •
o Is historical information available that would suggest that they are minimally disturbed?
• If these three questions are answered "yes" then the theoretical expectations and descriptions of
Tiers 1 and 2 may need to be reassessed and altered. If the candidate reference sites apparently
have more then than minimal or negligible levels of stressors, then they do represent examples of
Tiers 1 and 2, undisturbed or minimally disturbed conditions. In many areas, sites identified as
reference, especially those that are the "least disturbed," may be rated Tier 3 or even Tier 4 in the
BCG.
Following development of the tier descriptions, participants continue to assign sites to tiers using the
descriptions they have developed. Both the tier descriptions and the original taxa assignments may be
revisited and revised in order to resolve any anomalies or issues that arise throughout the assignment
process. Sites are frequently deemed intermediate (between adjacent tiers), and assigning sites to tiers
does not require group unanimity. See Case Example 3-3 on Maine's assignment of stream sites to
waterbody classes (tiers) using benthic macroinvertebrate metrics.
Tier assignments can also be tested against stressor gradients from the database. Stressor gradients (e.g.,
toxic metal concentrations, habitat conditions, nutrient concentrations, etc.) can be considered partial
components of the stressor gradient (Chapter 4). Figure 3-3 shows an example from Ohio, showing
copper concentration in the BCG tiers. In general, lower tier sites have a greater likelihood of elevated
copper above the criterion level, although all tiers except the poorest (NA; very poor) included at least
some sites with copper not exceeding the criterion.
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Ohio EPA Criteria
M
50-60
40-49
30-39
20-29
12-19
I
*
I-TD
EWH
WWH
MWH
LRW
NA
20 40 60 80
Standard Total
Recoverable Copper (ug/l)
too
FIGURE 3-3. Ohio BCG tiers and copper
concentration. Each horizontal bar
approximates the tier shown on the right:
EWH - exceptional warmwater habitat;
WWH - warmwater habitat; MWH -
modified warmwater habitat; LRW -
limited resource waters; NA • non-
attaining (very poor). Shaded areas are
interquartile ranges of copper
concentration in each BCG tier. Note that
all sites in the very poor tier had copper
concentration above the Ohio copper
criterion (dashed line).
Setting expectations in significantly altered landscapes
In some regions, the historical conditions describing Tier 1 and 2 sites no longer exist. Many native
species have been extirpated or greatly reduced, and the physical and chemical habitat of streams is
completely different from the pristine, or undisturbed, condition. For example, the breaking up of native
prairie sod and ongoing agricultural practices has resulted in high sediment and nutrient loads in
midwestern prairie streams (e.g., Kuzelka et'al. 1993). Removal of forest cover in eastern agricultural
areas (e.g., Cora Belt Plains, Interior Plateau, Southeastern Plains, Riverine Lowlands) has had similar
effects, although large tracts of forest cover remain or have regrown. In the western Great Plains,
damming of snowmelt-fed streams and rivers has eliminated annual scouring flows and reduced sediment
loads of rivers such as the Missouri, Platte, Arkansas, Rio Grande (e.g., Johnson 1994). Biological
conditions comparable to Tiers 1 and 2 may no longer exist in some ecological regions of the continent.
Mitigation of the resource to pristine conditions may not be currently possible (See Case Example 3-1).
3.3.4 Develop quantitative assessment methods
To developing a regional BCG water quality agencies should consider ecological information critically in
making assessments. Biological condition tiers are narrative statements on presence, absence, abundance,
and relative abundance of several groups of taxa, as well as statements on system connectivity and
ecosystem attributes (e.g., production, material cycling). The statements are consensus best professional
judgments based on the years of experience of many biologists in a region, and reflect accumulated
biological knowledge.
Consistent application of the BCG to routine assessment and ultimately to better define designated aquatic
life uses in water quality standards, will require an operational system that does not depend on
reconvening the same group of experts to rate all sites. Assessments should minimize individual
variability or bias, as might occur if individual assessors then interpret the rules developed by expert
consensus.
Accordingly, there are a variety of ways to automate the decision tool, ranging from application of
existing biotic indexes (multimetric IBI type indexes, RIVPACS indexes, BEAST applications) to
development of new expert systems that specifically replicate the decision-making of the expert group
that defined the BCG for the region (Appendix A; Davies et al. unpublished manuscript). Below are
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discussions of three methods for developing an operational assessment system, two of which use existing
indexes, and the third of which develops and calibrates a system specifically for identifying tiers of the
BCG. Other methods are also possible (e.g., expert systems), but the three explained below are currently
used for operational bioassessment into tiers of the BCG.
Any quantitative model or procedure that is developed to assign sites to tiers should be tested with
independent data that were not used to calibrate the model. This applies to all three quantitative model
approaches discussed here. In general, the models are calibrated using tier assignments developed by the
expert panel (Section 3.3.3). A second data set of tier assignments (also assigned by the expert panel) is
then required to test the model.
Calibrating biotic indexes to the BCG
Biotic indexes such as fflls (multimetric approaches under a variety of acronyms; Barbour et al. 1999),
predictive model indexes (RIVPACS approaches; Wright 2000), and true multivariate indexes (BEAST
models; Bailey et al. 2004) are all attempts to describe a biological condition gradient. As such, index
approaches may be suited to identifying tiers in the gradient and for assessment in the context of the
BCG.
Simple division of an index scoring range is not recommended because most indexes were not explicitly
developed on a BCG framework. For example, metrics in an IBI-type index may have been selected
because of strong responsiveness to stressors, rather than reflecting the conditions expressed in the BCG
(see Table 2-1). If a State is to develop tiered aquatic life uses based on the national BCG model, it
therefore may be necessary to recalibrate existing index models to the BCG or develop new biological
models and can be used to assign sites to tiers. For example, Vermont has designated aquatic life uses as
differentiated by biological threshold criteria (See Case Example 3-4).
Through an iterative process, scoring criteria may be developed for existing indexes that correspond with
biologists' consensus on narrative descriptions of the tiers in the biological gradient. If tiers are
established based on other designated uses (e.g., hydrologically modified canals), then each tier or use
class can be calibrated to an index score reflecting the best potential condition for that use. Ohio used this
approach to set biological criteria for four use classes (see Chapter 5).
An existing index may be calibrated to the BCG model at the level of index scores, or by deriving a new
index that better reflects the BCG. Both approaches require a set of sites that have been assigned to the .
tiers of the BCG that were determined by the expert panel to be appropriate for the specific aquatic
ecosystem (Section 3.3.3).
Calibrating index scores - The set of sites that have been assigned to tiers of the BCG are used to
calibrate index scores. Index scores for the sites are examined (Figure 3-4). If separation of the index
scores among tiers is good, then index thresholds can be selected to maximize the ability to discriminate
among the tiers. Figure 3-4 shows a hypothetical example with five tiers (BCG Tiers 2 - 6). Separation
of scores among tiers is generally good, and the solid lines indicate scoring thresholds between adjacent
tiers. The exception here is that the index does not discriminate as reliably between Tiers 2 and 3 as it
does between other pairs of tiers.
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80
70
g 60
w 50
*
"5 40
_E
30
20
10
1
Tier 2
Tier 3
Tier 4
TierS
Tier 6
345
Assigned Tier
FIGURE 3-4. Hypothetical example of biotic index scores
of sites assigned to BCG tiers, where the index is able to
discriminate tiers most of the time. Boxes represent
interquartile range of each tier; points are medians,
and whiskers represent range of score outside the
quartifes. Horizontal lines represent thresholds that
could be applied to discriminate tiers using the index
scores. In this example, there are no undisturbed
reference conditions in the region.
The British Environment Agency recalibrated two RIVPACS indexes in a similar way. Initially, index
scores were divided into four equal tier categories based on the statistical distribution of reference site
scores (90% interval; Helmsley-Flint 2000). However, regional field biologists observed that four equal
categories based on a 90% interval were insufficient to discriminate exceptional from good sites, and poor
from very poor sites (Helmsley-Flint 2000). Accordingly, the indexes were recalibrated so that categories
matched those determined by the regional experts. The resultant six categories are similar to the six tiers
of the BCG (Table 3-4). See Case Example 3-5 for a description of this process..
\
Calibrating metrics - However, index scores may show a great deal of variation within BCG tiers, such
that assigning tiers based on index scores is an inaccurate process (Figure 3-5). In the hypothetical
example shown in Figure 3-5, the index is unable to discriminate among Tiers 2 through 4. In this
instance, it would be necessary to revise the index to reflect tiers of the regionally calibrated BCG.
Revision and recalibration of an IBI, or of other indexes, can be part of a State's routine recalibration
process that occurs periodically when substantial new data have been collected.
30
25
20
I
<§ 15
I 10
5
0
?n
iip
$
E*
o o
It fl
3s-
toi
t"
I
o
1
1 T
»M>g iSHSjgl
2 3
4
m
0 —1—
5 6
Assigned Tier
Tiers 2-4
Tiers
Tier6
FIGURE 3-5. Hypothetical example of biotic index scores of sites assigned to
BCG tiers, where the index is not able to discriminate tiers.
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Model development to support BCG tiers: Discriminant model
Simple recalibration of index scores to BCG tiers may not yield distinct break-points (or benchmarks)
between adjacent tiers. This is the case when sites in different tiers (as determined by the expert panel)
have the same or similar index scores, showing that the index cannot discriminate among tiers of the
BCG. Development of an operational tiered assessment system may require a separate index or model
calibrated to the tiers.
Discriminant analysis may be used to develop a model that will divide, or discriminate, observations
among two or more classes. A discriminant function model is a linear function combining the input
variables. It obtains the maximum separation (discrimination) among the classes. The model is
developed from a "learning" dataset where the classes have been identified. The model is then used to
determine class membership of new observations where the class is unknown. Thus, a discriminant
function model can be developed from a biological data set where sites have been assigned to BCG tiers.
The analysis identifies variables that will discriminate among the tiers. The resultant model is then used
to identify the tier to which a site should be assigned. Maine uses this method to determine whether
streams are meeting biological criteria for multiple tiered uses. See Case Example 3-6 on Maine's
development of linear discriminant functions to assess tiers.
Although it requires considerable statistical expertise to develop, the advantage of discriminant analysis is
that it uses established and well-documented statistical methodology. However, it requires a relatively
large set of assigned sites to calibrate the model, approximately 20 per tier. Accuracy of the model to the
expert-assigned calibration and test sites can be as high as 89 - 97% (based on jack-knife tests; Davies et
al. unpublished manuscript).
Using a discriminant model to develop biocriteria requires both a set of training data to develop the model
and confirmation data to test the model. The training and confirmation data may be from the same
biosurvey, randomly divided into two, or they may be two or more years of survey data. All sites in each
data set are assigned to BCG tiers by the expert workgroup (Section 3.3.3).
One or more discriminant function models are developed from the training set to predict tier membership
from biological data. Once developed, the model is applied to the confirmation data set to determine how
well it can assign sites to classes using independent data not used to develop the model (See Case
Example 3-6). More information on discriminant analysis can be found in any textbook on multivariate
statistics (e.g., Jongman et al. 1987, Ludwig and Reynolds 1988, Legendre and Legendre 1998).
Quantitative rules for tier assignments
Tier descriptions in the conceptual model tend to be rather general (e.g., "reduced richness"). To allow
for consistent assignments of sites to tiers, it is necessary to operationalize, or codify, the general tier
descriptions into a set of rules that anyone can follow and obtain the same tier assignments as the group of
experts.
Operational rules are used to define the tier descriptions ("as naturally occur," "reduced," "greatly
reduced," etc.) to quantitative or semi-quantitative rules for each attribute ("Attribute II taxa > 50% of
any other attribute, ± 10%"). These rules preserve the collective professional judgment of the expert
group and set the stage for the development of models that reliably assign sites to tiers without having to
reconvene the same group. In essence, the rules and models capture the group's collective decision
criteria.
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Rule development can take place during the expert panel workshop to describe the detailed BCG and
assign sites to tiers (Section 3.3.3). It requires discussion and documentation of tier assignment decisions
and the reasoning behind the decisions. During this discussion, facilitators should elicit and record:
• each participant's tier decision ("vote") for the site;
• the critical or most important information for the decision - for example, the number of taxa of a
certain attribute, the abundance of an attribute, the presence of indicator taxa, etc.; and
• any confounding or conflicting information and how this was resolved for the eventual decision.
See Case Example 3-7 for an example of decision rules developed during New Jersey's calibration
exercise (Table 3-6).
Testing
Rule development should be iterative. Following the initial development phase, the draft rules should be
tested by a group of experts to ensure that new data and new sites are assessed in the same way. This
usually requires a second workshop, during which a set of test sites not used in the initial rule
development and also spanning the range of stress should be assessed. Any remaining ambiguities and
inconsistencies from the first iteration can also be resolved. Rules can be used directly for assessments,
for calibrating one of the previous assessment methods (IBI, discriminant model), or as the basis of an
expert system.
Thresholds and uncertainty
For each of the quantitative models described above, it is possible to estimate predictive uncertainties.
Index variability is estimated from repeated measures at sites over one or more years, and accuracy of the
quantitative model to expert consensus is estimated from the number of "correct" calls by the model.
Several methods exist to estimate overall predictive uncertainty. For uncertainty of the models discussed
here, see Helmsley-Flint (2000) and Davies et al. (unpublished manuscript).
Not all uncertainty is statistical, and not all issues of uncertainty can be reduced to a statistical probability.
Experience with the BCG workgroups suggests that there will always be sites that fall on the border
between tiers. It is important to recognize that some sites are borderline or intermediate, not that we are
uncertain about where they are. This is a consequence of forcing a more-or-iess continuous gradient into
discrete management categories.
While thresholds between tiers do not need to reflect true discontinuities in nature, the tiers should
represent detectable and consistent differences in assemblages, their taxonomic composition, and
ecological function. To the extent they are consistent and detectable, they serve to inform management
on how well we are protecting against degradation and making progress towards restoration goals.
Disagreement among assemblages
Once a BCG has been regionally calibrated, a possible scenario in assessment is that two assemblages
collected at the same site indicate different tiers of the BCG. For example, to what tier should a site be
assigned if the fish indicate Tier 2 but the macroinvertebrates indicate Tier 4? Options include:
averaging the,two assemblages (Tier 3 in this example),
selecting the lowest assessment among the assemblages (Tier 4), or
selecting the highest assessment among the assemblages (Tier 2).
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In making this decision, it is important to consider the level of rigor in the tier assessments among the
assemblages, particularly if an assessment is based on an absence, rather than presence, of information
(absence of evidence is not evidence of absence). This requires considering the strength of evidence for
each assemblage. Automatic calculation of an average or use of the highest assessment is neither
conservative nor protective of the resource. Both Ohio EPA and the British Environment Agency have
chosen to select the lowest assessment among indexes and assemblages for final tier assignments (Yoder
and Rankin 1995b, Helmsley-Flint 2000).
3.4 Key points from Chapter 3
1. The conceptual Biological Condition Gradient can be quantified and calibrated to local
conditions for use in assessment and water quality criteria. The tiers of condition described
in the BCG conceptual model can be applied to local or regional conditions by regional biological
experts with a sufficient monitoring database.
2. A quantified BCG is not defined by any one monitored assemblage or methodology. BCGs
have been developed from different assemblages and methodologies (fish, benthic
macroinvertebrates, artificial substrates, etc.) and by calibrating different assessment indicators to
the BCG (IBI, RIVPACS, and multivariate analysis).
3. Quantification and development of a BCG is data driven. A regional monitoring database
should be used to calibrate a BCG that meets performance requirements and QA requirements.
The monitoring agency should have access to biological expertise, and should be committed to
provide sustained support.
Chapter 3 has discussed transforming the conceptual scientific model of the BCG into a quantified and
calibrated model for biological assessment. Chapter 4 discusses the Stressor Gradient model, the x-axis
of the BCG. Chapter 5 discusses key concepts and milestones for developing tiered aquatic life uses in
water quality standards that two states, Maine and Ohio, have learned based on their experience in
adopting tiered uses, and is supported by their individual case histories of TALU development
(Appendixes A and B). Chapter 6 presents examples of how Maine and Ohio have applied tiered uses in
their water quality management program.
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Chapter 3 Case Examples
CASE EXAMPLE 3-1. USING HISTORICAL INFORMATION TO IDENTIFY
REFERENCE STREAMS IN KANSAS
Historical information can be used to reconstruct the pre-settlement biological baseline and estimate
undisturbed or minimally disturbed conditions. Potential sources of historical data include museum fish
and shellfish collections, historical notes and writings, journal entries, indigenous knowledge, published
archeological studies, photographs and maps, and early biological surveys or studies.
Some knowledge of pre-settlement baseline conditions is needed when planning long-term restoration
efforts in areas where undisturbed or minimally disturbed reference waterbodies no longer exist. For
example, in Kansas, few streams have completely escaped the effects of large-scale agricultural and
livestock practices implemented over the past 150 years. Therefore, biologists within the Kansas
Department of Health and Environment (KDHE) consider available information on historical stream
characteristics to estimate minimally disturbed conditions and support contemporary reference stream
selections.
KDHE recognizes six general categories TABLE 3.^ Kansas stream bio]0gicai integrity categories.
of aquatic biological responses to
increasing levels of disturbance (Table 3- :....C^i....:....^ .,„.,,,,,,,,,.,,.
1). Class A represents natural or pre- jJpiasYBiivXSCojite
settlement stream conditions, equivalent . ' ciastcr^
to Tier 1 in the BCG, m which "native :.., - ,.:,., ,:.,: .,.,:.,,,,4 .,..!;" ,,,,,,, K:,::,:, ,~, ,. .,,. >.,"< .,,,.,, :.: ,..,,, ,,:;:;s:;s:; ,,, ;;
structural, functional and taxonomic W^^^^^^^^^^^^^^^^^^B^
integrity is preserved; ecosystem function Class E: Non-supportive of designated aquatic life use
is presented within the range of natural s^v^wv;^^ ;^?'.?^?;
variability." Some indication of the ^^mm^^m^m^^^^m^M^m
native character of streams in the Great Source: Kansas Dept of Health and Environment
Plains can be found in the narrative
accounts of early nineteenth century explorers, including Lewis and Clark, Zebulon Pike, and George
Sibley, among others. Railroad surveys and other investigations yielded additional information on the
aquatic flora and fauna and generated maps and the earliest known photographs of many streams.
Although many of the biological surveys from the mid- 1800s were performed after the start of intensive
agriculture, they still provide valuable documentation of the occurrence of several freshwater species that
soon disappeared from specific watersheds or the region as a whole. Museum collections and other
historical records indicate that many creeks and smaller rivers in the Great Plains supported a variety of
predominately eastern fish and shellfish species, most requiring clear water and relatively stable stream
bottoms. In fact, this region was once home to more than 50 unionid mussel species. Today, several
mollusca species are no longer found in most of their original habitats (Figure 3-6). Over the past 150
years, at least 1 1 aquatic molluscan taxa have become extinct in Kansas, and an additional 23 species are
currently designated as endangered, threatened, or vulnerable.
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i.',, "i.';,--;; »', f'$f>,t -S *'" '"•*<""•'-!'}
'''>'i»til>iSt*>^^ *r+tf*fffrvAtrVXmi* '
6et>ti*vat «MM»ittimntt'w^-4^ 1?^ '"J,'"J ',","'•,
FIGURE 3-6. Decline in geographical distribution of black sandshell mussel in Kansas.,
Because typical biological indexes (e.g., IB I) are usually developed from ambient "least disturbed"
reference sites, they may lack sensitivity to discriminate among tiers or levels in the BCG. Surviving
populations of historically occurring key species and indicator taxa can be used to further verify the
minimally disturbed condition. KDHE considers historical fish, mussel, and prosobranch snail
communities, and has created a "mussel loss" indicator metric that compares the taxa richness of the
contemporary and historical unionid mussel assemblage for use in 305(b) and 303(d) list development
(Figure 3-7). Sites retaining 90-100 percent of their pre-settlement species are deemed fully supportive of
the aquatic life use, sites with 75-89 percent are considered partially supportive, and sites retaining 0-74
percent are assigned to the non-supportive category. In establishing long-term restoration goals, KDHE
intends to continue drawing upon historical information sources to help ensure that the projected changes
in aquatic plant and animal assemblages trend toward the pre-settlement biological condition.
There are some challenges and drawbacks when using historical data to reconstruct natural stream
conditions. It takes a great deal of time and commitment to piece together numerous bits of information,
especially considering the limitations and inconsistencies inherent in historical data. Much of the
information is not directly comparable to modern assessment data, largely because results from previous
studies and observations are often based on different sampling methodologies. Sometimes the data are
not applicable because they were obtained after settlers significantly impacted the land, but often such
physical habitat data are missing or incomplete. Finally, some regions settled early in the history of the
nation may simply lack definitive data on the baseline biological condition.
20
40 60
Extirpated mussel species (%)
FIGURE 3-7. Cumulative frequency
distribution for Kansas streams with
minimum three-year period-of-record and
five or more species historically.
too
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CASE EXAMPLE 3-2. NEW JERSEY TIER DESCRIPTION
Aquatic biologists in New Jersey described tiers of the BCG for benthic macroinvertebrate assemblages
of both high and low gradient streams of the state. The expert panel first assigned invertebrate laxa to
Attributes I to VI. The panel redefined Attribute II from "sensitive-rare" taxa to "highly sensitive" taxa
because rarity was not considered to be related to sensitivity to pollution, and sampling methods do not
capture rare taxa with any predictable reliability. In addition, the panel determined that five tiers are
applicable to New Jersey high gradient streams, and that four tiers describe the State's low gradient
streams. For both high and low gradient streams, the panel thought that Tier 1 sites may not exist.
Table 3-2 shows the attribute matrix for high gradient streams. Attributes VII to X are not measured for
the invertebrate assemblage at this time, and are not included in the matrix. The group was able to
distinguish five separate tiers (Tiers 2-6) for high-gradient streams of New Jersey. The first tier described
in the Maine model (Davies and Jackson in press) was not initially useful because it was not clear to the
group whether Tier 1 (pristine) sites occur in New Jersey based upon benthic macroinvertebrate data
alone. Other data sets (i.e. finfish communities and/or rare and endangered species) may be more useful
in determining whether a site is in Tier 1. The group also determined that several indicator taxa are useful
in discriminating tiers, in particular the tolerant hydropsychid caddisflies as indicators of moderate
organic enrichment for Tiers 3 and 4; abundance of tubificid worms as an indicator of extreme enrichment
and hypoxia for Tier 6; and complete absence of mayflies as an indicator of toxicity, also for Tier 6.
In contrast to high gradient streams, participants could only distinguish four separate tiers for low gradient
streams (Tier 2, Tiers 3-4 combined, Tier 5, and Tier 6) (matrix not shown). The best-known sites in the
Coastal Plain contain moderate numbers of tolerant taxa, which is a consequence of low water velocity
and absence of cobble habitat rather than poor water quality. As a result, the group concluded that it was
not feasible to distinguish Tier 3 from Tier 4, and combined them into a single tier.
In general, participants were able to achieve consensus on tier assignments for the sites reviewed. In
some cases, there was discussion and some disagreement on which of two adjacent tiers a site should be
assigned to. These intermediate sites, with characteristics of both adjacent tiers, are to be expected since
ecological response to stressors is relatively continuous.
TABLE 3-2. Summary attribute matrix for New Jersey high gradient streams.
Ecological
Attributes
1 Historically
documented,
sensitive,
long-lived or
regionally
endemic taxa
1
Natural
Condition
As predicted for
natural
occurrence
except for
global
extinctions
2
Minimal Loss
As predicted for
natural
occurrence
except for
global
extinctions
3
Some
Replacement;
Function
Maintained
Some may be
absent due to
global extinction
or local
extirpation
4
Notable
Replacement
Function
Largely
•Maintained
Some may be
absent due to
global, regional
or local
extirpation
5
Tolerants
Dominant,
Loss of
Function
Usually absent
6
Severe Alter
Structure and
Function
Absent
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TABLE 3-2. Summary attribute matrix for New Jersey high gradient streams.
Ecological
Attributes
II Highly
sensitive taxa
III Sensitive &
common taxa
IV Taxa of
intermediate
tolerance
i
V Tolerant taxa
VI Non-native
or Intentionally
Introduced
taxa
XI Potential
Supplemental
Attributes;
Indicator taxa
t
Natural
Condition
As predicted for
natural
occurrence,
with at most
minor changes
from natural
densities
As predicted for
natural
occurrence,
with at most
minor changes
from natural
densities
As predicted for
natural
occurrence,
with at most
minor changes
from natural
densities
As naturally
occur, with at
most minor
changes from
natural
densities. If
present, at very
low abundance.
Non -native
taxa, if present,
do not displace
native taxa or
alter native
structural or
functional
integrity
No apparent
response of
indicator taxa
2
Minimal Loss
Virtually all are
maintained and
well
represented
(both taxa and
abundance)
Present and
maybe
increasingly
abundant.
As naturally
present at low
abundances
As naturally
present at low
abundances.
May have
several taxa at
low
abundances.
Non-native taxa
may be present,
but occurrence
has a non-
detrimental
effect on native
taxa
No apparent
response of. .
indicator taxa
3
Some
Replacement;
Function
Maintained
Maybe
markedly
diminished (in
either taxa or .
abundance),
with replace-
ment by
functionally
equivalent
Sensitive and
common taxa
Common and
abundant;
relative
abundance
greater than
Highly Sensitive
taxa. Similar to
good taxa
(sensitive &
common taxa).
Often evident
increases in
abundance
May be
increases in
abundance of
functionally
diverse tolerant
taxa
Sensitive or
intentionally
introduced non-
native taxa may
dominate some
assemblages
(e.g. fish or
macrophytes)
Initial response
of indicator
taxa, (e.g.,
increase of
suspension
feeders with
enrichment)
4
Notable
Replacement
Function
Largely
Maintained
Significantly
diminished
(taxa and
abundance)
Present with
reproducing
populations
maintained;
some
replacement by
functionally
equivalent taxa
of intermediate
tolerance.
Common and
often abundant;
relative
abundance
greater than
Sensitive and
common taxa
Maybe
common but do
not exhibit
significant
dominance
Some
replacement of
sensitive non-
native taxa with
functionally
diverse
assemblage of
non-native taxa
of intermediate
tolerance
Some response
of indicator
taxa, (e.g.
increase of
Caenids with
silt, etc.)
5
Tolerants
Dominant,
Loss of
Function
Usually absent
Frequently
absent or
significantly
diminished (if
present
incidental)
Often exhibit
excessive
dominance
Often occur in
high densities
'and may be
dominant
Some
assemblages
(e.g., fish or
macrophytes)
are dominated
by tolerant non-
native taxa
Response of
indicator taxa
(e.g., loss of
mayflies with
toxic stress)
6
Severe Alter
Structure and
Function
Absent
Absent
Richness of all
taxa is low
Usually
comprise the
majority of the
assemblage;
often either very
low or very high
densities.
Often dominant;
may be the only
representative
of some
assemblages
(e.g., plants,
fish, bivalves)
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CASE EXAMPLE 3-3. MAINE BIOLOGISTS' ASSIGNMENT OF SITES TO CLASSES (TIERS)
Maine DEP assembled a panel of three biologists to assign sites to each of Maine's three stream classes
(A, B, C), and a fourth class representing non-attainment (NA). Each biologist independently reviewed
biological information for each sampling event, including identities and abundances of taxa occurring in
the biological sample and computed index values for the biological data (e.g. diversity, richness, EPT,
etc). Physical habitat information was also reviewed including water depth, velocity, substrate
composition, canopy cover, etc., in order to evaluate the effects of various habitat conditions on the
structure of the macroinvertebrate community. Sample information was reviewed for the values of the
given measures, relative to values for other samples in the data set. The actual classification assignment •
was determined by how closely the biological information conformed to the aquatic life classification
standards, correcting for habitat effects. Numerical ranges, per se, were not established, a priori, for
each measure. Instead, the information was reviewed for its compatibility with the mosaic of findings
expected for each Class, listed in Table 3-3. The biologists did not have any knowledge of the actual
location of the sampled sites, nor did they have knowledge of any pollution influences. Following the
independent assignment of classes the biologists established a consensus classification, following an open
exchange of justifications for each biologist's assignment.
Each biologist reviewed the sample data for the values of a list of measures of community structure and
function. Criteria used by biologists to evaluate each measure are listed in Table 3-3.
In 64% of the cases there was unanimous agreement among the independent raters, and in an additional
34% of the samples two of the raters were in agreement and one had assigned a different classification. In
three of the rated samples there was disagreement among all three raters (2%).
TABLE 3-3. Relative findings chart.
Measure of Community
Structure
Total Abundance of Individuals
Abundance of Ephemeroptera
Abundance of Plecoptera
Proportion of Ephemeroptera
Proportion of Plecoptera
Proportion of Hydropsychidae
Proportion of Ephemeroptera &
Plecoptera
Proportion of Glossosoma
Proportion of Brachycentrus
Proportion of Oligochaetes
Proportion of Hirudinea
Proportion of Gastropoda
Proportion of Chironomidae
Proportion of Conchapelopia &
Thienemannimyia
Relative Findings
A
often low
high
highest
highest
highest
intermediate
highest
highest
highest
low
low
low
lowest
lowest
B
often high
high
some present
variable depending
on dominance by
other groups
variable depending
on dominance by
other groups
highest
variable
low to intermediate
low to intermediate
low
variable
low
variable depending
on the dominance of
otheraroups
low to variable
C
variable
low
Low to absent
low
low
variable
Low
very low to
absent
very low to
absent
low to moderate
variable
variable
highest
variable
NA
variable: often
very low or high
low to absent
Absent
zero
zero
low to hiqh
absent
absent
absent
highest
variable to
highest
variable to
highest
variable
variable to
highest •
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TABLE 3-3. Relative findings chart.
Measure of Community
Structure
Proportion of Tribelos
Proportion of Chironomus
Generic Richness
Ephemeroptera Richness
Plecoptera Richness
EPT Richness
Proportion Ephemeroptera
Richness
Proportion Plecoptera Richness
Proportion Diptera Richness
Proportion Ephemeroptera &
Plecoptera Richness
EPT Richness divided by Diptera
Richness
Proportion Non-EPT or
Chironomid Richness
Percent Predators
Percent Collector, Filterers &
Gatherers divided by Percent
Predators & Shredders
Number of Functional Feeding
Groups Represented
Shannon-Weiner Generic Diversity
Hilsenhoff Biotic Index
Relative Findings
A
low to absent
low to absent
variable
highest
highest
high
highest
highest
low to variable
highest
high
high
low
high
variable
low to
intermediate
lowest
B
low to absent
low to absent
highest
high
variable
highest
high
variable
variable
high
highest
high
low
highest
highest
Highest
low
C
low to variable
low to variable
variable
low
low to absent
variable
low
low
highest
low to variable
low to variable
low
high to variable
low
variable
Variable to
intermediate
intermediate
NA
variable to
highest
variable to -
highest
lowest
very low to
absent
absent
low
low to zero
zero
variable to high
low to absent
lowest to zero
lowest
highest
lowest
lowest
lowest
highest
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CASE EXAMPLE 3-4. VERMONT'S USE OF EXISTING BIOLOGICAL INFORMATION FOR THE BCG
Vermont used reference condition as the anchor point for assessing biological condition, and tiers of
biological condition were established and described in terms of deviation from the reference condition.
Biological narratives were developed, which provided guidance for evaluating degrees of deviation from
the reference condition. The proposed language was intended to formalize Best Professional Judgment
(BPJ) assessments by technical experts while remaining close to historical implementation. It was also
critical that the new classification system maintain consistent assessment results, particularly for non-
attainment findings.
Vermont tapped into more than-20 years worth of biological data collected from wadeable streams to
develop biocriteria. Existing macroinvertebrate and fish assemblage monitoring data were evaluated for
"reference" and "non-reference" condition in order to classify wadeable stream ecotypes and define
biological reference conditions for each." Reference, or minimally disturbed, sites were determined based
on BPJ. Various macroinvertebrate and fish community metrics were evaluated in order to describe their
usefulness in detecting responses to disturbance.
Macroinvertebrate analysis identified four distinct wadeable stream ecotypes exhibiting unique biological
characteristics: small high-gradient mountain streams; medium-sized high gradient streams and rivers;
warmwater moderate gradient rivers and streams; low gradient soft bottom rivers and streams. A suite of
eight macroinvertebrate community metrics was selected for the purpose of setting threshold criteria
based on responsiveness to disturbance and impact. The eight metrics represent a range of structural and
functional characteristics and were evaluated to minimize information redundancy. The range of reference
condition was described for each metric and ecotype. Threshold criteria, based on deviation from the
reference condition, were established for each ecotype consistent with the language contained in the water
quality standards for each classification (Figure 3-8). Uncertainties associated with each threshold are
recognized through the establishment of threshold ranges. The eight metrics are not combined into a
single index number, but are evaluated separately in a BPJ analysis of use support status.
natural/
minimally
altered
a
3
t
i
EQ
severely
altered
Class A: Excellent - Biota within the
range of Hie natural condition
Class Bl: Very Good - Minor changes to
structure and function; tolerant/Intolerant
forms within the range of reference
Class Bff?; Good -Moderate change* ift
the relative proportions «t tolerant,
components,
Stressor Gradient
FIGURE 3-8. Vermont's designated aquatic life uses as differentiated by biological threshold criteria.
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Two fish community indices of biotic integrity differentiating between strictly coldwater and mixed water
assemblages were developed and calibrated to the Vermont Water Quality Standard narrative thresholds
based on deviations from the reference condition. The indices combine multiple metrics representing a
range of structural and functional characteristics into a single index number.
Since the BCG is continuous, it can be subdivided into any number of categories. The fish and
macroinvertebrate criteria thresholds used by the Department were able to differentiate four categories of
"support" status - Class A (near natural condition), high quality Class B1, general Class B2/3, and non-
support (Figure 3-8). Common narrative descriptors - excellent, very good, good and fair-very poor were
used to describe the thresholds. A determination of less than good was indicative of aquatic life use non-
support. Categories of non-support (fair, poor, very poor) were not described.
When Vermont'shew standards became effective in July 2000, all waters previously designated Class B
were categorized as general Class B2/3 by default. The idea was to use the watershed planning process to
propose and implement designated use reclassifications, particularly to the high quality Class Bl. VtDEC
is assembling candidate lists of waterbodies exhibiting high quality biological condition consistent with
the Class B1 designated use. Final consideration of candidates is made via public process in order to
ensure compatibility with local watershed plans and interests. Although no reclassifications have been
made to date, the BCG has provided a clear visualization of the concepts of disturbance and impact, and
this has been a useful tool in explaining the WQS to the public.
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CASE EXAMPLE 3-5. DEVELOPING BIOLOGICAL CONDITION TIERS IN GREAT BRITAIN
In the 1980s, the Environment Agency of the United Kingdom sponsored the development of a
nationwide monitoring and assessment program based on benthic macroinvertebrates. A four-year
initiative, aimed at determining whether the macroinvertebrate community at a site could be predicted
using physical and chemical features, led to the development of RIVPACS (River Invertebrate Prediction
and Classification System). Other countries, and some states in the U.S. such as Oregon and Illinois,
have subsequently integrated RIVPACS models into their biological assessment programs.
Predictive models like RIVPACS base assessments on the compositional similarity between observed and
expected biota. To create a RIVPACS model for a particular region, standard protocols are followed to
sample the region's biota and habitat at a network of reference sites that span the range of that region's
environmental conditions. Sites are then classified based on biological similarity. Next, a multivariate
model relates environmental setting (elevation, watershed area, geology) to the biological classification -
this is used to estimate, or predict, the probabilities of sites belonging to biologically-defined groups and
the probabilities of capturing each taxon. The current RIVPACS model, RIVPACS Ilia (Wright 2000),
estimates two indexes for assessment - one based on the total number of expected taxa and a second
based on expected average tolerance of the taxa. For both indexes, the model generates a list of taxa
expected to occur under unstressed conditions, at greater than 50% probability for a particular assessment
site. This list is then used to estimate the site's expected average tolerance value, and the probabilities are
summed to generate the expected number of species. Both the number of predicted taxa that were
actually observed and the tolerance value actually observed are divided by the expected values to obtain
the final indexes. These indexes are compared against the model predictions to determine if the values
are significantly different from the reference condition. Index values close to 1.0 indicate the site is
similar to reference, and values less than 1.0 indicate deviation from reference.
Initially, the Environment Agency created four categories for the indexes - the scoring range below the
5th percentile of the index distribution of reference sites was divided into three equal categories, and the
range above the 5th percentile made up the fourth. These categories, or grades, correspond to tiers of a
BCG (Wright et a!. 1994, Helmsley-Flint 2000). Review and application of the grades by regional
biologists revealed that they did not discriminate between "good" and "very good" sites, or between
"poor" and "very poor" sites (Helmsley-Flint 2000). Through cycles of data analysis and discussions
with regional biologists, the Environment Agency was able to establish index thresholds for six grades,
ranging from "very good" to "bad" (Table 3-4). The grades do not represent equal intervals of the index
scores (Helmsley-Flint 2000). Although the British grades are determined solely by benthic
macroinvertebrates, there is a distinct similarity between the narrative descriptions of the grades and the
tiers of the BCG.
Assignment of a site to a grade is based on both the tolerance and total taxa indexes (Table 3-4). The
indexes are independently applicable, and the lower of the two index scores determines the site grade.
For example, if the total taxa index indicates "Good" but the tolerance index indicates "Fair", the site will
be rated "Fair." To achieve the status of "Very Good", a site must have at least 85% of the expected taxa
of an equivalent reference site and must have a tolerance index value (average score per taxon) as high as
the expected value from a reference site.
Through an iterative process, the British Environment Agency was able to develop scoring criteria for
existing indexes (RIVPACS N-Taxa and RIVPACS ASPT) that corresponded to regional biologists'
consensus on tiers of a biological condition gradient.
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TABLE 3-4. Definitions of six biological grades, developed by regional biologists of the Environment Agency in
England and Wales (Helmsley-Flint 2000).
Grade
Grade a
VERY
GOOD
Grade b
GOOD
Grade c
FAIRLY
GOOD
Grade d
FAIR
Grade e
POOR
Grade 1
BAD
Definition
The biology is similar to (or better than) that expected for an
average and unpolluted river of this size, type and location. There
is a high diversity of Families, usually with several species in each.
It is rare to find a dominance of any one Family.
The biology shows minor differences from Grade a and falls a little
short of that expected for an unpolluted river of this size, type and
location. There may be a small reduction in the number of Families
that are sensitive to pollution, and a moderate increase in the
number of individual creatures in the Families that tolerate pollution
(like worms and midges). This may indicate the first signs of
organic pollution.
The biology is worse than that expected for an unpolluted river of
this size, type and location. Many of the sensitive Families are
absent or the n umber of individual creatures is reduced, and in
many cases there is a marked rise in the numbers of individual
creatures in the Families that tolerate pollution.
The biology shows big differences from that expected for an
unpolluted river of this size, type and location. Sensitive Families
are scarce and contain only small numbers of individual creatures.
There may be a range of those Families that tolerate pollution and
some of these may have high numbers of individual animals.
The biology is restricted to animals that tolerate pollution, with
some Families dominant in terms of the numbers of individual
creatures. Sensitive Families will be rare or absent.
The biology is limited to a small number of very tolerant families,
often only worms, midge larvae, leeches, and the water hoglouse.
These may be present in very high numbers. Even these may be
missing if the pollution is toxic. In the very worst case there may
be no life present in the river.
1 RIVPACS Index
Scores
Tolerance
Index
(EQI ASPT)
>1.0
>0.90
>0.77
>0.65
a 0.50
<0.50
Taxa Index
(EQI N-taxa)
S 0.85
>0.70
£0.55
>0.45
>0.30
<0.30
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CASE EXAMPLE 3-6. MAINE'S USE OF LINEAR DISCRIMINANT MODELS
TO ASSESS AQUATIC LIFE USE TIERS
Maine identifies three aquatic life use classes for its streams - A A/A, B, and C - and also has a 4th
category of non-attainment (NA) for streams that do not meet minimum water quality criteria (Table 3-5).
The Maine Department of Environmental Protection (DEP) has developed a procedure using linear
discriminant models (LDMs) to classify samples. LDMs are multivariate predictive models that use
biological variables to determine whether a stream meets the biological criteria for classes A, B, or C, or
if it falls into the category of non-attainment (Davies et al. 1995).
TABLE 3-5. Maine water quality classification system for rivers and streams, with associated biological
standards (Davies et al. 1995).
Aquatic
Life Use
Class
AA
A
B
C
NA
Management
High quality water for recreation and
ecological interests. No discharges or
impoundments permitted.
High quality water with limited human
interference. Discharges restricted to
noncontact process water or highly
treated wastewater equal to or better
than the receiving water.
Impoundments allowed.
Good quality water. Discharge of well-
treated effluent with ample dilution
permitted.
Lowest water quality. Maintains the
interim goals of the Federal Clean Water
Act {fishable/swimmable). Discharge of
well-treated effluent permitted.
Biological Standard
Habitat natural and free flowing.
Aquatic life as naturally occurs.
Habitat natural. Aquatic life as
naturally occurs.
Habitat minimally impaired. Ambient
water quality sufficient to support life
stages of all indigenous aquatic
species. Only nondetrimental changes
in community composition allowed.
Ambient water quality sufficient to
support life stages of all indigenous
fish species. Change in community
composition may occur but structure
and function of the community must be
maintained.
Discriminant
Class
A
A and AA are
indistinguishable
because biota are
"as naturally
occurs."
B
C
Not attaining
Class C
To calibrate the LDMs, stream biologists from Maine DEP assigned an initial set of streams to the four
aquatic life categories: A, B, C, and NA. Assignment of samples was based on presence-absence of taxa,
abundance of taxa, richness, community structure, and ecological theory. Four linear discriminant models
were calibrated from the initial data set. The four models function as a two-step process to evaluate
individual sites:
Step 1: First stage model - Estimates the probability of a site's membership into each of the four
classes (4-way test)
Step 2: Second stage models - Develop more accurate membership probabilities. Each is a two-
way discriminant function, which perform better than multi-way models. There are three second
stage models that estimate the probabilities of membership in a given class(es) versus any lower
classes (Figure 3-9).
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ra*.
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First Stage Model
(4-way test)
A vs. Bvs. Cvs. NA
1
"C or Better" Model
(2-waytest)
A/B/C vs. NA
I
"B or Better" Model
(2-way test)
A/B vs. C/NA
"A" Model
(2-way test)
A vs. B/C/NA
' Aquatic life use attainment decisions are based on the three 2-way tests.
FIGURE 3-9. Series of four linear discriminant models.
The models use 31 quantitative measures of community structure, including the Hilsenhoff Biotic Index,
Generic Species Richness, EPT, and EP values to classify sites. In operational assessment, monitored test
sites are run through the two-step hierarchical models and assigned to one of the four categories based on
the probability results. Uncertainty is expressed for intermediate sites that fall between two categories.
The assessment becomes the basis for management action if a site is rated as NA, or if its assessed
category (B, C, or NA; the result of the LDM) is less than the site's assigned life use class (A, B, or C).
Thus, if a site was assigned life use class A, but assessment shows that it only meets life use class B or C
(model assessment was B or C), then management action may be required. If a site has improved, it
requires further evaluation as a candidate for reclassification to a higher class.
Maine's numeric biocriteria provide an expert system for determining attainment of aquatic life uses. The
LDMs provide an empirical model for expert judgment, which in turn is ultimately derived from years of
empirical observations, ecological theory, data analysis, and clearly stated aquatic life management goals.
They establish a direct relationship between the model's outcomes and management objectives (the
aquatic life use classes). Therefore, broad resource goals and objectives can be directly translated to
scientifically defensible, quantitative thresholds (Table 3-5). The relationship is immediately viable for
management and enforcement as long as the aquatic life use classes remain the same. If the classes are
redefined, a complete reassignment of streams and a review of the calibration procedure would be
necessary. Details of Maine's approach and statistical analysis procedures are in Shelton and Blocksom
(2004) and Davies et al. (unpublished manuscript).
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CHAPTER 4. THE XTAXIS: A GENERALIZED STRESSOR GRADIENT
The x-axis of the Biological Condition Gradient Model (BCG) illustrates how increasing levels of
stressors in aquatic ecosystems change biological condition. This chapter presents a conceptual model
that helps characterize stressor gradients by focusing on the progression from sources (changes in key
environmental processes) to stressors and ultimately to their effects on biotic condition (Figure 4-1). The
model also looks at the mechanisms through which these biotic components are affected. The stressor
gradient model can be used to organize data and information on watershed characteristics, hydrologic
modifications and stressors to thoroughly evaluate these relationships. This information will provide a
foundation for States and Tribes to use the BCG to address both current conditions and ecological
potential of their waterbodies, develop realistic restoration options for impaired waters, and communicate
this information to the public.
4.1 The scientific foundation for the stressor gradient
Stressors affect biological assemblages and ecosystem processes both directly and indirectly, including
altering metabolic pathways, energy availability and behavior of the organisms (Karr et al. 1986, Adams
1990, Poff et al. 1997). Historically, point source pollution and in-stream hydrological modifications
were the dominant alterations (see 4.2.1) to fresh waters. While these issues continue today, water quality
management now faces a wider variety of changes stemming from mining, forest harvest, agriculture,
urbanization, industry, and even recreation (Richter et al. 1997, Bryce et al. 1999). In addition, non-
contaminant related changes to aquatic ecosystem factors (see text box below) commonly impact
biological conditions (Figure 1-3) and can also influence other stressors (Karr and Dudley 1981, Karr et
al. 1986, Poff et al. 1997, Slivitzky 2001). Consideration of these factors and their interactions in water
quality management can lead to greater improvements to biological condition than a focus on
contaminants alone (Karr et al 1986).
The influence of each factor on biological 1,Chetnlcal factors {a;g./hak!iiess;r9Jtri6nla, toxic ;
condition in specific waterbodies can be difficult compounds)
to evaluate and quantify because each of these 2,PI0» regime gnchHj'ing the timing and ameuel of
factors reflect both indirect and direct forces. water in the channel; diversfens)
Flow regime, for example, affects biological 3-Bioiic factors {Co*npe8flon. prsdafion, dfee?ss,
condition and the other in-stream factors (e.g., invading species, etc.}
habitat structure, water quality) (Poff et al. 1997). ^.Energy source {photosynthesis, input* from land, e*?,j
Altered stream flows are associated with poor 5,tteb!fcrt structure (channel shape and features,
channel habitats, erosion, bank instability, and siltaSon, etc,} (from Km et aL me, see Ftgum t-3)
lower base flows (Poff et al. 1997). Species
distributions, abundances, and competitive interactions all rely on natural flow regimes (Poff and Allan
1995, Greenburg et a!. 1996, Reeves et al. 1996, Poff et al. 1997). Stream ecosystem structure and
function (Vannote et al. 1980) and the riverscape concept (Ward 1998, Fausch et al. 2002) integrate the
influences of all stressors. These individual and collective influences, represented by the BCG model's x-
axis - the Generalized Stressor Gradient (GSG) - drive the biological condition of streams and reveal the
need for a more holistic approach to stream monitoring and management. Because of the dynamic nature
of aquatic ecosystems, however, all of these factors are in a state of constant flux. The natural range of
conditions that native biota are adapted to may be narrow, wide, or seasonally variable, depending on the
climate, topography and ecoregion in which the system occurs. A simplified model, therefore, is needed
to help organize environmental factors and their relationships to stressors and biological responses.
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4.2 The conceptual model for a Generalized Stressor Gradient
Building upon the Karr conceptual model, the Generalized Stressor Axis model characterizes the
environmental processes and mechanisms that generate stressors which lead to biological responses
within waterbodies (Figure 4-1). An event or activity that alters the aquatic system is called a
disturbance. Ecosystems normally have some level of disturbances that characteristically occur within a
range of natural variability. Disturbances beyond this range, however, can exert pressure1 upon an
aquatic system by altering fundamental environmental processes and ultimately generating stressors.
Stressors are physical, chemical or biological factors that cause an adverse response from aquatic biota
(U.S. EPA 2000b). The term "pressure" conceptually and mechanistically links larger scale landscape
and hydrological disturbances with the ecological processes that are ultimately changed, leading to
pressure(s) being "felt" by the aquatic biota. Stressors are what link pressures to effects on biota, via
exposure mechanisms. A Stressor, therefore, can be traced back to its source or tracked forward to the
biological response, via a causal pathway (Figure 4-1). For example, destabilized stream banks due to
removal of riparian plants could be the source of excess fine sediment to a stream. Erosion by high flows
is the mechanism by which the excess fine sediments are generated, and the resulting in-stream siltation is
the Stressor, Smothering of bottom substrate habitat and organism gills by these fine sediments are two
mechanisms by which biota are exposed and adversely affected. Invertebrate mortality and fish
emigration could be some of the environmental outcomes or changes in biotic condition.
o Source/activity
1 n
C Mechanism
1 1
o
1-
c o
n p
.«• c
Unstable Banks
n
Erosion of Fine
Sediments
E S> •
Stressor
Mechanism
In-stream Siltation
Smothering of
larger substrate
and gills
Response
(Biological Condition)
Fish and Invertebrate
mortality and emigration
(Biological Condition)
FIGURE 4-1. Conceptual model illustrating the linkages between pressure and biological
condition. The specific stressor(s) and their intensity (the BCG x-axis) are created via
pressure(s) acting through specific mechanisms. An example for each step of the model is
also shown.
The effects of stressors on biota, however, depend on the magnitude, frequency, and duration of exposure
to the stressors. Developing a BCG for a given system characterizes the general relationship between its
combined stressors (the model's x-axis) and its overall biological condition (the y-axis). Multiple
stressors are usually present, and thus the Stressor x-axis of the BCG seeks to represent their cumulative
1 The use of the word pressure in this context has a well-established history in the European environmental
literature. Pressure is a term originally used by the European Union in its Water Framework Directive (OECD
1993). SOLEC (State of the Lakes Ecosystem Conference) also used the term pressure and defined it to be the
outcomes of human activities that have the potential to cause environmental effects (Shear et al. 2005).
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influence as a Generalized Stressor Gradient (GSG), much as the y-axis generalizes biological
condition.
4.2.1 How the model supports development of a GSG
The conceptual model provides a theoretical basis for relating single or multiple stressors to biotic
responses and condition. This concept is taken further in developing a generalized stressor gradient,
which, as the BCG's x-axis, is used in relating cumulative stressors to cumulative biotic effects. The
factors that drive biological condition (Figure 1-3) and how condition is affected by a range of stressor
intensities are used in defining Ihe gradient. Two example GSGs are provided below.
Tables 4-1A and 4-1B outline example scenarios for humid-temperate (Table 4-1A) and arid (Table 4-1B)
regions of the U.S. under differing levels of stressors. The high, medium and no/low stressor levels are
used only to describe relative differences in magnitude and are not formal categories for classifying
stressors. The five factors from Figure 1-3 were modified to six factors by separating toxics (e.g.,
copper, cadmium, mercury) from conventional chemical pollutants (e.g., nitrates, phosphorous).
When stressors are absent or low, natural or near-natural conditions of the aquatic ecosystem prevail.
However, as stressors increase, one or more of the six factors can deviate from natural conditions. In
humid temperate regions, for example, the loss of a watershed's forested landscape generally increases in-
stream stressors by affecting flow, soil erosion, water quality and aquatic habitat structure. In arid
regions, loss of riparian vegetation and cryptogamic crusts (a tightly bound mesh of lichen, algae and
lower plants that prevent erosion and provide a hospitable environment for germinating plants) has the
same kind of effects.
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4.3 How the BCG model and management actions are linked
Pressure, as used.in this document, applies to the environmental processes that can be altered by certain
activities and the mechanisms from those activities that generate stressors. Many landscape altering
activities can be quantified with such measures as population density, proportion of land devoted to
agriculture, total miles of roadway, or quantities of water used /released. These activities, however, may
or may not generate stressors. Actions can be taken that insulate stream processes from the
environmental pressure of certain activities, helping to maintain or restore the ecological potential of an
aquatic system.
Controls and Best Management Practices (BMPs) are management actions designed to mitigate or reduce
the levels and effects of stressors that adversely alter stream ecosystem function. BMPs can function in a
number of ways: they may reduce the stressors being generated by sources, reduce the exposure of biota
to stressors, or increase the resistance of an aquatic ecosystem to adverse changes. For example,
urbanization without controlling for the effects of added impervious surface is a pressure that often results
in reduced biological condition. The typical alteration of water flow (such as more frequent flooding due
to increased runoff) causes stressors. The mechanism for flow alteration is the creation of large expanses
of impervious surfaces, characteristic of most cities. Impervious surface speeds up the flow of water over
the land during rain events often resulting in more frequent and more intense floods. Constructing
retention ponds to store run-off water is a control measure that doesn't alter the pressure of urbanization,
but may reduce the stressors acting on the stream system. Mechanistic processes operate between
pressures and stressors, and between stressors and biological response (Figure 4-1), Understanding these
mechanisms, and how they operate, is the key to identifying the likely effect of a particular management
action and its likelihood to produce the desired response in biological condition. In the retention ponds
example above, the pressure (urbanization) and mechanism for stressor generation (excessive surface run-
off) still exist, but their influence on in-stream stressors has been neutralized by a management action, and
therefore the exposure mechanism influencing the biological community was reduced or eliminated.
The basis of the BCG model is that increased pressures can generate increased stressors, and in turn,
increased stressors are associated with decreasing biological condition (Figure 4-2A through D). Systems
that are minimally affected by stressors exhibit natural condition (Tables 4-1A and 4-IB). Human
activities may exert pressure and generate stressors on aquatic systems, resulting in changes from the
natural state. Typically, the stressors on aquatic systems increase as pressures increase (Figure 4-2A
dashed line). Effective management practices, however, can alter the effects of pressures and reduce
stressors. The solid, curved line in Figure 4-2B represents this theoretical relationship graphically. With
effective controls and/or BMPs, a given amount of pressure (vertical fine dashed arrow rising from the
pressure axis) results in a lower stressor level (where the dashed arrow intersects the stressor axis). Figure
4-2B illustrates the influence of effective management in changing the pressure/stressor relationship in
ways that will subsequently improve the biological condition.
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£}
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SI
Pressure
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Pressure
LOT Hkjh
FIGURE 4-2. Relationship between pressure, stressors, and biological response.
Figure 4-2C is a 90 degrees clockwise rotation of Figure 4-2A. Stressors (which are shown to increase in
response to increasing pressure in Figure 4-2A) are now on the x-axis. Biological condition is shown as
the response variable on the y-axis. This represents the biological condition-stressor relationship
developed in Chapter 1. In this example, the moderate-high effect of the stressors (dashed arrow rising
from the stressor axis) results in poor biological condition (the point where the dashed arrow intersects the
biological condition axis).
Figure 4-2D shows Figure 4-2B rotated 90 degrees clockwise. As in Figure 4-2C, stressors are on the x-
axis, and biological condition is shown as the response variable on the y-axis. The effect of low levels of
stressors (dashed arrow rising from the stressors axis in Figure 4-2D) results in near excellent biological
condition (where the dashed arrow intersects the biological condition axis). The pressure-stressor
relationship has been shaded out. But it reminds us how, together, pressure and management actions (i.e.,
permit limits, BMPs, channel restructuring) can determine stressor levels, and ultimately, the condition of
the biota. The specific effects of stressors on biological responses will depend on the type, magnitude,
duration, and frequency with which the stressor occurs. These stressor attributes are, in turn, a result of
the cumulative pressures exerted on the ecosystem and relevant management decisions to mitigate these
pressures.
Different types of disturbances can exert pressure on an ecosystem through altering fundamental
processes such as water flow, transport of materials, watershed/riparian structural dynamics, channel
structural dynamics and biological activities. For example, dams and impoundments alter flow, natural
biological activities and material transport by creating lake conditions in a stream environment, and
creating barriers to fish movements and migration. Sediment, nutrient and organic matter transport are all
DRAFT: Uxe of Biological Information to Better Define Designated Aquatic Life Uses in State and
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reduced downstream of impoundments and water quality attributes such as natural temperature
fluctuations and dissolved oxygen are often altered by dams. When severe enough, these alterations act as
stressors to the downstream community.
Tools can be developed that characterize the relationships among pressures, altered processes, the
stressors they generate, and the resulting biological responses. Information from pressure and stressor
indicators provides insight on how changes in these fundamental processes may be affecting the
biological condition of water resources (Table 4-2). Understanding how specific stressors are generated
and the influence of specific stressors on biological condition, provides the underpinnings for the BCG's
stressor axis. Further, it reveals potential opportunities for management actions to reduce stressors and
counteract the alteration of fundamental processes.
DRAFT: Use of Biological Information to Better Define Designated Aquatic Life Uses in State and 78
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4.3.1 Additional considerations for the stressor axis
The concepts of spatial and temporal scale are critical issues in adequately defining a stressor axis.
Stressors may be introduced through diffuse or point sources delivered from upstream in the channel or
watershed, or laterally from riparian, floodplain or upland sources. Pollutants can also be delivered
through atmospheric sources from above, or below from groundwater sources. Activities in the watershed
or along the waterbody corridor will influence the connectivity and integrity of the water resource.
Stressors are expressed over temporal and spatial scales ranging from a one-time, localized event to
chronic exposures occurring continuously over vast landscapes. Pressures, Stressors, and responses
operate at different spatial and temporal scales (Figure 4-3). These are not independent of one another in
either space or time; therefore, consideration of multiple pressures is essential. An additional
consideration is that any given pressure creates multiple Stressors, which in turn affect biological
condition. The steady accumulation of small pressures in watersheds results in "cumulative impacts,"
which present added challenges for characterizing, evaluating, and managing Stressors.
lOOyt
lOyr
year
month
days
Water Regulation
and Diversions""-*
Microbial
production
1m 1km 100km 1000km
Spatial Scale
10,000km
100.000km
FIGURE 4-3. Perspective of scale for pressure-stressor-response variables (modified from Richards,
C. and L.B. Johnson. 1998. Landscape perspectives on ecological risk assessment. In Risk Assessment:
Logic and Measurement, M.C. Newman and C. Strojan (eds.)- Ann Arbor Press.).
The complexity of the relationships between biological condition and Stressors at various spatial and
temporal scales, underscores the importance of using sound information to identify and link these
Stressors back to the pressures that cause them. To a large degree, this is the critical step in gaining
stakeholder support for restoration and protection actions as well as for changes in activities or behaviors.
As discussed earlier, fine sediment is commonly identified as a stressor across the United States because
of the smothering of important habitat. Identifying the relative contributions of various sources of these
sediments is more challenging (e.g., bank erosion, upland erosion, spatial sources), but also critical to
remediation efforts.
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4.4 How a GSG can be developed and calibrated
Developing and calibrating a stressor gradient must be based on appropriately classifying aquatic
resources and establishing reference conditions or other scientifically defensible approaches.
Classification (e.g., biogeographic regions, basins, biological considerations) is a critical first step so that
the temporal and spatial scales of the dominant stressor categories and sources can be addressed (Herlihy
et al. in press, VanSickle and Hughes 2000, McCormick et al. 2000, Waite et al. 2000). Of equal
importance is establishing the appropriate reference condition for a particular area (Hughes 1985,1994;
Hughes et al. 1986; Moss et al. 1987; Stoddard et al. in press), because that is the benchmark against
which areas to be evaluated will be compared (as discussed in B CG Section 3.1.1).
Like the biological condition axis, the stressor axis is anchored in the natural, or undisturbed or minimally
disturbed, condition (i.e., Tier 1 BCG). However, reference may represent minimally-disturbed (i.e.,
nearly natural) or least-disturbed (i.e., best available) conditions depending on the level of disturbance
that exists across the geographic area of interest (Stoddard et al. in press, Hughes 1994). Linking regional
factors, pressures, and stressors with biological condition into a BCG will assist States and Tribes in
identifying levels of disturbance and the primary drivers of biological condition in their watersheds. If no
undisturbed or minimally disturbed reference sites exist in a region, a stressor axis provides a means for
determining the best condition or regional candidates to act as benchmarks for comparison, i.e., "least
disturbed" or "best available conditions." The stressor axis concept will enable managers to place the
status of their stream ecosystems into a regional context and prioritize actions. The reference condition
approach, which describes the potential biological condition of trie region's waters, provides a framework
to set appropriate restoration endpoints for that resource and region.
The next step involves quantification of in-stream stressors, riparian condition, landscape characteristics
and riverscape alterations, as well as point source discharges and other localized pressures. Calibrating
stressors along natural gradients (waterbody size, catchment area, stream power, elevation, latitude, and
geology) can improve ability to detect pressure effects by removing the confounding effects of stressor
gradients with natural gradients (Fausch et al. 1984, Hughes et al. 2004, Kaufmann and Hughes in press).
There have been many efforts to characterize pressures and incorporate quantitative information into
environmental assessment programs (Table 4-3). Riparian condition has been widely recognized as
affecting the physical habitat and biological condition of streams (Naiman and Decamps 1990, Fitzpatrick
et al. 2001, Lammert and Allan 1999, and Lattin et al. 2004). In some circumstances, watershed
condition was more important (Roth et al. 1996, Snyder et al. 2003). Wilhelm et al. (unpublished
manuscript) used both catchment (i.e., watershed) and riparian disturbance for the development of their
non-wadeable habitat index for streams in Michigan. Wang and others (in press) found that fish
assemblages were most influenced by local environmental factors in largely undisturbed catchments.
However, as the level of catchment disturbance increased, the importance of catchment-scale factors
increased and that of local-scale factors decreased. These studies indicate how important regional and
local factors are for determining the relationship among sources, stressors, and biological condition and
the most appropriate scale for addressing these relationships.
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TABLE 4-3. Percent variance in biological response (R2) explained by catchment and riparian land use, and
percent land use producing poor IBI scores (modified from Hughes et al. unpublished manuscript).
Authors
Biyce & Hughes (2002)
Fitzpatrick etal. (2001)
Hughes et al. (unpublished)
Kair&Chu(2000)
Klauda etal. (1998)
Lammert & Allan (1999)
Lattinetal. (2004)
Leonard & Orth (1986)
McCormick et al. (2001)
Mebaneetal.(2003)
Morley&Karr(2002)
Roth etal. (1996)
Snyder et al. (in press)
Steedrran (1988)
Wang et al. (1997)
Wang etal. (2000)
Wang etal. (2001)
YnHcrptal CMMm
Response Variable
Fish IBI
Fish IBI
Diatom IBI
Benthos IB 1
Fish IBI
Diatom IBI
Benthos IBI
Fish IBI
Benthos IBI
Fish IBI
Fish IBI
Benthos IBI
Fish IBI
Fish IBI
Fish IBI
Fish IBI
Fish IBI
Benthos IBI
Fish IBI
Fish IBI
Fish IBI
Fish IBI .
Fish IBI
.FishlBl
Rish IR1
R2 Catchment
0.40
0.35
0.29-0.36
0.48-0.67
0,31
0.16
ns
0.42
0.25
0.68
0.01
ns
ns
0.60
0.05-.08
0.45-0.56
0.56
0.53
0.50
0.16-0.64
QM
0.48
0.34
0.04-0.31
1141
R2 Riparian
0.58
ns
ns
0.38
0.22-0.28
ns
0.20-0.46
0.00-0.82
0.02-0.38
0.02-0.17 -
0.67
_.
0.26-0.34
N
13
16
16
16
25
25
25
104
66
61
18
18
25
44
313
41
.30
34
21
20
10
134
47
47
mi
Location & % Land Use for
"Poor" rating
OR/ 50% urban
Appalachia/ 15% urban
App./ declines w/ ag.
App./ 50% ag., 20% mined
Wl/ 70% ag.
W!/ag.
Wl/ag.
OR/ rd. density > 1.9 km/km2
WA/ 40% impervious
MD/ 60% urban
Ml/ declines w/ riparian ag.
Ml/ag.
OR/20% network riparian ag.
WV/rd. density > 1.7 km/krfl2
App./ declines as deforested
OR/ 25% deforested
ID/ 15% irrigated ag.
WA/ 45% impervious
-Ml/80%ag.
WV/ 15% urban
ONT/ 95% ag., 60% urban
WI/ declines w/ deforesting
WI/ 5% impervious
Wl/ 5% impervious
f»H/ 1fl<& nrtian
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Once the suite of stressors and pressures are measured or quantified for a given group of waterbodies, the
next step is to determine if more than one stressor gradient exists and how they are related (i.e., are there
several gradients based on different pressures, activities or landscapes?). Dealing with these multiple
stressors and pressures can be complicated. A direct multiple correlation approach was taken by EMAP in
the mid-Appalachian Highlands where poor quality streams were most often associated with alien fish,
channel sedimentation, and riparian habitat alteration out of several hundred possible stressors (U.S. EPA
2000a). Kaufmann and Hughes (in press) used correlation and multiple linear regression analyses to
determine that low stream IB I values were associated with excess streambed fines, bed instability, higher
water temperature, higher dissolved nutrient concentrations, and lack of deep pools and cover complexity.
These stressors were most strongly associated with riparian'disturbance and road density. Effects were
more pronounced in streams draining credible sedimentary bedrock than in those draining more resistant
volcanic terrain. States and Tribes could use similar multivariate approaches for identifying the
stressor(s) most associated with measures of biological condition in their regions
A method employed in the Great Lakes Environmental Indicators (GLEI) project to characterize
disturbance to the U.S. Great Lakes coastal region, used principle components analysis to reduce over 200
GIS variables into a single gradient (Danz et al. 2005). The GLEI approach individually considered six
different kinds of disturbance: agriculture, atmospheric deposition, land cover, human population, point
sources, and shoreline alteration. A watershed-based approach was used to reflect the premise that the
environmental effects of these activities in coastal watersheds can influence environmental conditions in
(downstream) coastal ecosystems. The first principle component from their analysis explained 73% of
the variance in the agriculture variables and was interpreted as an overall gradient in stressors across the
basin (Figure 4-4). Environmental responses such as water quality, fish assemblage metrics, and bird
abundances were strongly correlated with this stressor gradient.
FIGURE 4-4. The first principal component of the agricultural
variables for the U.S. Great Lakes basin. Darker shading indicates
greater amounts of agriculture.
When multiple sources and stressors interacted to form the stressor gradient for a given watershed, GLEI
found it desirable to develop a visual display of PCA axis 1 that subsumes the multiple stressors by
portraying a single disturbance gradient. While the pressure-stressor model could eventually be
developed and visualized as a single gradient from low to high levels of stressors (Figure 4-4), different
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individual and combinations of stressors are expected to dominate in different regions. Furthermore, the
depiction of individual categories of stress provides important information about potential mechanisms
affecting the state of the system. The GLEI researchers created a flow diagram (Figure 4-5) that details
their steps for quantifying a stressor gradient (modified from Danz et al. 2005).
Define sampling units
Compile & summarize
environmental variables
Evaluate & categorize
variables
Apply regional
classification system
Remove redundancy
(PCA is one method)
Compute overall stressor
gradient using PCA axes from
each stressor category
i >
Organize
Data
Generate
Stressor
Gradient
Map disturbance gradient
using color-coded scheme
FIGURE 4-5. Flow diagram detailing the steps used by GLEI researchers in
quantifying their stressor gradient (modified from Danz et al. 2005).
Whether using a single or multiple stressor gradient, all this information needs to be assembled to develop
a model that integrates the components of pressures and establishes a baseline for using stressors to
interpret biological responses. Relationship models that describe the associations among stressors, the
processes that generate them, and biological conditions (responses) need to be developed. If possible, the
extent of management actions (e.g., controls/BMPs) needs to be identified and ways to characterize these
actions need to be considered (although this is an area of active research). The degree of deviation from
natural conditions and the types of stressors present will affect restoration potential and therefore BMP
effectiveness. Examples of tools that are currently available for characterizing a suite of pressures are:
Analytical Tools Interface for Landscape Assessments (ATtiLA), National Land Cover Database
(NLCD), and air photos.
Calibrating a stressor axis depends on the scale of the question to be addressed. The stressor axis should
be developed independently of the biological information to avoid circularity when developing the BCG.
In the development of their non-wadeable habitat index (NWHI), Wilhelm et al. (unpublished manuscript)
used catchment and riparian disturbance gradients (CDG and RDG respectively) to select and weight
habitat metrics at both watershed and reach scales. While the final NWHI was strongly correlated to
disturbance measures and included habitat metrics that supported this relationship, a true test of the
relationship between their stream response measure and disturbance measures would require a new,
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independent data set. The GLEI researchers used a wide range of publicly available data sets to quantify
five different classes of disturbances. Their stressor axis is currently being calibrated. Stressor
development and calibration involves using sufficient information to characterize relative positions along
the axis and, in particular, being able to anchor the upper end (i,e,, low or no stressors) and the lower end
(i.e., high level of stressors) (Whittier et al. in press). This can be accomplished via a combination of
public consensus, best professional judgment, and empirical approaches (e.g., Areas Of Concern (AOQ,
Great Lakes Environmental Indicators (GLEI) approach, and index development) (Whittier et al. in press,
Danz et al. 2005, U.S. EPA 2000b).
4.5 Key points from Chapter 4
1. The stressor gradient provides a framework for organizing and interpreting information about
watershed characteristics and using those characteristics to predict aquatic ecosystem biological
responses. It helps us understand the observed biological conditions and the stressors related to
those conditions. It can help identify the predominant stressors affecting the aquatic biota and
develop effective management actions to mitigate their effects.
2. Understanding how specific stressors are generated and how they affect biotic condition provides
the underpinnings for the BCG's stressor axis and ultimately the basis for interpreting the
influence of stressors on biological condition.
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Incorporating Tiered Aquatic Life Uses Into
State and Tribal WQS: Case Examples
Tteted aqfcatfc /Ife uses #»
descriptive narratives of
supported wfth ntffiwfc
As a key component of State and Tribal water quality standards,
designated uses define the goals for a waterbody, determine the criteria to
protect it, guide management outputs, and, ultimately, environmental
outcomes. Aquatic life tiers couple descriptive narratives (tiered uses)
with supporting numeric criteria. The specificity of designated uses
greatly influences the level of precision at which a water quality
management program operates. Incorporating tiered aquatic life uses into
water quality standards can have a positive effect on water quality
management outcomes. States that have made this transition have
demonstrated that tiered aquatic life uses promote both the development of more appropriate aquatic life
use goals and biological criteria to measure attainment of those goals. The data and experience developed
from tiered uses supported by comprehensive monitoring have multiple uses in the water quality based
approach to pollution control (Figure 5-1).
The preceding chapters of this document
describe ways of better characterizing and
defining the biological and physical condition of
waterbodies and their aquatic life uses. These
next two chapters discuss the underlying
principles and processes involved in developing
tiered aquatic life uses and applying them in
water quality management based on "lessons
learned" from State experiences. Maine and
Ohio are two States that have adopted tiered
aquatic life uses in their WQS and have
implemented them through systematic
monitoring and assessment. The experiences of
Maine and Ohio provide a sequence of steps, or
milestones, that can serve as a template for other
States to follow. These milestones are:
1. Establish conceptual foundation
2. Merge scientific and policy foundations
Chemical^
Physical
Biological
Tiered Aquatic Life
Vs&tt&lp better
FIGURE 5-1. U.S. EPA Water Quality Based Approach to
Pollution Control based on Chapter 7, Water Quality
Standards Handbook.
3. Establish monitoring program
4. Develop and validate quantitative thresholds
5. Apply tiered uses in water quality management
Both States developed tiered aquatic life uses for similar reasons: 1) to incorporate ecologically relevant
outcomes in goal setting; 2) to guide cost-effective, defensible management decisions; 3) to measure
incremental progress in meeting management goals; and 4) to merge the design and practice of
monitoring and assessment with the development and implementation of WQS. Chapter 5 captures the
"lessons learned" by Maine and Ohio in their development of tiered uses (Milestones 1 - 4) and Chapter 6
presents case examples about how each State has benefited from this approach (Milestone 5).
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(Appendixes C, D, and E). Karr et al. (1986) recommended six key elements in the development of
bioassessment tools and biocriteria: '•'•..
I) measure(s) must be biological
2) measure(s) should be interpretable at different trophic levels and provide a connection to other
organisms and assemblages not included in the biological assessment process
3) measure(s) must be sensitive to the environmental conditions being assessed
4) response range must be suitable for the intended application, i.e., encompassing the full range of
theBCG " ' ' ' '
. 5) measure(s) must be reproducible and precise within acceptable limits for data collected over
space and through time ^
6) variability of the measure(s).must be low enough to detect changes along the entirety of the BCG
Representative indicator assemblages are used to measure attainment of the biocriteria as part of the
derivation process. As such, biocriteria represent the measurable ecological properties of a tiered aquatic
life use.
5.2 Key milestones for developing tiered aquatic life uses
The Maine and Ohio case histories (Appendixes A and B) reveal conceptually consistent, but technically
different ways of developing tiered uses including numeric biological criteria and a comprehensive
monitoring and assessment program. However, the process followed by each demonstrates common tasks
and milestones that States and Tribes can use as a template for developing tiered uses. These milestones
and tasks are illustrated in Table 5-1 and consist of five major steps:
Milestone I. Establish Conceptual Foundation (Maine and Ohio Case Histories, part I)
• Establish an interdisciplinary, collaborative approach to the development of tiered uses .
(ecological, technical, and legal)
• Identify and acquire appropriate staff and management expertise
Milestone 2. Merge Scientific & Policy Foundations (Maine and Ohio Case Histories, part II)
.• . Link management objectives with technical program
• Evaluate for consistency with existing water quality standards framework
• Draft or refine narrative aquatic life use descriptions
Milestone 3. Establish Monitoring Program (Maine and Ohio Case Histories, part III)
• •- Developimethods and monitoring design, establish reference conditions, build baseline
database and database management system
• Logistics: staffing, facilities, and equipment
Milestone 4. Develop/Validate Quantitative Thresholds (Maine and Ohio Case.Histories, part IV)
* Program implementation: develop biocriteria and water quality program support
(initiating the process of using TALUs and biological assessments to support water
quality management tasks)
• Validate the accuracy of ecological expectations with empirical data .
• Program maintenance: refine biocriteria and maintain water quality program support
(maintaining the process of using TALUs and biological assessments including the
continuous evaluation of tools, criteria, and processes based on what is being learned via
a systematic approach to monitoring and assessment; includes expansion to other aquatic
ecotypes) .-
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Milestone 5. Application in Water Quality Management (Chapter 6; Maine Case History, part IV)
• Apply biocriteria to support WQS
• Integrate tiered biocriteria with other types of chemical and physical criteria
Milestones 1-4 describe the key tasks in the development of tiered aquatic life uses. Milestone 5
addresses the application of tiered uses in water quality management. Ideally, the milestones can be
accomplished sequentially, each laying the appropriate scientific or policy foundation for the next step.
However, many States will have already accomplished some or even a majority of the tasks, particularly
under Milestone 3 (Establish Monitoring Program). Some may also use biological assessments for
support functions beyond status assessments, but perhaps lack the formal tiered use framework in their
WQS or have remaining technical development issues. Maine and Ohio found that capacity for
conducting biological assessments is an equally important issue and generally included 5-10% of State
water quality management program resources, they found that this level of funding should make
available sufficient resources to carry out the development, maintenance, and assessment tasks on a
statewide basis.
Table 5-1 and Figure 5-2 include many of the major tasks in the development of a program and they can
serve as a "road map" to determine where a particular State program stands regarding the goal of
developing and applying tiered uses in its water management programs. Figure 5-2 can also be used as a
guide for identifying, prioritizing, and organizing outstanding and remaining tasks. Furthermore, there is
a transition under Milestone 4 from an emphasis on development of a tiered aquatic life use approach to
program maintenance. Program maintenance includes ongoing evaluation and "fine tuning" of the
bioassessment tools and criteria as the program matures. It also includes the further development and
refinement of assessment and management tools and criteria as data, experience, and knowledge are
gained via systematic monitoring and assessment. Maine and Ohio initially developed tiered uses and
biocriteria for streams and wadeable rivers and currently either have developed or are evaluating tiered
uses and biocriteria for other waterbody types (e.g. nonwadeable rivers, wetlands, lakes and estuaries).
Program maintenance can also include the development of tiered uses for these other types of
waterbodies. Evaluating whether there is a need to change existing use designations for specific
waterbodies is another important task. This is accomplished during the triennial review process with
decisions based directly on outcomes from systematic watershed monitoring and assessment and historic
data.
Milestones 1-4 and Figure 5-2 reflect a sequence of strategic steps in the development of tiered aquatic
life uses. A functional and effective program will emerge if essential theoretical, technical, and legal
elements are addressed and fully integrated throughout the development process. Table 5-1 shows typical
tasks associated with each founding element and the type of professional expertise required to accomplish
them. One of the key "lessons learned" in Maine and Ohio is that problems arise when technical and
management activities are done in isolation from each other. A collaborative and interdisciplinary
approach that blends technical and management activities yields better decisions at all levels.
The triennial review process is readily adaptable to developing and then refining uses on a watershed
basis, and to making needed adjustments to bioassessment tools and criteria. As the program develops
and matures over time, and as resources become available, application of a tiered use framework can
advance from condition assessment to formal incorporation into water quality standards.
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TABLE 5-1. Expertise and tasks for key TALU milestones.
Conceptual Foundations
Technical Foundations
Policy/Legal Foundations
Professional Expertise Required
^ Senior professional biologists
^ Regional ecological experts
Milestones 1, 2 and 4
S Professional biologists
•/ Taxonomists
•/ Field support staff
•/ Statistician
S Database managers
Milestones 3 and 4
Initial concept formulation:
•/ S enior professional biologists
•S WQS managers
Later stages:
All of me above plus . . .
S Senior management
•S State legal counsel
S Legislature or WQS board
S Stakeholders
Milestones 1, 2 and 4 ,
Essential Elements
* Literature review of stress
ecology studies for locale
• Develop regional BCG model
• Determine expected biological
assemblage response to typical
stressor scenarios;
• . Identify ecological attributes
. necessary to maintain a
functioning ecosystem (to help
establish goals for protection or
restoration)
• Clarify classification issues
(confounding natural gradients of
. locale);
• ' Define reference conditions
• Determine monitoring approach
and strategy
• Exploratory data analyses to
validate/refine BCG model
• Best available, best tested metrics
to assess status of ecological
attributes of interest
• Set thresholds that correspond to
• BCG tiers, that protect essential
ecological attributes
• Determine management objectives;
• Identify priority aquatic resources
• Cross-walk BCG to WQS context- (how
good a fit is provisional BCG/TALU
conceptual model to existing use classes
and WQ criteria)
• Seek early review of the legal standing of
any proposed changes to WQS- strengthen
and clarify language
• Account for public values and economic
constraints/realities
Based on the commonalities between Maine and Ohio's experiences, several important "lessons learned"
were identified for States and Tribes that are considering developing tiered aquatic life uses.
• Interdisciplinary approach to development: Development of tiered aquatic life uses is most
successful when active cooperation and close working relationships exist among the individuals
charged with technical/scientific development and oversight of water quality standards.
• Plan enough to be certain of success... and use adaptive management approach: Clear
knowledge of scientific and legal principles should guide every step of planning and
development. An adaptive management approach is beneficial throughout the development
process because new technical information and management understanding are gained as part of
the process. An adaptive management approach incorporates needed flexibility into a program by
building on the new knowledge and insights.
• "Proper" sequencing versus logical decisions: The exact sequence of developmental events is
not as critical as the necessity of following a plan that is logical for a particular State or Tribe,
builds on current program strengths and reflects rigorous adherence to scientifically and legally
sound foundations.
• Graduated application to support water quality management decisions: Some level of
condition assessment and regulatory decision-making (application in water management) can
happen as soon as a credible monitoring program is established and linked to narrative TALU
goal statements.
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T«( wewt* aotJ (tevetop is
ftWfptte FaelHtfss ft Eqpipnenf
ConsKfer spatial Sifatiifeafion
issues
««af QuaHty Pifti^
3 8e«te r Uevetap toStes fteveiopwftol
'Analyie tort rasuBs ~ c.cios,i fa±i!33m±n( fasueft
shsuW t* toS
Continuously evaluate program - develop and Implement refinements
Quality Improvement Process
Evaluate effectiveness of Initial decisions - make needed adjustments
FIGURE 5-2. TALU and biocriteria program development tasks: Timeline and key milestones. A process of
sequential tasks and milestones that States can follow in the development and implementation of tiered
aquatic life uses and attendant biological criteria.
5.3 Using TALUs to support water quality management
The adoption of tiered uses should positively influence water quality management outputs and outcomes.
Tiered uses in State and Tribal water quality standards, coupled with a systematic and comprehensive
monitoring and assessment program, can provide an essential link among a wide variety of water quality
management programs. In Maine and Ohio, the end result have supported baseline CWA management
programs such as NPDES permitting, construction grants, and, more recently, the revolving loan
program, basin planning (including TMDLs, listings of impaired waters, development of restoration
plans), and nonpoint source assessment. The comprehensive support of water quality management that
emerges from systematic monitoring and tiered aquatic life uses in Maine and Ohio is made'possible by
following the milestones shown in Table 5-1 and Figure 5-2 to establish and develop a program.
Monitoring supports day-to-day water quality management needs and can take place at multiple scales
including a statewide, regional, watershed, or site-specific basis.
A sustained monitoring and assessment program naturally incorporates strategic functions and results in
improved criteria, tools, policies, awareness, and legislation. The aggregated database comprises the
experience gained by conducting systematic assessments and includes the regular resampling of reference
sites and long-term monitoring of reference condition. The database allows comprehensive analysis and
interpretation of spatial and temporal trends and tracking the effectiveness of different water quality
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management programs. The overall program thereby fosters continuous improvement through adaptive
management because the relevant information and the interpretation of that information is made available
to managers.
As an example, full documentation of the results and benefits of improvements in wastewater treatment
on multiple waterbodies in both Ohio and Maine would not have been possible without a comprehensive
biological monitoring network and tiered uses to put the results into a communication and management
context (See Case Example 6-4. Long-term Monitoring and Use Re-establishment in Maine).
Furthermore, tiered uses allowed the two States to secure and retain the gains made by upgrading some of
the affected rivers to higher tiers, a development that had not been anticipated before the wastewater
treatment was improved. These examples also validated the process of setting TALU-based WQS and
using them to develop regulatory requirements. The outcomes allayed many of the original uncertainties
about the cost-effectiveness of water quality based permitting and gave regulatory programs the
confidence to implement new requirements. This was critical in Ohio where the virtues of municipal
wastewater treatment more stringent than secondary treatment were widely debated and doubted in the
early 1980s. Advanced treatment (also known as best available demonstrated control technology or
BADCT) is now widely supported because not only did it work as a treatment technology, but it delivered
the end outcome of improved biological condition.
The comprehensive, long-term programs in Ohio and Maine have demonstrated their value by improving
prioritization of management actions and enabling more effective targeting of resources. Chapter 6
summarizes several case examples of how biological monitoring and tiered uses contribute to many
different aspects of the water quality management cycle (Figure 5-1).
5.4 Key points from Chapter 5
States that have successfully implemented a TALU approach have found that:
1. The specificity of designated uses greatly influences the level of precision at which a water
quality management program operates. Incorporating more refined, or tiered, aquatic life uses
into water quality standards can have a positive effect on water quality management outcomes.
States that have made this transition have demonstrated that tiered aquatic life uses promote both
the development of more appropriate aquatic life use goals and biological criteria to measure
attainment of those goals.
2. Tiered uses in State and Tribal water quality standards, coupled with a systematic and
comprehensive monitoring and assessment program, can provide comprehensive support to water
quality management programs. In Maine and Ohio, the end result supports baseline CWA
management programs such as NPDES permitting, construction grants, and, more recently, the
revolving loan program, basin planning (including TMDLs, listings of impaired waters,
development of restoration plans), and nonpoint source assessment.
3. Though based on different technical approaches, their development of tiered aquatic life uses
followed common tasks and milestones. Development of tiered uses has been most successful
when there was early and consistent collaboration among their monitoring, criteria, and standards
programs.
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CHAPTER 6. How HAVE STATES AND TRIBES USED TALUs IN WATER
QUALITY STANDARDS AND MANAGEMENT?
Tiered aquatic life uses supported by systematic assessments can provide the information needed for
water quality management at watershed, regional, and statewide scales. A comprehensive monitoring and
assessment program is a critical aspect of implementation of tiered aquatic life uses. The same data and
information that provide baseline status assessments also address watershed-specific management needs
such as the appropriate designation of individual waterbodies, TMDL development, and NPDES permits.
This chapter presents several case examples in Maine and Ohio of how tiered uses and monitoring
contribute to all aspects of the water quality based approach to pollution control (Figure 5-1). These
include setting criteria and standards; problem identification and establishing priorities (stressor
identification); defining and allocating control responsibilities (source identification); determining source
controls or BMPs (TMDLs, UAAs, WLAs); and enforcement and compliance (NPDES permits and other
compliance agreements). The following are case examples of how TALUs, coupled with systematic
monitoring and assessment, have and can be used to support key water quality management programs and
functions. These examples further exemplify what can be accomplished by following the developmental
process described in Chapter 5. Accompanying each case example is a diagram of U.S. EPA's Water
Quality Management Cycle (Figure 5-1) with the key component for that particular example shaded.
Most of the following examples were accomplished during the Program Maintenance phase of the TALU
development milestones (Figure 5-2) and demonstrate what can be produced as the bioassessment
program matures; however, some of the initial assessments can be accomplished during the Program
Implementation phase.
CASE EXAMPLE 6-1. REFINING WATER QUALITY CRITERIA IN OHIO
Chamlealx,
Physical
Biological
Ohio EPA developed empirical associations between aquatic
life and ambient stressor levels for parameters such as dissolved
oxygen from its monitoring program data beginning in the late
1970s. The known prevalence of organic enrichment from
point sources and intensive watershed surveys identified
dissolved oxygen (D.O.) as a major stressor limiting aquatic life
throughout the 1980s (Ohio EPA 1988, 2000).
When the Exceptional Warmwater Habitat (EWH) aquatic life
use was established in 1978, Ohio also established tiered
dissolved oxygen criteria to protect "highly sensitive aquatic
organisms; growth and reproduction of recreationally and commercially important species; [and]
maintenance of populations of imperiled species" (Ohio EPA 1996). This was in contrast to the goal for
the Warmwater Habitat (WWH) use, which was the "maintenance of typically representative warmwater
aquatic organisms and recreationally important species" (Ohio EPA 1996). The original single criteria for
EWH streams of 6 mg/1 was largely based on pertinent literature of the time, best professional judgment .
using the knowledge that these streams supported populations of very sensitive aquatic species, and that
the D.O. criteria should be more stringent than the WWH criterion (5 mg/1 daily average, 4 mg/1
minimum).
Since the original adoption of the EWH use and associated tiered D.O. criteria, analyses of ambient
biological and chemical data suggested that the 6 mg/1 minimum criterion was over-protective for these
waters. Both statewide and reach specific data were used to document streams with dissolved oxygen
concentrations below 6 mg/1 (but typically above 5 mg/1) that fully attained the EWH aquatic life use as
measured by the numeric biocriteria. These results were used to justify a two-number criterion of 6 mg/l
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average, 5 mg/1 minimum for the EWH use (Ohio EPA 1996). Two examples of these data include the
stressor-response relationship between grab sample D.O. data (Figure 6-1) and continuous D.O. data
(Figure 6-2) and the IBI in the E. Com Belt Plains (ECBP) and Huron/Erie Lake Plain (HELP) ecoregions
of Ohio. Both graphs show an expected gradient of response between D.O. and IBI scores and show that
minimum dissolved oxygen values between 5 and 6 mg/1 were commonly associated with IBI scores in
the EWH range.
Figure 6-1 illustrates a relationship that is commonly observed between stressors and biological measures
where multiple stressors are prevalent On Figure 6-1, to the left of the dashed line at 5.0 mg/1 (grab
samples), numerous D.O. values are found associated with low IBI scores, but very few at IBI scores
above 50 (EWH). If D.O. is >5.0 mg/1, IBI scores are much more likely to attain WWH (>40) and EWH
(>50). Figure 6-2 shows continuous D.O. data vs. IBI ranges that correspond to quality tiers ranging from
exceptional to very poor. This also supports a similar conclusion as Figure 6-1, but captures the full range
of D.O. values that occur over a 24-hour period, especially the early morning hours when the diel cycle
yields the lowest values.
60
50
40
30
20
10
Data-1994-2001
ECBP & HELP Ecoregions
._
fll «#• * »M'WaM'
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CASE EXAMPLE 6-2. DEVELOPMENT OF MORE PRECISE TARGETS FOR RESTORATION IN OHIO
Physical
^ Biologic*!
Diflro & Allocate Control
RnponsbUltlis
Nutrients have been identified as a major stressor to aquatic life
across the U.S. (U.S. EPA 2002b). Nutrients are not directly
toxic under most conditions, but rather exert their influence on
higher organism groups via interactions within energy pathways
and by influencing D.O. dynamics within streams and rivers.
Ohio EPA described biological gradients of response to nutrient
concentrations in streams and rivers (Ohio EPA 1999a). This
was accomplished by linking the primary nutrients (nitrate, total
phosphorus) and other parameters to the biocriteria (IBI, ICI,
etc,) on a statewide, ecoregion, and stream/river size basis. Thus
ranges of these parameters consistent with attainment of the
tiered aquatic life uses were accomplished (Ohio EPA 1999a;
Table 6-1). While the values in Table 6-1 are not explicit water quality criteria, they are used as TMDL
targets given the direct linkage they have with aquatic life use attainment. In addition to ambient fish and
invertebrate data, ambient chemical data, and stream habitat data, Ohio is currently collecting information
on chlorophyll and algal assemblages to improve understanding of the mechanisms of nutrient impact on
aquatic life (Bob Miltner, Ohio EPA, personnel communication). This work should result in refined
targets that can be used to determine which restoration activities should be most effective at restoring
aquatic life. The identification of nutrient targets for each aquatic life use tier provides an appropriate and
achievable level of protection for specific waterbodies. This application provides restoration targets for
TMDLs that, if achieved, should result in full attainment of aquatic life uses.
TABLE 6-1. Statewide total phosphorus targets.(mg/L) for Ohio rivers and streams.
Watershed Size
Headwaters (drainage area <20 mi2)
Wadeable rivers (20 mi 2 1,000 mi
Aquatic Life Use
EWH
0.05
0.05
0.10
0.15
WWH
1 0.08
0.10
0.17
0.30
MWH
0.34
0.28
0.25
0.32
EWH =Exceptional Warmwater Habitat; WWH =Warmwater Habitat; MWH =Modified Warmwater Habitat
As for nutrients, Ohio does not have explicit habitat and sediment criteria in the WQS. However, targets
for habitat and sedimentation outcomes were developed by demonstrating a relationship between specific
good quality and poor quality attributes and their ratios. Unlike water quality parameters, single numeric
criteria for habitat and sedimentation do not exist and are inappropriate because 1) there are complexities
in identifying expected values or ranges of values for specific attributes, 2) the resultant effects on the
aquatic biota are explained by aggregations of good (warmwater) and poor (modified; see HIMA in Table
6-2) habitat attributes, and 3) the spatial scale over which these stressors exert their effects on aquatic life
includes multiple dimensions (Rankin 1995). Rather than generating tiered criteria for habitat and
sediment attributes, Ohio has developed quantitative habitat and sediment targets for TMDLs based on
regional stream types (e.g., low vs. high gradient) and stream-size dependent "dose-response"
relationships with the numeric biocriteria associated with the tiered aquatic life uses (Rankin 1995). The
Stillwater River TMDL (Ohio EPA 2004) in the E. Corn Belt Plains (ECBP) ecoregion is an example of
how nutrient, sediment, and habitat targets ("criteria") were developed and used along with more
traditional chemical criteria to direct TMDL development in the watershed (Table 6-2).
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TABLE 6-2. Numeric targets for biological, habitat, and water quality parameters for the Stillwater River
in western Ohio. From Ohio EPA (2004) TMDL report for the Stillwater River watershed. The targets
and criteria vary in accordance with the tiered uses, which are resolved prior to impaired water
delineations and TMDL development.
Aq. Life
Use
MWH
WWH
EWH
Biological
Criteria
Min.
ICI
22
32
42
Min.
Ifil
24
36
46
Habitat Targets
QHE1
45
60
75
HIMA'
£3
<1
0
Water Quality Criteria
Ammonia-N
Max
7.3
7.3
4.5
Mean
1.2
0.8
0.8
Dissolved
Oxygen*
Min
3.0
4.0
5.0
Mean
4.0
5.0
6.0
Nutrient Targets
TKN"
4.0
1.0
1.0
Nitrate11
3.0
1.0
0.5
TPb
0.30
0.08
0.05
"HIMA - High Influence Modified Habitat Attributes
'Target values are adopted from Ohio EPA (1999)
"Specific numeric water quality exist in OAC 3745- 1-07, Tables 7-3 through 7-8; target values are guidelines based on the
75th percentile values of temperature (24°C) and field pH (8.1) from all samples collected during the 1999 Stillwater survey.
MWH = Modified Warmwater Habitat; WWH = Warmwater Habitat; EWH = Exceptional Warmwater Habitat
All of the targets in Table 6-2 were either wholly or partially generated based on responses between the
parameters, biological assemblage data, and the tiered aquatic uses to which they are related. This is
important because most of these parameters, habitat in particular, are not amenable to the traditional
laboratory based derivation. When these parameters are altered from "naturally occurring" conditions,
they can induce an adverse response for the biota, thus behaving as stressors. Targets for TMDLs or other
restoration strategies would either be difficult to generate, or lead to potentially incomplete solutions
without being ground-truthed in ambient data relationships and a tiered aquatic life use framework, the
latter of which is typically associated with a stressor gradient based on habitat or landscape
characteristics. Since many of the targets in Table 6-2 were generated directly from ambient stressor and
response relationships, their interpretations are likely less ambiguous than a rote application of lab
'derived criteria, although causative associations may be weaker. This approach is consistent with a
recommendation in the NRC TMDL report (NRC 2001) that criteria or targets be positioned as closely as
possible to the designated use and that indicators representing the full causal chain of events from stress
to exposure to response be used.
Understanding the role of habitat as an influence on the biological restoration potential for a waterbody
may be one of the greatest values of tiered aquatic life uses coupled with a systematic assessment process.
Habitat and landscape changes compose a common stressor gradient along which States and Tribes may
derive tiered uses. Tiered uses provide a useful framework for evaluating restoration potential,
prioritizing management actions, and allocating abatement resources.
CASE EXAMPLE 6-3. DETERMINING APPROPRIATE LEVELS OF PROTECTION IN OHIO
Hurford Run is a small stream located in an urban/industrial area
(steel finishing, petroleum refineries) of Canton, Ohio that drains
an area of 8.5 square miles (Figures 6-3, 6-4). The entire stream
has been subjected to direct channel modifications from the 1900s
up to the time of the study. During the biological surveys in the
mid 1980s, the stream was severely impaired by chemical
pollutants, so much so that some sites had no fish. Because of the
severity of the impairment, the use attainability analysis (UAA)
relied on the assessment of habitat quality by the Qualitative
Habitat Evaluation Index (QHEI; Rankin 1995).
Physical
Chemical^ I
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'
LRW
MWH WWH
FIGURE 6-3.1986 photograph of Hurford Run near
Canton, Ohio looking upstream at the reach that is
classified as a Limited Resource Water. Disturbed
soil was caused by efforts to remove soils
contaminated by nearby industrial operations.
FIGURE 6-4. Map of Hurford Run near Canton,
Ohio showing Ohio EPA IBI (solid circles) and
habitat (QHEI, triangles) sampling stations.
Spatial extent of stream aquatic life use
designations is denoted along the top.
Established relationships between attributes of habitat as measured by the QHEI and levels of biological
performance consistent with the tiered aquatic life uses provide an important tool to evaluate use
attainability and assign appropriate uses to specific'streams and rivers (Rankin 1989, 1995; Ohio EPA
1990). For example, Ohio has identified which habitat features may limit aquatic communities and which
are predictive of streams with warmwater (WWH) and exceptional warmwater (EWH) biological
communities. Figure 6-5 summarizes the IBI (left) and QHEI scores (right) for Hurford Run from 1985
to 1998. Very poor habitat quality from recent and historical channelization in the upper reach (RM 1.8 -
2.5) of Hurford Run and the associated hydrological characteristics (e.g., ephemeral flows) resulted in a
Limited Resource Waters (LRW) designation for this upper reach. The middle reach beginning at the
confluence of Domer Ditch (RM 1.7-1.0) was subject to extensive, maintained channel modifications and
resulted in degraded habitat features (Figure 6-5, right), but water was always present. Channel
maintenance practices resulting in poor quality substrates, undeveloped pools and riffles, and a lack of
instream cover preclude biological recovery to assemblages consistent with the WWH use. Following a
use attainability analysis (UAA), the middle reach was designated as Modified Warmwater Habitat
(MWH), reflecting the biological restoration potential for a channel-modified stream.
The lower one mile of Hurford Run, although previously relocated and channelized, naturally recovered
sufficient warmwater (good) habitat attributes such as coarse substrates and better developed riffle and
pool features to achieve QHEI scores (>60-70) that are typical of the WWH use for this ecoregion, hence
this segment was left at WWH. The tiered aquatic life uses that were assigned represent the highest
attainable potentials given the existing level of sanctioned channel maintenance in this urban stream.
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IBI
60
50
40
30
20
10
LRW
MWH
111
X
a
1980s19981980s19981980s1998
Upper Middle Lower
Stream Reach
WWH
Upper Middle Lower
Stream Reach
FIGURE 6-5. Box and whisker plots of IBI (left) and QHEI (right) by stream segment in Hurford Run
near Canton, Ohio. Aquatic life use designations for segments are denoted along the top of each plot.
1998 data is separated from the 1980s data for the IBI, but data are combined for the QHEI. Data
collected between 1985 and 1998. Lines are sites with no variability in scores (IBIs = 12). The hatched
bars denote Ohio biocriteria for each tiered use.
All of the designated uses required additional abatement of the major point sources discharging to
Hurford Run. Following the initial abatement of point source discharges in the late 1980s, data collected
in 1998 demonstrated recovery of the IBI score near the mouth of the stream to the WWH biocriterion as
predicted by the QHEI (Figure 6-5, left). Because this reach was designated WWH, it is protected from
any further alteration below this quality. The MWH designated middle reach and LRW designated upper
reach of Hurford Run have been subjected to ongoing channel maintenance activities (e.g., dredging, bank
mowing), which has limited the amount of biological restoration that can be expected. However, even
these less-than-CWA goal uses are impaired due to unresolved toxic impacts (reflected in very poor IBI
scores; Figure 6-5, left) presumably from the point sources and/or legacy impacts associated with the
industrial sites bordering the stream.
Urban/industrial streams such as Hurford Run present challenges in terms of setting and attaining
restoration goals. Visually, the lower reach of Hurford Run may not exemplify the classic depiction of a
natural stream because of its urban/industrial setting and location adjacent to major highways. The
instream habitat, however, indicated a WWH potential, which was eventually verified as the effects of
chemical stressors were reduced. The feedback provided by bioassessments based on the systematic
collection of biological and habitat data, which is essential to using tiered aquatic life uses, is an
important impetus for achieving water quality goals.
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CASE EXAMPLE 6-4. LONG-TERM MONITORING AND USE RE-ESTABLISHMENT IN MAINE
Chemical^
Biological
Between 1974 and 1981, an estimated 33 million dollars was
spent by industry, State, and federal sources to implement
primary and secondary wastewater treatment technology on
facilities discharging into a 100 km section of the Penobscot
River between Millinocket and Costigan, Maine. These
expenditures resulted in an 80% reduction in loadings of
biochemical oxygen demand and total suspended solids
discharged from the kraft and sulfite pulp and paper mills in
the study area. In 1974, the benthic macroinvertebrate
community was determined to be highly degraded at three
stations in closest proximity to pulp and paper effluents (Stas.
129, 131, 133). An additional two sites, somewhat downstream of pollution outfalls (Stas. 125, 126),
were determined to be degraded (Rabeni 1977). The benthic community of the study area has been re-
evaluated several times following major water quality changes in the 1970s, with the conclusion that the
investments have resulted in dramatic improvements in the river's ability to support aquatic life.
Station 129 is located 4 km downstream of the Lincoln Pulp and Paper Company outfall. Figure 6-6
provides a graphical summary of changes in two metrics of aquatic community structure for the period of
record at Station 129. »Maine DEP uses the metrics shown in a linear discriminant model to assign aquatic
life classification attainment. In 1974, Station 129 was designated as "highly polluted." The substrate at
Station 129 was covered with sewage bacteria (Sphaerotilus) and the invertebrate community was
restricted to worms, leeches, and pollution tolerant midge larvae. Numbers of individuals were very high,
indicating a "bloom" of tolerant, opportunist organisms. Diversity and richness values were very low
(Figure 6-6), and there was a complete absence of pollution-sensitive mayflies and stoneflies. In terms of
aquatic life classification, this station did not meet minimum State or federal standards.
Generic Richness
o 60 -i
"g « 50-
§ 8 10-j
0 S 30
I o 20-1
> 0
1974 1981 1983 1985 1992 1995
Year
Generic Diversity
1974 1981 1990 1992 1993 1994 1995
Year
FIGURE 6-6. Scatter plots showing values for two biological community variables, generic richness (left)
and generic diversity (right), from Sta. 129, the Penobscot River below Lincoln Pulp and Paper, between
1974 and 1996.
i
Dramatic improvements in the benthic macroinvertebrate community were evident by 1981 (Davies
1987). Total abundance was down, richness and diversity were greatly improved (Figure 6-6), and the
proportion of tolerant midge larvae was lower. Low numbers of stoneflies and mayflies were also
present. Overall, attainment had improved to Class C standards. The station has been sampled four times
since 1981, each time meeting Class B standards and showing continued improvement in community
structure, including high diversity and richness and healthy stonefly and mayfly populations. This long-
term dataset provides a valuable example of the responsiveness of biota to water quality improvements. It
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also highlights the unique usefulness of biological monitoring to document and summarize the real world
benefits of responsible stewardship of aquatic resources.
As a result of investment in wastewater control, the Penobscot River improved dramatically, from not
attaining Class C standards in 1974 to attaining Class B standards throughout most of the river today. As
a result, Maine upgraded the river from Class C to Class B in two steps. As of 1999, the entire mainstem,
with the exception of an impounded section, is now Class B, and must attain Class B standards. Without
TALUs, the upgrade could not have taken place and the river would be maintained today as the equivalent
of Class C. With Maine's TALUs, the river is now protected as Class B, which has been demonstrated to
be attainable throughout. Documentation of the improvement and subsequent protection of the improved
conditions is not possible without TALUs.
In addition to the Penobscot, many other streams in Maine have been upgraded in class as a result of
effective wastewater treatment or dam removal, which has led to dramatic improvements in biological
condition and class attainment.
CASE EXAMPLE 6-5. DEVELOPMENT OF LIMITS FOR NPDES PERMITS IN MAINE
Decoster Egg Farm, located in Turner, Maine, is the largest
producer of brown eggs in New England. The Farm has a long
history of environmental concerns including levels of ammonia
and nitrates in violation of drinking water standards. This case
example presents a unique example of the detection of biological
impacts in a stream attaining surface water quality standards but
affected by polluted groundwater recharge. Permitting staff had
recorded nutrient levels in leachate draining poorly managed
manure and chicken carcass waste piles. Stream violations were
not sufficiently high to trigger enforcement action based on
surface water quality violations but the high levels resulted in
contaminated leachate entering groundwater on the Decoster property. In 1989, the Department brought
enforcement action against Decoster Egg Farm to prohibit any further spreading of manure on the
property and to enforce proper management of other animal waste products.
In 1991, the company was required to evaluate the condition of the aquatic life in streams affected by
leachate or groundwater upwelling. Two of the streams, Lively Brook and House Brook, were designated
by the State to maintain Class B water quality conditions. The use designation process had deemed this to
be an appropriate management goal for these streams based on the tiered use designations of other
streams of comparable habitat and watershed condition. Field investigations included probes of the
hyporheic zone (the water flowing through the stream substrate) to measure the conductivity of the
upwelling groundwater. Conductivity is a measure of the ionic strength of water and is a very good
means of detecting certain types of pollutants. The streambed investigation uncovered several areas of
contaminated groundwater recharge to the stream. Aquatic life sampling, completed in 1992, confirmed
impacts to the benthos at three stations affected by groundwater upwelling on Lively Brook and one
station on House Brook. Station 188, on House Brook, is located downstream of a failing treatment
system that receives waste from the egg washing operation. The waste stream is severely contaminated
by nitrates. This station failed to attain minimum Class C aquatic life standards in 1992. Repeat
sampling in 1997 demonstrated attainment of Class C standards but the stream still failed to attain its
assigned Class B status, indicating the need for additional management intervention. Biomonitoring
information was used to issue a consent order requiring termination of manure spreading practices and
improved treatment of the products of the egg washing facilities. The egg washing facility was removed.
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The Lively and House Brooks case study illustrates the full water program cycle (Figure 5-1).
Monitoring and characterization of the habitat and watersheds of the two streams revealed that, with best
management practices in place, they should be able to attain Class B status, but in fact were not attaining
minimum Class C status. Problem identification showed that contaminated groundwater due to poor
management practices was causing the impairment. A set of source controls were applied, the facility
complied with the controls, and monitoring of the streams' condition continued. The monitoring showed
that although the streams had improved to Class C, they were still not attaining their designated Class B
status. Maine DEP applied further source controls on the facility to achieve Class B status.
Ongoing monitoring, iterative management intervention, and tiered use goals confirmed that the streams
had the potential to attain Class B status. Without tiered uses, source controls would have stopped when a
minimal condition was reached (consistent with a Class C condition) and the two streams would never
have recovered to Class B. Tiered aquatic life uses create attainable goals and best uses for waterbodies,
resulting in better quality waters than are possible with a single use. If a general aquatic life use system
had been in force, it likely would have resulted in a biological quality comparable to Maine's Class C,
with no impetus for improvement to the actual potential (Class B).
CASE EXAMPLE 6-6. NPDES PERMITTING AND USE ATTAINABILITY ANALYSIS IN OHIO
Ctiwnlcal
Physical
Biological
Ecologically-based TALUs, a systematic approach to
monitoring and assessment, and a sound UAA process can
provide substantial benefits for NPDES permitting related to
both the derivation of permits and assessing the effectiveness of
a permit in restoring an aquatic life use. A system for
identification of the attainable potential for the aquatic life of a
waterbody using a systematic approach can set credible
restoration goals and support measured responses to
environmental risks. This case example illustrates the use of
TALUs, systematic monitoring and assessment, and a consistent
process for conducting UAAs in support of NPDES permitting
issues.
The Ottawa River in northwest Ohio has been heavily polluted for more than a century. The river is
impacted by the city of Lima, rural communities, and agricultural activities (row crops). Heavy industry
in Lima was identified as a major source of water pollution since the 1880s (Leeson 1885 c.f. Ohio EPA
1992) being especially severe in the 1960s "... when more than 37 miles were devoid of fish, including
the Auglaize River downstream from the'Ottawa River" (Ohio EPA 1992). Point sources include one
major municipal and two major industrial discharges, industrial contributors to the Lima sewer system,
combined sewer overflows (CSOs), and partial or untreated sewage discharges from semi-rural areas in
the watershed. The effluent flow from the three major point sources enter the Ottawa River within a 0.8
mile reach and comprise the majority of the river flow during dry weather months. Improvements
consistent with CWA technology standards have been made at the major wastewater treatment facilities
since the late 1970s. The major causes of impairment include organic enrichment and low D.O., general
toxicity, habitat alterations (impoundments), nutrients, ammonia, heavy metals, oil and grease, and
chlorine in both the water column and bottom sediments (Ohio EPA 1998).
This case example focuses on a 25-mile segment of the Ottawa River that is directly impacted by major
point sources (Figure 6-7) and includes zones of immediate and acute impacts and various phases of
recovery downstream. Physical habitat in the mainstem downstream from the major point sources is good
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to excellent, and the mainstem is designated WWH as the result of a use attainability analysis and upgrade
conducted in the late 1980s. Prior to this analysis, most of the river was assigned the Limited Warmwater
Habitat (LWH) aquatic life use, which was assigned to rivers thought to be so polluted that restoration
was considered unfeasible. The LWH use was developed and applied prior to the development and
adoption of TALUs by Ohio EPA and is no longer used.
• Biological samp ing site
O Community -
•^ Discharger
k CSO or land III
\ Dam location
, LhiaWWTPy
FIGURE 6-7. Map of the Ottawa River with magnification of
two reaches in the Lima, Ohio area (after Ohio EPA 1998).
Toxic stressors, exposures, and responses reached a maximum in the segment directly impacted by the
three major point sources {Ohio EPA 1998; Yoder and DeShon 2003). Evidence of multiple toxic
exposures occurred in the water column chemistry, sediment chemistry, whole effluent toxicity,
frequency of DELT anomalies, fish tissue contaminants, and biochemical markers (Table 6-3). These
indicators pointed strongly to impacts of a toxic character and the biological response signatures provided
the corroborating feedback. Low D.O. can occur in the Ottawa River (Ohio EPA 1998), but the more
serious toxic effects that are evident in the biological response signatures presently mask its less serious
effects.
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TABLE 6-3. A matrix of stressor, exposure, and response indicators for the Ottawa River mainstem
based on data collected in 1996 (after Ohio EPA 1998). The darkness of shading indicates the degree of
severity of effect or exceedance expressed by an indicator.
SEGNBJT
DBS.
USE
rent
anus
RESPONSE
INDICATORS
QHH
Mwb
IO
EXPOSURE INOCSTORS
Wfetef
Ctem
Sed-
nent
Chem
Tox-
icity
DELT
Rsh
Ttes.
Bio-
#
Oam/
Roots
Urban-
Indusl.
Landuse
Currolative
Loads
CSO
SSOs
OttaHBfVuermahstetn-1996
TheyerRdto
Sugar a
RJLL-
PART
Gaod
Ntrates Low
Mb*
low
Ma*
Sugars, to
LJmaWWTP
Mxt-
BUN
LJmaWWTP
Atertowndam
72
fcfc
to
toKaiicia
Qxri
Qxri
-Be.
Kalidalomarfi
FUL
Good
Good
Be.
TSS La«v
law
Low
QHEI scores for the Ottawa indicated more than adequate habitat to support the WWH use designation
(Rankin 1989, 1995). In a growing recovery zone immediately below the impacted reach, the biota
eventually exhibited recovery to WWH status in the lower reaches of the river. In .the impaired sections,
the biological response signatures strongly indicate general toxicity, which is a fundamentally different
response than what would occur in response to habitat or low D.O. alone (Figure 6-8; Yoder and Rankin
1995b; Yoder and DeShon 2003). Results from a similar time period for the Scioto River are shown for
comparison. This river is impacted by non-toxic causes and sources including organic enrichment and
oxygen demanding wastes from sources that dominate the low flow of the river and emanate from a
similar municipal infrastructure and watershed setting. Taken together, these considerations led Ohio
EPA to redesignate (upgrade) the Ottawa River from LWH to WWH in 1989. The redesignation was
controversial and resulted in legal actions challenging the WWH use. Plaintiffs contended that the habitat
could not support a WWH assemblage and further argued that D.O. concentrations consistent with WWH
criteria were unattainable due to upstream impoundments and the flow regime. The WWH designation
was upheld because Ohio had a substantial record demonstrating the relationship between habitat
condition (as QHEI) and attainable biological condition described in the tiered uses. The response
signatures indicated that the cause of non-attainment in the Ottawa River was primarily toxicity.
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8
DC
HI
Q.
§
in
o
§
m
x
Ui
D
OTTAWA RIVER: FREQUENCY OF DELT ANOMALIES
10
5 60
1985 1987 1989 1991
OTTAWA RIVER: IBI
1996
WWH Blocrlterlan
(IBI,40)
Toxic ftesonw
Threshold (IBI *22)
n-30 n-8
n-31
n-18 n-28
SCIOTO RIVER: FREQUENCY OF DELT ANOMALIES
n • 38 n - 22
n-54
fl-48
1981 1986 1988 1991
SCIOTO RIVER: IBI
1996
1985
1987 1989
1991
1996
1981
1986 1988
1991
1996
FIGURE 6-8. Results for two key fish assemblage measures (%DELT anomalies, upper left panel and IBI,
lower left panel) showing the thresholds for toxic responses in the Ottawa River study area between 1985
and 1996. The results are shown with those from the Scioto River between 1981 and 1996 to illustrate the
different responses shown in a river impacted by non-toxic stressors.
The WWH redesignation and the subsequent permitting of the three major point sources could have taken
a significantly different path in the absence of the TALU approach employed by Ohio EPA. Instead of
keeping the focus on the most limiting problem of complex toxicity, the outcome could have been
diverted by the initial claims of habitat limitations and D.O. issues. Ohio's systematic approach to
monitoring directly tied to its TALUs was upheld in a court case on the redesignation to WWH, which
has averted subsequent legal actions in other similar permitting cases. This is related to the soundness
and consistency of the UAA approach and the perception that the TALUs are reasonably attainable and
protective.
One tool the NPDES program uses to identify potential problems from dischargers is non-compliance
with permit terms and conditions. In this case, none of the individual point sources involved were
considered in non-compliance of their NPDES permits at the time of the assessments. However, their
cumulative effect on biological condition resulted in severe biological impairment of the river. As a
result, Ohio EPA imposed controls to significantly improve water quality, including chronic WET limits,
close scrutiny of intermittent releases and spills, and internal audits conducted by two of the industrial
facilities involved. In addition, an unregulated landfill leachate was discovered and subsequently required
remediation.
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Under a tiered system, the biocriteria endpoints vary with the specific use and thus can affect the NPDES
permit. For example, a WWH designation requires better biological condition (higher ffil, MCI and
MIwB scores) than the LRW use. Accordingly, LRW waters can tolerate higher nutrients and lower D.O.
than WWH waters (See Figure 6-2, Table 6-2, and Appendix B), which would affect permit limits. A
decision that the stream was either habitat limited or dissolved oxygen limited alone would have diverted
attention away from the severe toxic impacts that were in reality limiting the aquatic life in this river. The
magnitude of these influences would have been underestimated on the sole basis of administrative
measures, without the stressor analysis that identified the causes of impairment in the Ottawa River. •
CASE EXAMPLE 6-7. SUPPORT FOR DREDGE AND FILL PERMITTING IN OHIO
The losses of habitat diversity or habitat-mediated stressors such as
increased siltation are now the most prevalent causes of aquatic
impairment in Ohio (Figure 6-9, Ohio EPA 2000). This is also true
across much of the U.S. (U.S. EPA 2002b). Environmental effects
of extensive landscape changes and in stream habitat alterations
are a primary stressor gradient along which the tiered aquatic life
uses were developed. Some habitat alterations are readily
restorable while others are essentially permanent either because
they are continuously maintained for flood control or drainage
purposes or they exceed the natural capacity for recovery.
Physical
Chamlcaly V ^ Biological
Monitoring
ir Asstssn
DHIW & Allocate Cortw
Risponslbllki**
Habitat A Herat ions
Siltation
Organic Enrichment
Sbtrients
Flow Alteration
Metab
ZOO 400 600 600 1000 1200
Miles Impaired By Cause
MOO
States can use Sections 401 and 404 of the CWA to
manage direct alterations to aquatic habitats. Tiered
aquatic life uses have proved useful in 404 permitting
and 401 certification of those permits. Those wanting
to modify a stream that will result in the discharge of
dredge or fill material into waters of the U.S. must
obtain a Section 404 permit from the U.S. Army Corps
of Engineers (ACOE) and a Section 401 water quality
certification from the State. The State must certify that
proposed activities will comply with, not violate, WQS.
The existence of biocriteria in the Ohio WQS makes
this linkage a valid tool for evaluating the impacts of
habitat alterations that are covered under the CWA.
Ohio EPA used a 20+ year database to develop habitat
stressor gradients along several aspects of habitat
quality at both site and watershed scales, including
overall habitat quality as measured by the QHEI and for specific attributes such as substrate and channel
condition. Examples of these stressor gradients from the E. Corn Belt Plains (ECBP) and Huron/Erie
Lake Plain (HELP) ecoregions are illustrated in Figure 6-10.
Tiered aquatic life uses have enabled a range of management responses to dredge and fill projects related
to the quality and sensitivity of the waterbody in question. Tiered uses are an important consideration in
the implementation of nationwide permits. Nationwide permits are designed to minimize site-specific
oversight where ecological risks are assumed to be low. Frequently, however, the criteria for which
places are eligible can overlook high quality waters and lead to their alteration. The Ohio EWH use
designation requires high habitat quality and stable hydrological regimes (especially in headwater and
wadeable streams). Because these essential attributes can be altered by direct modifications to the stream
FIGURE 6-9. Six leading causes of aquatic life
impairment in Ohio up to the year 2000 (from
Ohio EPA 2000).
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channel and other habitat features, Ohio requires individual reviews of projects that occur in such high
quality streams. Under a general use system, these would be lumped with all other streams under the
nationwide permit system.
The^ame information embodied in the tiered aquatic life uses allows Ohio to expend less oversight on
streams that cannot attain the WWH use designation. Such streams are generally ephemeral or
continuously maintained as drainage conveyances. This does not mean that physically degraded streams
are ignored. The attention gained by habitat impacts has prompted the development of mitigation
standards that will take the tiered aquatic life uses into account and require enhancement or restoration
wherever feasible. The stressor-response relationships (Figure 6-10) that have been developed between
biological assemblages and key habitat attributes have been applied to the 401 program in Ohio. For
nationwide 404 permits a series of general and specific exclusions and conditions have been derived that
vary with tiered aquatic life uses (ACOE 2002). These include a general exclusion (of nationwide
permits) for streams that are EWH and for certain antidegradation tiers (State Resource Waters and
Outstanding State Resource Waters), the delineation of which was based primarily on the same biological
assemblage attributes that are in common with Ohio's tiered aquatic life uses.
Data by Site All Years
ECBP d HELP Ecoreglons
Reference Sites ONLY
Data by Site All Years
ECBP A HELP Ecorcjions. Wodeable Streams
Reference Sites ONLY
Site Specific QHEI
Site Specif icQHH
Substrate Score
Data by Hue Watershed - 1994-2001
ECBPaHELPEcoregiwis
Mean Watershed
QHEI
Data by Site All Years
KKMHELPEcoregions
Reference Sites ONLY
Site Sped ficQHEI
Channel Scare
FIGURE 6-10. Examples of habitat stressor gradients vs. IB1 for Ohio wadeable
streams in the ECBP and HELP ecoregions.
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Aside from the general considerations discussed above, tiered uses have also proved useful for specific
nationwide permits. For example, Nationwide Permit 21 is for surface coal mining activities. Higher
quality uses such as WWH or EWH and Coldwater Habitat (CWH) require individual 404 permits in all
cases. Only MWH or LRW uses can be exempted from site-specific review under a nationwide permit
for mining (and for these there are stream length limitations). Again this is a significant benefit of having
tiered uses and the knowledge of the relationships between activities (e.g., habitat alterations) and the
biological responses in the indexes that compose the tiered biocriteria. The 404/401 program in Ohio is
still evolving. One goal is to move away from a case-by-case review of every permit by developing
mitigation standards tied directly to the tiered aquatic life uses that will be protective, relatively rapid,
accurate, and efficient in terms of resource expenditures. Making similar decisions within a single use
system would be more difficult and require either more case-by-case oversight to account for habitat
gradients, or risk being over-protective in some cases and under-protective in others.
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Glossary
Ambient Monitoring
Allochthonous
Anadromy
Antidegradation Statement
Aquatic Assemblage
Aquatic Community
Aquatic Life Use
Attribute
Autochthonous
BEAST
Beneficial Uses
Benthic Macroinvertebrates or Benthos
Best Management Practice
Biological Assessment or Bioassessment
Biological Criteria or Biocriteria
sampling and evaluation of receiving waters not necessarily associated with
episodic perturbations
organic matter that was produced outside the system (e.g., wood, leaves,
berries, insects etc.)
fish that live most of life in oceans or lakes and migrate to streams to spawn
statement that protects existing uses, prevents degradation of high quality
waterbodies unless certain determinations are made, and which protects the
quality of outstanding national resource waters
an association of interacting populations of organisms in a given waterbody,
for example, fish assemblage or a benthic macroinvertebrate assemblage
an association of interacting assemblages in a given waterbody, thebiotic
component of an ecosystem
a beneficial use designation in which the waterbody provides suitable habitat
for survival and reproduction of desirable fish, shellfish, and other aquatic
organisms; classifications specified in State water quality standards relating to
the level of protection afforded to the resident biological community by the
State agency
measurable part or process of a biological system
organic matter produced within the system (e.g., algae, macrophytes)
used in parts of Canada, the BEAST (BEnthic Assessment of SedimenT)
multivariate technique uses a probability model based on taxa ordination space
and the "best fit" of the test site(s) to the probability ellipses constructed
around the reference site classes
desirable uses that water quality should support. Examples are drinking water
supply, primary contact recreation (such as swimming), and aquatic life
support.
animals without backbones, living in or on the sediments, of a size large
enough to be seen by the unaided eye and which can be retained by. a U.S.
Standard No. 30 sieve (28 meshes per inch, 0.595 mm openings). Also
referred to as benthos, infauna, or macrobenthos
an engineered structure or management activity, or combination of these, that
eliminates or reduces an adverse environmental effect of a pollutant
an evaluation of (he biological condition of a waterbody using surveys of the
structure and function of a community of resident biota.
Scientific meaning: quantified values representing die biological condition of
a waterbody as measured by structure and function of the aquatic communities
typically at reference condition.
Regulatory meaning: narrative descriptions or numerical values of the
structure and function of aquatic communities in a waterbody necessary to
protect the designated aquatic life use, implemented in, or through water
quality standards.
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Biological Diversity or Biodiversity
Biological Indicator or Bioindicator
Biological Integrity
Biological Monitoring or Biomonitoring
Biological Survey or Biosurvey
Bioregion
Clean Water Act
Clean Water Act 303(d)
Clean Water-Act 30S(b)
Cosmopolitan Species
Criteria
DELT Anomalies
Designated Uses
Disturbance
Ecological Integrity
Ecoregion
refers to the variety and variability among living organisms and the ecological
complexes in which they occur. Diversity can be defined as the number of
different items and their relative frequencies. For biological diversity, these
items are organized at many levels, ranging from complete ecosystems to the
biochemical structures that are the molecular basis of heredity. Thus, the term
encompasses different ecosystems, species, and genes.
an organism, species, assemblage, or community characteristic of a particular
habitat, or indicative of a particular set of environmental conditions
the ability of an aquatic ecosystem to support and maintain a balanced,
adaptive community of organisms having a species composition, diversity, and
functional organization comparable to that of natural habitats within a region
use of a biological entity as a detector and its response as a measure to
determine environmental conditions. Ambient biological surveys and toxicity
tests are common biological monitoring methods.
collecting, processing, and analyzing a representative portion of the resident
aquatic community to determine its structural and/or functional characteristics
any geographical region characterized by a distinctive flora and/or fauna
an act passed by the U.S. Congress to control water pollution (formally
referred to as the Federal Water Pollution Control Act of 1972). Public Law
92-500, as amended. 33 U.S.C. 1251 et seq.
This section of the Act requires States, territories, and authorized Tribes to
develop lists of impaired waters for which applicable water quality standards
are not being met, even after point sources of pollution have installed the
minimum required levels of pollution control technology. The law requires
(hat these jurisdictions establish priority rankings for waters on the lists and
develop TMDLs for these waters. States, territories, and authorized Tribes are
to submit their list of waters on April 1 in every even-numbered year.
biennial reporting requires description of the quality of the Nation's surface
waters, evaluation of progress made in maintaining and restoring water
quality, and description of the extent of remaining problems
species with worldwide distribution or influence where there is suitable habitat
limits on a particular pollutant or condition of a waterbody presumed to
support or protect the designated use or uses of a waterbody. Criteria may be
narrative or numeric.
percentage of Deformities, Erosions (e.g., fins, barbels), Lesions and Tumors
on fish assemblages
those uses specified in water quality standards for each waterbody or segment
whether or not they are being attained
human activity that alters the natural state and can occur at or across many
spatial and temporal scales
(he condition of an unimpaired ecosystem as measured by combined chemical,
physical (including physical habitat), and biological attributes. Ecosystems
have integrity when they have their native components (plants, animals and
other organisms) and processes (such as growth and reproduction) intact.
a relatively homogeneous ecological area defined by similarity of climate,
landform, soil, potential natural vegetation, hydrology, or other ecologically
relevant variables
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Ecosystem-level functions •
Existing Uses
Function
Heterotrophic
Hyporheic Zone
Historical Data
Historically documented taxa
Index of Biological/Biotic Integrity
Invasive species
Life-history requirements
Lithophils
Lithopelagophils
Maintenance of populations
Metric
Multimetric Index
Multivariate Analysis
Narrative Biocriteria
processes performed by ecosystems, including, among other things, primary
and secondary production; respiration; nutrient cycling; decomposition. See
discussion concerning how this function is considered in the draft biological
condition gradient in transmitted memorandum under "outstanding issues" and
in die file: attribute explanation.
those uses actually attained in a wateibody on or after November 28,1975,
whether or not they are included in the water quality standards (November 28,
1975 is the date on which U.S. EPA promulgated its first water quality
standards regulation). Because an existing use has been attained, it cannot be
removed unless uses are added that require more stringent criteria.
processes required for normal performance of a biological system (may be
applied to any level of biological organization)
obtaining organic matter from other organisms rather than synthesizing it from
inorganic substrates
area below the streambed where water percolates through spaces between the
rocks and cobbles. Also known as the interface between surface water and
groundwater.
data sets from previous studies, which can range from handwritten field notes
to published journal articles
taxa known to have been supported in a waterbody or region prior to
enactment of the Clean Water Act, according to historical records compiled by
state or federal agencies or published scientific literature
an integrative expression of site condition across multiple metrics. An index
of biological integrity, is often composed of at least seven metrics
a species whose presence in the environment causes economic or
environmental harm or harm to human health. Native species or non-native
species may show invasive traits, although this is rare for native species and
relatively common for non-native species. (Please note - this term is not
currently included in the biological condition gradient)
environmental conditions necessary for completing life cycles (including,
among other things, reproduction, growth, maturation, migration, dispersal)
organisms that thrive on rocks or stones
organisms that spawn in open gravelly areas and have no guarding behavior
sustained population persistence; associated with locally successful
reproduction and growth
a calculated term or enumeration representing some aspect of biological
assemblage, function, or other measurable aspect and is a characteristic of the
biota that changes in some predictable way with increased human influence
an index that combines indicators, or metrics, into a single index value. Each
metric is tested and calibrated to a scale and transformed into aunitless score
prior to being aggregated into a multimetric index. Both the index and metrics
are useful in assessing and diagnosing ecological condition. See Index of
Biotic Integrity.
statistical methods (e.g. ordination or discriminant analysis) for analyzing
physical and biological community data using multiple variables
written statements describing the structure and function of aquatic
communities in a waterbody necessary to protect a designated aquatic life use
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Native
Non-detrimental effect
Non-native or intentionally introduced
species
Numeric Biocriteria
Periphyton
Piscivore
Polyphils
P/R
Presently Attained Uses
Rapid Bioassessment Protocols
Reference Condition
(Biological Integrity)
Reference Condition
(Biological Integrity), cent
an original or indigenous inhabitant of a region; naturally present
*
does not displace native taxa
with respect to a particular ecosystem, any species that is not found in that
ecosystem. Species introduced or spread from one region of the U.S. to
another outside their normal range are non-native or non-indigenous, as are
species introduced from other continents.
specific quantitative measures of the structure and function of aquatic
communities in a waterbody necessary to protect a designated aquatic life use
abroad organismal assemblage composed of attached algae, bacteria, their
secretions, associated detritus, and various species of microinvertebrates
predatory fish that eats mainly odier fish
organism with no specialized spawning requirements, behavior, or preferred
habitat
ratio of photosynthesis to respiration in a system
those uses actually being attained in a waterbody at the present moment
cost-effective techniques used to survey and evaluate the aquatic community
to detect aquatic life impairments and their relative severity
the condition that approximates natural, un-impacted conditions (biological,
chemical, physical, etc.) for a waterbody. Reference condition (Biological
Integrity) is best determined by collecting measurements at a number of sites
in a similar waterbody class or region under undisturbed or minimally
disturbed conditions (by human activity), if they exist. Since undisturbed or
minimally disturbed conditions may be difficult or impossible to find, least
disturbed conditions, combined with historical information, models or other
methods may be used to approximate reference condition as long as the
departure from natural or ideal is understood. Reference condition is used as a
benchmark to determine how much other water bodies depart from this
condition due to human disturbance.
Least Disturbed Condition: the best available existing conditions with regard
to physical, chemical, and biological characteristics or attributes of a
waterbody within a class or region. These waters have the least amount of
human disturbance in comparison to others within the waterbody class, region
or basin. Least disturbed conditions can be readily found, but may depart
significantly from natural, undisturbed conditions or minimally disturbed
conditions. Least disturbed condition may change significantly over time as
human disturbances change.
Minimally Disturbed Condition: the physical, chemical, and biological
conditions of a waterbody with very limited, or minimal, human disturbance in
comparison to others within the waterbody class or region. Minimally
disturbed conditions can change over time in response to natural processes.
Best Attainable Condition: a condition that is equivalent to die ecological
condition of (hypothetical) least disturbed sites where the best possible
management practices are in use. This condition can be determined using
techniques such as historical reconstruction, best ecological judgment and
modeling, restoration experiments, or inference from data distributions
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Reference Site
Refugia
Regional Reference Condition
Rheophils
Restoration
River Invertebrate Prediction and
Classification System (RIVPACS)
Sensitive taxa
Sensitive or regionally endemic taxa
Sensitive - rare taxa
Sensitive - ubiquitous taxa
Spatial and temporal ecosystem
connectance
Stressors
a site selected for comparison with sites being assessed. The type of sites
selected and the type of comparative measures used will vary with the purpose
of the comparisons, For the purposes of assessing the ecological condition of
sites, a reference site is a specific locality on a waterbody that is undisturbed
or minimally disturbed and is representative of the expected ecological
integrity of other localities on the same waterbody or neaiby waterbodies
accessible microhabitats or regions within a stream reach or watershed where
adequate conditions for organism survival are maintained during
circumstances that threaten survival, e.g., drought, flood, temperature
extremes, increased chemical stressors, habitat disturbance, etc.
a description of the chemical, physical, or biological condition based on an
aggregation of data from reference sites that are representative of a waterbody
type in an ecoiegion, subecoregion, watershed, or political unit
organisms that flourish in free-flowing water
the re-establishment of pre-distuibance aquatic functions and related physical,
chemical, and biological characteristics
a predictive method developed for use in the United Kingdom to assess water
quality using a comparison of observed biological species distributions to
those expected to occur based on a model derived from reference data
intolerant to a given anthropogenic stress; first species affected by the specific
stressor to which they are "sensitive" and the last to recover following
restoration
taxa with restricted,'geographically isolated distribution patterns (occurring
only in a locale as opposed to a region), often due to unique life history
requirements. May be long-lived, late maturing, low fecundity, limited
mobility, or require mutualist relation with other species. May be among
listed E/T or special concern species. Predictability of occurrence often low,
therefore, requires documented observation. Recorded occurrence may be
highly dependent on sample methods, site selection and level of effort.
naturally occur in low numbers relative to total population density but may
make up large relative proportion of richness. May be ubiquitous in occurrence
or may be restricted to certain micro-habitats, but because of low density,
recorded occurrence is dependent on sample effort. Often stenothemtic
(having a narrow range of thermal tolerance) or cold-water obligates;
commonly k-strategists (populations maintained at a fairly constant level;
slower development; longer life-span). May have specialized food resource
needs or feeding strategies. Generally intolerant to significant alteration of the
physical or chemical environment; are often the first taxa observed to be lost
from a community.
ordinarily common and abundant in natural communities when conventional
sample methods are used. Often having a broader range of thermal tolerance
than Sensitive- Rare taxa. These are taxa that comprise a substantial portion of
natural communities, and that often exhibit negative response (loss of
population, richness) at mild pollution loads or habitat alteration.
access or linkage (in space/time) to materials, locations, and conditions
required for maintenance of interacting populations of aquatic life; the
opposite of fragmentation; necessary for metapopulation maintenance and
natural flows of energy and nutrients across ecosystem boundaries
physical, chemical, and biological factors that adversely affect aquatic
organisms
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RIVPACS River Invertebrate Prediction and Classification System
TALU Tiered Aquatic Life Use
TMDL Total Maximum Daily Load
SCI Stream Condition Index
STP Sewage Treatment Plants
UAA Use Attainability Analyses
WLAs Waste Load Allocations
WQS Water Quality Standards
WWTP Wastewater Treatment Plant
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Appendix A
MAINE TALU IMPLEMENTATION CASE HISTORY1
I. Establish conceptual foundation
Since the early 1970s, prior to adoption of the CWA, Maine water quality law has had a tiered structure,
based on a gradient of water quality conditions. An early articulation of the conceptual basis for a tiered
approach to establishing aquatic life uses was made by John Cairns and others in a U.S. EPA-sponsored
symposium on the biological integrity objective of the Clean Water Act (Ballentine and Guarraia 1977),
with further elaboration in Cairns et al. (1993) and Karr and Chu (2000). The underlying basis depicts
biological condition declining across a gradient of stressors.
Maine's goal-based management classes range from Class AA, the highest water quality standard and
greatest restrictions on human activity, to Class C (and formerly Class D, discontinued), the lowest
quality standard with more flexible allowances for human activities (MDEP 2004 305b report). Maine's
current water quality classification law for rivers and streams establishes four tiers of aquatic life use
(ALU) that represent the upper end of a gradient of biological condition that occurs in the State (State of
Maine 1985, Courtemanch et al. 1989, Courtemanch 1995). Conditions worse than this upper end (i.e.,
worse than Class AA/A, B, or C) are deemed unacceptable. Numeric biocriteria are based on assessment
of benthic macroirivertebrates (State of Maine 2003,'Davies et al. unpublished manuscript). Assessment
of algal assemblages also occurs in most waterbodies but numeric criteria have not yet been developed.
Maine relies on the response of benthic macroinvertebrates to human influences for several reasons:
• Diverse life history strategies and a wide range of pollution tolerance;
• Relatively long-lived (+/- 1 year) compared to algae and bacteria;
• Limited mobility diminishes stressor avoidance behavior and emigration;
• The indigenous fish assemblage in Maine is not very diverse and information is limited to just a
few species.
Biologists in Maine and elsewhere have long observed clear-cut differences in community structure and
composition of benthic macroinvertebrate samples that are collected from waters across a continuum of
increasing stressors. The conceptual foundation of the Maine Department of Environmental Protection
(MDEP) Biological Monitoring Program (and resulting biocriteria) was framed by three factors: 1) the
first-hand observations of such biological response patterns, 2) published empirical and theoretical work
in aquatic stress ecology, and 3) Maine's pre-existing water management context. The first two factors
are discussed in sequence in this section. The water management context is discussed in the next section,
II. Merge Scientific & Policy Foundations.
Empirical Observations of Maine Biologists
Differences in resident biological assemblages are evident even to the untrained eye when there are
substantial differences in water quality (Figure A-l). This can be illustrated with a very simple example
based on a gradient of increasing enrichment. In the initial years of biological assessment in Maine,
biologists observed that minimally disturbed sampling locations tended to support many invertebrate taxa
(high diversity ),'but at low to moderate density. In contrast, streams receiving well-treated or well-diluted
domestic effluents exhibited higher organism densities, though the types of organisms were similar.
1 Appendix A was written by Susan Davies, Maine Department of Environmental Protection.
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Streams receiving heavy loadings of sewage or nutrient-laden industrial effluents showed obvious
differences in taxa and numbers from that expected in minimally disturbed streams. Streams receiving
toxic amounts of chlorine or industrial waste showed much lower densities and many more hardy types of
organisms than would be expected in undisturbed areas.
Undisturbed Watershed Sample
Urban Stream Sample
FIGURE A-l. Differences in numbers and types of organisms that are associated with
different levels of disturbance can be evident even to the untrained eye.
Published Empirical and Theoretical Work in Aquatic Stress Ecology
The very obvious differences in biological responses for Maine streams, described above, are consistent
with published conceptual models and empirical findings of stress ecology. The subsidy-stress gradient
model of Reibesell (1974), and further developed by Odum et al. (1979) and Odum (1985), provided
Maine DEP biologists with a theoretical model of expected patterns of biological change that was
consistent with their own empirical observations (Figure A-2a and A-2b). Development of numeric
biocriteria proceeded from this underlying ecological paradigm with the goal to statistically characterize
the observed biological condition groups to determine aquatic life use class attainment.
Subsidy
Paradox of Enrichment
Lethal
FIGURE A-2a. Subsidy-stress gradient: The ecological
theory basis for Maine's aquatic life use descriptions
(Odura et al. 1979). Some disturbances have an
enriching or subsidizing effect on biological
assemblages because they provide more than normal
usable resources (nutrients, organic matter, etc.).
Inputs in excess of what can be processed by the
resident community have a detrimental effect
(increased biochemical oxygen demand,
accumulation of unusable resources, etc.) and lead to
negative community response. Toxic or poisonous
inputs have an immediate detrimental effect.
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FIGURE A-2b. Empirically observed
subsidy-stress gradient in Maine
streams, documented by changes in
benthic macroinvertebrate density.
Low levels of conductivity are an
indicator of slight enrichment while
high levels are often associated with
toxic contamination.
Stress ecology recognizes biological changes in response to increasing levels of stressors (i.e., gradients
of environmental quality) as distinct from those that occur in responses to natural gradients, such as
elevation, climate, alkalinity, stream size, and geographic location. While natural and ecoregional
gradients can and do influence biological expectations in important ways, biological responses from the
high to the low end of generalized stressor gradients in Maine streams tend to be far more obvious
(Davies et al. 1999, Davies et a!., unpublished manuscript). Odum's model .supported our observation that
structurally distinct biological groups exist across a gradient of water quality. Identifying predictable,
characteristic differences among those biological condition groups could serve as the underlying
conceptual basis for development of tiered aquatic life uses. Four biological condition groups would also
fit well with the State's four-tiered standards for dissolved oxygen, bacteria, and habitat described in the
existing water quality classification law.
II. Merge scientific and policy foundations
The narrative aquatic life use statements in Maine's TALUs describe conditions ranging from "as
naturally occurs" (Class AA and Class A- the highest ALU designations) to "maintenance of structure and
function" (Class C- the lowest ALU designation allowed in Maine) (Table A-l). The subsidy-stress
gradient model helped guide the development of the ecologically-based definitions in the law. These
specific definitions establish the biological characteristics that are required for attainment of each ALU
classification (Table A-2).
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TABLE A-l. Maine's narrative aquatic life and habitat standards for rivers and streams (M.R.SA Title 38 Article
4-A § 464-465).
CLASS
AA*
A
B
C
Impound-
ments
MANAGEMENT
High quality water for recreation and ecological
interests. No discharges or impoundments
permitted.
High quality water with limited human interference.
Discharges limited to non-contact process water or
highly treated wastewater of quality equal to or
better than the receiving water. Impoundments
allowed.
Good quality water. Discharge of well-treated
effluent with ample dilution permitted.
Impoundments allowed.
Acceptable water quality. Maintains the interim
goals of the Federal Water Quality Act
(fishable/swimmable). Discharge of well-treated
effluent permitted. Impoundments allowed.
Riverine impoundments not classified as Great
Ponds and managed for hydropower generation
BIOLOGICAL STANDARD
Habitat shall be characterized as natural and free
flowing. Aquatic life shall be as naturally occurs.
Habitat shall be characterized as natural. Aquatic life
shall be as naturally occurs
Habitat shall be characterized as unimpaired.
Discharges shall not cause adverse impacts to aquatic
life. Receiving water shall be of sufficient quality to
support all aquatic species indigenous to the receiving
water without detrimental changes in the resident
bioloqical community.
Habitat for fish and other aquatic life. Discharges may
cause some changes to aquatic life, provided that the
receiving waters shall be of sufficient quality to support
all species of fish indigenous to the receiving water and ,
maintain the structure and function of the resident
biological community.
Support all species of fish indigenous to those waters
and maintain the structure and function of the resident
biological community.
'The narrative aquatic life standard is the same for Class AA and Class A.
TABLE A-2. Definitions of terms used in Maine's water classification law.
1. Aquatic life any plants or animals that live at least part of their life cycle in fresh water.
2. As naturally occurs conditions with essentially the same physical, chemical and biological characteristics as
found in situations with similar habitats, free of measurable effects of human activity.
3. Community function mechanisms of uptake storage and transfer of life-sustaining materials available to a
biological community, which determine the efficiency of use and the amount of export of the materials from the
community.
4. Community structure the organization of a biological community based on numbers of individuals within
different taxonomic groups and the proportion each taxonomic group represents of the total community,
5. Indigenous supported in a reach of water or known to have been supported according to historical records
compiled by State and Federal agencies or published in scientific literature.
6. Natural living in or as if in, a state of nature not measurably affected by human activity.
7. Resident biological community aquatic life expected to exist in a habitat, which is free from the influence of
the discharge of any pollutant. This shall be established by accepted biomonitoring techniques.
8. Unimpaired without a diminished capacity to support aquatic life.
9. Without detrimental changes in the resident biological community no significant loss of species or excessive
dominance by any species or group of species attributable to human activity.
Consistency with other applicable WQ criteria
As shown in Figure A-3, MDEP designed the narrative ALUs to be parallel to the tiered dissolved oxygen
and bacteria standards. This was done because Department biologists recognized that differences in
allowed human activities and water quality criteria of the different classes (AA, A, B, C) would inevitably
yield different expectations for aquatic community response. For example, it is unreasonable to expect
the same biological assemblages to thrive in both Class AA waters (dissolved oxygen: "as naturally
occurs"- >7 ppm for Maine; dams and discharges prohibited) and Class C waters (minimum dissolved
oxygen 5 ppm; dams, industrial and municipal discharges allowed).
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As naturally
Nate
mppuft aii Irxttgtviflus
sprefcs.
Elsbiiat:'
K:* fish
Nun-
• jMaine's Water Quality Management Classes :..::••::
CLASS AA CLASS A. CLASS B
No bj'uraloi'i': WC JBcuot to o»' tX): 7n>r.i
jfJieiarJWT, IX) btfhn', i;y'.ln> 9fjw.i .r«f sajji-iouid
tffiti I'j.li'fi/ny 2* iv^j^'J.d; [x:*: 'Jnrw-v .HTjywninR: Bswwia;
riautf'itj W;* s2n;r:v)f>T:: f'-ViOOm
basucti as «a!.ui--jl
NA
•tectefei «!/•!>:• r.-«)
FIGURE A-3. Relation between Maine TALUs and other water quality standards and criteria.
The final language of the narrative aquatic life uses was the result of extensive negotiations between
MDEP biologists and stakeholder biologists, under the purview of a legislative subcommittee. Lawyers
on both sides weighed in regularly to ensure the fairness and legality of the statute. MDEP biologists
drafted the narrative standards and definitions with careful attention to retaining a sound foundation in
ecological theory. Furthermore, careful attention was given to how each biological attribute could be
quantified (and thus assessed for attainment), with credible and widely accepted biological metrics (Table
A-3).
TABLE A-3. Maine tiered uses based on measurable ecological values.
Narrative Standard
Ecological Value
Quantifiable Measures
CLASS A
natural
CLASS B
unimpaired, maintain
indigenous taxa
CLASS C
maintain structure
and function
Taxonomic and Numeric
Equality; Presence of
Indicator Taxa
Retention of taxa and
numbers; Absence of
hyperdominance; Presence of
sensitive taxa
Resistance, Redundancy;
Resilience; Balanced
Distribution .
Energy exchange; Resource
assimilation; Reproduction
Similarity, Richness, Abundance,
Diversity; EPT, Indicator Taxa, Biotic
Index
Community loss; Richness; Abundance;
Diversity; Equitability; Evenness; EPT;
Indicator taxa, Biotic Index
Richness; Diversity; Equitability;
Evenness
Trophic groups; Richness; Abundance;
Community loss; Fecundity; Colonization
rate
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How do Maine's tiered aquatic life uses relate to the Biological Condition Gradient?
Maine's aquatic life standards specify different levels (tiers) of water quality necessary to maintain
designated aquatic life uses. These standards correspond to the tiers of the Biological Condition Gradient
in Figure A-4.
natural condition
I
Natural
1
5
Severely
Altered
Minima! («S5 of •speciss s'tnre
density change? may secw
foiKCtoii .Silly
aicintaintt!
Tohnutt sfitdcs slxiw
incnwsiag iJnminancs:
s?r.?Jt?i« ^iKiet *rs rsre;
Setae 6jS«radvi> sf
BtrueiiiM antt IntKiion {j
Um Stressor Gradient
FIGURE A-4. Maine TALUs in relation to the BCG tiers.
Class AA and Class A have the same narrative aquatic life uses requiring that aquatic life be "as
naturally occurs." This phrase is defined in the statute as "conditions with essentially the same physical,
chemical, and biological characteristics as found in situations with similar habitats, free of measurable
effects of human activity." The stated goal condition for Class AA/A thus conforms to Tier 1 or high Tier
2 conditions on the BCG.
Samples attaining MDEP Class A numeric criteria cover a range of conditions, some of which are fully
consistent with BCG Tier 1 but some of which would have to be interpreted as BCG Tier 2. Examples of
the latter are mildly enriched locations showing higher abundance of organisms {than "natural" for
Maine) and increased algal biomass, and Class A locations that are influenced by dams.
Class B aquatic life standards require that there be "no adverse impacts" and that water quality be
"sufficient to support all indigenous aquatic species without detrimental changes in the resident biological
community." This phrase is defined as "no significant loss of species or excessive dominance by any
species or group of species attributable to human activity." This wording was carefully chosen to allow
for commonly observed increases in measures of biomass, density, and richness that occur in response to
mild enrichment (as depicted by Odum's "subsidy hump" in Figure A-2a and A-2b) but to prohibit
negative biological changes, such as notable loss of indigenous taxa. Thus the expectation for Class B is
that sensitive taxa should be well represented with community structure comparable to Class A.
Samples attaining MDEP Class B numeric criteria cover a range of conditions, some of which are fully
consistent with BCG Tier 2 but some of which would have to be interpreted as BCG Tier 3 because of the
degree of structural change or the failure to collect Sensitive-Rare taxa. Dams, well-managed landscape
changes, and well-treated point sources are allowed in Class B waters. These changes may result in
detectable signals such as absence of migratory taxa, increased algal biomass, higher total abundance of
organisms, and increased abundance of sensitive-ubiquitous taxa (i.e., higher relative abundance of some
mayflies and some filter feeders; higher abundance of Perlid stoneflies) resulting in a community
structure more consistent with Tier 3.
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Class C aquatic life standards require that structure and function of the resident biological community be
maintained. Numeric biocriteria in Maine document that waterbody segments meeting Class C dissolved
oxygen and bacteria standards, but not attaining Class B standards, show obvious differences in biological
assemblages. In terms of benthic macroinvertebrates, differences can be generally described as lower
numbers and richness of cold-water obligate taxa and those taxa that have high dissolved oxygen
requirements (e.g., gill-breathing mayflies and stoneflies), higher densities of filter-feeding organisms,
and increased densities of some types of chironomid midges and other facultative or tolerant groups.
Samples attaining MDEP Class C numeric criteria cover a range of biological conditions, most of which
are fully consistent with BCG Tier 3 and/or Tier 4. About 10% of samples that attain MDEP Class C
numeric criteria would have to be interpreted as BCG Tier 5 because of the degree of structural change or
very low numbers of.Sensitive taxa (e.g., the mean abundance of Ephemeroptera in sites attaining Class C
numeric criteria is 86 individuals per sampler but about 10% have less than 10 mayflies). Attainment of
Class C numeric criteria usually indicates that other community structure attributes are present (e.g.,
evenness of distributions, richness and/or diversity of the assemblage of taxa of intermediate tolerance).
Hyper-dominance of filter-feeders, complete absence of expected sensitive insect taxa (especially
stoneflies and mayflies), and high proportions of tolerant taxa signal assemblages that fail to meet Class C
water quality standards. These conditions represent BCG Tiers 5 and 6.
III. Establish technical program
How does Maine DEP collect biological data?
The MDEP's Biological Monitoring Program began standardized sampling of river and stream
macroinvertebrates in 1983 (less rigorously standardized biological assessments had begun at least 10
years before). Experience gained on the Penobscot River (Davies 1987, Rabeni et al. 1988) had
demonstrated the practical usefulness and reliability of rock-filled basket artificial substrates (Klemm et
al. 1990). Maine has adapted the basic design of these devices to enable sampling of waterbody depths
ranging from as little as 5 cm (using rock-filled mesh bags; Davies et al. 1999) to about 10 meters in large
riverine impoundments (using boat-retrievable cones; Courtemanch 1984, Davies and Tsomides 2002,
http://www.state.me.us/depMwq/docmomtoring/biologicainDiorep2000.htm). The success ofthese
devices has enabled the MDEP to apply comparable field and analytical methods to nearly all rivers and
streams of significant regulatory interest (Davies and Tsomides 2002), greatly simplifying the
development and application of river and stream biocriteria. Further, the physiography of Maine is quite
homogeneous with roughly 85% of the State falling within just two relatively similar ecoregions
(Omernik 1987). For this reason stratification by ecoregion was not the critical concern that it is for
States in some other regions of the country (Davies et al. unpublished manuscript).2
In 1999, Maine began an algal monitoring program to strengthen the interpretation of ecological condition
by providing information from a second biological assemblage. Maine's fish assemblage is naturally
depauperate, limiting its suitability as a candidate for bioassessment. The algal monitoring program will
assist the Department in the development of river and stream nutrient criteria. The Department also has a
companion biomonitoring program to assess wetland biological condition.
Database development
By the late summer of 2004, the Department had established about 800 monitoring stations in all major
watersheds throughout the State (Figure A-5). Data from macroinvertebrate samples are stored in an
Oracle® database and all stations are geo-referenced in the Department's geographic information system
2Maine' s southern ecoregion is very small but recent data suggest that some improvement in accuracy of class
prediction could result from better accounting for ecoregional differences there.
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FIGURE A-5. Macroinvertebrate sampling
stations in Maine.
(Arclnfo0). Data collected in accordance with Maine's biocriteria protocol are analyzed using statistical
models that estimate to which of the four water quality classes a sample belongs. Findings of the
Biological Monitoring Program are used to document existing conditions, identify problems, set water
management goals, assess the progress of water resource management measures, and trigger needed
remedial actions.
Sampling methods
Samples of benthic macroinvertebrates are collected from
flowing streams in rock bags (or baskets or cones). At least
three substrate samplers are exposed in the waterbody for 28
days during the late summer, low flow period (July 1 to
September 30). The MDEP usually conducts sampling, but
others may also perform monitoring to determine attainment of
classification if done according to a quality assurance plan.
Laboratory methods
Samples are retrieved, sorted, and stored for identification by a
professional freshwater macroinvertebrate taxonomist.
Organisms are identified to species whenever possible or
otherwise to the lowest taxonomic level possible.
Analytical methods
If a sample satisfies the minimum data requirements (total mean
abundance of at least 50 individuals, generic richness of at least
15 taxa for 3 replicate samplers), data are entered into the MDEP's computer software for further analysis
through the numeric criteria statistical model. The model is able to take large amounts of information
generated from a biological sample, describe which variables appear to be most significant in the
classification decisions, and provide a mathematical summary that integrates the information. The model
produces probability scores from 0 to 1 that indicate the likelihood that a sample attains each water
quality class.
IV. Develop'and validate quantitative thresholds
How does Maine quantify the tiered aquatic life uses so that attainment can be assessed?
In the late 1980's, the MDEP quantified the narrative aquatic life goals for each water quality class by
developing a probability-based statistical model to serve as numeric biocriteria (Courtemanch et al. 1989,
Courtemanch 1995, Davies et al. unpublished manuscript). The model uses 31 biological variables, many
of which were specifically chosen because of their utility in measuring some important ecological
attribute in the narrative standard. The model quantifies and standardizes the expert judgment of
biologists and it now serves as an expert system for decision-making (See Case Examples 3-3 and 3-6).
To develop the model, biologists used agreed-upon decision rules and a Delphi technique (Bakus et al.
1982) to assign an aquatic life attainment classification (A, B, C, or non-attainment) to 144 samples of
benthic macroinvertebrate data, based on conformity of the sampled community to one of the 3 narrative
aquatic life standards in Maine's statute, or to a fourth category representing non-attainment of minimum
State standards (Shelton and Blocksom 2004, Davies et al. unpublished manuscript). The samples
evaluated represented 300 distinct taxonomic units and 70,000 organisms collected from rivers, streams,
and riverine impoundments. Those data and their classification assignments were used as the baseline for
construction of the expert system, in the form of a linear discriminant model, to evaluate future
" macroinvertebrate samples for water quality classification attainment. The original model was used from
1992 through 1999 when the model was recalibrated with an additional 229 (for a total of 373) sampling
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events. The recalibration resulted in relatively minor changes to the structure of the original model,
involving simplification of the structure of two of the sub-models, the elimination of two poorly '
performing variables, and changes in model coefficients to account for the new data.
How has Maine established reference conditions?
Maine has taken a conceptually different approach to establishing baseline reference conditions from
which to develop numeric biological criteria. Because we determined that detection of four distinct
biological condition groups, characterized by differences in specified ecological attributes, was our
management goal, it was also our goal for statistical analysis. We desired to develop numeric criteria that
would enable us to assign sites to one of those four condition groups (A, B, C, non-attainment).
Therefore, our task for characterizing reference conditions was to conceptually and then statistically
• define those four groups. Thus in a sense, initially by expert judgment and then by multivariate analysis,
we created a Class A reference condition (deemed to be close to natural), a Class B reference condition, a
Class C reference condition, and non-attainment reference conditions. Use of biological information to
establish a minimally disturbed reference has been criticized due to the dangers of a too circular process.
We have tested our biology-based a priori assignment of sites to Class A using more traditionally
identified reference locations (i.e., based on high percent natural landcover) and found good
correspondence with the biologically-defined Class A sites.
Adoption of the Numeric Biocriteria Rule
On April 17, 2003 the Maine Board of Environmental Protection adopted numeric freshwater biocriteria
in rule. The biocriteria rule describes the process that the MDEP uses to make decisions about attainment
of aquatic life uses in rivers and streams. The rule describes protocols for biological sampling of benthic
macroinvertebrates, laboratory analyses, modeling analysis of laboratory data, and selective use of expert
judgment. Adoption of this rule quantitatively interprets Maine's existing narrative 'aquatic life'
standards for each riverine water quality classification.
V. Application in water quality management
How does the MDEP decide which waterbodies and locations
to monitor?
For purposes of biological monitoring, the MDEP divided the
State.into five major river basins, which are sampled on a 5-
year rotational schedule (Figure A-6): Androscoggin,
Kennebec and Mid-Coast, Penobscot, St. Croix and North
Coastal Rivers, Piscataqua, Saco and Southern Coast, St. John
and Presumpscot. The decision to monitor specific locations
on a waterbody can be based on a variety of factors such as:
«
• prior knowledge of human activities that could have a
detrimental effect on a waterbody: sampling seeks to
detect actual impacts on biological communities;
• knowledge of future potential threats to a waterbody:
sampling can be done to collect baseline data before, for
example, development occurs or a discharge is licensed;
follow-up sampling can determine the effect, if any, on the
biological community by said development or discharge;
• requirement/desire to monitor the effects of remediation
activities or water quality management changes;
• desire to expand coverage of the monitoring program and to
more fully document natural variability.
FIGURE A-6. Maine five-year rotating basin
sampling schedule.
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How are tiered aquatic life uses designated in Maine?
The quality of Maine's waters is described in terms of physical, chemical and biological characteristics
associated with the State's water classification program. As established in Maine statute (38 MRSA
Sections 464-470), the classification program consists of designated uses (e.g. drinking water supply,
recreation in and on the water, habitat for fish and other aquatic life), criteria (e.g. bacteria, dissolved
oxygen and aquatic life), and characteristics (e.g. natural, free flowing) that specify levels of water quality
necessary to maintain the designated uses. All State waters have a classification assignment (Rivers and
streams: AA, A, B, C; Lakes: GPA; Marine and estuarine": SA, SB, SC). Tiered narrative aquatic life uses
specific to wetlands are currently under consideration by MDEP and a supporting wetland biomonitoring
program is in place.
The classification system in Maine is goal-based in that assignment of a given waterbody to a use class
(AA, A, B or C) may not necessarily reflect its current conditions. Rather, it establishes the level of
quality the State has deemed the waterbody must achieve. Maine's classification system is also more risk
based than quality based. Water quality differences among the various classes are not large, however, the
different levels of restrictions put on human activities associated with each class establishes the level of
risks that water quality could be degraded resulting in increased threats to designated use attainment.
Rivers and streams are assigned to a tiered aquatic life use goal (Table A-l: A A and A -"as naturally
occurs," B- "no detrimental change," C- "maintain structure and function and water quality sufficient to
support salmonids") that represents the best fit after considering:
• The current condition in terms of dissolved oxygen, bacteria, and aquatic life (Figure A-3) and
• The highest attainable goal condition (taking into account ecological and socioeconomic factors).
The State water quality assessment provided in Maine's 305b report gives the status of attainment of the
water resource goals established in the classification program. Thus, some waters may be listed as
impaired even though they have relatively good water quality (Table A-4), e.g., a Class A river may be
listed because it does not fully attain the standards of that class but may be of sufficiently good quality to
attain Class B or C, and the Clean Water Act interim goal. The classification program is reviewed every
three years (Triennial Review) by the Department and the Board of Environmental Protection (Board).
The Board may, after opportunity for public review and hearing, make recommendations to the
Legislature for changes in water quality standards or reclassification of selected waters. The most recent
revisions to the classification program were completed in 2002-2003 when the Legislature authorized
classification upgrades to 75 river, stream and coastal segments totaling over 800 miles of waters (Figure
A-7).
TABLE A-4. Examples of how numeric biocriteria results determine whether
or not a waterbody attains designated aquatic life uses in Maine.
Legislative Class Monitoring Result Attains Class?
Next Step.
A
C
A
B
A
B
B
NA
Yes
Yes
No
No
TMDL
TMDL
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Classification Upgrades for Major Rivers in Maine, 1970 to 2004
800-
700
600
2 »uo
5
•S-400
|
§300
200
100
T
V
/s
s
x -r
AA&A
B
C
D
1970
1979
1986
1990
1999
2004
Year
FIGURE A-7. Increased designation of Class AA and Class A uses on major Maine rivers (as shown
by river miles) between 1970 and 2004, as a result of water quality improvements and public
support for the Class AA/A goal in the Triennial Review Process.
What is the management perspective for TALU designations in Maine?
Class AA water-bodies, as compared to Class A, have significantly greater restrictions on allowed
activities. For example, no discharge of wastewater and no dams are allowed in Class AA waterbodies.
Class A waters carry a higher risk of degradation because discharges are allowed, though the risk is small
because they must be of "equal to or better" water quality than the receiving water. Dams are also
allowed. Obstructions to flow, whether man-made or natural can alter assemblage structure from free-
flowing conditions (Poff et al. 1997, Davies et al. 1999). The definition in water quality standards for the
term "natural" sought to limit the effects of altered flows to no greater than what could be expected from
a "natural" obstruction to flow (e.g., a natural hydrological control or a beaver dam). Thus to
accommodate dams in Class A, "natural" is defined as "occurring in, or as if in, a state of nature not
measurably affected by human activities." Assemblages that are characteristic of the waters above and
below beaver dams or low-head, run-of-river, man-made dams are deemed to pass this standard. Most
dams in Class A provide for passage of anadromous fish.
Class B was originally applied as the default ALU for unmonitored waters though current use
designations are nearly equal in stream miles for Class A and Class B, both of which far exceed Class C
miles when all rivers and streams in the State are considered (Figure A-8). From the management
perspective, a Class B designation often applies to waterbody segments exposed to well-treated or well-
diluted domestic discharges or to areas subjected to landscape alterations that result in moderate increases
in the nutrient and organic matter load.
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Class C narrative aquatic life standards prohibit any
activities that result in the loss of structure and function
of the resident biological community. "Community
structure" is defined as "the organization of a biological
community based on numbers of individuals within
different taxonomic groups and the proportion each -
taxonomic group represents of the total community,"
while community function is defined as "mechanisms of
uptake storage and transfer of life-sustaining materials
available to a biological community which determine the
efficiency of use and the amount of export of the
materials from the community." This management class
is applied to waterbodies that may be impounded, altered
by landscape changes, or that receive industrial
wastewater.
2% 6%
47%
45%
H Class AA
El Class A
EH Class B
O Class C
FIGURE A-8. Percent of linear miles of all rivers
and streams in each of Maine's designated use
classes (year 2000).
What process was used to bring the Maine TALU biocriteria rule through adoption?
The MDEP Biological Monitoring Program completed provisional numeric biocriteria in 1990. Those
numeric thresholds were the basis for extensive regulatory and non-regulatory Department decisions
between 1990 and 2003, e.g., issuance or denial of 401 water quality certificates and recommendations
for flow management changes, 303d and 305b listings, prioritization of at-risk waterbodies, and problem
identification. In April 2003, the State formally adopted tiered numeric biocriteria rules that were the
result of the analysis of 15 years of biological data and the experience gained through 20 years of
regulatory decision-making based on numeric biocriteria (Table A-5). Remarkably, the biocriteria rule
was one of the most complicated and important, but least contested water quality rules that the Maine
Department of Environmental Protection has adopted in the last 15 years. Stakeholders from all sides had
become convinced of the merits of the approach.
TABLE A-5. Chronology of Maine's biocriteria development.
1983 The MDEP Biological Monitoring Program began a standardized program of sampling stream invertebrate communities.
1986 The revised Water Classification Program, which defined tiered narrative standards for aquatic life, became law.
1989 MDEP staff and University of Maine statistical ecologist, Dr. Frank Drummond embarked on the development of numeric
criteria to support the narrative standards of the law.
1990 A technical advisory committee of stakeholder scientists was convened to provide peer review and oversight of the
biocriteria development process. Over the course of approximately 2 Vi years, MDEP staff, Dr. Drummond, and the
committee developed a statistical model based on expert judgment and linear discriminant analysis to address the
scientific goals, as well as the policy and regulatory goals of the new biocriteria program.
1991 - Pubiic informational workshops on the process were held in March 1991, September 1993, and December 1993.
1993
1999 The original statistical model was recalibrated to take advantage of the expanded dataset available at that time.
2002 During a formal stakeholder review process, meetings were held in March and April and comments were solicited from
representatives of the hydropower and paper industry, environmental advocacy groups, other State agency biologists
(e.g., fish and wildlife), university scientists, and private consultants.
2002 A workshop on the rule and its background was held in early October for the Maine Board of Environmental Protection.
2003 The Board of Environmental Protection adopted the rule on April 3 and it was subsequently adopted by the Maine State
Legislature.
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Appendix B
OHIO TALU IMPLEMENTATION CASE HISTORY1
In 1990, Ohio EPA adopted numeric biological criteria in the Ohio Water Quality Standards (Ohio WQS;
Ohio Administrative Code 3745-1). These criteria have been used to guide and enhance water quality
management programs and assess their environmental outcomes. The numeric biocriteria are an
outgrowth of an existing framework of tiered aquatic life uses and narrative biological assessment criteria
that has been in place since 1980. This case history is intended to summarize the evolutionary
development of the components of the WQS and monitoring and assessment programs that took place in
the late 1970s and throughout the 1980s and 1990s.
I. Establish conceptual foundation
Initially developed and adopted by Ohio EPA in 1978, tiered aquatic life uses represented a major
revision to the existing general use framework that was adopted in 1974. This level of tiered uses
recognized the different types of warmwater aquatic assemblages that corresponded to the mosaic of
natural features of the landscape and nearly two centuries of human-induced changes. The eventual
development of more refined tiered uses and the attendant numeric biocriteria that are in place today was
the result of a decade long development process. The important concepts that spurred and guided these
developments in the Ohio EPA program are described as follows:
Natural History and Zoogeography
The empirical evidence used to develop the initial concepts for tiered uses can be found in comprehensive
works on the natural history and zoogeography of the Midwest such as Fishes of Ohio (Trautman 1957,
1981) and Fishes of Illinois (Smith 1979). These texts documented the natural and human-induced
variations in the distribution, composition, and abundance of biological assemblages over space and
through time. Trautman (1957) not only provides a lesson in Ohio's natural history, but also describes the
biological evidence that was used to formulate the initial concepts about biological integrity that emerged
in the late 1970s and early 1980s. Such works also described the key features of the landscape that
influence and determine the potential aquatic fauna of waterbodies and were the forerunners of the
regidnalization tools that appeared soon after. As an alternative to a'"one-size-fits-all" approach, these
provided an important foundation for the development of Ohio's tiered uses.
Landmark Stream and River Pollution Studies
The earliest studies of the effects of pollution on biological assemblages were the precursors of the
approach eventually developed and used by Ohio EPA. Campbell (1939), Brinely (1942), and Wurtz
(1955) described the classical zones of pollution in flowing waterbodies. Ellis (1937) conducted one of
the first comprehensive studies of water pollution in the U.S. including an emphasis on the chronic
impacts of wastewater discharges. Patrick (1950, 1953) employed the concept of species (or taxa)
diversity as an indicator of the "health and well-being" of aquatic assemblages and described a
"biodynamic cycle." Gaufin and Tarzwell (1953) also described pollutional zones using aquatic
assemblages and were the first to advocate cost-effective assessments of one or two representative
assemblages (e.g., fish and macroinvertebrates). Subsequent studies of that time included landmark
pollution investigations of rivers and streams (Krumholz and Minckley 1964; Mills et al. 1966; Tsai 1968,
1973; Sparks and Starrett 1975; Gammon 1976), some of which introduced standardized approaches to
1 Appendix B was written by Chris Yoder, Midwest Biodiversity Institute, Columbus, Ohio.
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biological data collection and analysis. These were the key citations in the original proposal for the
present-day Ohio EPA biological assessment program (Yoder.1978). Such works also provided the
impetus for articulating the linkage between ecological symptoms of aquatic health and human-induced
changes in aquatic ecosystem quality that came later.
Concepts of Biological Integrity
The articulation of a practical definition of biological integrity by Karr and Dudley (1981) provided a
theoretical framework for the development of Ohio's numeric biological criteria. Key components of this
framework are: 1) using biological assemblages as a direct measure of aquatic life use attainment status
(Herricks and Schaeffer 1985, Karr et al. 1986), 2) the development and use of multimetric assessment
tools (Karr 1981, Karr et al. 1986), 3) derivation of regional reference condition to determine appropriate
aquatic life use goals and assessment endpoints (Hughes et al. 1986), and 4) systematic monitoring and
assessment of the State's waters. This represented a major advancement over previous attempts to define
and develop a workable framework to address the concept of integrity (Ballentine and Guarraia 1977).
Embedded in this framework is the recognition that water quality management must be approached from
an ecological perspective that is grounded in sound ecological theory and validated by empirical
observation. This means developing monitoring and assessment and WQS to encompass the five factors
that determine the integrity of a water resource (Figure 1-3; Karr et al. 1986).
Experiences in Applying Systematic Biological Assessments
A major aspect of the development of the Ohio biological assessment program and tiered uses is the
experience gained through the initial and sustained development of systematic bioassessments beginning
in the late 1970s and through the 1980s. This is where the previously described methods, concepts, and
theories were applied, tested, and developed, resulting in a tractable system for measuring biological
quality at multiple spatial scales and through time. An evolutionary process occurred in which
qualitative, narrative biocriteria were initially used to assess rivers and streams via systematic watershed
monitoring and assessments. The data and experiences gained in this process provided the raw materials
for incorporating the concepts of biological integrity that emerged simultaneously. This resulted in
further refinements to the biological assessment tools and criteria and the tiered uses including how they
are assigned and assessed. Key to the success of this approach was the initial decisions about indicator
assemblages and methods. These have remained stable throughout the entire development and
implementation process, with no major modifications that would have resulted in major disconnections of
the database. The specific methods, tools, and criteria are described in Section II.
When numeric biocriteria and refined uses were adopted in 1990, the development process continued with
adaptations of that system to different waterbody types. A systematic process for classifying and
assessing wetlands was developed in the early 1990s and narrative biocriteria were adopted in the Ohio
WQS. Biological assessment methods and indexes were also developed for the Lake Erie near shore and
lacustuary habitats (Thoma 1999). Routine application of the numeric biocriteria in support of dredge and
fill permitting and 401 certifications exposed the need to develop new assessment tools for primary
headwater streams, i.e., those draining less than one square mile, Dealing with these waters required a
change in indicator groups emphasizing aquatic amphibians and invertebrates and a modified
classification scheme (Ohio EPA 2003). Finally, the Ohio River Valley Water Sanitation Commission
(ORSANCO) developed a systematic approach for assessing fish (Emery et al. 2003) and
macroinvertebrate assemblages of the Ohio River mainstem as a precursor to the adoption of numeric
biocriteria. Other innovations are expected to follow and include recalibration of the stream and river
biocriteria following the resampling of reference sites that took place during 1990-1999, urban stream
classification issues (Yoder et al. 2000, Miltner et al. 2003), and adaptation to level IV ecoregions and
other geomorphic classification schemes. These are examples of a continuous improvement process that
naturally follows the adherence to the fundamentals of integrating WQS with systematic monitoring and
assessment.
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II. Merge scientific and policy foundations
From the outset, biological and water quality assessments were intended to play a pivotal role in the
application of tiered uses. Since designated uses were formulated and described in ecological terms, it
followed that they should be applied and measured on an ecological basis. At that time, the readily
available criteria were chemical-specific and the development of practical and systematic biological
assessments was in pilot testing and development stages. The operational execution of tiered uses (WQS)
was dependent on developing a more comprehensive and systematic approach to monitoring and
assessment that supported the watershed and waterbody specific application of tiered uses. However,
time was required to develop standardized data, tools and criteria, spatial design, and spatial coverage,
which were part of the monitoring and assessment program that delivered full support for tiered uses (and
all other water quality management programs). Figure B-l illustrates the evolutionary and incremental
process of the development of tiered uses, allied tools and criteria, and the monitoring and assessment
approach that were necessary to achieve full implementation of TALU in Ohio.
• General ALU
• Few Specific
Chemical Criteria
• Narrative "Free
Froms"
• "Pilot" biological
monitoring program
• Fixed station M&A
design (chemical
only; 100« sites)
0974-1978)
•NarratlveTALUs
•More Specific
Chemical Criteria
• Initial designation
of specific waters
(BPJ baaed; system-
atic M&A envisioned)
• Fixed Station M&A
design (chemical
only; 100+ sites)
• "Pilot" biological
monitoring program
(10-15 sit es/yr.)
(1978-1980)
• NarratlveTALUs
• More Specific
Chemical Criteria
• Narrative Blocrlterla
(Initial WQ program
support)
• Designation of
specific waters
based on M&A (UAA
process)
• Intensive river &
watershed surveys
Initiated (Integration
of bid, chem, and
physical Indicators;
100-ZOOsltes/yr.)
(1980-1987)
• Refined TALUs
• Specific & Complex
Chemical Criteria
• Numerical Blocrlterla
(BCG implicit)
• Physical Habitat
Assessment
• WET Testing
• Geometric watershed
design (Integration of
blol, chem, and
physical Indicators;
400-600 sHes/yr.)
• Integrated
Reassessments
(systematic WQ
program support)
(1987 - present)
FIGURE B-l. Evolutionary development of TALU and allied tools, criteria and assessments from the
baseline of the 1974 WQS based on general uses and few specific water quality criteria to refined
TALUs and specific chemical, physical, and biological criteria implemented via an integrated
monitoring and assessment framework. The three time periods beginning with 1978-1980
approximate the first three phases of biocriteria development and implementation in Figure 5-2.
Pre-development Phase: 1974-1978
The first WQS adopted in 1974 were consistent with the technology available at that time consisted of
general uses, "free from" statements, and few numeric criteria of any kind (chemical, physical, or
biological). The monitoring and assessment program adhered to contemporary U.S. EPA guidance,
consisting of a fixed station network (approximately 100 sites, monthly and quarterly chemical sampling)
and a "pilot" biological program. The baseline water quality management programs (i.e., NPDES
permitting, funding, planning) were also in their initial stages of development and implementation. A
comprehensive water quality based approach to pollution abatement and management had not yet been
developed or envisioned - abatement efforts focused on technology based limitations for major point
sources. The linkage between WQS and monitoring and assessment had not yet been made, the latter
being viewed as a less important, optional activity.
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Initial TALV Development Phase: 1978-1980
In 1978, tiered aquatic life and other uses (e.g., recreation, water supply) were described and adopted
along with the development of numeric chemical criteria for parameters such as dissolved oxygen (D.O.),
temperature, ammonia, and common heavy metals (e.g., copper, cadmium, lead, zinc, iron, chromium,
and nickel). The tiered uses emanated from recognition of the broader ecological concepts described in
section I, as well as the belief that a "one-size-fits-all" approach to water quality management {i.e., the
result of applying general uses) was neither realistic, cost-effective, nor saleable to stakeholders and the
public. While tiered uses promised more customized and cost-effective management outcomes, the
integration of WQS and monitoring and assessment, which is necessary before these stated objectives
could be realized, had not yet taken place.
Ohio's First Tiered Use Designations
Tiered aquatic life uses are articulated as narrative statements describing the ecological attributes that
should be supported by each tier. The criteria associated with each tier consisted of pollutant-specific,
single value criteria for a limited set of water quality parameters (i.e., D.O., temperature, ammonia,
common heavy metals). There were no biological criteria at that time, although the vision was to
eventually develop a biologically-based assessment process. The tiers included variations on a theme of
warmwater aquatic assemblages as written in the narrative for the warmwater habitat (WWH) use
designation:
"These are waters capable of supporting reproducing populations of fish, normally
referred to as warmwater species, and associated vertebrate and invertebrate organisms
and plants on an annual basis. These standards apply outside of the mixing zone." (Ohio
Administrative Code 3745-1-07 c. 1978)
The intent of the exceptional warmwater habitat (EWH) use designation is illustrated by the phrase
"These are waters capable of supporting exceptional and unusual populations of fish..." In essence,
the EWH designation required evidence of an exceptional or unusual assemblage of fish or associated
aquatic organisms and plants on an annual basis. Initially, EWH designations were made based on the
known locations of self-sustaining populations offish and other aquatic species that were considered of
exceptional value, most of which had exhibited historical declines in distribution throughout Ohio and the
Midwest in response to human-induced changes. These locations also corresponded to a congruence of
natural landscape features associated with Ohio's glacial geology that "insulated" these assemblages from
the cascade of effects from alteration in the landscape that adversely impacted the same species in other
more vulnerable waterbodies. The result was waters with more intact habitats, less altered hydrological
characteristics, and water quality that was "much better than most." As such, a goal of EWH is to protect
such aquatic habitats as a refuge for rare and sensitive species and is vital to the broader restoration goals
of the 1972 Federal Water Pollution Control Act (FWPCA) amendments. A greater degree of protection
was initially afforded to these waters via more stringent water quality criteria for key parameters such as
D.O., ammonia, and temperature (Ohio Administrative Code 3745-1-07 c. 1978). WWH became the
default designation for all other waters that lacked such "exceptional and unusual attributes", but which
retained or had the potential to exhibit {he minimum quality that met the baseline provisions of the
FWPCA (Sec. 101 [a][2]).
A coldwater habitat (CWH) designation was also developed, but primarily focused on fishery attributes
(i.e., Salmonids), which are largely artificially propagated and maintained in Ohio. However, the
possibility of incorporating broader ecological attributes into this use narrative was included in the
designated use narrative as follows:
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"These are waters capable of supporting populations of fish, normally referred to as
coldwater species and associated vertebrate and invertebrate organisms and plants on an
annual basis. These waters are not necessarily capable of supporting successful
reproduction of Salmonids and may be stocked periodically. These standards apply
outside of the mixing zone." (OAC 3745-1-07)
The monitoring and assessment program was initially based on fixed stations and emphasized chemical
assessments, but experimental approaches such as small-scale intensive surveys and biological
assessments were being developed and tested. There were no empirically derived or narrative biological
criteria to decide between EWH and WWH. Specific assignments of waters were made using expert
consensus and best professional judgment based on the known ecological attributes inherent in each
designation. Thus the assignments of individual water bodies were only as good as the information
available for such waters, which was later found to be incomplete or inadequate. Other tiers in the Ohio
aquatic life use designations included seasonal warmwater habitat (SWH) and limited warmwater habitat
(LWH). Water quality criteria for common chemical parameters were tiered and/or varied for each use
designation. Criteria were the most stringent for CWH and EWH and the least stringent for LWH, the
latter use essentially functioning as a temporary variance to WWH.
Initial TALV implementation and Development Phase: 1980-1987
While the tiering provided by EWH and WWH is conceptually consistent with the intent and attributes of
the biological condition gradient (BCG; Chapters 2 and 3), the tools to quantify and implement the
associated concepts were lacking in 1978. The inclusion of the concepts of biological integrity (Karr and
Dudley 1981), operational measures of biological condition (Karr et al. 1986), and the concepts of
regionalization and reference sites (Hughes et al. 1986, Omernik 1987) led to further refinements of the
tiered uses in this phase. These refinements resulted in the present day hierarchy of the exceptional
warmwater, warmwater, modified warmwater, and limited resource waters use designations. The
narrative descriptions were modified to reflect the operational definition of biological integrity (Karr and
Dudley 1981), further integrating the parallel development of numeric biological criteria.
The original tiered uses were devised with an eye toward the eventual development of a biological
assessment based approach to their implementation. These initial developments took place in the early
1980s and included narrative (or qualitative) biological "criteria" (Tables B-l and B-2) supported by
biological assessments and the implementation of an intensive survey design executed on a mainstem
river or watershed basis (Ohio EPA 1981). These early biocriteria were based on the experiences and best
professional judgment of the agency biologists and reflected the analytical and assessment tools of that
time. At the same time, t chemical criteria were being further developed and whole effluent toxicity
(WET) testing was being explored.
The use of monitoring and assessment in support of water quality management programs emphasized
WQS (assigning tiered uses), construction grants (advanced treatment justifications), and NPDES permits
(water quality based effluent limits). At the same time, the statewide database that would support the
eventual and more comprehensive development of biological, chemical, and physical assessment tools
and criteria was being amassed via the systematic implementation of a an intensive survey and watershed
assessment process. Comparatively complex chemical-specific criteria were adopted for 126 priority
pollutants and included chronic, acute, and lethal endpoints for aquatic life; criteria were also adopted for
human health exposures. Whole effluent toxicity testing was introduced and developed as a water quality
based permitting tool (Figure B-l).
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TABLE B-l. Biological criteria (fish) for determining aquatic life use designations and attainment of Clean
Water Act goals (November, 1980; after Ohio EPA 1981).
Evaluation
Class
Category
"Exceptional"
Class I
(EWH)
"Good"
Class II
(WWH)
"Fair"
Class III
"Poor"
Class IV
t.
2.
3.
4.
5.
6.
Exceptional or unusual
assemblage of species
Sensitive species •
abundant
Exceptionally high
diversity
Composite index
>9.0-9.5
Outstanding recreational
Fishery
Rare, endangered, or
threatened species
present
Usual association of
expected species
Most expected species
absent
Some expected species
absent, or in very low
abundance
Sensitive species present Sensitive species absent, Sensitive species absent
or in very low '
abundance
High diversity
Composite index
>7.0 - 7.5; <9.0 - 9.5
Declining diversity
Composite index
>4.5 - 5.0; <7.0-7.5
Tolerant species
increasing, beginning to
dominate
Low diversity
Composite index
<4.0-4.5
Tolerant species
dominate
Conditions: Categories 1,2,3, and 4 (if data is available) must be met and 5 or 6 must also be met in order to designated in a
particular class.
TABLE B-2. Biological criteria (macroinvertebrates) for determining aquatic life use designations and
attainment of Clean Water Act goals (November, 1980; after Ohio EPA 1981).
Evaluation "Exceptional"
Class Class I
Category (EWH)
1. Pollution sensitive
species abundant
"Good"
Class II
(WWH)
Pollution sensitive
species present in
moderate numbers
"Fair"
Class III
Pollution sensitive
species present in low
numbers
"Poor"
Class IV
Pollution sensitive
species absent
2.
3.
Intermediate species
present in low numbers
Intermediate species
present in moderate
numbers
Tolerant species present Tolerant species present
in low numbers in low numbers
Intermediate species Intermediate species
abundant present in low numbers
or absent
Tolerant species present Tolerant species
in moderate numbers abundant (all types may
be absent if extreme
toxic conditions exist)
4.
5.
Number of taxa >30'
Exceptional diversity
Shannon index <3.5
Number of taxa 25-30
High diversity
Shannon index 2.9-3.5
Number of taxa 20-25
Moderate diversity
Shannon index 2.3-2.9
Number of taxa <20
Low diversity
Shannon index <2.3
Number of quantitative taxa from artificial substrates
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A key development that took place during this time period was the pilot testing of ecoregions (Omernik
1987) and the development of the regional reference condition concept (Hughes et al. 1986). Along with
the emerging concepts of biological integrity (Gakstatter et al. 1981, Karr and Dudley 1981) and
multimetric assessment tools (Karr 1981, Karr et al. 1986), these advances represent the foundational
development of the tools and criteria that emerged out of this phase. During this phase, integrated
biological, chemical, and physical assessments were emphasized in support of a wider array of
management issues (including nonpoint sources) in addition to the mainstay priorities of construction
grants and NPDES permitting. The results of these assessments were documented in Comprehensive
Water Quality Reports, the production of which included the first true integration of the monitoring and
assessment, WQS, water quality modeling, and peYmitting programs. Study teams were formed for each
project and included staff membership from each program. The analyses and recommendations included
in these reports provided the basis for WQS use revisions, water quality based NPDES permits (including
water quality certifications), advanced treatment justifications, and other findings related to the observed
impacts of nonpoint sources.
The WQS were modified in 1985 to include a listing of designations by individual waterbody, as opposed
to default designations or tributary membership (Table B-3). The original listing of individual
waterbodies in the WQS was based on the Gazetteer of Ohio Rivers and Streams (Ohio Dept. of Natural
Resources 1960). 'Waterbodies listed in the Gazetteer that had not been assessed via the biological and
water quality assessment process were assigned a "default" designation of WWH. Waterbodies that were
originally designated in 1978, or subsequent to that version of the WQS, retained those uses and this was
denoted for each waterbody in the rules (Table B-3). Unconfirmed non-WWH uses required validation
by site-specific monitoring and assessment due to a public notice issued by Ohio EPA in 1981. In reality,
many "default" WWH designations also required reassessment because the variations in watershed
settings and stressor gradients had only begun to be recognized. The Gazetteer of Ohio Rivers and
Streams did not include all jurisdictional streams in the State; thus "unlisted" streams were assigned use
designations as they became known via the systematic assessment of Ohio watersheds and/or as site-
specific management issues arose. This further emphasized the role of monitoring and assessment in the
designation of individual waterbodies.
Ongoing TALU Implementation and Maintenance Phase: 1987- present
Prompted by the testing and developments that took place in the initial implementation and development
phase, Ohio EPA proposed and adopted numerical biological criteria (Figure B-2) and further refinements
to the tiered uses. The narratives of the tiered uses first developed in 1978 were revised and new uses
were added, both of which were influenced by the developments and the monitoring and assessment
experience that took place in the preceding time period. The aquatic life use narratives were revised to
reflect the operational definition of biological integrity (Karr and Dudley 1981) and provided direct
reference to how the numerical biological criteria were developed and derived. These definitions follow:
"Warmwater" - these are waters capable of supporting and maintaining a balanced,
integrated, adaptive community of warmwater aquatic organisms having a species
composition, diversity; and functional organization comparable to the twenty-fifth
percentile of the identified reference sites within each of the following ecoregions: the
interior plateau ecoregion, the Erie/Ontario lake plains ecoregion, the western Allegheny
plateau ecoregion and the eastern corn belt plains ecoregion. For the Huron/Erie lake
plains ecoregion, the comparable species composition, diversity and functional
organization are based on the ninetieth percentile of all sites within the ecoregion. For all
ecoregions, the attributes of species composition, diversity, and functional organization
will be measured using the index of biotic integrity, the modified index of well-being,
and the invertebrate community index as defined in "Biological Criteria for the Protection
of Aquatic Life: Volume II, Users Manual for Biological Field Assessment of Ohio
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Surface Waters," as cited in paragraph (B) of rule 3745-1-03 of the Administrative Code.
In addition to those water body segments designated in rules 3745-1-08 to 3745-1-32 of
the Administrative Code, all upground storage reservoirs are designated warmwater
habitats. Attainment of this use designation (except for upground storage reservoirs) is
based on the criteria in Table 7-14 of this rule. A temporary variance to the criteria
associated with this use designation may be granted as described in paragraph (F) of rule
3745-1-01 of the Administrative Code.
TABLE B-3. Example of individual stream and/or segment use designations in the Ohio water quality standards
showing aquatic life, water supply, and recreational use designations. Designation with a "+" means the use has
been confirmed by monitoring and assessment. Designation with an "*" indicates a "default" designation or
unverified designation - these waters will eventually be assessed via the rotating basin approach [excerpted from
Ohio Administrative Code 3745-1-09],
Waterbody Segment
111.11111
Scioto River - Frank Rd. (RM 127.7) to .
downstream from Bridge St. in
Chillicothe(RM70.7)
- Greenlawn Dam (RM 129.8) to
Frank Rd. (RM 127.7)
- Olentangy R. (RM 132.3) to
Greenlawn Dam (RM 129.8)
- Dublin Rd. WTP dam (RM 133.4)
to Olentangy R. (RM 132.3)
- O'Shaughnessy Dam (RM 148.8)
To Dublin Rd. WTP dam (RM
133.4)
- all other segments
Scippo Cr.
Congo Cr. (Scippo Cr. at RM 1.64)
Unnamed trib. Scippo Cr. (RM 16.31)
Unnamed trib. Scippo Cr. (RM 18.87)
Yellowbud Cr. - Ebenhack Rd. (RM 3.0)
to mouth
- all other segments
RCA Tributary (Scioto R. RM 96.5)
Use Designations
S
R
W
+
+
+
+
Aquatic Life Habitat
W
W
H
+
+
+
+
*
+
+
E
W
H
+
+
+
M
W
H
+
S
S
H
C
W
H
L
R
W
+
+
Water
Supply
P
W
S
+
A
W
S
+
+
+
+
+
*
+
+
+
+
+
+
I
W
S
+
+
+
+
+
*
+
+
4.
+
+
+
Recreation
B
W
P
C
R
+
+
+
+
+
*
+
+
+
+
S
C
R
+
+
Comments
ECBP ecoregion
- impounded
MWH
Cmnll
omaii
drainageway
maintenance
Small
drainageway
maintenance
SRW = State Resource Water; WWH = Warmwater Habitat; EWH = Exceptional Warmwater Habitat; MWH = Modified Warmwater Habitat;
SSH = Seasonal Salmonid Habitat; CWH = Coldwater Habitat; LRW = Limited Resource.Waters; PWS = Public Water Supply; AWS = Agricultural
Water Supply; 1WS = Industrial Water Supply; BW = Bathing Waters; PCR = Primary Contact Recreation; SCR = Secondary Contact Recreation
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162
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Huron Erte Late Plato (HELP)
Erie Ontario Lake Plain (EOLP)
: ;Size IBI;^MIwb^ ;: ICI
i!::24iNA!;iiii;22
Eastern Com BeS Plain (ECBP)
••
Use ; ;-Slze IBI: Mlwfa: ^ id:
Statewide Exceptional Criteria
FIGURE B-2. Numeric biological criteria adopted by Ohio EPA in 1990, showing stratification of
biocriteria by biological assemblage, index, site type, ecoregion for the warrawater habitat (WWH) and
exceptional warrawater habitat (EWH) use designations.
The narrative for the exceptional warmwater habitat (EWH) use designation retained the same application
language with the following differences (in-bold italics):
"Exceptional warmwater" - these are waters capable of supporting and maintaining an
exceptional or unusual community of warmwater aquatic organisms'having a species
composition, diversity, and functional organization comparable to the seventy-fifth
percentile of the identified reference sites on a statewide basis ... all lakes and
reservoirs, except upground storage reservoirs, are designated exceptional warmwater
habitats. Attainment of this use designation (except for lakes and reservoirs) is based on
the criteria in Table 7-14 of this rule."
The narrative for coldwater habitat (CWH) was also revised and reflected a broader application of this use
for reasons other than the existence of maintenance stocking of Salmonid fish species:
(i) "Coldwater habitat, inland trout streams" - these are waters which support trout
stocking and management under the auspices of the Ohio department of natural
resources, division of wildlife, excluding waters in lake run stocking programs, lake
or reservoir stocking programs, experimental or trial stocking programs, and put and
take programs on waters without, or without the potential restoration of, natural
coldwater attributes of temperature and flow. The director shall designate these
waters in consultation with the Director of the Ohio department of natural resources.
(ii) "Coldwater habitat, native fauna" - these are waters capable of supporting
populations of native coldwater fish and associated vertebrate and invertebrate
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163
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organisms and plants on an annual basis. The director shall designate these waters
based upon the result of use attainability analyses.
The WWH, EWH, and CWH use designations are considered consistent with the minimum goals of the
CWA (Section 101[a][2]) and the associated Federal Regulation (40CFR Part 130). However, the public
notice issued in 1981 by Ohio EPA required that designated uses other than WWH be validated on a
waterbody specific basis prior to basing permitting requirements on the attendant water quality criteria.
Furthermore, a waterbody must reflect the capability to attain the EWH biological criteria at a sufficient
number of sampling locations to be designated EWH (Ohio EPA 1987) and the CWH designation has its
own set of requirements in the narrative. Such showings are not required for WWH, except that the
potential to attain must be determined by biological and habitat assessments.
"Coldwater" - these are waters that meet one or both of the characteristics described in
paragraphs (B)(l)(f)(i) and (B)(l)(f)(ii) of this rule. A temporary variance to the criteria
Use designations that do not meet the minimum goals of the CWA, and thus require a use attainability
analysis on a water body specific and/or segment-by-segment basis include:
"Modified warmwater" - these are waters that have been the subject of a use attainability
analysis and have been found to be incapable of supporting and maintaining a balanced,
integrated, adaptive community of warmwater aquatic organisms due to irretrievable
modifications of the physical habitat. Such modifications are of a long-lasting duration
(i.e., twenty years and longer) and may include the following examples: extensive stream
channel modification activities permitted under sections 401 and 404 of the act or
Chapter 6131 of the Revised Code, extensive sedimentation resulting from abandoned *
mine land runoff, and extensive, permanent impoundment of free-flowing water bodies.
The attributes of species composition, diversity and functional organization will be
measured using the index of biotic integrity, the modified index of well-being, and the
invertebrate community index as defined in "Biological Criteria for the Protection of
Aquatic Life: Volume II, Users Manual for Biological Field Assessment of Ohio Surface
Waters," as cited in paragraph (B) of rule 3745-1-03 of the Administrative Code.
Attainment of this use designation is based on the criteria in Table 7-14 of this rule. The
modified warmwater habitat designation can be applied only to those waters that do not
attain the warmwater habitat biological criteria in Table 7-14 of this rule because of
irretrievable modifications of the physical habitat. All water body segments designated
modified warmwater habitat will be reviewed on a triennial basis (or sooner) to determine
whether the use designation should be changed. A temporary variance to the criteria
associated with this use designation may be granted as described in paragraph (F) of rule
3745-1-01 of the Administrative Code.
The Limited Resource Waters (LRW) use designation is defined as:
"Limited resource water - these are waters that have been the subject of a use
attainability analysis and have been found to lack the potential for any resemblance of
any other aquatic life habitat as determined by the biological criteria in Table 7-14 of this
rule. The use attainability analysis must demonstrate that the extant fauna is substantially
degraded and that the potential for recovery of the fauna to the level characteristic of any
other aquatic life habitat is realistically precluded due to natural background conditions or
irretrievable human-induced conditions. All water body segments designated limited
resource water will be reviewed on a triennial basis (or sooner) to determine whether the
use designation should be changed. Limited resource waters are also termed nuisance
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prevention for some water bodies designated in rules 3745-1-08 to 3745-1-30 of the
Administrative Code. A temporary variance to the criteria associated with this use
designation may be granted as described in paragraph (F) of rule 3745-1-01 of the
Administrative Code. Waters designated limited resource water will be assigned one or
more of the following causative factors. These causative factors will be listed as
comments in rules 3745-1-08 to 3745-1-30 of the Administrative Code.
(i) "Acid mine drainage" - these are surface waters with sustained pH values below
4.1 s.u. or with intermittently acidic conditions combined with severe streambed
siltation, and have a demonstrated biological performance below that of the
modified warmwater habitat biological criteria.
(ii) "Small drainageway maintenance" - these are highly modified surface water
drainageways (Usually less than three square miles in drainage area) that do not
possess the stream morphology and habitat characteristics necessary to support
any other aquatic life habitat use. The potential for habitat improvements must
be precluded due to regular stream channel maintenance required for drainage
purposes.
(iii) Other specified conditions.
The designation of specific waterbodies as MWH or LRW requires a use attainability analysis (UAA)
based on a waterbody specific.assessment. These do not meet the minimum conditions prescribed by the
CWA (Section 101[a][2]). All of these were adopted in the Ohio WQS in 1990.
Relationship of Ohio's Tiered Uses to the Biological Condition Gradient
Ohio's current tiered uses represent refinements to the original tiered uses adopted in 1978 and reflect the
developments that benefited from ten years of experience in applying a tiered use system. The practical
impacts of these refined and tiered uses on water quality management are described in Table B-4 and
include the designated use, the key attributes of that use, why a waterbody would be designated for that
use, and some of the practical impacts to water quality management. All of the biological criteria and
some of the chemicaVphysical criteria associated with each use are tiered in a logical relationship to the
ecological attributes, which are ascribed by the designated use narrative and the translation of that
narrative to specific criteria. This is consistent with the concepts of the BCG in that expectations and
attainment of each use are measured by the biological criteria that are in turn designed to describe and
measure increments in quality along the BCG (Figure B-3). Chemical-specific and physical parameters
are cast in the role of stressor and exposure indicators and criteria (i.e., they are best used as design
criteria in modeling and TMDLs). They directly support the development and implementation of
abatement and management strategies via water quality management programs by providing the
translation between associations of cause and effect via monitoring and assessment to enforceable
controls via permitting and best management practices via TMDLs. The biological criteria are cast in the
role of response indicators and as the primary criteria for determining use attainment status, measuring
relative quality, and documenting the effectiveness of abatement and management strategies (Yoder and
Rankin 1998, Karr and Yoder 2004). The logical relationship between exposure and response follows in
that some of the key chemical criteria are more stringent for the uses that are representative of the higher
tiers of the BCG (i.e., EWH) and least stringent for the lowest tiers (i.e., MWH, LRW). These are then
translated accordingly to wastewater and other water quality management requirements. However,
criteria that do not demonstrate an empirical relationship along the BCG are not tiered.
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TABLE B-4. Key features associated with tiered aquatic life uses in the Ohio WQS (OAC 3745-1-07),
Aquatic Life
Use
Warm water
Habitat
(WWH)
Exceptional
Warmwater
Habitat
(EWH) '
Coldwater
Habitat
(CWH)
Modified
Warmwater
Habitat
(MWH)
Limited
Resource
Waters
(LRW)
Key Attributes
Balanced assemblages of
fish/invertebrates comparable to
least impacted regional reference
condition
Unique and/or diverse
assemblages; comparable to upper
quartile of statewide reference
condition
Sustained presence of Salmonid or
non-salmonid coldwater aquatic
organisms; bonafide trout fishery
Warmwater assemblage dominated
by species tolerant of low D.O.,
excessive nutrients, siltation,
and/or habitat modifications
Highly degraded assemblages
dominated exclusively by tolerant
species; should not reflect acutely
toxic conditions
Why a Waterbody Would Be
Designated
Either supports biota consistent with
numeric biocriteria for that ecoregion
or exhibits the habitat potential to
support recovery of the aquatic fauna
Attainment of the EWH biocriteria
demonstrated by both organism
groups
Bioassessment reveals coldwater
species as defined by Ohio EPA
(1987); put-and-take trout fishery
managed by Ohio DNR
Impairment of the WWH biocriteria;
existence and/or maintenance of
hydrological modifications that
cannot be reversed or abated to attain
the WWH biocriteria; a use
attainability analysis is required
Extensive physical and hydrological
modifications that cannot be reversed
and which preclude attainment of
higher uses; a use attainability
analysis is required
Practical Impacts'
(compared to a baseline of WWH)
Baseline regulatory requirements
consistent with the CWA "fishable"
and "protection & propagation"
goals; criteria consistent with U.S.
EPA guidance with State/regional
modification.1; as appropriate
More stringent criteria for D.O.,
temperature, ammonia, and nutrient
targets; more stringent restrictions
on dissolved metals translators;
restrictions on nationwide dredge &
fill permits; may result in more
stringent wastewater' treatment
requirements
Same as above except that common
metals criteria are more .stringent;
may result in more stringent
wastewater treatment requirements
Less stringent criteria for D.O.,
ammonia, and nutrient targets; less
restrictive applications of dissolved
metals translators; Nationwide
permits apply without restrictions or
exception; may result in less
restrictive wastewater treatment
requirements
Chemical criteria are based on the
prevention of acutely lethal
conditions; may result in less
restrictive wastewater treatment
requirements
AQL DESIG-
NATED USES
STRESSOR iliiEFFEGTI:::
ii FIGURE B-3. The relationship of Ohio's
tiered designated uses and numerical
biological criteria to the Biological
Condition Gradient.
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Because of bioaccumulation concerns, many toxicant criteria are designed to protect all aquatic life uses
even though they may demonstrate a graded response to the numeric bidcriteria and tiered uses. For some
of the heavy metals criteria where translators were developed between dissolved and total forms, concerns
about the effects of potentially increased discharges of total metals resulted in a risk assessment that
examined the relationships between the numeric biocriteria and total metals (Ohio EPA 1999a). This led
to the derivation of "caps" on the amount of additional total metals that are permitted as a result of the
dissolved metals translator process. These caps varied in accordance with the relationships demonstrated
with the numeric biocriteria and tiered uses. Other parameters that do not demonstrate an empirical
relationship along the BCG are not tiered. Future data exploration may well result in tiered chemical or
physical criteria for stressors that are presently based on fixed, single value criteria. Such refined
chemical criteria are expected to provide benefits to watershed-based management related to the
prioritization of BMPs and in the application of emerging tools such as pollutant trading.
III. Establish technical program
From the outset, the implementation of tiered uses was intended to include a comprehensive and
systematic monitoring and assessment program. The integration of the tiered uses with monitoring and
assessment was an evolutionary development that followed the process outlined in Chapter 5 (Table 5-1;
Figure 5-2) and Figure B-l.
How Does Ohio Collect Biological Data?
Ohio EPA employs a multiple chemical, physical, and biological indicators approach that utilizes each
according to their most appropriate roles as indicators of stress, exposure, and response (Yoder and Rankin
1998). This approach leads to more effective regulation of pollution sources, improved assessment of diffuse
and non-chemical impacts, and improves our ability to implement management strategies for successfully
protecting and restoring the ecological integrity of watersheds. Key attributes that the biological indicators
were developed to reflect include:
1) cost-effective collection of data
2) readily available science
3) be indicative of or extend to dif ferent trophic levels
4) integrate multiple effects and exposures
5) exhibit reasonable response and recovery times
6) be precise and reproducible
7) be responsive to a wide range of perturbations
8) be relevant to managerial and programmatic issues
Because it is impractical to monitor the entire organism assemblages present in an aquatic ecosystem,
choices must be made. Ohio's choice of two organism groups (benthic macroinvertebrates and fish) is
consistent with the ITFM (1992, 1995) recommendations and was done for a number of reasons. Each
assemblage has been widely used in assessments and there is abundant information about their life
histories, distributions, and environmental requirements. The benefit of having two different groups
independently showing the same result is obvious and lends considerable strength to a bioassessment.
However, differences in the responses by each group can lead to the definition of problems that might
otherwise have gone undetected, underrated, or misunderstood in the absence of information from either
organism group. For example, representatives of one assemblage may be able to tolerate and metabolize
toxic substances that are highly detrimental to representatives of the other assemblage. The differences in
recovery rates between each assemblage provide an added dimension to the understanding of how
abatement processes work and document incremental changes through time. The value of such
information in a risk management process should be obvious. Comparisons between the performance of
fish and macroinvertebrates as arbiters of aquatic life use attainment showed non-agreement between
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assemblages at 33% in non-wadeable rivers, 21.2% in wadeable streams, and 28.2% in headwater streams
(Yoder and Rankin 1995a). Assessments based on a single group would have overlooked proportions of
the impairment that actually existed, let alone the loss of signal in diagnosing causal associations. Some
of the concepts in Appendix C are based on this knowledge and experience.
Overview of the Technical Approach
The development and refinement of Ohio's biological assessment tools and criteria reflects an
evolutionary process that is summarized in Figure B-l and in Chapter 5 (Figure 5-2). The standardization
of sampling and laboratory methods occurred first and illustrates the importance of the initial decisions
about methods, taxonomic resolution, and professionalism early in die process (Ohio EPA 1987, DeShon
1995, Rankin 1995, Yoder and Smith 1999). From the outset of the systematic collection of biological data
in Ohio, choices about sampling methods and laboratory procedures were the most important of the initial
decisions that were made. These determine the attributes and characteristics of the resulting data and the
usefulness and accuracy of the analytical tools and criteria that are developed. This, in turn, determines the
quality of the entire approach including its ability to accurately determine biological impairments and
discriminate relative quality along the BCG. Because of its primary role as a response indicator, it determines
our perceptions of environmental quality and the effectiveness of our responses via water quality
management programs and policies.
Sampling Methods
A number of decisions need to be made concerning the adoption of sampling methods. Decisions about
sampling methods and gear, seasonal considerations, which organism groups to monitor, which parameters to
measure and record, which level of taxonomy to use, etc. all were made early in the process. This was a
critical juncture in the process since the decisions made here determined the effectiveness of the
bioassessment effort.
The development of standardized sampling methods was the most important initial task in the
implementation of Ohio's biological monitoring program. While many sampling methods and techniques
existed for both macroinvertebrates and fish, many lacked adequate testing or standardization. The primary
task was the testing, development, and validation of the chosen methods, which involved testing each for its
ability to deliver good information at a reasonable cost. The goal was to use methods and protocols that
would require 1-3 hours at a sampling site making it possible to sample several sites each day, tens of sites
each week, and hundreds of sites each sampling season. A seasonal index period was also established during
the summer-early fall (mid June to mid October).
For macroinvertebrates, artificial substrates were the method of choice and this was consistent with the U.S.
EPA guidance of that time. The application of this method was further tested to refine the general approach
in the early 1980s. A cluster of five artificial substrates bound to a concrete block are set in detectable current
for a colonization period of six weeks. A dip net/hand pick sample of the surrounding natural substrates
including all available habitats is collected at the time of substrate retrieval. This technique, known as
qualitative sampling, employs a triangular frame dip net and can be used as a stand-alone sampling method.
A site description data sheet is completed by a crew leader and includes information about the site habitat,
environmental setting, and other pertinent information. Samples are retrieved, preserved in 10% formalin in
the field, and transported to the laboratory for later processing. The specific methods are documented in
written guidance manuals (Ohio EPA 1980,1987,1989b) that are codified by reference in the Ohio WQS.
Fish are collected using various wading and boat-mounted pulsed D.C. electrofishing gears, depending on the
width and depth of the stream or river. These also had their origin hi already available techniques, but the
stratification of their use in different sizes of waterbodies was an issue that required prior testing and
development. Sampling is standardized by lineal distance of stream or river and reach lengths were
determined by sampling standard increments at methods test sites in the early 1980s. Fish samples are
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processed in the field and include identification to species, enumeration (counts and biomass) by age groups
(adult, 1+, 0+), and delineation of external anomalies. A qualitative habitat assessment (QHEI; Rankin 1989,
1995) is completed over the entirety of the electrofishing reach. Fish sites are sampled once, twice, or three
times within the seasonal index period, the frequency being determined by the complexity of the setting and
the potential for episodic impacts. The specific methods are documented in written guidance manuals (Ohio
EPA 1980,1987, 1989b) that are codified by reference in the Ohio WQS.
Laboratory Methods
Each artificial substrate (quantitative) and natural substrate (qualitative) sample is processed in accordance
with standardized procedures (Ohio EPA 1989b). This includes an initial pre-pick and visual scan for rare
and large organisms, subsampling by major taxa group (mayflies, stoneflies, caddisflies, midges, others), and
identification and enumeration to the lowest practicable taxonomic level. Ohio EPA staff perform both field
sampling and laboratory processing.
Fish specimens that cannot be verified in the field are preserved in 10% formalin and transported to the
laboratory for later processing. These are changed to 70% ethyl alcohol and identified to species.
Verification of difficult specimens is performed by at least one qualified non-Ohio EPA taxonomist.
Analytical Methods
Ohio EPA analyzes biological data using routines available in the Ohio ECOS data storage, retrieval, and
management system. Data is entered into Ohio ECOS following a data validation and QA/QC process to
eliminate transcription and other errors. The principal indexes are based on multimetric techniques that
were modified and calibrated for use in Ohio. For fish this includes the Index of Biotic Integrity (IBI;
Karr 1981, Fausch et al. 1984, Karr et al. 1986) and the Index of Well-Being (IWB; Gammon 1976,
Gammon et al. 1981). For macroinvertebrates it includes the Invertebrate Community Index (ICI; Ohio
EPA 1987, DeShon 1995). hi addition to the primary indexes, data analyses include the index metric
values, relative abundance, and other aggregations of the data that exhibit ecologically meaningful
patterns and information over space and time. This can include the use of multivariate analyses,
parametric and non-parametric statistical techniques, and data mapping.
Staffing and Professionalism
Qualified and regionally experienced staff are employed to carry out the sampling and data analysis activities.
Skilled and experienced staff direct, manage, and supervise all activities. This includes a high level of
expertise in the field since many of the critical pieces of information are recorded and, to a degree, interpreted
here. The same professional staff who collect the field data also interpret and apply the information derived
from the data in a "cradle to grave" fashion. Thus the same staff who perform the field work also plan that
work, process the data into information, interpret the results, and apply the results via assessment and
reporting. Such staff, particularly those with sufficient experience, also contribute to policy and program
development. The majority of data used by Ohio EPA is collected by agency staff. However, the methods
and approach can be carried out by other entities and practitioners. Since 1999, Ohio EPA has operated a
voluntary certification process and this will soon be mandated by the Ohio Credible Data Law.
How Does Ohio Decide What Waterbodies and Locations to Monitor?
In 1980, Ohio EPA initiated an intensive watershed survey design that included chemical/physical and
biological assessments or surveys. A biological and water quality survey, or "biosurvey," is an
interdisciplinary monitoring effort coordinated on a waterbody specific or watershed scale. The effort
may involve a relatively simple setting focusing on one or two small streams, one or two principal
stressors, and a handful of sampling sites or a much more complex effort including entire drainage basins,
multiple and overlapping stressors, and tens of sites. Through the 1980s, Ohio EPA conducted
biosurveys in 6-10 different study areas with an aggregate total of 250-300 sampling sites sampled/year.
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• Rotating basin approach
for determining annual
monitoring activities.
•Correlated with NPDES
permit schedule.
• Supports annual WOS
use designation rule-
making.
•Aligned with 15 year
TMDL schedule in 1998.
While the purpose of these
surveys was to support multiple
program objectives, the schedule
of water quality management
program outputs was not always
coordinated with the biosurvey
schedule. In 1990, this process
was formally coordinated
beginning with a revision to the
schedule for reissuance of major
and significant NPDES permits.
Ohio EPA formally adopted a five
year basin approach in which
biosurveys were scheduled two
years in advance of the reissuance
of NPDES permits (Figure B-4).
The rotating basin approach
proved its utility in two other
instances. The first was in
support of Ohio nonpoint source assessment in 1990, and the second when TMDLs became a major
priority in 1998. The latter was seamlessly integrated into the rotating basin approach (Ohio EPA 1999b).
In the 1990s, the demand for the watershed assessments increased further with up to 700 sites being
sampled within 10-12 study areas in some years. The process of program integration was further
institutionalized with a structured process for selecting watersheds, planning the monitoring, and
analyzing and reporting the results (Table B-5).
FIGURE B-4. Five-year basin approach for determining annual
watershed monitoring and assessment activities and correspondence
to support major water quality management programs.
TABLE B-5. Important timelines and milestones in the planning and execution of the rotating basin approach
conducted annually and since 1990 by Ohio EPA.
Milestone
Timeline
December - February:
(Months 1-3)
February - March:
(Months 3 thru 4)
March - May:
(Months 4 thro 5)
May - June:
(Months 5 thru 6)
June - October:
(Months 6 thru 10)
October - February:
(Months 10 thru 14)
November - May:
(Months 11 thru 17)
May - December
(Months 17 thru 24)
Initial screening of the major hydrologic areas takes place by soliciting input from the various program
offices and other stakeholders.
Final prioritization of issues and definition of specific study areas. Resource allocation takes place and
study team assignments are made.
Study planning takes place and consists of detailed map reconnaissance, review of historical
monitoring efforts, and initial sampling site selection by the study team. Final study plans are
reviewed and approved.
Final study plans are used to develop logistics for each field crew. Preparation!; are made for full-scale
field sampling.
Field sampling takes place with field crews operating somewhat independently on a day-to-day basis,
but coordinated by die study plan and the team leader. Study team communication takes place as
necessary, especially to resolve unexpected situations.
Laboratory sample analysis takes place for chemical and biological parameters. Raw data is entered
into databases for reduction and analysis. The study team meets to review the information base
generated by the field sampling and to coordinate die data analysis and reporting effort.
Information about indicator levels 3-6 is retrieved, compiled, and used to produce analyses that will
support the evaluation of status and trends and causal associations within the study area. Integration of
the information (i.e., assessment) is initiated.
The assessment process is completed by producing working copies of the assessment for review by the
study team and a final edit for an internal peer review. Final assessment approved by management for
use within and outside of Ohio EPA. It is used to support 305b /303d, NPDES permitting, water
quality standards {e.g., use designation revisions), and other programs where surface water quality is of
DRAFT: Use of Biological Information to Better Define Designated Aquatic Life Uses in State
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170
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Each biosurvey is designed and conducted to meet three major objectives:
1) determine the extent to which use designations assigned in the Ohio WQS are either attained or not
attained;
2) determine if use designations assigned to a given waterbody are appropriate and attainable; and
3) determine if any changes in key ambient biological, chemical, or physical indicators have taken place
over time, particularly before and after the implementation of point source pollution controls or best
management practices.
The data gathered by a biosurvey is
processed, evaluated, and
synthesized in a biological and
water quality report. Each
biological and water quality study
contains a summary of major
findings and recommendations for
revisions to WQS (e.g., Table B-6),
future monitoring needs, or other
actions which may be needed to
resolve existing impairments) of
designated uses. At the same time,
the systematic execution of basin
surveys builds a long-term database
over space and time, creating and
sustaining a resource of the
development and improvement of
tools, criteria, policies, and
legislation (Figure B-5).
The systematic accumulation of information
across spatial and temporal scales
Policy
Development
• TMDL Usttng/De-Ufftfrtfl
' Refined WQS Uses
• Antideqradatiort
• NPDES (WET, CSOs,
Stormwater)
• 404/401 dredge & fit!
» Stream Protection
• Nutrietamsnaserfietii
* Overall program/policy
effectiveness
• Environments! audits
Program
Development
• Environmental indica-
tors
WQCriteria
• fteferenc$ WQ $
Sediment benchmarks
• f)lolQtifc$l Cr!t$f!a
• Biological Response
Signatures
• Regional stratification
fecoregians, .subreg,!
\ Statewide/Reglonai
Applications
-
• T$IDL § f?0%*J
• Status/Trends (30Sb)
• Local projects
-h»«/BMP effective-
ness evslustions
• NAWQA/REMAP
• Watershed mgmt.
• SWAP
• UWA
• IW1 "ground
trulhtng"
FIGURE B-5. Strategic support provided over time by systematic
monitoring and assessment; functions related to the implementation
of TALUs are italicized and underlined.
The recommendations for use designation revisions are a direct result of the biological and water quality
assessment. Uses are designated on demonstrated potential to attain a particular use based on the
following sequence (in order of importance):
1) attainment of the biocriteria (if attaining WWH or higher - attainment of EWH is required to be
designated as EWH); and
2) if a WWH biocriterion is not met, the habitat potential determined by the Qualitative Habitat
Evaluation Index (QHEI; Rankin 1989,1995) and an associated assessment of warmwater:
modified habitat attributes is used to determine the potential to attain WWH.
For uses less than WWH (i.e., MWH or LRW), a use attainability analysis is required and includes
consideration of the factors that essentially preclude WWH attainment including the feasibility of
restoring the waterbody. A use attainability analysis requires the following information:
' 1) the present attainment status of the waterbody based on a biological assessment performed in
accordance with the requirements of the biocriteria, the Ohio WQS, and the Five-Year
Monitoring Strategy (the latter pertains to adequacy of spatial design);
2) a habitat assessment to evaluate the potential to attain at least WWH; and
DRAFT: Use of Biological Information to Better Define Designated Aquatic Life Uses in State
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171.
-------
3) a reasonable relationship between the impaired-status and the precluding human-induced
activities based on an assessment of multiple indicators used in their appropriate indicator roles
and a demonstration consistent with 40CFR Part 131.10 [g] [ I -6].
In the example from the Big Darby Creek watershed assessment conducted in 2000, all of the streams and
segments listed in Table B-6 were sampled in accordance with Ohio EPA's geometric and intensive
survey design. A number of the streams in Table B-6 were originally assigned aquatic life use
designations in the 1978 and 1985 WQS based largely on best professional judgment or by tributary
membership, while others were not yet designated. The current biological assessment methods and
numerical biocriteria did not exist at that time. Most of the larger tributaries and the mainstem were
previously designated based on biosurveys of specific segments and streams in 1979, 1981, 1988, and
1992. The use designations of most of the mainstem and some of the major tributaries were resolved by
those efforts. However, many of the smaller streams in this watershed were evaluated for the first time
using a standardized biological approach in 2000. Ultimately, the designations for each stream and river
segment are based on direct sampling and assessments of each individual waterbody and the processes
previously described. Extrapolation of sampling results for this and other purposes (e.g., status
assessment) is minimal and occurs only within individual waterbodies. The application of the geometric
watershed and intensive survey design included all tributaries and resulted in the addition of 26
previously unlisted and/or undesignated streams. Of these 26 streams, four were designated EWH, 18 as
WWH, four as MWH, and two as LRW; an additional five stream segments were simultaneously
designated CWH. Under the 1978 WQS, all 26 tributaries would have been designated as EWH by virtue
of their tributary membership in the Big Darby watershed. This was extended to only the 19 named
tributaries in the 1985 WQS, of which nine were later changed based on earlier biosurvey data. This
example illustrates the comparative lack of accuracy in extrapolating uses by tributary membership within
a watershed and the need to sample and assess individual streams for use designation purposes.
TABLE B-6. Summary of recommendations for use designations in the Big Darby Creek watershed based on a
biological and water quality assessment completed in 2000. Symbols are listed for the existing
designation/recommended designation C - undesignated; 4 - verified by biosurvey; * - unverified default
designation from 1978 or 1985 WQS).
Water Body Segment
Big Darby Creek (02-200)" - Headwaters to RM 79.2
- RM 79.2 to mouth
Flat Branch (02-223) (RM 78.48)*
Tributary to Flat Branch (02-365) (RM 1.5)
Uttle Darby Creek (02-251) (RM 78.34) RM 3.5 to mouth
U.T. to B. Darby Cr. (02-361) (RM 74.91) RM 0.75 to mouth
Spain Creek (02-222) (RM 74.3) - Headwaters to RM 5.0
RM 5.0 to mouth
Pleasant Run (02-221) (RM 72.01)
Use Designations
S
R
W
Aquatic Life
Habitat
W
W
H
*
+
E
W
H
+
*+
*
+
_•¥
*
*+
*+
M
W
H
+
_+
SS'
H
C
W
H
+
+
+
+
L
R
W
Water
Supply
P
W
S
A
W
S
*+
+
+
+
+
+
+
+
+
I
W
S
*+
+
+
_+
+
+
+
+
-t-
Recreation
B
W
P
C
R
*+
+
+
_+
+
*+
*+
*+
S
C
R
_+
DRAFT: Use of Biological Information to Better Define Designated Aquatic Life Uses in State
and Tribal Water Quality Standards: Tiered Aquatic Life Uses - Appendix B-August 10, 2005
172
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Water Body Segment
U.T. to Big Darby Creek (02-360) (RM 69,4) RM 1.8 to mouth
Hay Run (02-220) (RM67.6) RM 1.1 to mouth
Prairie Run (02-219) (RM 63.84)
Buck Run (02-209) (RM 63.74)
Robinson Run (02-207) (RM 53.69)
Sweeney Run (02-357) (RM 52. 1 1) RM 1.7 to mouih
Sugar Run (02-206) (RM 50.92) - Headwaters to RM 7.0
- RM 7.0 to mouth
U.T. to Sugar Run (02-358) (RM 7.39)
Worthington Ditch (02-2356) (RM 50.62) RM 0.4 to mouth
Ballenger-Jones Ditch (02-355) (RM 49.68) RM 3.72 to mouth
Yutzy Ditch (02-364) (RM 47.1) RM 1.38 to the mouth
Fitzgerald Ditch (02-272) (RM 44.96) RM 1.75 to mouth
Little Darby Cr.(02-2 10) (RM34.1) Headwaters to RM 36.9
Little Darby Cr.(02-210) (RM 34.1) RM 36.9 to mouth
Clover Run (02-2 18) (RM 39.8)
Lake Run (02-216) (RM 36.9)
Jumping Run (02-217) (RM 3.9)
Treacle Creek (02-213) (RM 31.3)
Howard Run (02-215) (RM 5.4)
ProctorRun (02-214) (RM3.69)
Barron Creek (02-212) (RM 24.4)
Wamp Ditch (02-363) (RM 23.0)
Spring Fork (02-2 1 1 ) (RM 1 7.46)
Bales Ditch (02-362)(RM 3.64) RM 1.72 to mouth
Smith Ditch (02-353) (RM 3 1 .69)
Tributary to Smith Ditch (02-354)(RM0.06)
Gay Run (02-298) (RM 26.48)
Hellbranch Run (02-204) (RM26.1) Headwaters to RM 5.0
Hellbranch Run (02-204) (RM 26. 1 ) RM 5.0 to mouth
Hamilton Ditch (02-259) (RM 11.19) -Hdwtrs to Feder Rd.
Use Designations
S
R
W
Aquatic Life
Habitat
W
W
H
_+
+
+
+
+
+
_+
+
+
+
•»•
+
+
+
+
+
+
E
W
H
+
*
*
*
*
*+.
*+
*+
*+
*+
*+
+
_+
*
*4
M
W
H
+
+
_+
ss
H
C
W
H
+
L
R
W
+
Water
Supply
P
W
S
A
W
S
+
+
_+
+
+
_+
+
+
_+
•_+
+
_-»-
_+
+
•f
*+
*+
*+
*+
*+
*+
*+
+
*+
+
+
+
+
+
4-
*+
I
W
S
_+
+
•H
+
_+
+
+
_+
_+
_+
+
_+
+
+
*+
*+
*+
*+
*+
*+
*+
+
*+
+
+
_+
_+
+
+
*-!-
Recreation
B
W
P
C
R
*+
_+
*+
+
*+
*+
_+
+
+
+
+
+
+
*+
*+
*+
*+
*+
*+
+
+
+
+
*+
•f
S
C
R
+
+
+
•»-
+
+
DRAFT: Use of Biological Information to Better Define Designated'Aquatic Life Uses in State
and Tribal Water Quality Standards: Tiered Aquatic Life Uses - Appendix B-August 10, 2005
173
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Water Body Segment
Feder Rd. to mouth
Clover Groff Ditch (02-245) (RM 1 1.19 - Hdwtrs to Feder Rd.
Feder Rd. to month
Springwater Run (02-203) (RM 24.0) '
U.T. to Big Darby Creek (02-352) (RM 23.77)
U.T. to Big Darby Creek (02-270) (RM 20.2)
U.T, to Big Darby Creek (02-366) (RM 18.41)
Greenbrier Creek (02-202) (RM 16.75)
Georges Creek (02-201) (RM 14.4)
Lizard Run (02-273) (RM 12.93)
Use Designations
S
R
W
Aquatic Life
Habitat
W
W
H
_+
_+
+
+
_+
_+
+
+
E
W
H
*
«
*
M
W
H
_+
ss
H
C
W
H
L
R
W
+
Water
Supply
P
W
S
A
W
S
*+
*+
*+
+
+
+
+
+
+
•f
I
W
S
*+
*+
*+.
+
+
_+
-t-
+
+
+
Recreation
B
W
P
C
R
•»•
_+
+
*+
+
*+
*
S
C
R
_+
+
+
+
a - River code of the river or stream segment; • b - River Mile of the confluence point with applicable receiving stream
While the principal focus of a biosurvey is on
the status of aquatic life uses, the status of
other uses such as recreation and water supply,
as well as human health concerns are also
addressed (Table B-6). The findings and
conclusions of a biological and water quality
study may factor into regulatory actions taken
by Ohio EPA (e.g., NPDES permits, Director's
Orders, the Ohio Water Quality Standards
[OAC 3745-1]), and are eventually
incorporated into Water Quality Permit
Support Documents (WQPSDs), State Water
Quality Management Plans, the Ohio Nonpoint
Source Assessment, and the Integrated Report
(combined 303[d] and 305[b] report). Periodic
rulemakings are conducted to incorporate the
use revision recommendations into the Ohio
WQS, thus resolving the issue prior to the
application of water quality management (see
Figure 5-1, U.S. EPA's Water Quality
Management Cycle). Figure B-6 summarizes
the number of stream and river segments (mostly
whole streams) where aquatic life uses have
been revised as the result of a biological and
water quality assessment in Ohio since 1978.
This became a routine practice once the
assessment criteria and decision-making process
AQUATIC LIFE USE CHANGES:
OHIO WQS (1978 -2001)
CO
•UPGRADES"
•DOWNGRADES'
PREVIOUSLY
UNDESIGNATED
TYPE OF CHANGE
FIGURE B-6. The number of individual stream and river
segments in which aquatic life use designations were
revised during 1978-1992 and 1992-2001. Cases where
the use was revised to a higher use are termed
"upgrades" and cases where a lower use was assigned are
termed "downgrades". Previously undesignated refers to
streams that were not listed in the 1985 WQS, but which
have been added via the Five-Year Basin Approach to
monitoring and assessment.
DRAFT: Use of Biological Information to Better Define Designated Aquatic Life Uses in State
and Tribal Water Quality Standards: Tiered Aquatic Life Uxes - Appendix B - August 10, 2005
174
-------
for UAAs were established earlier in the assessment process. It required the development of reliable'
tools, particularly for determining status, assessing habitat, and determining causal associations, all of
which are part of the developmental process described in Figure 5-2. The terms "upgrade" and
"downgrade" are used figuratively here and in Figure B-6 as descriptors of the direction of change from
the default use to that produced by a standardized assessment process. The majority of these changes are
from the baseline of the original designations made in 1978 or 1985 without the benefit of systematic
monitoring and assessment data, numerical biocriteria, and refinements in the process that occurred in the
late 1980s. Thus, the original'use designations are merely being "corrected" to the appropriate use based
on a standardized process and more robust criteria and assessments.
Monitoring and assessment information, when based on a sufficiently comprehensive and rigorous system
of environmental indicators, is integral to protecting human health, preserving and restoring ecosystem
integrity, and sustaining a viable economy (ITFM 1992). Such a strategy is intended to achieve a better
return on public and private investments in environmental protection and natural resources management.
More and better monitoring and assessment information is needed to answer the fundamental questions
about the condition of our water resources and to shape the strategies needed to address both existing and
emerging problems within the context of watershed-based management. These principles have guided the
development of surface water monitoring and assessment at Ohio EPA for the past 25 years and will
continue to do so in the future.
IV. Develop and validate quantitative thresholds
The lack of adequate and reliable decision criteria'for biological assessment has historically limited its
usefulness, reliability, and wider acceptance in water quality management. In 1980, Ohio EPA developed an
initial set of decision criteria for fish and macroinvertebrate assemblages that consisted of narrative quality
ratings based in part on numerical biological index "guidelines" (Tables B-l and B-2). These were intended
to more directly reflect and assess the ecological goals espoused by the tiered aquatic life uses adopted in
1978. These early narrative biocriteria were comprised of contemporary measures such as taxa richness,
indicator guilds, the Shannon diversity index, and the Index of Well-Being (Gammon 1976). Attainable
expectations for a set of narrative community attributes were based on Ohio's experience with sampling
approximately 150-200 sites statewide. This approach was used between 1980 and 1987 and was applied
uniformly on a statewide basis. As the technology did not yet exist, no effort was made to account for
background variability by using landscape partitioning frameworks such as ecoregions.
The narrative classification system consisted of assigning narrative quality ratings such as exceptional
(consistent with the Exceptional Warmwater Habitat use), good (Warmwater Habitat use), fair, and poor.
Exceptional and good met the goals of the Clean Water Act while fair and poor reflected a failure to attain
those goals (Tables B-l and B-2). The purpose of this narrative classification system was essentially two
fold: 1) to provide an objective, systematic basis for assigning aquatic life uses to surface waters; and 2) to
provide an objective, standardized approach for determining the magnitude and severity of aquatic life
impairments for assessment purposes. Considerable judgment was used in applying these early narrative
biological criteria on a site-specific basis and the system was characteristic of between a level 2 and 3
program (See Appendix C). The aggregate impact of these assessments played a major role in setting and
evaluating WQS use designations, designing water quality management plans, and devejoping advanced
treatment justifications for municipal sewage treatment plants. These criteria also provided a basis for
designating stream and river segments as attaining, partially attaining, or not attaining designated aquatic life
uses in the 1982,1984, and 1986 Ohio EPA 305b reports. They were, however, inherently prone to under-
estimating impairment (DeShon 1995).
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175
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Regionally Referenced Numerical Biological Criteria
In 1986, a major effort was undertaken to develop regionally referenced and calibrated numeric biological
criteria using a statewide set of regional reference sites. This was spurred by the Ohio Stream
Regionalization Project in which the application of Omernik's (1987) ecoregions and the regional reference
site concept (Hughes et al. 1986) was tested. For the fish assemblage, the Index of Well-Being was modified
(Ohio EPA 1987) and the Index of Biotic Integrity (IB I; Karr 1981, Karr et al. 1986) was added. For
macroinvertebrates, the Invertebrate Community Index (ICI; Ohio EPA 1987, DeShon 1995) replaced the
narrative evaluations used previously. The IBI and ICI consist of metrics that include community production,
function, tolerance, and reproduction in an aggregated index. This provides for a more rigorous, ecologically
oriented approach to assessing aquatic community health and well-being. The process of deriving the
numerical biological criteria is described more extensively in Ohio EPA (1987,1989a,b) and Yoder and
Rankin(1995a)..
The derivation of the current numerical biological criteria is based on the biological "performance" that is
demonstrated at least impacted, regional reference sites. This is consistent with the operational definition of
biological integrity as-defined by Karr and Dudley (1981), which provides the theoretical basis for this
framework. The numerical biological criteria resulting from the application of this framework represent the
assemblage performance that can reasonably be attained given contemporary background conditions.
Although these do not emanate from an attempt to define "pristine," pre-Columbian conditions, the design
framework includes a provision to "maintain" the biocriteria by continually resampling the reference sites -
reference condition is monitored so that all reference sites are resampled once each decade. This promotes
the periodic and orderly reassessment of reference condition and the database that drives the calibration of
the biological indexes and the derivation of the numeric biocriteria. Furthermore, the knowledge base used
in the development of the multimetric indexes includes an awareness of pre-settlement faunas and their
characteristics. This is entirely consistent with the BCG and the description of attributes from "as naturally
occurs" to an increasingly disturbed state. Thus, if pristine conditions do return this would be reflected by
the periodic adjustments to the multimetric indexes, their calibration, and/or the numerical biological
criteria.
Biological criteria in Ohio are based on two principal organism groups, fish and macroinvertebrates.
Numerical biological criteria for rivers and streams were derived by utilizing the results of sampling
conducted at more than 400 reference sites that represent the "least impacted" conditions within each
ecoregion (Ohio EPA 1987, 1989a). This information was then merged within the existing framework of
tiered aquatic life uses to establish attainable, baseline biological assemblage performance expectations on a
regional basis. Biological criteria vary by ecoregion, aquatic life use designation, site type, and biological
index (Figure B-2).
The framework within which biological criteria were established and used to evaluate Ohio rivers and
streams includes the following major steps:
• selection of indicator organism groups;
• establish standardized field sampling, laboratory, and analytical methods;
• selection and sampling of least impacted reference sites;
• calibration of multimetric indexes (e.g., IBI, ICI);
• set numeric biocriteria based on attributes specified by each tiered aquatic life use designation;
• reference site re-sampling (10% of sites sampled each year beginning in 1990); and,
• making periodic (i.e., once per 10 years) adjustments to the multi-metric indexes, numeric
biocriteria, or both as determined by reference site resampling results (Note: this latter step has yet
to be undertaken by Ohio EPA).
DRAFT: Use of Biological Information to Better Define Designated Aquatic Life Uses in State 176
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-------
The major steps in the biological criteria calibration, derivation, and application process are summarized in
Figure B-7. The process integrates the technical process of index derivation and calibration with narrative
statements about the desired biological assemblage condition and regionalization (e.g., ecoregions). This
latter step is particularly important as it is needed to stratify regional landscape variability within a tractable
framework. Figure B-7 portrays the calibration of the IB I for wading sites. A similar stepwise procedure
was used to calibrate the Invertebrate Community Index for macroinvertebrates (Ohio EPA 1987, DeShon
1995) and the IBIs for the headwater and beatable site types. Once reference sites are selected and sampled
(Step 1 in Figure B-7) the biological data is first used to calibrate the ffil (Step 2) and ICI. For fish three
different IBIs were derived, one each for headwaters, wading (Step 3), and boat sites. The reference site
IBIs are then used to establish numerical biological criteria (Steps 4 and 5). A notched box-and-whisker
plot method was used to analyze the distribution of IBIs by ecoregion (Step 4). These plots contain sample
size, medians, ranges with outliers, and 25lh and 75lh percentiles. Box plots have one important advantage
over the use of means and standard deviations (or standard errors) because they do not assume a particular
distribution of the data. Furthermore, outliers (i.e., data points that are two interquartile ranges beyond the
25th or 75* percentiles) do not exert an undue influence as they can on means and standard errors. In
establishing biological criteria for a particular area or ecoregion we attempted to represent the "typical"
biological community performance, not the extremes and outliers. These can be dealt with on a
case-by-case or site-specific basis, if necessary. Once numerical biological criteria are determined, they are
then used in making assessments of specific rivers and streams (Step 6).
Metric
reference Sites
II. Calibration of IBI metrics
Number ol Species Varies x Drainage Area
Mo. of Darter Spp. Varies x Drainage Area
No. of Sunfish Spp. >3 2-3 <2
No. of Sucker Spp. Varies x Drainage Area
Intolerant Species
>1QOsq. mi. >5 3-5 <3
<100sq.mi. Varies x Drainage Area
%Tolerant Species Varies x Drainage Area
%0mnivores «19 19-34 >34
%lnsectivores
<30 sq. mi. Varies x Drainage Area
>30sq. mi. >55 26-55 <26
%Top Carnivores >5 1-5
Relative Abundance >750 200-750 <200
III. Calibrated IBI modified for
Ohio waters
': H£i*:.;
v''•::"' V:'•'.•'' ' r'-•::"'-•:$:'"-•'.- ?•••:) "• ''•'• '••.':,"-,:::--
IV. Establish ecoregional
patterns/expectations
criteria: codify in WQS
VI. Numeric biocriteria are
used in bioassessments
FIGURE B-7. The major steps of the Ohio EPA numeric biological criteria calibration and derivation
process leading to their application in biological and water quality assessments; this example is for the
Index of Biotic Integrity (IBI) for wading sites.
DRAFT: Use of Biological Information to Better Define Designated Aquatic Life Uses in State
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177
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The outcome is a systematic process for measuring the essential products of aquatic structure and function
that represent symptoms of ecosystem health. BCG derived and calibrated numeric biocriteria provide
tangible measures of aquatic assemblages by which ecosystem health and well-being can be inferred. The
tangible products of healthy watersheds are desirable biomass, water quality that is suitable for all uses, and
an ability to assimilate background inputs that do not alter the key characteristics or processes associated with
the aquatic assemblages detailed in the BCG (Table B-7). The key indicators of each are biological
assemblage performance consistent with the designated use (measured by the biological indexes and
compared to the numeric biocriteria) and chemical and physical quality comparable to least impacted regional
reference conditions and other acceptable exposure thresholds.
TABLE B-7. The tangible products that are symptomatic of aquatic ecosystem health and
the measurable biological, chemical, and physical indicators of healthy and degraded
aquatic systems.
Tangible "Products"
Healthy
Degraded
Biomass
Water Quality
Assimilative Capacity
Desirable forms (quality biodiversity,
game fish, birds, mammals, inverts.,
plants, algae, microbes)
Comparable to regional reference
Processes background runoff and
materials without adverse changes in
biota
Undesirable forms (low quality
biodiversity, nuisance abundances,
tolerant species dominate)
Poorer than regional reference
Inability to process background
inputs due to reduced capacity to
biologically and physically process
excess materials
Measurable Indicators:
Biological assemblages
Chemical indicators
Physical Indicators
Meet or exceed numeric biocriteria
for TALU
Meets numeric criteria (some are
TALU based) and is within reference
thresholds
Provides essential habitat attributes
and hydrology
Does not meet biocriteria for TALU;
response varies by impact type and
severity of impairment
Exceeds numeric criteria and/or
reference thresholds
Degraded habitat and altered
hydrology
What Process Was Used to Adopt Biocriteria in the Ohio WQS?
The adoption of numeric biocriteria and tiered uses in the Ohio WQS has been an evolutionary process
over the preceding 25 years. There were many important events that determined the make-up and
acceptance of the biocriteria and TALU in Ohio. These milestones are summarized in Table B-8. Some
of the key events that resulted in a wider acceptance of the present day biocriteria and tiered uses were the
legal proceedings on the use changes that occurred in the lower Cuyahoga River in 1988 and Ottawa
River in 1989. Ohio EPA adopted a recommendation that the use designation of the Cuyahoga River
mainstem be changed from a Limited Warmwater Habitat use designation to Warmwater Habitat based on
biological and water quality surveys conducted between 1984 and 1987 and the ensuing UAA process.
The former use was adopted in 1978 as a variance for specific point source derived pollutants. The
biological assessments concluded that while the mainstem was severely impaired, the potential to attain
WWH with achievable water quality based management of point sources was supported by the habitat
assessment that showed a sufficiently intact habitat. This was eventually resolved via a legal process that
included appeals of the initial decision up to the Ohio Supreme Court.
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TABLE B-8. Key events and milestones that occurred in the evolutionary development, adoption, and
implementation of biological assessments, numeric biocriteria, and tiered aquatic life uses in Ohio between
1974 and the present.
YEAR MILESTONE
DESCRIPTION
1974 First Ohio WQS
1978 Initial TALUs
1980 Narrative "biocriteria"
1983-4 Stream Regionalization Project
1986-7 Derivation of numeric biocriteria
1987 Biocriteria proposed in WQS
1987-89 Hearings on Cuyahoga River use
change
1989 Hearings on Ottawa River use
change
1990 Biocriteria adopted
1990 Five-Year Basin Approach
1991 Internal training and orientation
Lake Erie Bioassessment
1995
Wetlands bioassessment methods
1998 and biocriteria
1998 TMDL development process &
schedule
1999 Re-sampling of regional reference
sites
2003 Primary Headwater Habitat
2003 Ohio River
General use, few numeric criteria, narrative "free froms"
Tiered uses adopted, specific chemical criteria
First organized approach to biological assessment; systematic monitoring &
assessment
Testing and validation of Omemik's ecoregions and reference site concepts in
Ohio
Statewide data collected to date was used to develop, derive, and calibrate
numeric biocriteria based on multimetric indexes; biocriteria "User Manuals"
published
Initial proposal for numeric biocriteria
Litigation of revision of a segment of the river form LWH to WWH;
regulated entities Contested basis for the "upgrade"; the first test of the
technical and policy aspects of the numeric biocriteria and TALL)
implementation; resolved at Ohio Supreme Court
Litigation of revision of a segment of the river from LWH to WWH;
regulated entities challenged; issue settled after Cuyahoga case ruling; led to
more stringent regulation of point and nonpoint sources.
Numeric biocriteria and refinements to TALUs were formally adopted in
WQS
A rotating basin approach that integrated key WQ management program
outputs (e.g., NPDES permits) was initiated; use changes processed in annual
rulemakings
All .water program staff receives training in WQS, monitoring & assessment,
modeling, and permit development and their integration.
Biological assessment methods and indexes developed for application to Lake
Erie near shore and lacustuary habitats
Bioassessment methods and narrative criteria were developed for wetlands;
includes various standardized assessment methods (beyond delineation) and a
classification scheme.
TMDL development was integrated into the Five-Year Basin Approach ad
schedule through 2015
First re-sampling of regional reference sites was completed via the Five-Year
Basin Approach
Assessment and classification scheme for primary headwater streams that are
not included in the existing numeric biocriteria are developed as a result of
stream management applications.
ORSANCO develops biological assessment tools and indexes as a precursor
to numeric biocriteria for the Ohio R. mainstem.
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Data collected via follow-up monitoring between 1984 and 2000 shows that attainment of the WWH
biocriteria is increasing in the mainstem and proving the validity of both the WWH designation and the
water quality based pollution abatement that the redesignation spurred (Figure B-8). A similar case
involving the Ottawa River was resolved when this legal decision was made. No other appeals of the
hundreds of use changes that have been made since that time have been filed. The systematic process of
resolving use designation issues ahead of water quality management actions (permitting, listing, funding,
planning) has proceeded as one of. the most important outcomes of the Five-Year Basin Approach since
that time. The next major milestone for the program will be the analysis of the first set of reference sites
re-sampling that took place in the 1990s. In addition, level IV subregions have been delineated, which
offers an additional level of potential stratification to the biocriteria derivation process.
The developments that occurred in the late 1990s including biological assessment and classification
schemes for wetlands, Lake Erie near shore and lacustuary habitats, primary headwater stream habitat,
and the Ohio River all happened as a result of the ground work laid in the 1980s for streams and rivers. It
illustrates the natural growth process that can occur once the fundamentals of the approach are developed,
tested, and adopted.
s
UJ
CUYAHOGA RIVER: ICI
Toxic Response
Threshold (ICI <18)
1984 1986 1987 1988 .1991 1996 2000
FIGURE B-8. Box-and-whisker plots of Invertebrate Community Index
(ICI) results in the mainstem of the Cuyahoga River between Akron and
Cleveland between 1984 and 2000.
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Appendix C
Technical Guidelines: Technical Elements
of a Bioassessment Program
(SUMMARY OF DRAFT DOCUMENT)
[This document has undergone review by State and U.S. EPA Regional biologists and managers. Data
analyses are currently being conducted to refine certain technical elements (e.g., subsampling level,
taxonomic resolution, spatial array of sites) that determine the level of rigor. A revised version will be
prepared for a more comprehensive review by States and Tribes prior to finalization. A draft
document will be available to the public in 2006.]
What are these technical guidelines and what is the purpose of the document?
This document is intended primarily for use by State and Tribal program managers and staff responsible
for monitoring and assessment and WQS programs. States and Tribes can use this information to assess
and communicate the precision of biological programs and, if deemed necessary, to refine and modify
those programs. As States and Tribes increasingly use biological assessments and criteria to refine
designated aquatic life uses, the need to recognize and communicate the level of precision of the
biological program takes on greater importance. In addition, when the majority of States are in various
stages of developing and improving their biological assessment programs, States and Tribes can use the
type of detailed guidelines and milestones provided in this document to evaluate their progress.
Bioassessment is a major component of monitoring and assessment programs that include other chemical,
physical, and environmental measures and indicators (ITFM 1992, 1995; Yoder arid Rankin 1998). This
document describes the critical, or key, technical attributes and processes of State and Tribal biological
assessment programs. State and Tribal monitoring programs can also use the technical information
presented in this document as a procedural template for evaluating the technical elements of their
chemical and physical monitoring and assessment approaches. Ultimately, the integration of chemical
and physical assessment with biological assessment will provide information to help States and Tribes
better determine priorities and make more informed management decisions. State and Tribal programs
can achieve appropriate levels of precision
in their monitoring and assessment programs t he 11 Key Technical Etements of a BiMumessmeta Program
using currently available methods and
technologies, and these approaches will • $*&$#% pestea
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articulate the underlying rationale for each. The technical elements will be described in detail in the draft
document that is being prepared for review.
How do environmental managers use these guidelines to evaluate the precision of their bioassessment
program?
Included in the Technical Guidelines document is a checklist that enables managers and technical staff to
evaluate their program's level of rigor for each of the 12 key technical elements. The checklist includes
four levels of rigor, with Level 4 being the most rigorous. For an overall assessment of a water quality
agency's bioassessment program, a checklist should be completed for each assemblage and waterbody
ecotype, as bioassessment programs may have different levels of rigor for different waterbody ecotypes.
It is important for the water quality agency to determine and reconcile these for management purposes
since differing levels of rigor provide different levels of confidence in decision-making.
Evaluation of a program's level of rigor should be conducted collaboratively with State and Tribal
technical staff and managers. Documentation will support completion of the checklist regarding aspects
of the technical elements. Some variation between different elements will likely occur in terms of
performance level (i.e., one element may receive a Level 4, while another is determined to be Level 2).
Therefore, a scale that combines the rating of all elements will provide an overall indication of
bioassessment program rigor. This cumulative evaluation provides a detailed analysis of the strengths
and weaknesses of the comprehensive bioassessment and biocriteria program. In this rating system, we
have considered all elements to be of equal weight. However, the data acquisition (sampling, processing)
and treatment (analysis) phase is the linchpin of any program. One of the questions under discussion in
preparation of this draft document is how to evaluate the influence of these particularly key elements.
What are the implications of having a bioassessment program with a high level of rigor?
The rigor and quality of biological assessments may vary among water resource agencies. The quality of
the biological data is integral to effectively and accurately answering questions about condition,
protection, restoration, or other management decisions regarding surface water resources. For example,
bioassessment data obtained using a low level of rigor may provide a lesser degree of resolution needed to
differentiate many stressor effects from natural variability.
The guidelines focus on four levels of rigor,
where Level 4 is the most rigorous and provides
the highest quality of data. The lower levels of
rigor may detect and describe severely altered
waters, and to a more limited extent,
waterbodies in the best condition. As the level
of rigor increases, the ability to discern more
precisely different levels of biological condition
increases. Figure C-l illustrates the theoretical
performance of the four levels of rigor of
bioassessment techniques in assessing condition
and the level of confidence in those assessments.
Detecting and quantifying intermediately
stressed sites, accurately describing associated
causes and sources, and measuring along a
stressor gradient will be done more accurately
and with more confidence as the level of rigor
High
e •
u
•3
Low
Undisturbed Intermediate Severe
Level of Stress on Ecosystem
FIGURE C-l. Conceptual illustration of confidence in
detecting different stress levels as a function of assessment
rigor (Levels 1-4 with 4 being most rigorous).
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Level 3 Level 2
Level 1
increases. In Figure C-l, Level 4 provides the highest confidence in the biological assessment along the
stressor gradient. Progressively less rigorous methods provide higher confidence in the assessment at the
extremes of the stressor continuum, often only useful for status assessments. The difference in levels of
rigor will be more apparent in applications requiring diagnostic capability. By first identifying the level
of rigor attained by each of the key elements and the overall approach, States and Tribes can better use the
data and information. For instance, States and Tribes may need a high level of confidence in an
assessment, such as that associated with a Level 3 or 4 bioassessment, to determine level of stress along a
gradient (Figure C-l). Less rigorous methods would not reliably detect disturbance.
Figure C-2 is a conceptual illustration depicting how increasingly comprehensive bioassessments better
detect and discriminate differences along the BCG. As currently defined, Level 4 employs numeric
biocriteria, based on calibrated and refined assessment tools (e.g., calibrated indexes or model output)
that, in turn, are based on regional reference conditions at a sufficiently detailed level of geographic
stratification and classification of aquatic ecotypes. This approach can discriminate different condition
tiers (e.g., as in the Biological Condition Gradient) within a known margin of uncertainty. Level 3
usually employs a numeric and/or
narrative assessment methodology that
discriminates among fewer condition
categories and reflects an ordinal scale
of measurement (i.e., excellent, good,
fair, poor). Assessment programs that
rate as Level 2 may be unable to
differentiate more than two broad
categories or classes of condition.
This level has a large degree of
uncertainty about assessing stressors,
and the pass/fail boundary may reflect
an under- or over- protective
threshold. Level 1 functions as a
general screening tool and may
identify best conditions from the worst
in only a very coarse sense. The
uncertainty with a Level 1 rated
program precludes resolution to
many management questions without
further monitoring and assessments.
1 0
Level 4
Natural
Condition
Minimal
Changes
Evident
Changes
fc ;-:;>^l<:.'v-'-^^;|
Moderate
Changes
Ma/or
Changes
Severe
Changes
Excellent
Pass
Fall
Poor
HIGHEST
CAPABILITY TO DETECT STRESSORS
(RESOLUTION OF ASSESSMENT)
LOWEST
FIGURE C-2. Conceptual illustration of the capability of increasingly
comprehensive bioassessments to detect and discriminate along the
biological condition gradient. Shaded areas represent relative degree of
uncertainty.
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Appendix D
The Role of Reference Condition in Biological Assessment and Criteria
(INTRODUCTION TO DRAFT DOCUMENT ON DEVELOPMENT AND
APPLICATION OF THE REFERENCE CONDITION CONCEPT)
The Clean Water Act's biological integrity objective and fishable swimmable goals pose significant
challenges to States and Tribes charged with evaluating whether aquatic resources under their
management achieve the objective and goals. One of the critical challenges is the development of a
standard or benchmark by which to judge whether particular water bodies are in accord with the objective
and goals. The concept of a "reference condition" and its implementation form the foundation on which
to make such judgments.
This document provides States, Tribes, and other practitioners with guidelines on the reference condition
concept and how to apply it in their water management programs, particularly for assessing the condition
of aquatic resources. These guidelines are intended to broaden the implementation of biological
monitoring and assessment, to increase the consistency among States and Tribes, and to improve the
success of individual programs.
States, Tribes, and others have developed and implemented the concept of reference condition in a variety
of ways to meet their individual needs, without comprehensive guidance from the U.S. EPA. This
"bottom-up" approach has both advantages and disadvantages. Advantages include the exploration of a
variety of interpretations of the concept and their implementation, yielding information on successes and
difficulties. From these experiences comes an evaluation of what works and what does not.
Disadvantages include the diversity of opinions about the concept and its role, leading to potential
confusion and sometimes contradictory interpretation and implementation. The technical and policy
challenges inherent in this effort have resulted in considerable variation in how individual States and
Tribes define and use the concept. Establishing and using the reference condition concept appropriately is
critical to implementing biological criteria and tiered aquatic life uses to protect and restore water
resource quality. Part of the purpose of this document is to encourage consistency, both in the language
that is used to express the concept, and in its everyday application.
This document will cover the following topics: a description of the concept of reference condition as well
as related terms and concepts (including minimally disturbed, least disturbed, and best attainable
conditions); methods for characterizing reference and related conditions; using water body classification
to partition natural variability; setting thresholds to determine achievement of a target condition; and
application of the concept in heavily modified regions (e.g., urban landscapes, agricultural regions) and
waterbodies (reservoirs, regulated rivers). Both technical and implementation issues are addressed to
increase the understanding of the concepts. A section on frequently asked questions and answers is
included to address topics of particular concern to practitioners. Throughout the document, examples are
drawn from existing State and Tribal programs to illustrate specific applications that are consistent with
the guidelines.
In April 2003, U.S. EPA's Office of Water sponsored a National Biological Assessment and Criteria
Workshop in Coeur d'Alene, Idaho. This workshop contained sessions on a variety of related topics
including sessions on the reference condition concept, water quality standards, biocriteria, tiered aquatic
life uses, and index development. A CD that contains many of the presentations at this workshop is
included as an appendix to provide a snapshot of the state of the science at that time, and a means to flesh
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out some of the issues not addressed in detail in the body of this document. Material in this document
supersedes any contradictory material presented on the CD because thinking has evolved since that time.
Technical and implementation issues
A principal technical challenge facing States and Tribes is accurately determining a reference or related
condition from the range of historical and current ecological conditions. This may involve the analysis of
data from existing reference sites and/or the modeling of historical information and expert opinion.
Technical issues include understanding and taking into account natural variability through classification
and/or modeling of natural gradients. Both classification and modeling need to be ecologically valid, yet
practical for States and Tribes. A related issue is determining whether an existing condition is
significantly (both ecologically and statistically) different from a specified condition (e.g., as specified in
water quality standards). Scientific rigor is necessary, tempered by ease of understanding and
implementation.
Implementation issues revolve around how States and Tribes can apply the reference condition concept to
protect and improve an existing biological condition through application in water quality standards,
including:
« Refinement of aquatic life uses through a) setting condition thresholds, b) interpreting/translating
narrative aquatic life uses, and c) establishing subcategories of tiered aquatic life uses;
• Establishment of numeric biological criteria;
" Quantitative biological description of existing designated uses through bioassessments; and
• Determination of departure of existing condition from biological integrity.
U.S. EPA guidance on the implementation of the reference condition concept balances the need for
scientific rigor and the need for practical application, that together result in the protection and
improvement of water quality.
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Appendix E
Statistical Guidance for Developing Indicators for Rivers and Streams:
A Guide for Constructing Multimetric and Multivariate Predictive
Bioassessment Models
(SUMMARY OF DRAFT DOCUMENT)
[This document has undergone various levels of review by a technical workgroup and U.S. EPA
representatives. The current version is being prepared for a more comprehensive review prior to
finalization: The final document is anticipated in 2005.]
States are faced with the challenges of not only developing tools that are both appropriate and cost-
effective (Barbour 1997), but also the ability to translate scientific data for making sound management
decisions regarding water resources. The approach to analysis of biological :(and other ecological) data
should be straightforward to facilitate a translation for management application. This is not meant to
reduce the rigor of data analysis but to ensure its place in making crucial decisions regarding the
protection, mitigation, and management of the nation's aquatic resources. In fact, biological monitoring
should combine biological insight with statistical power (Karr 1987). Karr and Chu (1999) state that
knowledge of regional biology and natural history (not a search for statistical relationships and
significance) should drive both sampling design and analytical protocol.
A central premise of biological assessment is comparison of the biological resources of a waterbody to an
expected reference condition. The condition of the waterbody is evaluated by its departure from the
expected condition. Biological assessment of waterbodies depends on our ability to define, measure, and
compare an assessment endpoint between similar systems. This guidance outlines analytical
methodologies to perform two tasks:
• Characterize biological expectation.
• Determine whether a site deviates from that expectation.
The methods considered here use the same general approach: sites are assessed by comparing the
assemblage of organisms found at a site to an expectation derived from observations of many relatively
undisturbed reference sites. The expectations are modified by classifying the reference sites to account
for natural variability. Biological variables are tested for response to stressors by comparison of
undisturbed or minimally disturbed reference sites and disturbed sites. A set of "rules" is developed from
this information, which are then used to determine if the biota of a site deviate from the expectation,
indicating the degree to which the site is impacted.
Several analytical methods have been developed to assess the condition of water resources from
biological data, beginning with the saprobien system in the early 20th century to present-day development
of biological markers (Cairns and Pratt 1993). This document provides guidance for two methods for
analyzing and assessing waterbody condition from assemblage and community-level biological
information:
1. Multimetric assessment using an index that is the sum of several metrics. This is the basis of the
Index of Biotic Integrity (IBI) (Karr et al. 1986), the Invertebrate Community Index (ICI) (Ohio
EPA 1990); the Rapid Bioassessment Protocol (Plafkin et al. 1989); and State indexes developed
from these (e.g., Southerland and Stribling 1995, Barbour et al. 1996a, Barbour et al. 1996b).
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2. Assessment comparing actual species composition at a site to an idealized reference site predicted
from a multivariate statistical model. This is the basis of the River Invertebrate Prediction And
Classification System (RIVPACS; Wright et al. 1984, Furse et al. 1984, Moss et al. 1987, Wright
1995, Wright 2000) and the Australian RIVer Assessment System (AUSRTVAS; Davies 2000,
Simpson and Norris 2000).
Many other methods are possible, as well as permutations of the two methods above, all of which are
beyond the scope of this document. The two approaches were selected because:
• They use community and assemblage data.
• The methods are not restricted to any one assemblage. The examples all use freshwater benthic
macroinvertebrates, but any other assemblage could also be used, such as fish phytoplankton,
zooplankton or macrophytes.
• The methods are general, and have been used by several agencies in many areas. The examples
used to illustrate the methods have also been carried out over wide geographic areas with many
sites, demonstrating the generality of the methods.
• The methods have been fully documented and illustrated with case examples.
• These analysis methodologies are cost-effective and easy to communicate to managers and the
public. .
Once the framework for bioassessment is in place, conducting bioassessments becomes relatively
straightforward. Either a targeted design that focuses on site-specific problems or a probability-based
design, which has a component of randomness and is appropriate for 305(b), area-wide, and watershed
monitoring, can be done efficiently. Routine monitoring of reference sites may be based on a probability
designs which will allow cost efficiencies in sampling while monitoring the status of the reference
condition of a State's streams. Potential reference sites of each stream class would be randomly selected
for sampling, so that an unbiased estimate of reference condition can be developed. A randomized subset
of reference sites can be resampled at some regular interval (e.g., a 4-year cycle) to provide information
on trends in reference sites.
This document outlines the steps required to complete multimetric and multivariate predictive assessment
models. It includes sections briefly covering the conceptual principles behind each step and then uses an
example dataset.that demonstrates the practical application of those principles step by step. It begins with
a discussion of some concepts and approaches common to both techniques and then moves into
multimetric and multivariate predictive models. At the end, it concludes with a discussion of how
biocriteria can be developed from either of the approaches.
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United States Environmental Protection Agency
Office of Water
Washington, DC 20460
(4304T)
EPA-822-R-05-001
August 2005
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