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United States EnvironmentalProtection Agency
Office of WaterWashington, DC 20460
EPA 822-R-02-014March 2002
Methods for evaluating wetland condition
#1 Introduction toWetland Biological Assessment
United States EnvironmentalProtection Agency
Office of WaterWashington, DC 20460
EPA 822-R-02-014March 2002
Methods for evaluating wetland condition
#1 Introduction toWetland Biological Assessment
Principal Contributor
Maine Department of Environmental Protection
Thomas J. Danielson
Prepared jointly by:
The U.S. Environmental Protection AgencyHealth and Ecological Criteria Division (Office of Science and Technology)
and
Wetlands Division (Office of Wetlands, Oceans, and Watersheds)
ii
Notice
The material in this document has been subjected to U.S. Environmental Protection Agency (EPA)technical review and has been approved for publication as an EPA document. The informationcontained herein is offered to the reader as a review of the “state of the science” concerning wetlandbioassessment and nutrient enrichment and is not intended to be prescriptive guidance or firm advice.Mention of trade names, products or services does not convey, and should not be interpreted asconveying official EPA approval, endorsement, or recommendation.
Appropriate Citation
U.S. EPA. 2002. Methods for Evaluating Wetland Condition: Introduction to Wetland Biologi-cal Assessment. Office of Water, U.S. Environmental Protection Agency, Washington, DC.EPA-822-R-02-014.
Acknowledgments
EPA acknowledges the contributions of the following people in the writing of this module: CandyBartoldus (Environmental Concern, Inc.), Robert Brooks (Penn State University), Thomas J. Danielson(Maine Department of Environmental Protection), Jeanne Difranco (Maine Department of Environmen-tal Protection), Mark Gernes (Minnesota Pollution Control Agency), Judy Helgen (Minnesota PollutionControl Agency), James Karr (University of Washington), Ken Kettenring (New Hampshire Depart-ment of Environmental Services), Richard Lillie (Wisconsin Department of Natural Resources), and BillyTeels (Natural Resources Conservation Service, Wetland Science Institute).
This entire document can be downloaded from the following U.S. EPA websites:
http://www.epa.gov/ost/standards
http://www.epa.gov/owow/wetlands/bawwg
iii
Contents
Foreword .............................................................................................................. v
List of “Methods for Evaluating Wetland
Condition” Modules........................................................................................... vi
Summary ................................................................................................................. 1
Purpose .................................................................................................................. 1
Introduction ........................................................................................................ 2
Evaluating Wetland Health ............................................................................ 4
Bioassessment Methods ................................................................................... 8
Using Biological Information To Improve
Management Decisions ....................................................................................19
Acknowledgments ........................................................................................... 26
References ........................................................................................................ 27
Glossary............................................................................................................. 30
Appendix .............................................................................................................. 33
List of Tables
Table 1: Reports Related to Wetland
Bioassessments in the Monitoring
Wetland Condition Series ...................................................... 10
Table 2: Strengths and Limitations of Assemblages
for Use in Wetland Bioassessments ..................................... 11
Table 3: Types of Water Quality Criteria ........................................... 22
iv
List of Figures
Figure 1: Annual average rate of wetlands loss. ................................ 4
Figure 2: Continuum of human disturbance on biological
condition of wetlands ................................................................ 5
Figure 3: Ecosystem influences on biological integrity. ................... 7
Figure 4: Number of beetle genera plotted against a human
disturbance gradient ................................................................ 18
Figure 5: Floristic quality assessment index plotted against
a human disturbance gradient ................................................ 18
Figure 6: Number of Diptera taxa Plotted against Rapid
Assessment Method (RAM) scores, a rapid
functional assessment ............................................................ 18
Figure 7: A 10-metric macroinvertebrate IBI plotted
against turbidity ......................................................................... 18
Figure 8: Framework for improving wetland management .............. 20
Figure 9: The management context of the Stressor
Identification (SI) process ....................................................... 25
Figure 10: Watershed Management Cycle ............................................... 26
v
Foreword
In 1999, the U.S. Environmental Protection Agency (EPA) began work on this series of reports entitledMethods for Evaluating Wetland Condition. The purpose of these reports is to help States andTribes develop methods to evaluate (1) the overall ecological condition of wetlands using biologicalassessments and (2) nutrient enrichment of wetlands, which is one of the primary stressors damagingwetlands in many parts of the country. This information is intended to serve as a starting point for Statesand Tribes to eventually establish biological and nutrient water quality criteria specifically refined forwetland waterbodies.
This purpose was to be accomplished by providing a series of “state of the science” modules concerningwetland bioassessment as well as the nutrient enrichment of wetlands. The individual module formatwas used instead of one large publication to facilitate the addition of other reports as wetland scienceprogresses and wetlands are further incorporated into water quality programs. Also, this modularapproach allows EPA to revise reports without having to reprint them all. A list of the inaugural set of20 modules can be found at the end of this section.
This series of reports is the product of a collaborative effort between EPA’s Health and EcologicalCriteria Division of the Office of Science and Technology (OST) and the Wetlands Division of theOffice of Wetlands, Oceans and Watersheds (OWOW). The reports were initiated with the supportand oversight of Thomas J. Danielson (OWOW), Amanda K. Parker and Susan K. Jackson (OST),and seen to completion by Douglas G. Hoskins (OWOW) and Ifeyinwa F. Davis (OST). EPA reliedheavily on the input, recommendations, and energy of three panels of experts, which unfortunately havetoo many members to list individually:
� Biological Assessment of Wetlands Workgroup
� New England Biological Assessment of Wetlands Workgroup
� Wetlands Nutrient Criteria Workgroup
More information about biological and nutrient criteria is available at the following EPA website:
http://www.epa.gov/ost/standards
More information about wetland biological assessments is available at the following EPA website:
http://www.epa.gov/owow/wetlands/bawwg
vi
List of “Methods for Evaluating Wetland
Condition” Modules
1 ................. Introduction to Wetland Biological Assessment
2 ................. Introduction to Wetland Nutrient Assessment
3 ................. The State of Wetland Science
4 ................. Study Design for Monitoring Wetlands
5 ................. Administrative Framework for the Implementation of a
Wetland Bioassessment Program
6 ................. Developing Metrics and Indexes of Biological Integrity
7 ................. Wetlands Classification
8 ................. Volunteers and Wetland Biomonitoring
9 ................. Developing an Invertebrate Index of Biological
Integrity for Wetlands
10............... Using Vegetation to Assess Environmental Conditions
in Wetlands
11 ............... Using Algae to Assess Environmental Conditions in
Wetlands
12 ............... Using amphibians in Bioassessments of Wetlands
13 ............... Biological Assessment Methods for Birds
14 ............... Wetland Bioassessment Case Studies
15 ............... Bioassessment Methods for Fish
16 ............... Vegetation-Based Indicators of Wetland Nutrient
Enrichment
17 ............... Land-Use Characterization for Nutrient and Sediment
Risk Assessment
18............... Biogeochemical Indicators
19 ............... Nutrient Load Estimation
20 .............. Sustainable Nutrient Loading
Module # Module Title
1
Summary
Biological assessments (bioassessments)evaluate the health of a waterbody by di-
rectly measuring the condition of one or moreof its taxonomic assemblages (e.g.,macroinvertebrates, plants) and supportingchemical and physical attributes. A majorpremise of bioassessments is that the commu-nity of plants and animals will reflect the under-lying health of the waterbody in which they live.When a waterbody is damaged by human ac-tivities, biological attributes such as taxonomicrichness, community structure, trophic structure,and health of individual organisms will change.For example, in disturbed systems the numberof intolerant taxa typically decreases and the pro-portion of tolerant individuals typically in-creases. The biological community will reflectthe cumulative effect of multiple stressors,whether they be chemical (e.g., toxic chemical),physical (e.g., sedimentation), or biological (e.g.,non-native species).
In recent years, a growing number of State andFederal organizations have started to developbioassessment methods and Indexes of Biologi-cal Integrity (IBI) for wetlands. An IBI is anindex that integrates several biological metricsto indicate a site’s condition. A common ap-proach among these organizations is to firstsample attributes of a taxonomic assemblage inwetlands ranging from good condition to poorcondition. The data are reviewed to identifymetrics, which are attributes of the assemblagethat show a predictable and empirical responseto increasing human disturbance. After themetrics are tested and validated, they are com-bined into an IBI, which provides a summaryscore that is easily communicated to managersand the public.
Once wetland bioassessment methods are de-veloped, wetland managers can use them for avariety of applications. Wetland managers canuse bioassessments to evaluate the performanceof wetland restoration activities or best manage-ment practices, such as buffer strips, in restor-ing and protecting wetland health. Wetlandmanagers can also use bioassessments to moreeffectively target resources for restoring, protect-ing, and acquiring wetlands. Many States aredeveloping bioassessments to better incorporatewetlands into water quality programs.Bioassessments can help States refine their wa-ter quality standards to reflect typical conditionsfound in wetlands. Using bioassessment infor-mation, States can refine the components ofwater quality standards by designating ecologi-cally based beneficial uses of wetlands andadopting numeric and narrative biological cri-teria (biocriteria). After improving water qual-ity standards, States can use bioassessments todetermine if wetlands are meeting the identifiedbeneficial uses, track wetland quality, and in-corporate wetlands into Clean Water Act Sec-tion 305(b) water quality reports. Rigorous stan-dards will also help States improve water qual-ity certification decisions for activities that re-quire Federal permits, such as dredge-and-fillpermits. Under Section 401 of the Clean WaterAct, States can certify, grant, or deny State per-mits if a proposed activity will harm the chemi-cal, physical, or biological integrity of a wet-land as defined in their water quality standards.
Purpose
T his module provides an overview of wet-land bioassessments and refers the reader to
other modules for details on particular topics.
2
Introduction
Wetlands are important components of wa-tersheds and provide many valuable func-
tions to the environment and to society(Richardson 1994, NRC 1995, Mitsch andGosselink 2000). Wetland ecosystem functionsinclude the transfer and storage of water, bio-chemical transformation and storage, the pro-duction of living plants and animals, the decom-position of organic materials, and the commu-nities and habitats for living creatures(Richardson 1994). Based on these and otherecological functions, wetlands provide “values”to humans and naturally functioning ecosystems.Important values include, but are not limited to,flood control, filtering and cleansing water, ero-sion control, food production (shrimp, ducks,fish, etc.), timber production, recreation (boat-ing, fishing, bird watching, etc.), winter deeryards, and habitat for plants and animals, includ-ing many rare or endangered species (Box 1).
Wetlands have not always been appreciated fortheir many benefits. Historically, wetlands wereperceived as potentially valuable agriculturalland, impediments to development and progress,and harbors of vermin and disease (Fischer 1989,NRC 1995, Dahl and Alford 1996, Mitsch andGosselink 2000). Prior to the mid-1970s, drain-age and destruction of wetlands were acceptedpractices and even encouraged by public poli-cies, such as the Federal Swamp Land Act of1850, which deeded extensive wetland acreagefrom the Federal Government to the States forconversion to agriculture (NRC 1995, Mitschand Gosselink 2000). Some people today stillhold many of these beliefs. These public per-ceptions of wetlands shaped wetland policy andmanagement during much of the past century.Consequently, wetland policy and managementhave taken a very different path compared to thepolicy and management of streams, rivers, and
lakes. These other aquatic systems have alsobeen damaged by human activities, but they havenot been subject to the same intense onslaughtof development and agricultural pressures aswetlands. As a result, whereas most Federal andState policies since the establishment of theClean Water Act have focused on maintainingand restoring streams, rivers, and lakes, mostwetland policies have been focused on prevent-ing wetlands from being converted to uplands.
During the 1970s and 1980s, Federal and Stateagencies did not focus many resources on wet-land quality. They were attempting to slow therate of wetland loss and increase the rate of wet-land restoration through various regulatory andvoluntary programs. Today, wetlands are stillbeing converted to uplands, but the national rateof wetland loss has decreased over time(Figure 1).
Even though estimates of wetland acreage arenot exact, they can show general trends. Ac-cording to the U.S. Fish and Wildlife Service,more than half of the original wetlands in thecontinental United States have been lost. (Wilenand Frayer 1990). An estimated 105.5 millionacres of wetlands remained in the conterminousUnited States in 1997 (Dahl 2000). Between1986 and 1997, the net loss of wetlands was644,000 acres. The loss rate during this periodwas 58,500 acres/year, which represents an 80%reduction in the average rate of annual loss com-pared with the period between the mid-1970sand mid-1980s. Various factors have contrib-uted to the decline in the loss rate, includingimplementation and enforcement of wetland pro-tection measures, strengthened Federal and Statewetland regulatory programs, and elimination ofsome incentives for wetland drainage. Publiceducation and outreach about the value and func-tion of wetlands, private land initiatives, coastalmonitoring and protection programs, and wet-
3
land restoration and creation actions have alsohelped reduce overall wetland losses.
As the Nation draws closer to achieving a “nonet loss” in wetland acreage, it is becoming in-creasingly apparent that more attention and re-sources must be devoted to addressing the qual-
ity of wetlands. The main goal of the CleanWater Act is to “maintain and restore the chemi-cal, physical, and biological integrity of theNation’s waters,” including wetlands. However,we know very little about the quality of ourNation’s wetlands and whether or not we are
Box 1: Examples of Wetland Values
� 80% of America’s breeding bird population and more than 50% of protected migratorybird species rely on wetlands (Wharton et al. 1982).
� More than 95% of commercially harvested fish and shellfish in the United States aredirectly or indirectly dependent on wetlands (Feierabend and Zelazny 1987).
� Most of the United States’ frogs, toads, and many salamanders require wetlands duringtheir life cycle for reproduction or survival.
� A mosaic of small wetlands is important for maintaining local populations of turtles,small birds, and small mammals (Gibbs 1993).
� Although wetlands account for only 3.5% of the United States’ land area, about 50% offederally listed endangered animals depend on wetlands for survival (Mitsch andGosselink 2000).
� Wetlands help prevent flood damage by storing storm runoff and slowly releasing waterto streams and groundwater, thereby decreasing the severity of peak floods (Thibodeauand Ostro 1981).
� Removal of floodplain forested wetlands and confinement by levees has reduced thefloodwater storage capacity of the Mississippi River by 80% (Gosselink et al. 1981).The severity of the 1993 Great Midwest Flood, which caused $20 billion of propertydamage, was partially increased by the historical loss of wetlands in the Missouri andupper Mississippi river basins (NOAA 1994, Tiner 1998).
� Wetlands help maintain the quality of streams and rivers by preventing erosion, filteringrunoff, reducing peak floods, maintaining base flows, and providing food for streamanimals. Streams with drainage areas that contain higher percentages of naturallyvegetated land, particularly wetlands, tend to have healthier fish communities, as shownby biological assessments (Roth et al. 1996, Wang et al. 1997).
� Wetlands enhance water quality in streams and watersheds by trapping sediment and byaccumulating and transforming a variety of nutrients and other chemical substances(Jones 1976, Mitsch et al. 1979, Lowrance et al. 1984, Whigham et al. 1988, Kuenzler1989, Faulkner and Richardson 1989, Johnston 1991).
4
meeting this goal. This limited knowledge isillustrated in the 1998 National Water Inventory(U.S. EPA, 1999). The quality of only 4% of theNation’s wetlands was estimated, and only afraction of these estimates were based on actualmonitoring data. State and Federal agencies arereceiving increasing pressure to move away fromusing the number of permits issued or numberof wetlands lost as primary data influencing man-agement decisions. Rather, they must developand use more meaningful measurements toevaluate the quality of the environment and todemonstrate the effectiveness of their programsat improving the environment.
Evaluating
Wetland Health
W etlands and other waterbodies are shapedby the landscape and climate in which
they exist (Brinson 1993). Climatic conditions,topography of the landscape, chemical and
physical characteristics of underlying geology,and the amount and flow of water within a wa-tershed all contribute to determining what kindof plants and animals survive in a location. Thecollective interaction of plants and animals withtheir physical and chemical environment formwhat we call wetlands and provide many of thefunctions that are both ecologically and eco-nomically important. Many wetlands have beenshaped over thousands of years by complex in-teractions between biological communities andtheir chemical and physical environment. Thevery presence of a wetland’s natural biologicalcommunity means that the wetland is resilientto the normal variation in that environment (Karrand Chu 1999).
Certain human activities can alter the interac-tions between wetland biota and their chemicaland physical environment. Figure 2 provides asimplified illustration of the relationship be-tween (a) the health of biological communitiesof wetlands and (b) human disturbances to wet-
Figure 1: Annual average rate of wetlands loss.
-290,000
100,000
-458,000
-58,000
-500,000
-400,000
-300,000
-200,000
-100,000
0
100,000
200,000
1950s-1970s*
1970s-1980s*
1980s-1990s*
2005Goal**
Ann
ualc
hang
ein
wet
land
acre
age
(acr
es)
* U.S. Fish and Wildlife Service National Wetland Inventory, 2000** U.S. EPA goal (U.S. EPA 1998b)
5
lands and their watersheds. When human ac-tivities within a wetland or its watershed areminimal, the biological communities are resil-ient and continue to resemble those that wereshaped by the interaction of biogeographic andevolutionary processes. At this end of the con-tinuum of biological condition, the communityis said to have biological integrity, which is theability to “support and maintain a balanced adap-tive community of organisms having a speciescomposition, diversity, and functional organiza-tion comparable to that of natural habitats withina region” (Karr and Dudley 1981). At somethreshold (T), which is difficult to measure overshort time scales, is the point where degrada-tion of the biological community creates an un-healthy situation because a natural communityis no longer sustainable (Karr 2000).
Some human activities are ecologically benignwhereas others can alter the environment to thepoint where there are changes in the biologicalcommunities. As the severity, frequency, or du-
ration of the disturbances increase, a wetlandmay eventually reach a point where many of itsplants and animals can no longer survive. Whenthe interaction of wetland plants and animalswith their environment is disrupted, many of thefunctions provided by wetlands will be dimin-ished or lost. At a large scale, the subsequentecological and economic effects can be dramatic.A wetland’s biological community may recoverover time and move back up the continuum ifthe pressures from the environmental distur-bances are alleviated. The amount of time re-quired to move back up the continuum will de-pend on the severity and nature of the distur-bance. It may take some wetlands hundreds ofyears to recover.
The challenge facing wetland biologists is todevelop practical ways to measure the biologi-cal condition of wetlands in order to make in-formed resource management decisions aimedat minimizing loss of wetland acreage and func-tion. It is neither scientifically nor economically
Gradient of Human Disturbance
Biological Integrity
Gra
die
nt
of
Bio
log
ical
Co
nd
itio
n
No or minimaldisturbance
SevereDisturbance
NothingAlive
Pristine
T
healthy =sustainable
unhealthy =unsustainable
Figure 2: Continuum of human disturbance on biological condition of
wetlands (adapted from Karr 2000).
6
practical to monitor every way that human ac-tivities can damage wetlands. For instance,wetlands can be dredged, filled, mowed, logged,plowed, drained, inundated, invaded by non-native or invasive organisms, grazed by live-stock, and contaminated by countless kinds ofpesticides, herbicides, and other toxic sub-stances. Therefore, wetland biologists must fo-cus on measuring the attributes of wetlands thatwill reflect biological condition without havingto measure each and every disturbance that con-tributes to that condition.
As mentioned earlier, wetlands are shaped bythe interaction of biological communities withtheir physical and chemical environment. Theplants and animals have evolved over time tosurvive within a given range of environmentalconditions. The interaction of wetland organ-isms with each other and their environment canbe altered chemically, physically, or biologically(Figure 3). For example, pesticides and herbi-cides applied to a golf course can enter andchemically alter a wetland after a rainstorm, re-sulting in lethal and sublethal affects to aquaticanimals. Humans can physically damage wet-land biological communities by plowing a wet-land or discharging stormwater runoff into wet-lands and altering wetland hydrology. Wetlandbiological communities can be biologically al-tered by introducing non-native or invasiveplants. Wetlands are rarely damaged by a singlestressor. Rather, a mixture of chemical, physi-cal, and biological stressors typically impactsthem. Measuring all of the stressors that couldaffect a wetland in a way that is ecologicallymeaningful is virtually impossible. The onlyway to evaluate the cumulative effect of all thestressors is to directly measure the condition ofthe biological community.
The most direct and cost-effective way toevaluate the biological condition of wetlands isto directly measure attributes of the community
of plants and animals that form a wetland. Withlimited financial and staff resources, it is notpractical to focus the evaluation of wetland con-dition on chemical endpoints because there aretoo many to monitor. Also, the interaction ofmany chemicals in the environment is poorlyunderstood. Stream bioassessment programshave also found that bioassessments are lessexpensive than many of the chemical measure-ments (Yoder and Rankin 1995, Karr and Chu1999). A focus on physical parameters is im-practical because our knowledge of interactionsof biological communities and many physicalparameters is incomplete. In addition, focusingmonitoring efforts on physical parameters wouldoverlook damage caused by chemical and bio-logical stressors.
In addition to reflecting the cumulative effectsof multiple stressors, biological communities in-tegrate the effects of stressors over time, includ-ing short-term or intermittent stressors. In con-trast, it is often difficult to detect changes inchemical and physical stressors over time. Thebiological effect of many chemicals is oftenmuch longer lasting than the pollution event it-self. Some chemicals can enter a wetland, dam-age the biological community, and be biochemi-cally or photochemically altered rather quickly.Even if researchers are attempting to detect achemical, they may completely miss it unlessthey are sampling at the right time. The highcosts associated with processing water and sedi-ment chemistry samples make it far too expen-sive to sample with enough frequency to detectmany chemicals. Physical alterations can alsopose problems with respect to the ability to de-tect changes in biological condition over time.Some physical alterations to wetlands canchange the structure and composition of biologi-cal communities for years after the ability toobserve the physical alteration has been lost. Forexample, more than 50 years after some farmedwetlands in Montana were removed from pro-
7
In summary, the most direct and effective wayof evaluating the biological condition of wet-lands is to directly monitor the biological com-ponent of wetlands through the use of
duction, their biological communities are stillrecovering and are noticeably different fromminimally disturbed wetlands (RandyApfelbeck, MT DEQ, pers. comm.).
Figure 3: Ecosystem influences on biological integrity (adapted from
Karr et al. 1986, Yoder 1995).
Alkalinity
Orgnanics
Nutrients Turbidity
Transformation
pH
D.O.
Human-madechemicals
ConductivityChemicalVariables
EvapotranspirationDepth
Frequency
Duration
Land Use
Precipitation
Runoff
Groundwater
FlowHigh/LowExtremes
Hydrology
Life StagesReproduction
DiseaseFeeding
Competition
Parasitism
Disease
Keystone Species
BioticFactors BIOLOGICAL
INTEGRITY
NutrientsSunlight
SeasonalCyclesOrganic
MatterInputs
Primary andSecondaryProduction
EnergySource
Water Depth Topography
BufferVegetation
SubstrateComposition
Water FlowCanopy Erosion
HabitatStructure
8
bioassessments and to support that informationwith chemical and physical data. Relying onsurrogate measurements (e.g., water chemistry)or using monitoring tools designed for otherpurposes (e.g., rapid functional assessments)may provide incomplete and misleading results.Bioassessments can help prioritize where to fol-low up with additional monitoring, help diag-nose the causes of degradation, and provide datato make informed management decisions aboutprotecting and restoring wetlands.
Bioassessment
Methods
During the past decade, wetland biologistsbegan to develop bioassessment methods
to evaluate the condition of wetlands and deter-mine whether these wetlands are maintainingbiological integrity. Bioassessment methods fo-cus on measuring attributes of a wetland’s bio-logical community that are reliable indicatorsof wetland condition. Many bioassessmentprojects also include measures of physical andchemical attributes that are used to help diag-nose potential sources of degradation.
Bioassessments are based on the premise thatthe community of plants and animals living in awetland will reflect the health of a wetland.When a wetland is damaged, the diversity ofanimals and plants often decreases and the com-position of species changes. Typically, the pro-portion of organisms that are intolerant to hu-man disturbances will decrease while the pro-portion of individuals or species that are moretolerant to the disturbance will increase. In com-parison to a minimally disturbed site, a plowedwetland located in a cornfield may have fewerplant and animal species. It also may be domi-nated by organisms that can tolerate poor envi-ronmental conditions. After examining an as-semblage of plants or animals in wetlands rang-
ing from high quality to poor quality, scientistscan use this known range to estimate the rela-tive health of other wetlands.
Wetland biologists are fortunate to have sev-eral decades of knowledge and experience re-lated to evaluating the biological condition ofstreams and rivers to help guide them. Althoughwetlands and their biological communities aredifferent from streams and rivers, many of theapproaches and experiences from streambioassessments can be applied to any biologicalsystem. In fact, bioassessment methods devel-oped for streams and rivers have been adaptedto wetlands, lakes, estuaries, and terrestrial sys-tems (U.S. EPA 1998a, 2000a, Karr and Chu1999, Rader et al. 2001).
The U.S. Environmental Protection Agency(EPA) formed the Biological Assessment of Wet-lands Workgroup (BAWWG, pronounced “bog”)in 1997 to help State agencies develop and ap-ply wetland bioassessments (Box 2). ManyBAWWG members are conducting pilot projects,which are described in Wetland BioassessmentCase Studies (U.S. EPA, in prep.). BAWWGhas produced a series of reports to help otherState, Federal, and Tribal agencies develop andimplement bioassessment methods for wetlands(Table 1). The remainder of this report will in-troduce the development and application of wet-land bioassessments, provide recommendationsfrom BAWWG, and refer to the other reports inthe series for more detailed information.
Wetland bioassessments involve the followingsix general stages of development:
� Selecting one or more biological assem-blages to monitor
� Classifying wetlands
� Selecting wetlands across a gradient of hu-man disturbance
9
Box 2: The Biological Assessment of Wetlands Workgroup (BAWWG)
The Biological Assessment of Wetlands Workgroup (BAWWG, pronounced “bog”) wasformed in 1997 to help advance the science and application of wetland bioassessments.Many people have participated in BAWWG meetings over the years, but the following listof people includes the core BAWWG members who have dedicated a considerable amountof time to advancing the goals of the workgroup. The New England Biological Assessmentof Wetlands Workgroup (NEBAWWG) was formed in 1998 and its members have alsohelped advance wetland bioassessments.
Paul Adamus, Oregon State UniversityBill Ainslee, U.S. EPA, Region 4Randy Apfelbeck, Montana Department of Environmental QualityRob Brooks, Penn State Cooperative Wetlands CenterMark Brown, University of Florida, Center for WetlandsTom Danielson, Maine Department of Environmental ProtectionJeanne DiFranco, Maine Department of Environmental ProtectionNaomi Detenbeck, U.S. EPA, Ecology DivisionMike Ell, North Dakota Department of HealthSue Elston, U.S. EPA, Region 5Chris Faulkner, U.S. EPA, Office of Wetlands, Oceans, and WatershedsRuss Frydenborg, Florida Department of Environmental ProtectionMark Gernes, Minnesota Pollution Control AgencyMike Gray, Ohio Environmental Protection AgencyJudy Helgen, Minnesota Pollution Control AgencyDenice Heller Wardrop, Penn State Cooperative Wetlands CenterDoug Hoskins, Connecticut Department of Environmental ProtectionSusan Jackson, U.S. EPA, Office of Science and TechnologyJames Karr, University of WashingtonRyan King, Duke University Wetlands CenterDon Kirby, North Dakota State UniversityPeter Lowe, USGS Biological Resources DivisionJohn Mack, Ohio Environmental Protection AgencyEllen McCarron, Florida Department of Environmental ProtectionMick Micacchion, Ohio Environmental Protection AgencySteve Pugh, U.S. Army Corps of Engineers, Baltimore DistrictKlaus Richter, King County Department of Natural Resources, WashingtonMatt Schweisberg, U.S. EPA, Region 1Don Sparling, USGS Biological Resources DivisionArt Spingarn, U.S. EPA Region 3Jan Stevenson, Michigan State UniversityLinda Storm, U.S. EPA, Region 10Rich Sumner, U.S. EPA, Environmental Research LaboratoryBilly Teels, NRCS Wetlands Science InstituteDoreen Vetter, U.S. EPA, Office of Wetlands, Oceans, and Watersheds
10
� Sampling chemical and physical character-istics of wetlands
� Analyzing data
� Reporting results
Choosing Assemblages
As discussed in Wetland Bioassessment CaseStudies (U.S. EPA, in prep.), BAWWG mem-bers have used a variety of biological assem-blages in wetland bioassessments, including al-gae, amphibians, birds, fish, macroinvertebrates,and vascular plants. Each assemblage has itsown strengths and limitations for developingwetland bioassessment methods. Convenience,money, and time are often key factors in select-
ing a biological assemblage (Karr and Chu1999). The selected assemblage must be cost-effective to sample and identify. However, anumber of other factors affect an assemblage’spractical usefulness and ability to reflect realchanges in wetland condition (Table 2). Plantsand macroinvertebrates are the most commonlyused assemblages in wetland bioassessments.Vegetation is a convenient assemblage becauseit occurs in most wetland types and there arewell-established sampling protocols; however,identifying metrics can be challenging (U.S. EPA2002a). Macroinvertebrates have been widelyused in stream bioassessments and show a lotof promise for wetlands, but current samplingmethods focus on wetlands with standing water(U.S. EPA 2002b). Algae have been used to a
Table 1: Reports Related to Wetland Bioassessments in the
Monitoring Wetland Condition Series
11
Numerical Scores: 1 = best, 2 = intermediate, 3 = worst.
a Fish are restricted to small number of wetland types.b Sampling methods are easy, but may require multiple site visits.c Analysis will likely require multiple site visits during season.d Adults are easy to identify, but some larvae are difficult to identify and may require rearing for positive identification.e Many amateurs are sufficiently trained to identify birds.f Identification of diatoms is aided by pictorial keys, but relatively few people are trained.g Wisconsin DNR is attempting to develop family-level assessment methods instead of identifying macroinvertebrates to genus and species.h Dip net and especially stovepipe samples can involve a lot of time-consuming picking; however, Minnesota PCA uses method to reduce
time. Activity traps generally require less picking because they do not pick up as much detritus.i Amphibians and fish may have insufficient taxonomic diversity to be effectively used in bioassessment in some wetland types or parts of the
country.j Historical land use practices and immediate landscape have significant influence on community.k Algae are sensitive to copper sulfate.l Many of these chemicals have very high affinities to charged particles and end up in higher concentration in the sediments than in the water
column. Minnesota PCA has found strong responses in the plant community to sediment concentrations of Cu, Zn, Cd, and other metals.m Deformities, lesions, etc. have been found in the field, but typically appear only in highly contaminated situations.
Table 2: Strengths and Limitations of Assemblages for Use
in Wetland Bioassessments
12
limited degree but offer an inexpensive and ef-fective alternative for some wetland types (U.S.EPA 2002c). Amphibians offer many advantagesbut have insufficient taxonomic diversity insome regions for traditional bioassessment meth-ods (U.S. EPA 2002d). The mobility of birdsmakes them well suited for landscape-level as-sessments (U.S. EPA 2002e). Fish have manyadvantages that have been demonstrated in otherwaterbodies, but the fish assemblage is limitedto a few wetland types, such as emergent wet-lands on the fringes of lakes and estuaries. Insummary, different assemblages have differentadvantages depending on the purpose of theproject, region of the country, and wetland typesbeing evaluated. BAWWG members recom-mend sampling two or more assemblages be-cause it provides more confidence in manage-ment decisions and substantially improves theability to diagnose the causes of degradation.
Classifying Wetlands
The goal of bioassessments is to evaluate thecondition of wetlands as compared to referenceconditions and determine if wetlands are beingdamaged by human activities. An obvious chal-lenge facing wetland scientists is to distinguishchanges in biological communities caused byhuman disturbances from natural variations.This challenge is complicated by the naturalvariation found among the variety of U.S. wet-land types (Cowardin et al. 1979, Mitsch andGosselink 2000, Brinson 1993). One way tosimplify the evaluation is to classify the wet-lands and only compare wetlands with otherswithin the same class. BAWWG members havefound that some type of classification method isnecessary when developing bioassessment meth-ods for wetlands (U.S. EPA 2002f).
Consider an easy example of comparing a saltmarsh to an oligotrophic bog. Each wetland isshaped by the interaction of plants and animals
with a variety of factors, including its landscapeposition, hydrologic characteristics, water chem-istry, underlying geology, and climatic condi-tions. Each type of wetland consists of plantsand animals with adaptations to survive and re-produce in a certain range of environmental con-ditions. For example, organisms that inhabit saltmarshes must have physical, chemical, or be-havioral adaptations to withstand variable salin-ity and alternating wet and dry periods. In con-trast, organisms that inhabit oligotrophic bogsmust have adaptations to tolerate acidic condi-tions and obtain and retain scarce nutrients. Anorganism adapted for life in a bog would notlikely survive in a salt marsh, and vice versa. Asa result, the biological community of a bog willbe much different from the biological commu-nity of a salt marsh. No one would disagree thatit is inappropriate to directly compare the bio-logical communities of a salt marsh to a bog.
The validity of making other comparisons isoften debated. For example, is it appropriate tocompare the biological communities of an emer-gent marsh on the edge of a pond to an emer-gent marsh on the edge of a slow-moving river?Are the biological communities similar enoughto lump into one class or do they need to be splitinto two classes? There are no easy answers tothese questions. They must be answered, how-ever, to ensure scientific validity of thebioassessment results and management deci-sions. The use of a classification system pro-vides a framework for making these decisions.
For purposes of developing bioassessmentmethods, the goal is to establish classes of wet-lands that have similar biological communitiesthat respond similarly to human disturbances.As discussed in Wetland Classification (U.S.EPA 2002f), a variety of wetland classificationsystems have already been developed for a vari-ety of purposes. BAWWG members have usedmany of these classification systems (U.S. EPA
13
2002f; in prep.) to avoid “comparing apples tooranges” and have come up with the followinglist of observations and recommendations:
� Do not reinvent the wheel. BAWWG mem-bers suggest starting with one or more ex-isting methods and, if necessary, modifyingthe classification to establish classes of bio-logically similar wetlands. Developing anentirely new system should not be necessary.
� Classification is often an iterative process.Researchers often start with one or more sys-tems and then lump or split classes as neededto end up with an appropriate number ofgroups of biologically distinct wetlands. Forexample, when the Montana Department ofEnvironmental Quality (MT DEQ) devel-oped its IBI, it used ecoregions as a first tierand then further separated wetlands by land-scape position and other characteristics (e.g.,acidity and salinity). MT DEQ later deter-mined that it could lump the wetlands of twoecoregions because their macroinvertebratecommunities were similar and respondedsimilarly to anthropogenic stressors. Whileestablishing classes, examine other naturalfactors that may affect wetland communi-ties (e.g., size, successional stage, age of thewetland, salinity) to determine if they shouldbe included in the classification system.
� Do not become preoccupied with classifica-tion. Even though proper classification isnecessary to minimize natural differencesamong wetlands, the goal of this exercise isnot to develop a new classification method.Rather, the goal is to improve the ability ofwetland scientists to detect signals from thebiology about the condition of wetlands.
� Classify wetlands to a suitable level. Ecolo-gists need to develop wetland classes thatare broad enough to allow comparisons ofseveral wetlands, yet narrow enough to pro-vide biologically meaningful comparison.All ecologists are faced with a dilemma: the
more ecologists learn about natural systems,the more they realize how little they actu-ally know. As a result, it is tempting to delveever deeper into biology to help identify dif-ferences between wetlands and developmore subclasses. However, ecologists arefaced with another dilemma: limited finan-cial and staff resources. For each wetlandclass that is identified, a new set of wetlandsmust be sampled to calibrate analytical meth-ods. The endpoint therefore represents a bal-ance of (1) a need to have broad inclusiveclasses that will facilitate the comparisonsof many wetland types, (2) a desire to havea narrow classification that includes detailedbioassessment data, and (3) constraints onfinancial and staff resources. Another lim-iting factor when classifying wetlands ishaving enough wetlands of each class to cali-brate analytical methods.
� Recognize that the wetland classificationand classes used for one assemblage maynot be suitable for another assemblage. Forexample, wetland classes developed to ob-tain biologically similar macroinvertebratecommunities may not work when applied toanother assemblage, such as plants. Alwaystest existing wetland classes to ensure thatthey are biologically meaningful in identi-fying the effects of human disturbances onthe selected assemblage(s).
Selecting Wetlands Across a
Disturbance Gradient
After classifying wetlands, researchers selectsampling sites across a disturbance gradient foreach wetland class. These sites are used to docu-ment how a biological assemblage responds toincreasing levels of anthropogenic stressors(U.S. EPA 2002g). A common way of portray-ing bioassessment results is to create a graphwith a measure of human disturbance along theX-axis and a biological endpoint along the Y-
14
axis (Figure 2). As discussed in DevelopingMetrics and Indexes of Biological Integrity (U.S.EPA 2002g), no standard method for establish-ing gradients of human disturbance exists. SomeBAWWG members have tried to quantify dis-turbance by using surrogates such as the per-centage of impervious surfaces or agriculture ina watershed. Other projects have used qualita-tive indices of human disturbance that incorpo-rate a combination of watershed and wetland in-formation. Regardless of the gradient used, it iscrucial to select wetlands that range from mini-mally disturbed reference sites to severely de-graded wetlands, with some sites in between.BAWWG members have the following obser-vations and recommendations about gradientsof human disturbance:
� Do not become preoccupied with disturbancegradient. It is impossible to develop a distur-bance gradient that incorporates every waythat humans can damage wetlands. The dis-turbance gradient should provide a gross es-timate that can be used in the site selectionprocess and the calibration of metrics. Thebiological information will ultimately bemuch more reliable and trustworthy in evalu-ating wetland condition than the disturbancegradient (Karr and Chu 1999).
� Define and describe the expected distur-bance gradient before sampling sites. If thedisturbance gradient is established after thesites are sampled, then there is the risk ofsampling too few wetlands at either end ofthe gradient.
� Use targeted sampling while developingbioassessment methods. As discussed inStudy Design for Monitoring Wetlands(U.S. EPA 2002h), statistical sampling de-signs provide many advantages when at-tempting to estimate the percentage ofwaterbodies that are meeting their designateduses. However, BAWWG members havefound that the targeted selection of sampling
sites is preferable when developingbioassessment methods. It is important toget sufficient numbers of minimally disturbedsites and severely degraded sites to (1) docu-ment the condition of a biologicalassemblage at the two extremes and (2) cali-brate analytical methods. Statistical samplingmethods often fail to select enough wetlandsat either end of the disturbance gradient.
Selecting Sampling Methods
Sampling methods used in a wetland bioassess-ment project will depend on the taxonomic as-semblage and wetland class being sampled. Spe-cific sampling methods for each assemblage, ex-cept fish, are described in the reports listed inTable 3. Regardless of the assemblage selected,BAWWG members have the following obser-vations and recommendations:
� Use standardized sampling methods. It isvery important to standardize samplingmethods and establish quality assurance pro-tocols to ensure the comparability of data.In addition, equal sample effort must begiven to each wetland. EPA recommendsdeveloping Quality Assurance Project Plans(QAPP) to help maintain consistency at ev-ery stage of sampling from collection totransportation of samples and laboratory pro-cedures (U.S. EPA 1995b).
� Ensure that sampling methods are repeat-able. BAWWG members recommend test-ing all sampling methods to make sure thatthey provide repeatable and consistent re-sults in different wetlands and with differ-ent field technicians.
� Standardize the sampling period. The com-position and abundance of taxa in a biologi-cal assemblage will change during the courseof a year. Individual taxa within a biologi-cal assemblage breed at different times ofthe year, mature at different rates, and have
15
a variety of behavioral and physical adapta-tions for life in wetlands. Depending on theassemblage, sampling the same wetland atdifferent times of the year can yield strik-ingly different communities. It is necessaryto establish a standard period of time withinthe year to collect samples that (1) minimizesvariation caused by natural, seasonal changesin community composition; (2) providessufficient differentiation of communitiesacross a disturbance gradient; and (3) is lo-gistically practical.
� Retain some flexibility in sampling period.Although it is important to maintain a stan-dard sampling period, it helps to retain someflexibility in scheduling sampling. Annualclimatic variations can delay or acceleratebiological processes. For example, a par-ticularly warm winter can cause adult am-phibians to breed much earlier than theynormally would. It is important to pay at-tention to these variations and adjust thesampling scheme accordingly to securesamples that are not biased toward certaintaxa and do not misrepresent relative abun-dance.
� Consider time and resource constraints. Bi-ologists are often tempted to create elabo-rate sampling designs using several meth-ods to ensure that all species are capturedand represented in a sample. However, thecomplexity of sampling methods must bebalanced with the time and resources avail-able. Remember that the goal of the assess-ments is to evaluate the condition of a wet-land relative to a known range of conditionfrom wetlands across a disturbance gradi-ent. It is not necessary to monitor every-thing within a wetland to detect differencesin biological communities across this gradi-ent. Rather, the sampling effort should befocused on identifying characteristics of bio-logical communities that show measurable
and consistent relationships. For example,the Maine Department of EnvironmentalProtection is focusing macroinvertebratemonitoring in emergent wetlands at the tran-sition zone between open water and emer-gent vegetation rather than attempting tosample every microhabitat within a wetland(Jeanne Difranco, Maine DEP, pers. comm.).Recognizing that wetlands are often mosa-ics of different vegetative communities andmicrohabitats, the Minnesota Pollution Con-trol Agency targets an area of the wetlandthat is representative of the wetland as awhole and uses a releve sampling method toevaluate the plant assemblage (U.S. EPA2002a).
Collecting Chemical and
Physical Data
Used independently, measurements of awetland’s physical characteristics or chemicalsin a wetland’s water or sediment are not appro-priate for estimating wetland health because theydo not adequately reflect the condition of bio-logical communities. The ability to infer bio-logical condition from physical and chemicaldata is often limited to severely altered or pol-luted conditions. Water chemistry, in particu-lar, is very expensive to analyze, can vary widelyover time, and can be difficult to interpret.Methods that focus primarily on a wetland’sphysical structure, such as functional assessmentmethods, fail to detect damage from subtle stres-sors such as the effects of pesticides. Physicaland chemical information can be very usefulwhile classifying wetlands, interpreting biologi-cal data, and identifying potential stressors.BAWWG members use a variety of physical andchemical data in their projects, including:
� Water chemistry (e.g., nutrients, pH, DO,conductivity, dissolved metals, turbidity)
16
� Substrate (e.g., type of soil, sedimentchemistry)
� Wetland topography and water depth (e.g.,functional assessment data)
� Characteristic vegetative structure
� Characteristics of immediate surroundingland use
� Watershed characteristics (e.g., land use, per-cent natural vegetation, nearest wetland)
These chemical/physical data provide valuableinformation for interpreting biological data, veri-fying wetland class, and diagnosing potentialstressors. However, these data should not beused alone to infer biological condition. Sev-eral States have found that using chemical datato infer the biological condition of streams isdangerously misleading. States that have in-vested in strong stream bioassessment capabili-ties have discovered that chemical assessmentsvastly overestimated the quality of their streams.Using the traditional chemical assessments, OhioEPA estimated that approximately 30% ofstreams were not meeting the minimum stan-dards for maintaining chemical, physical, andbiological integrity. Using their bioassessmentmethods, Ohio EPA now estimates that about70% of the same streams are not meeting theirdesignated uses (Chris Yoder, Ohio EPA, pers.comm.). Other States, such as Delaware, havecome to a similar conclusion (John Maxted,Delaware Department of Natural Resources andEnvironmental Control, pers. comm.). Usingchemistry data or physical data to infer biologi-cal condition of wetlands would likely producesimilar misleading and inaccurate results. Ex-periences like these show that one of the mostmeaningful ways to evaluate the health ofstreams, and arguably any habitat, is to directlyevaluate the plant and animal communities thatlive in them.
Analyzing Data
After biologists sample and identify the taxain an assemblage, they can prepare a list of taxanames and the abundance or percent cover foreach. The challenge facing the biologists is toidentify ways to analyze these data to providemeaningful measures of biological condition.Remember that the goal is to evaluate the dataand determine to what degree the wetlands arebeing damaged by human activities. Bothmultimetric indexes, such as Indexes of Biologi-cal Integrity (IBI), and statistical approacheshave been used in stream, lake, and estuarybioassessments (Davis and Simon 1995, Barbouret al. 1999, U.S. EPA 1996a,b, 1998a, 2000a).The virtues of the two analytical methods havebeen debated in the scientific literature (Norrisand Georges 1993, Suter 1993, Gerritsen 1995,Norris 1995, Wright 1995, Diamond et al. 1996,Fore et al. 1996, Reynoldson et al. 1997, Karrand Chu 1999).
As described in Wetland Bioassessment CaseStudies (U.S. EPA, in prep.), most wetlandbioassessment projects use IBIs to analyze data.Some States are exploring the use of advancedstatistics to analyze data. Maine Department ofEnvironmental Protection is exploring the useof a combination of metrics and statistics toevaluate macroinvertebrate data. Montana De-partment of Environmental Quality uses canoni-cal correspondence analysis and TWINSPAN toevaluate wetland algal data. Magee and othersused canonical correspondence analysis andTWINSPAN to illustrate the extent to which wet-lands in urbanizing landscapes are floristicallydegraded in comparison to relatively undisturbedsystems (Magee et al. 1999).
IBIs and related multimetric indexes identifyattributes of an assemblage that show empiricaland predictable responses to increasing human
17
disturbance (Karr 1981). Each metric is scoredindividually. These scores are then combinedinto an overall index. The process of identify-ing metrics and developing IBIs is discussed indetail in Developing Metrics and Indexes ofBiological Integrity (U.S. EPA 2002g). Datafrom most attributes can be used to generate scat-ter plots, i.e., plot each measure for an attribute(Y variable) against a measure for human dis-turbance (X variable). Some attributes (e.g.,abundance, density, production) typically formshotgun patterns because they are naturally vari-able. Figure 4 provides an example of an at-tribute that shows no dose-response relationshipwhen compared to a disturbance gradient; thisattribute would not be used as a metric. Otherattributes will show clear dose-response patternsand thus would be considered as potentialmetrics. Figures 5 and 6 illustrate attributes withdose-response relationships when compared todisturbance gradients; these attributes could beused as metrics.
After graphically and statistically analyzing po-tential metrics, researchers select the best per-forming metrics to include in an IBI. Ideally, anIBI should consist of approximately 8-12 metrics(Karr and Chu 1999). One way of combiningmetrics into an IBI is to assign values of 5, 3, or1 to the measures for each metric, where a 5corresponds with the least disturbed condition,a 3 corresponds to intermediate disturbance, anda 1 corresponds to the most disturbed condition(U.S. EPA 2002g). For a metric such as the num-ber of intolerant taxa, a wetland with a lot ofintolerant taxa may receive a 5 and a wetlandwith no intolerant taxa may receive a 1. Themetric scores associated with a wetland are usu-ally added together to calculate the IBI score.Figure 7 provides an example of IBI scores ofindividual wetlands plotted across a gradient ofhuman disturbance. The IBI consists of 10metrics, which were scored using the 5/3/1 sys-tem and then added together. Thus the highest
possible IBI score in this example is 50 and thelowest possible IBI score is 10. Some Statesuse different scoring values (e.g., 6/4/2/0 or 10/7/3/0) to make the lowest possible IBI scoreequal 0.
On the basis of their experience, BAWWGmembers have the following recommendationsrelated to developing metrics and IBIs:
� Develop a separate IBI for each assemblage.BAWWG members recommend developingseparate IBIs for each assemblage becauseit makes it easier for other organizations touse or adapt the IBI. Advantages of havingtwo or more IBIs include (1) having addi-tional data that may reinforce thebioassessment findings, and (2) a second IBImay reveal different findings because someassemblages may respond more to certainstressors.
� Never use an attribute as a metric withouttesting it first. BAWWG members recom-mend that all sampling and analytical meth-ods, including metrics, should be tested, veri-fied, and calibrated to regional conditionsbefore they are used in a new area of thecountry (U.S. EPA 2002g).
� Investigate outliers. Scatterplots of the met-ric or IBI values of individual wetlands plot-ted against a disturbance gradient often haveoutliers, or values that are inconsistent withthe majority. BAWWG members have foundthat outliers are often the result ofmisclassifying the wetland or damage to thewetland from a stressor that is not accountedfor in the human disturbance gradient. In-vestigation of outliers can identify importantstressors and land use characteristics.
� Avoid directly comparing the IBI scores ofwetlands in different classes. IBI scoresshould be calibrated for each wetland classas defined by the classification system used.Consider an IBI consisting of 10 metrics,
18
Figure 4: Number of beetle
genera plotted against a human
disturbance gradient
(Source: Maine DEP).
Figure 5: Floristic quality
assessment index plotted against
a human disturbance gradient
(Source: Ohio EPA).
Figure 6: Number of Diptera taxa
Plotted against Rapid Assessment
Method (RAM) scores, a rapid
functional assessment
(Source: Ohio EPA).
Figure 7: A 10-metric
macroinvertebrate IBI
plotted against turbidity
(Source: Minnesota PCA).
19
each scored with a 5, 3, or 1 where 5 repre-sents good condition and 1 represents poorcondition. The best potential IBI score for abog, when compared with similar bogs,should be 50 (i.e., 10 metrics × 5 = 50). Simi-larly, the best potential marsh IBI scoreshould be a 50 when compared with othermarshes (i.e., 10 metrics × 5 = 50). Whenthe same metrics are used, avoid establish-ing a scoring system where a minimally dis-turbed bog would receive a significantlylower score (IBI = 25) than a minimally dis-turbed marsh (IBI = 50).
Reporting Results
Perhaps the greatest benefit of an IBI is that itsummarizes and presents complex biological in-formation in a format that is easily communi-cated to managers and the public. Most peoplecan more easily understand plant and animal IBIsthan complex statistical calculations or abstractchemical and physical data. Although an IBIscore is helpful for quickly communicating theoverall condition of a wetland, most of the valu-able information lies in the individual metrics.When reporting bioassessment results, the IBIscore should be accompanied by the followinginformation:
� Narrative description of overall biotic con-dition in comparison to reference wetlandsof the same region and wetland type
� Number values (e.g., number of taxa) andscores (e.g., 5, 3, or 1) for each metric
� Narrative descriptions of each metric in com-parison to reference conditions of the sameregion and wetland type
Using Biological
Information To
Improve Management
Decisions
B iological monitoring provides a frameworkfor improving wetland management, pro-
tection, and restoration. Bioassessments provideinformation about a wetland’s present biologi-cal condition compared to expected referenceconditions. By studying biology, wetland sci-entists can better understand how a wetland’sbiological community is influenced by thewetland’s present geophysical condition andhuman activities within a watershed (Figure 8).Managers, policymakers, and society at large canuse this information to decide if measuredchanges in biological condition are acceptableand set policies accordingly (Courtemanch et al.1989, Courtemanch 1995, Yoder 1995, Karr andChu 1999). As shown by many of the projectsin Wetland Bioassessment Case Studies (U.S.EPA, in prep.), States can use information fromwetland bioassessments to improve many man-agement decisions, including:
� Strengthening water quality standards
� Strengthening State wetland regulatory pro-grams
� Improving wetland tracking
� Improving water quality decisions
� Improving plans to monitor, protect, and re-store biological condition
� Evaluating the performance of regulatory,protection, and restoration activities
� Incorporating wetlands into watershed man-agement
� Improving risk-based management decisions
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Figure 8: Framework for improving wetland management
(adapted from Karr and Chu 1999).
21
Strengthening Water
Quality Standards
The most common application of wetlandbioassessments is to improve the way wetlandsare incorporated into State water quality stan-dards. States can use the information frombioassessments to develop ecologically baseddesignated uses and biocriteria to determine ifthose uses are being met. Under CWA Section303, States and eligible Tribes develop waterquality standards to ensure that their waters sup-port beneficial uses such as aquatic life support,drinking water supply, fish consumption, swim-ming, and boating. As envisioned by Section303(c) of the Clean Water Act, developing wa-ter quality standards is a joint effort betweenStates and the EPA. The States have primaryresponsibility for setting, reviewing, revising,and enforcing water quality standards.
EPA develops regulations, policies, and guid-ance to help States implement the program andoversees States’ activities to ensure that theiradopted standards are consistent with the re-quirements of the CWA and relevant water qual-ity standards guidelines (40 CFR Part 131). EPAhas authority to review and approve or disap-prove State standards and, where necessary, topromulgate Federal water quality standards. Awater quality standard defines the environmen-tal goal for a waterbody, or a portion thereof, bydesignating the use or uses to be made of thewater, setting criteria necessary to protect thoseuses, and preventing degradation of water qual-ity through antidegradation provisions (U.S. EPA1991) (Appendix). Criteria are the narrative ornumeric descriptions of the chemical, physical,or biological conditions found in minimally im-pacted reference areas (Table 3). By comparingthe condition of a wetland to appropriate crite-ria, States can determine if the wetland is sup-
porting its designated uses. For examples of howStates have incorporated wetlands into waterquality standard programs, please refer to theWetland Bioassessment Case Studies module(U.S. EPA, in prep.).
Most States do not have wetland-specific des-ignated uses or criteria to adequately protect wet-land biological integrity. In their absence, Statesmust rely on designated uses and criteria devel-oped for lakes, streams, or other waterbodies thatoften have different ecological conditions. Inaddition, States historically focused on devel-oping chemical and physical criteria based onsampling ambient water column conditions andconducting laboratory toxicity tests. The infor-mation on ambient water column conditions andtoxicity tests was then used to infer biologicalcondition of aquatic habitats. The developmentand widespread use of formal biocriteria haslagged behind chemical-specific and toxicitybased water quality criteria (U.S. EPA 1996a,b).However, EPA requires that States adoptbiocriteria as part of their water quality criteriafor wetlands (U.S. EPA 1990).
States can use bioassessment methods to es-tablish standards and criteria that are ecologi-cally appropriate for conditions found in wet-lands. Biocriteria for aquatic systems describe(in narrative or numeric criteria) the expectedbiological condition of a minimally impairedaquatic community (U.S. EPA 1992, 1996a).These criteria can be used to define ecosystemrehabilitation goals and assessment endpoints.Bioassessments are especially useful for assess-ing damage from hard-to-detect chemical prob-lems and nonchemical stressors. Thus,biocriteria fulfill a function missing from EPA’straditionally chemical-oriented approach to pol-lution control and abatement (U.S. EPA 1994d).
22
Strengthening State Wetland
Regulatory Programs
Wetland bioassessments can help strengthenState wetland regulatory programs and improveconfidence in management decisions. Ohio En-vironmental Protection Agency’s (Ohio EPA)work with an IBI and rapid functional assess-ment provides a good example. The Ohio RapidAssessment Method (ORAM) is a rapid func-tional assessment, which was developed by the
State for use in reviewing numerous wetlandpermit applications. Recognizing that it couldnot perform bioassessments with all wetlandpermit applications, Ohio EPA calibrated itsdetailed bioassessments with ORAM. Ohio EPAnow has more confidence in ORAM resultswhen the scores are within given ranges. WhenORAM scores are inconclusive, Ohio EPA canjustify delaying a decision on the application toperform a detailed bioassessment to provide amore reliable assessment of wetland condition.
Table 3: Types of Water Quality Criteria
(adapted from Elder et al. 1999)
23
Improving Wetland Tracking
Under Section 305(b) of the Clean Water Act(CWA), States submit reports to EPA every 2years that summarize the quality of their aquaticresources. In the 305(b) reports, States summa-rize the amount of streams, rivers, lakes, estuar-ies, and wetlands that are (1) meeting their des-ignated uses, (2) partially supporting their des-ignated uses, and (3) not supporting their desig-nated uses. In the 1998 National Water QualityInventory, a summary of the State 305(b) reportsprovided by EPA to the U.S. Congress, Statesdetermined designated use support for only 4%of the Nation’s wetlands. Of the 4% that wereincluded in the report, only a small fraction ofthe decisions were based on actual monitoringdata. Wetland bioassessments provide badlyneeded information to track wetland conditionand determine if wetlands are supporting theirdesignated uses. In addition, a number of Fed-eral funding sources are tied to the informationprovided in 305(b) reports. By not includingwetlands in the report, States are potentiallymissing out on resources for their programs.
Improving Water Quality
Decisions
Water quality standards provide a program-matic foundation for a number of other waterquality programs. By using bioassessment datato improve water quality standards, States canalso improve these other water quality programs.For example, bioassessments can help assess theimpacts from nonpoint-source pollution (CWASection 319) or from point-source discharges(CWA Section 402). States can usebioassessments to evaluate the effects ofstormwater discharges on the biological condi-tion of wetlands. Another potentially powerfultool is the water quality certification process.Under CWA Section 401, States have the au-thority to grant or deny “certification” of feder-
ally permitted or licensed activities that may re-sult in a discharge to wetlands or otherwaterbodies. The certification decision is basedon whether the proposed activity will complywith State water quality standards. Under thisprocess, a State can use information frombioassessments to determine if a proposed ac-tivity would degrade water quality of a wetlandor other waterbodies in a watershed. If a Stategrants certification, it is essentially saying thatthe proposed activity will comply with Statewater quality standards. Likewise, a State candeny certification if the project would harm thechemical, physical, or biological integrity of awetland as defined by water quality standards.A State’s Section 401 certification process is onlyas good as its underlying water quality standards.States can use bioassessments to refine narra-tive and numeric criteria to make them moresuitable for conditions found in wetlands andsubsequently improve the Section 401 certifi-cation process.
Improving Plans To Monitor,
Protect, and Restore
Biological Condition
Wetlands are often damaged by a complex mixof chemical, physical, and biological stressors.It can be difficult to pinpoint specific stressorsusing biological information or any single sourceof information alone. However, properlyplanned, designed, and implementedbioassessments are not performed in a vacuum(Yoder 1995). Proximity to known sources ofpollution, knowledge of the surrounding land-scape, and supporting chemical and habitat dataare all important sources of information to helpidentify how and why a wetland is being dam-aged. Recent advances in stressor identificationand evaluation provide a framework for system-atically examining all available data, identify-ing probable stressors, and documenting thedecisionmaking process (U.S. EPA 2000b). The
24
Stressor Identification framework offers threeapproaches to identify probable causes: (1)eliminate, (2) diagnose, and (3) assess strengthof evidence (Figure 9). The strength-of-evidenceapproach will often be the most helpful approachwhen the biota exhibits impairment and there isno clear stressor. In some cases, the stressoridentification process will indicate that addi-tional monitoring of the biological communityis required or will provide a shortened list ofpotential chemical or habitat stressors to be in-vestigated. Thus, bioassessments and the stres-sor identification process can help States iden-tify problem areas and then target the use of moreexpensive chemical and physical measurementson these sites. When the stressor identificationprocess identifies a probable stressor, appropri-ate actions can be taken to restore wetland con-dition. Under Section 303(d) of the Clean Wa-ter Act, States are required to submit lists to EPAof waterbodies that do not attain their designateduses and criteria, such as biocriteria. Subse-quently, States can use bioassessment data andthe stressor identification process to apply a va-riety of management tools (e.g., total maximumdaily loads, Section 319 nonpoint source pollu-tion reduction, NRCS wetland conservation pro-grams) to improve wetland condition.Bioassessment data will also be useful for Statesand municipalities when they target resourcesto protect or purchase easements on high-qual-ity wetlands.
Evaluating the Performance of
Regulatory, Protection, and
Restoration Activities
States can evaluate the success of restorationactivities and best management practices, suchas buffer strips, by requiring followup assess-ments in management plans. By periodicallyconducting bioassessments, States can track thecondition of wetlands and learn which manage-ment activities work best. States can use this
information to improve future managementplans and save time and money by targeting themost effective restoration projects and best man-agement practices that achieve greater environ-mental benefits. Wetland biologists can also usebioassessment data to track wetland biota recov-ery time and to identify which features of wet-land restoration projects, such as diversemicrotopography, are most important in improv-ing biological condition. The USGS BiologicalResources Division, NRCS Wetland Science In-stitute, and EPA Wetlands Division coopera-tively worked on a project to developbioassessment methods to evaluate the condi-tion of restored wetlands on the Delmarva Pen-insula in Maryland.
Incorporating Wetlands into
Watershed Management
The watershed management cycle is based onsound monitoring data (U.S. EPA 1995a, 1996c).Collectively, watershed stakeholders employsound scientific data, tools, and techniques inan iterative decisionmaking process (Figure 10).This process includes:
� Strategic monitoring. Target monitoring toinform management decisions
� Assessment. Evaluate data to determine con-dition of waterbodies, identify stressors, orevaluate effectiveness of prior managementplans
� Assigning priorities and targeting resources.Rank water quality concerns and decide howto allocate resources to address priority con-cerns
� Developing management strategies. De-velop clear goals and objectives to addresspriority concerns, identify a range of man-agement strategies, and evaluate their effec-tiveness
25
Figure 9: The management context of the Stressor
Identification (SI) process
(the SI process is shown in the center box with bold line).
26
Figure 10: Watershed
management cycle.
� Management plans. Specify how goals willbe achieved, who is responsible for imple-mentation, on what schedule, and how theeffectiveness of the plan will be assessed
� Implementation. Implement activities de-scribed in management plans
Information from wetland bioassessments isnecessary to evaluate the condition of wetlands,set environmental objectives, and evaluate thesuccess of management actions. Without infor-mation from bioassessments, watershed manage-ment plans will not adequately address or willcompletely overlook the biological condition ofwetlands. Wetlands will continue to be includedin watershed management plans as buffers tomaintain streams and lakes, but not as impor-tant components of the environment that shouldbe maintained and protected based on their ownintrinsic functions and values. Failure to pro-tect wetland condition in watershed plans willlikely diminish the health of other aquatic sys-tems in a watershed.
Improving Risk-Based
Management Decisions
By identifying the biological and ecologicalconsequences of human actions, biologicalmonitoring provides an essential foundation forassessing ecological risks (Karr and Chu 1999).To date, most ecological risk assessments focuson using laboratory analysis of chemical end-points and extrapolate the results to the naturalenvironment because of perceived shortcomingsin ecosystem-level risk assessment (Suter et al.1993). The combined information frombioassessments and stressor identification mayfulfill many of the perceived shortcomings ofecosystem-level risk assessments. Through theprocess of developing wetland bioassessments,wetland biologists identify a biological endpoint(i.e, a biological assemblage), group wetlandsinto classes that respond similarly to stressors,establish standard sampling methods, determinewhat time of year to sample, establish knownreference conditions, and provide a way to mea-sure divergence from biological integrity. Re-sults from bioassessments are combined withother available data in the stressor identificationprocess to determine the most probable stressorcausing damage. The combined informationfrom wetland bioassessments and the stressoridentification process provide a foundation forimproving whole-ecosystem studies. In manycases, bioassessments may provide more realis-tic predictions than chemical laboratory tests ofthe impacts that stressors have on the naturalenvironment (Perry and Troelstrup 1988). Thesetypes of analyses also will be useful for projectsinvolving the cleanup of contaminatedSuperfund and RCRA sites.
27
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U.S. EPA. 1996a. Biological Criteria: TechnicalGuidance for Streams and Small Rivers. Office ofWater, Washington, DC. EPA 822-B-96-001.
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ing or depending on each other for existence.
Competition Utilization by different speciesof limited resources of food or nutrients, refu-gia, space, ovipositioning sites, or other re-sources necessary for reproduction, growth, andsurvival.
Criteria A part of water quality standards. Cri-teria are the narrative and numeric definitionsconditions that must be protected and maintainedto support a designated use.
Continuum A gradient of change.
Designated use A part of water quality stan-dards. A designated use is the ecological goalthat policymakers set for a waterbody, such asaquatic life use support, fishing, swimming, ordrinking water.
Disturbance “Any discrete event in time thatdisrupts ecosystems, communities, or popula-tion structure and changes resources, substrateavailability or the physical environment” (Picketand White 1985). Examples of natural distur-bances are fire, drought, and floods. Human-caused disturbances are referred to as “humandisturbance” and tend to be more persistent overtime, e.g., plowing, clearcutting of forests, con-ducting urban stormwater into wetlands.
Diversity A combination of the number of taxa(see taxa richness) and the relative abundanceof those taxa. A variety of diversity indexes havebeen developed to calculate diversity.
Dominance The relative increase in the abun-dance of one or more species in relation to theabundance of other species in samples from ahabitat.
Ecological risk assessment An evaluation ofthe potential adverse effects that human activi-ties have on the plants and animals that makeup ecosystems.
Glossary
Aquatic life use A type of designated use per-taining to the support and maintenance of healthybiological communities.
Assemblage An association of interacting popu-lations of organisms that belong to the samemajor taxonomic groups. Examples of assem-blages used for bioassessments include: algae,amphibians, birds, fish, amphibians,macroinvertebrates (insects, crayfish, clams,snails, etc.), and vascular plants.
Attribute A measurable component of a bio-logical system. In the context of bioassessments,attributes include the ecological processes orcharacteristics of an individual or assemblageof species that are expected, but not empiricallyshown, to respond to a gradient of human dis-turbance.
Benthos The bottom fauna of waterbodies.
Biological assessment (bioassessment) Usingbiomonitoring data of samples of living organ-isms to evaluate the condition or health of a place(e.g., a stream, wetland, or woodlot).
Biological integrity “the ability of an aquaticecosystem to support and maintain a balanced,adaptive community of organisms having a spe-cies composition, diversity, and functional or-ganization comparable to that of natural habi-tats within a region” (Karr and Dudley 1981).
Biological monitoring Sampling the biota of aplace (e.g., a stream, a woodlot, or a wetland).
Biota All the plants and animals inhabiting anarea.
Composition (structure) The composition ofthe taxonomic grouping such as fish, algae, ormacroinvertebrates relating primarily to thekinds and number of organisms in the group.
Community All the groups of organisms liv-ing together in the same area, usually interact-
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Ecosystem Any unit that includes all the or-ganisms that function together in a given areainteracting with the physical environment so thata flow of energy leads to clearly defined bioticstructure and cycling of materials between liv-ing and nonliving parts (Odum 1983).
Ecoregion A region defined by similarity of cli-mate, landform, soil, potential natural vegeta-tion, hydrology, and other ecologically relevantvariables.
Gradient of human disturbance The relativeranking of sample sites within a regional wet-land class based on degrees of human distur-bance (e.g., pollution, physical alteration of habi-tats, etc.)
Habitat The sum of the physical, chemical, andbiological environment occupied by individu-als of a particular species, population, or com-munity.
Hydrology The science of dealing with theproperties, distribution, and circulation of wa-ter both on the surface and under the earth.
Impact A change in the chemical, physical (in-cluding habitat), or biological quality or condi-tion of a waterbody caused by external forces.
Impairment Adverse changes occurring to anecosystem or habitat. An impaired wetland hassome degree of human disturbance affecting it.
Index of biologic integrity (IBI) An integra-tive expression of the biological condition thatis composed of multiple metrics. Similar to eco-nomic indexes used for expressing the condi-tion of the economy.
Intolerant taxa Taxa that tend to decrease inwetlands or other habitats that have higher lev-els of human disturbances, such as chemical pol-lution or siltation.
Macroinvertebrates Animals without back-bones (insects, crayfish, clams, snails, etc.) thatare caught with a 500-800 micron mesh net.
Macroinvertebrates do not include zooplanktonor ostracods, which are generally smaller than200 microns in size.
Metric An attribute with empirical change invalue along a gradient of human disturbance.
Minimally impaired site Sample sites withina regional wetland class that exhibit the leastdegree of detrimental effect. Such sites helpanchor gradients of human disturbance and arecommonly referred to as reference sites.
Most-impaired site Sample sites within a re-gional wetland class that exhibit the greatestdegree of detrimental effect. Such sites helpanchor gradients of human disturbance and serveas important references, although they are nottypically referred to as reference sites.
Population A set of organisms belonging to thesame species and occupying a particular area atthe same time.
Reference site (as used with an index of bio-logical integrity) A minimally impaired site thatis representative of the expected ecological con-ditions and integrity of other sites of the sametype and region.
Stressor Any physical, chemical, or biologicalentity that can induce an adverse response.
Taxa A grouping of organisms given a formaltaxonomic name such as species, genus, family,etc. The singular form is taxon.
Taxa richness The number of distinct speciesor taxa that are found in an assemblage, com-munity, or sample.
Tolerance The biological ability of differentspecies or populations to survive successfullywithin a certain range of environmental condi-tions.
Trophic Feeding, thus pertaining to energytransfers.
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Wetland(s) (1) Those areas that are inundatedor saturated by surface or groundwater at a fre-quency and duration sufficient to support, andthat under normal circumstances do support, aprevalence of vegetation typically adapted forlife in saturated soil conditions [EPA, 40 C.F.R.§230.3 (t) / USACE, 33 C.F.R. § 328.3 (b)]. (2)Wetlands are lands transitional between terres-trial and aquatic systems where the water tableis usually at or near the surface or the land iscovered by shallow water. For the purposes ofthis classification, wetlands must have one ormore of the following three attributes: (a) at leastperiodically, the land supports predominantlyhydrophytes, (b) the substrate is predominantlyundrained hydric soil, and (c) the substrate isnonsoil and is saturated with water or covered
by shallow water at some time during the grow-ing season of each year (Cowardin et al. 1979).(3) The term “wetland” except when such termis part of the term “converted wetland,” meansland that (a) has a predominance of hydric soils,(b) is inundated or saturated by surface or groundwater at a frequency and duration sufficient tosupport a prevalence of hydrophytic vegetationtypically adapted for life in saturated soil condi-tions, and (c) under normal circumstances doessupport a prevalence of such vegetation. Forpurposes of this Act and any other Act, this termshall not include lands in Alaska identified ashaving a high potential for agricultural devel-opment which have a predominance of perma-frost soils [Food Security Act, 16 U.S.C.801(a)(16)].
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Appendix: Water Quality Standards
and Criteria
The main objective of the Clean Water Act(CWA) is to “restore and maintain the chemi-cal, physical, and biological integrity of theNation’s water.” To help meet these objectives,States must adopt water quality standards (WQS)for all “waters of the U.S.” within their bound-aries, including wetlands. Water quality stan-dards, at a minimum, consist of three major com-ponents: (1) designated uses, (2) narrative andnumeric water quality criteria for supportingeach use, and (3) an antidegradation Statement.
Designated Uses
Designated uses establish the environmentalgoals for water resources. States and Tribes as-sign designated uses for each waterbody, or seg-ment of a body of water, within their boundaries.Typical uses include public water supply, pri-mary contact recreation (such as swimming), andaquatic life support (including the propagationof fish and wildlife). States and Tribes developtheir own classification system and can desig-nate other beneficial uses including fish con-sumption, shellfish harvesting, agriculture, wild-life habitat, and groundwater recharge.
Since designated uses can vary, States andTribes may develop unique water quality require-ments or criteria for their designated uses. Statesand Tribes can also designate uses to protectsensitive or valuable aquatic life or habitat, suchas wetlands. When designating uses for wet-lands, States may establish an entirely differentformat to reflect the unique functions and val-ues of wetlands. At a minimum, designated usesmust be attainable uses that can be achievedusing best management practices and othermethods to prevent degradation. States andTribes can also designate uses that have not yet
been achieved or attained. Protecting and main-taining such uses may require the imposition ofmore stringent control programs.
Water Quality Criteria
Federal water quality regulation requires Statesto adopt criteria sufficient to protect and main-tain designated uses. Water quality criteria mayinclude narrative Statements or numeric limits.States and Tribes can establish physical, chemi-cal, and biological water quality criteria. Wet-land biological monitoring and assessment pro-grams can help States and Tribes refine theirnarrative and numeric criteria to better reflectconditions found in wetlands.
Narrative water quality criteria define condi-tions that must be protected and maintained tosupport a designated use. States should writenarrative criteria to protect designated uses andto support existing uses under Stateantidegradation policies. For example, a Stateor Tribe may describe desired conditions in awaterbody as “waters must be free of substancesthat are toxic to humans, aquatic life, and wild-life.” In addition, States and Tribes can writenarrative biological criteria to describe the char-acteristics of the aquatic plants and animals. Forexample, a State may specify that “ambient wa-ter quality shall be sufficient to support lifestages of all native aquatic species.”
Narrative criteria should be specific enoughthat States and Tribes can translate them intonumeric criteria, permit limits, and other con-trol mechanisms including best managementpractices. Narrative criteria are particularly im-portant for wetlands, since States and Tribes
34
cannot numerically describe many physical andbiological impacts in wetlands by using currentassessment methods.
Numeric water quality criteria are specificnumeric limits for chemicals, physical param-eters, or biological conditions that States andTribes use to protect and maintain designateduses. Numeric criteria establish minimum andmaximum physical, chemical, and biologicalparameters for each designated use. Physicaland chemical numeric criteria can include maxi-mum concentrations of pollutants, acceptableranges of physical parameters, minimum thresh-olds of biological condition, and minimum con-centrations of desirable parameters, such as dis-solved oxygen.
States and Tribes can adopt numeric criteria toprotect both human health and aquatic life usesupport. For example, numeric human healthcriteria include maximum levels of pollutantsin water that are not expected to pose signifi-cant risk to human health. The risk to humanhealth is based on the toxicity of and level ofexposure to a contaminant. States and Tribescan apply numeric human health criteria (suchas for drinking water) to all types of waterbodies,including wetlands.
Numeric chemical or physical criteria foraquatic life, however, depend on the character-istics within a waterbody. Since characteristicsof wetlands (such as hydrology, pH, and dis-solved oxygen) can be substantially differentfrom other water bodies, States and Tribes mayneed to develop some physical and chemicalcriteria specifically for wetlands.
Numeric biological criteria can describe the ex-pected attributes and establish values based onmeasures of taxa richness, presence or absenceof indicator taxa, and distribution of classes of
organisms. Many States have developed bio-logical assessment methods for streams, lakes,and rivers, but few States and Tribes have de-veloped methods for wetlands. Several States,including Florida, Maine, Massachusetts, Min-nesota, Montana, North Dakota, Ohio, and Ver-mont are currently developing biological assess-ment methods for monitoring the “health” ofwetland plant and animal communities. Wet-land biological assessment methods are essen-tial to establish criteria that accurately reflectconditions found in wetlands.
Antidegradation Policy
All State standards must contain anantidegradation policy, which declares that theexisting uses of a waterbody must be maintainedand protected. Through an antidegradationpolicy, States must protect existing uses and pre-vent waterbodies from deteriorating, even ifwater quality is better than the minimum levelestablished by the State or tribal water qualitystandards. States and Tribes can useantidegradation Statements to protect watersfrom impacts that water quality criteria cannotfully address, such as physical and hydrologicchanges.
States and Tribes can protect exceptionally sig-nificant waters as outstanding national resourcewaters (ONRWs). ONRWs can include waterswith special environmental, recreational, or eco-logical attributes, such as some wetlands. Nodegradation is allowed in waters designated asONRW. States can designate waters that needspecial protection as ONRWs regardless of howthey ecologically compare to other waters. Forexample, although the water of a swamp maynot support as much aquatic life as a marsh, theswamp is still ecologically important. A Stateor Tribe could still designate the swamp as anONRW because of its ecological importance.
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Applications of WQS
Water quality standards provide the foundationfor a broad range of management activities andcan serve as the basis to:
� Assess the impacts of nonpoint source dis-charges on waterbodies under CWA §319,
� Assess the impacts of point source dis-charges on waterbodies under CWA §402,
� Determine if federally permitted or licensedactivities maintain WQS under CWA §401water quality certification
� Track and report if waterbodies are support-ing their designated uses under CWA§305(b)
