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Water: Monitoring & Assessment

Impacts on Quality of Inland Wetlands of the United States: A Survey of Indicators, Techniques, and Applications of Community Level Biomonitoring Data

(Excerpts from Report #EPA/600/3-90/073, now out of print, prepared for US EPA Wetlands Research Program by Paul Adamus and Karla Brandt and currently being updated).

Based on a synopsis of the literature prior to 1990, this report describes the potential effects upon wetland community structure of eutrophication, organic loading, contaminant toxicity, acidification, salinization, sedimentation, turbidity/shade, vegetation removal, thermal alteration, dehydration, inundation, and fragmentation of habitat. Information is provided concerning the effect of each stressor on potential indicators of wetland condition, such as microbes, algae, vascular plants, invertebrates, fish, amphibians, reptiles, birds, mammals, and selected biological processes.

The report describes options for using potential indicators to (a) develop and incorporate biocriteria for the protection of wetland ecological condition, and (b) help identify and prioritize degraded wetlands that may be candidates for restoration. Because of the lack of appropriate comparative studies of wetlands, the report does not provide biocriteria for wetlands, evaluate or prioritize potential indicators of wetland condition, nor endorse specific techniques for wetland biomonitoring and data analysis. Its intended use is mainly as a technical source document for future design, testing, and reporting of indicators.

The focus is primarily on community-level (as opposed to individual-organism) responses to the stressors. Techniques for sampling each of the taxonomic groups in wetlands are described generally. To the extent allowed by published data, the range of density, richness, and diversity within some taxonomic groups is reported, and most-sensitive species are noted.

Technical comments and suggestions on this document are appreciated. As of February 1998 the senior author (Paul Adamus) can be reached at:

Adamus Resource Assessment, Inc.
6028 NW Burgundy Dr.
Corvallis, OR, USA 97330
email: adamusp@ucs.orst.edu
phone: (541) 745-7092

The original document was funded by the United States Environmental Protection Agency (EPA) and conducted through contract 68-C8-006 to NSI Technology Services Corporation. It was subjected to the Agency's peer review process. Any opinions expressed are those of the authors and do not necessarily reflect those of EPA. The official endorsement of the Agency should not be inferred.


Contents

Introduction
General Guidelines for Wetland Biological Characterization
Microbial Communities
Wetland Algae
Non-woody (Herbaceous) Vegetation
Wooded Wetland Vegetation
Invertebrate Communities
Fish Communities
Amphibians and Reptiles
Bird Communities
Mammal Communities
Biological Process Measurements in Wetlands
Literature Cited
Literature by State
List of Wetland Profile Reports
Summary of Advantages and Disadvantages of Use of Major Taxa


1.0 INTRODUCTION

The widespread physical loss of North American wetlands has been generally documented (e.g., Tiner 1984). However, uncertainty exists regarding the ecological condition of the wetlands that remain. Although wetlands passively provide for many public uses—e.g., water purification, flood control, aquatic life and wildlife support--the extent to which these functions are being impaired in the remaining wetland resources is unclear. The Environmental Protection Agency (EPA) has the responsibility under several legal mandates (Table 1) for determining this.

Wetland ecological quality assumes special significance because of current State and Federal interest in adopting a policy of "no net loss" of the nation's wetlands. As expressed by EPA's Wetlands Action Plan, this implies no net loss of either acreage or function. To determine whether particular functions or uses, such as support of aquatic life, are being impaired in wetlands, "indicators" of these functions must be identified and protocols articulated for their measurement and interpretation.

1.1 SCOPE OF COVERAGE AND ORGANIZATION

This report focuses on inland wetlands of the conterminous United States. Except for those bordering the Great Lakes, these are not subject to significant tidal fluctuations. They are generally fresh water wetlands, except for saline wetlands in some mid-continent and western regions. Other tidal, tundra, and tropical wetlands were not included because their consideration would have involved a greatly expanded scope of work. Protocols for biological sampling of tidal wetlands have been presented by Simenstad et al. (1989) and others. For purposes of this report, "wetlands" are considered to be vegetated areas transitional between uplands and open water.

A principal goal of this report is to encourage each state to track progress in protecting wetland ecological condition. As one of many components needed to achieve this, this report identifies data gaps and provides guidance that describes (a) how existing resource data might be applied in the designation of "uses" for wetlands, (b) ambient biological criteria for wetlands might be developed or modified, and (c) how wetlands might be periodically sampled (and data interpreted) to estimate their relative ecological condition, compliance with biological criteria, or need for restoration. Publication of this report is not intended to imply that sufficient knowledge exists to develop community-based biocriteria for all wetlands at the present time.

This report emphasizes the biological functions of wetlands--habitat for fish, wildlife, and related organisms--and the processes that support biological functions. Its purpose is to provide State and Federal water quality and wetland managers with a synopsis of selected literature describing the community-level response of wetlands and similar aquatic systems to particular stressors. In most cases, this document does not synthesize the literature into statements applicable to all wetlands, or to all wetlands, taxa, or stressors of a certain type. Such a synthesis was generally avoided because the technical literature lacks a sufficient number of studies that demonstrate causal relationships (as opposed to correlation) or that allow statistical extrapolation (i.e., synthesis) to entire taxa, stressor types, or wetland types, regions, or states.

Biological sampling can be carried out at several ecological levels--the organism, the population, the community, or the ecosystem (Table 2). This report focuses on measurements of biological communities, that is, associations of interacting populations, usually delimited by their interactions or by spatial occurrence. Tables 3 and 4 show specific metrics (that is, characteristics or indices) used to describe the communities. This report also discusses, to a more limited extent, the measurement and use of biological processes as indicators of anthropogenic stress.

Table 1. Examples of Major Federal Laws, Directives, and Regulations for the Management and Protection of Wetlands
Directive Date Responsible Agency
Executive Order 11990
Protection of Wetlands
May 1977 All agencies
Executive Order 11988
Floodplain Management
May 1977 All agencies
Federal Water Pollution
Control Act (PL 92-500)
as Amended
1972, 1977  
Section 401- Water
Quality Certification
  EPA, States
Section 404- Dredge and
Fill Permit Program
  EPA, Corps of Engineers
Reporting requirements for
Section 305(b)
  States
National Environmental
Policy Act
1975 All agencies
Coastal Zone Management Act 1972 Office of Coastal Zone Management

This report's focus on biological communities does not mean other measurements are less important or useful. Indeed, there are numerous situations where alternative indicators--in particular, wetland flooding regime, bioaccumulation of contaminants, sedimentation rate, population demographics, and habitat structure --can more cost-effectively reflect the ecological condition, impact causes, and sustainability of a wetland than can community-level biological methods. Quantitative literature on the community ecology of wetlands has been singled out for focus, largely because of current EPA interest in applying this approach when assisting States with the development of community-based biocriteria for surface waters (Plafkin et al. 1989, USEPA 1987, 1990).

This focus on community-level measurements coincides with a growing body of literature which suggests that, at least for many applications in flowing waters, monitoring of biological community structure provides cost-effective information about ecological condition or as some have termed it, "health" (Krueger et al. 1988). Biological monitoring directly addresses the result of pollution, not its possible cause. Measurements of community structure can integrate intermittent stressor conditions. They can also detect impacts from many sources for which chemical criteria are poorly suited to detect (e.g., alteration of hydrologic regimes, synergistic pollutant effects, nonpoint runoff). If community-level measurements suggest that a stress is occurring, traditional methods (e.g., direct hydrologic monitoring, tissue analysis, chemical sampling) can be:

Table 2. Potential Metrics for Wetland Biomonitoring.
Organismal Level
Altered Behavioral Responses
  • foraging/feeding effectiveness
  • response to odors, pheromones, temperature, chemicals
  • reproductive behavior (courtship, mating, maternal/paternal)
  • predator avoidance (reaction time, evasiveness)
  • migratory/dispersal behavior
  • social interactions/territoriality
Altered Metabolism/Homeostasis
  • thermo/osmo/hydro regulation
  • oxygen consumption, photosynthesis
  • nutrient uptake and translocation, food conversion efficiency
  • enzyme/protein activation/inhibition (e.g., cholinesterase)
  • hormone balances
Altered Reproductive Success
  • seed set, tillering, flowering, vegetative (clonal) growth
  • sexual maturity, conception/implantation, parturition
Altered Growth and Development
  • growth rate (e.g., tree ring analysis)
  • size at age, morphological abnormalities
Decreased Disease Resistance
Direct Tissue/Organ Damage (e.g., lesions, tumors)
Changes in Stamina (e.g., plant vigor)
Bioaccumulation
Population Level
  • survival/mortality
  • sex ratio, fecundity
  • population abundance, biomass, density
  • age structure and recruitment
  • gene pool
  • intraspecific competition
  • population behavior, migration, dispersal
  • susceptibility to predation
  • population rate of decline or increase
Community Level (see Table 3 for details)
Structure (taxonomic and functional)
Function (process)
Ecosystem Level
Mass
Balance of Nutrients

 

Table 3. Examples of Biological Metrics Describing Wetland Community Structure and Function.

Community Structure

  • Abundance. The number of individuals of an organism or organisms. As an analytic metric, tends to exaggerate the importance of small, abundant species.
  • Biomass. The weight of living material in all or part of a community. For this report, it includes measurements of chlorophyll or caloric content as well. As an analytic metric, tends to exaggerate the importance of large, uncommon species.
  • Density. The number of individuals of an organism or organisms, per unit area or per unit volume.
  • Richness. The number of species, size classes, or other functional groups, per unit area or volume, or per number of individuals.
  • Diversity. The variety (richness) of species, life forms ( physiognomy), genetic material, or functional groups, taking into account the relative abundance ( evenness and dominance) of each species or group.
  • Community Composition. Qualitative descriptions of the members of a community (e.g., species lists), perhaps describing as well their relative abundance and grouped by their attributes (e.g., exotic vs. native, migrant vs. resident, response guild).
  • Community Attributes
  • Colonization rates
  • Stability
    • resistance, assimilation capacity
    • resilience, recovery rate
  • Successional relationships Food web structure, trophic interactions Competition among species Predator/prey relationships Grazing/herbivory relationships Parasite/host relationships, symbiosis

Community Function (Process)

  • Decomposition/leaching Productivity
  • Photosynthesis
  • Respiration Denitrification
  • Nitrogen Fixation
  • Other Biogeochemical Functions (e.g., methanogenesis)

 

Table 4. Examples of Analytical Metrics, Indices, and Procedures Used for Wetland Community Studies.

Similarity (Comparative) Indices. Metrics that reflect the number of species or functional groups in common between multiple wetlands or time periods. May be weighted by relative abundance, biomass, taxonomic dissimilarity, or caloric content of the component species. Includes Jaccard coefficient, Bray-Curtis coefficient, rank coefficients, overlap indices, the "community degradation index" (Ramm 1988), and others.

Cluster Analysis and Ordination. Procedures that detect statistical patterns and associations in community data. Can be used to hypothesize relationships to a stressor. Includes principal components analysis, reciprocal averaging, detrended correspondence analysis, TWINSPAN, canonical correlation, and others. Can be used to identify guilds (see below). A useful reference is Pielou (1984), and a cautionary note is expressed by Beals (1973).

Food Web Analysis. Procedures that measure length of food chains, number of trophic levels, ratio of number of trophic species to trophic links, and similar measures (e.g., Patten et al. 1989, Turner 1988). As yet, they have seldom been tested in stressed wetlands.

Tolerance Indices. Metrics that reflect proportionate composition of tolerant vs. intolerant taxa. Includes saprobic indices, macroinvertebrate EPT index, Hilsenhoff index, and others detailed and compared in Hellawell (1984) and Washington (1984). "Tolerance" usually means tolerance to organic pollution; tolerance to many toxicants and physical habitat alterations may not be well-reflected by available indices.

Guild Analysis. Procedures in which individual species are assigned to functional groups (species assemblages) based on similar facets of their:

  • life history
  • habitat preference
  • trophic level, assumed niche breadth
  • size, biomass, caloric content
  • toxicological sensitivity
  • behavioral characteristics
  • phenological characteristics
  • sensitivity to human presence
  • status as an exotic or indigenous species
  • resident vs. migrant status
  • harvested vs. protected status
  • other factors

Indices of Biotic Integrity. Indices that are a composite of weighted metrics describing richness, pollution-tolerance, trophic levels, abundance, hybridization, and deformities. Widely used in stream fish studies (see Karr 1981). .

This report's focus on biological communities does not mean other measurements are less important or useful. Indeed, there are numerous situations where alternative indicators--in particular, wetland flooding regime, bioaccumulation of contaminants, sedimentation rate, population demographics, and habitat structure --can more cost-effectively reflect the ecological condition, impact causes, and sustainability of a wetland than can community-level biological methods. Quantitative literature on the community ecology of wetlands has been singled out for focus, largely because of current EPA interest in applying this approach when assisting States with the development of community-based biocriteria for surface waters (Plafkin et al. 1989, USEPA 1987, 1990).

This focus on community-level measurements coincides with a growing body of literature which suggests that, at least for many applications in flowing waters, monitoring of biological community structure provides cost-effective information about ecological condition or as some have termed it, "health" (Krueger et al. 1988). Biological monitoring directly addresses the result of pollution, not its possible cause. Measurements of community structure can integrate intermittent stressor conditions. They can also detect impacts from many sources for which chemical criteria are poorly suited to detect (e.g., alteration of hydrologic regimes, synergistic pollutant effects, nonpoint runoff). If community-level measurements suggest that a stress is occurring, traditional methods (e.g., direct hydrologic monitoring, tissue analysis, chemical sampling) can beused to help determine cause. Moreover, ambient biological criteria can directly provide realistic evaluations of whether specific areas designated for protection of aquatic life are meeting this objective, or require restoration.

In most cases, if biological community monitoring data are to be correctly interpreted, they should be collected over time periods spanning several years, and should be accompanied with hydrologic and water quality measurements. Hydrologic measurements typically describe the variability, temporal pattern, extent, frequency, depth, and duration of surface waters and/or saturated condition (e.g., Gunderson 1989, Poff and Ward 1989). They may be expressed, for example, as water residence time distribution, water yield (net water balance), and stage or flow exceedence curves (i.e., percentage of time a particular water level or discharge is exceeded). Typical equipment for measuring these includes precipitation gauges, flourescent dyes, stage-discharge recorders, piezometers, redox probes, and sediment traps. For further information on the use of hydrologic and sediment measurements in wetland monitoring, readers may find the following references particularly useful:

Faulkner et al. 1989, Gunderson 1989, Heliotis and DeWitt 1987, Kadlec 1984, Kadlec 1988, LaBaugh 1986, Rosenberry 1990, USEPA 1985, Van Haveren 1986, Welcomme 1979, and Zimmerman 1988.

Monitoring protocols for estimating bioaccumulation in wetlands will be published in a manual by the U.S. Fish and Wildlife Service in 1990. General summaries of aquatic bioaccumulation processes and effects are contained in Biddinger and Gloss 1984, Fagerstrom 1979, Phillips 1980, Robinson-Wilson 1981, and Sonstegard 1977. Examples of bioaccumulation studies in wetlands include:

Anthony and Kozlowski 1982, Aulio 1980, Behan et al. 1979, Lambing et al. 1988, Larsen and Schierup 1981, McIntosh et al. 1978, Metcalf et al. 1984, Mouvet 1985, Niethammer et al. 1985, Schierup and Larsen 1981, Stephenson and Mackie 1988, Taylor and Crowder 1983, and others.

It is assumed that each state will determine how best to sample wetlands, incorporate wetland biological criteria into its water quality management programs, and establish restoration priorities. For this reason, much of the information contained in this report is presented as "could's" or "might's," and details regarding "how" the many technical statements should be interpreted and implemented are left to other agencies and institutions which have diverse goals and which encounter a wide variety of political and environmental conditions. To date, only a single state (Florida) has drafted survey-based biological criteria for some of its wetland resource (described by Schwarz 1987).

This report is also intended to serve as once source of technical support for the EPA's National Guidance on Water Quality Standards for Wetlands, prepared jointly by the Office of Wetlands Protection and the Office of Water Regulations and Standards. This report pursues this goal partly by providing just one input--a literature review--for identifying and interpreting biological indicators of wetland ecological condition.

Many factors other than technical data must be considered in developing biological criteria and setting restoration priorities. Decisions concerning selection of which resources, uses, or functions to protect or enhance are inevitably complex, since the criteria for protecting one resource or use may be counter to protecting another (Duinker and Beanlands 1986, Graul and Miller 1984, Smith and Theberge 1987). A generalized list of wetland functions or uses that might be the focus of protection or restoration is contained in Section 404 of the Clean Water Act. These are as follows (from 33 CFR 320 (b)(2)):

  1. Food Chain Production (i)
  2. General Habitat (i)
  3. Research, Education, and Refuges (ii)
  4. Hydrologic Modification (iii)
  5. Sediment Modification (iii)
  6. Wave Buffering and Erosion Control (iv)
  7. Flood Storage (v)
  8. Ground Water Recharge or Discharge (vi)
  9. Water Purification (vii)
  10. Uniqueness/Scarcity (viii)

Any such list could include many additional or more specific values of wetlands, e.g., maintenance of biodiversity, landscape value as corridors or habitat islands, role in global climate change, timber harvest.

This report begins, in Section 2, with a description of possible technical approaches that state and local agencies might use in designating "uses" for wetlands and eventually, perhaps, developing community-level biological criteria. Section 3 then describes general considerations in the design of wetland biomonitoring studies. Remaining sections of the report are delimited by major taxonomic groups (e.g., birds, fish). Each of these taxonomic sections is divided according to the following themes:

Use as Indicators
Sampling Protocols and Equipment
Spatial and Temporal Variability, Data Gaps

Originally, our intent was to organize the discussions by wetland type. This is because wetland types are generally believed to differ in their community-level responses to particular stressors. Thus, wetland "type" may be an important qualifier of any biocriteria that might be developed in the future. However, studies of specific anthropogenic stressors within individual types of wetlands were often so few that attempts to organize sections by wetland type proved futile. Nonetheless, within the discussions of particular taxa and stressors, statements about indicator metrics and taxa have been couched whenever possible in terms descriptive of wetland type/region. Also, attempts were made to organize the descriptions of sampling techniques according to wetland type. Although sampling protocols and appropriate equipment differ between flowing-water wetlands, wetlands with standing surface water, and wetlands without surface water, a finer classification of types is difficult to specify without knowledge of study objectives. Usually, having a clear definition of the objectives of a particular study is more important to study design than is knowledge the particular types of wetlands that happen to be included in a study.

The subsection discussions of Use as Indicators attempt to document community-level shifts that occur as a result of particular anthropogenic stressors. Stressors considered in this report are listed and defined in Table 5. Their effects on biota are often cumulative and interactive, thus complicating the use of biota as indicators of any individual stressor. Although several previous documents have summarized impacts to wetland biota (e.g., Brennen 1985, Brown et al. 1989, Darnell et al. 1976, Davis and Brinson 1980, USEPA 1983, USEPA and USFWS 1984), not all taxa, wetland, and stressor types have been covered and inferences have commonly been drawn from non-wetland aquatic environments.

It is important to understand that statements made in this report reflect strongly the particular wetland locations and types that were studied, and considerable uncertainty exists regarding whether such conclusions (e.g., about the value of specific taxa as indicators) can be transferred to other wetland types and regions. Many cited studies reflect one-visit or one-season data collections from a single wetland type, rather than recurrent monitoring. There are very few statistically-valid studies that adequately quantify the exposures of wetland organisms to stressors using factorial designs, e.g., studying areas both with/without treatment and staggered before/after measurements (Stewart-Oaten et al. 1986, Walters et al. 1988). Although it may appear, from the quantity of studies contained in the maps, in their bibliographies, and in the extensive literature citations in the text that inland wetlands in some regions have been extensively monitored, in truth relatively little is known about wetland biological response to anthropogenic stressors. Compared to monitoring of streams and lakes, sampling of wetlands on a recurrent or comparative regional basis has been almost non-existent, partly due to lack of government sponsorship of wetland biomonitoring programs.

Also, the response of a wetland community to anthropogenic stress depends not only on the taxa present and the severity of the stressor, but also on the geomorphic, physical, and chemical environment of the wetlands (Adamus et al. 1987, Adamus and Stockwell 1983). For example:

  • Wetland biological communities most vulnerable to sedimentation effects might be those located in shallow basins without outlets, so sediment quickly accumulates;
  • Wetland biological communities most vulnerable to eutrophication and contaminant effects might be those in wetlands that get most of their water directly from precipitation (e.g., ombrotrophic bogs), which have low alkalinity, and/or which have types of sediments that adsorb (but do not render biologically unavailable or harmless) the nutrients and contaminants during the short time that runoff passes through the wetland, e.g. Goldsborough and Beck (1989).
  • Wetland biological communities most vulnerable to effects of many anthropogenic changes might be those that:
    (a) have no prior exposure to similar levels or types of stress; and/or
    (b) exist in wetland types or regions that are characteristically stable (relatively speaking) over time; and/or
    (c) are physically isolated from sources of colonizers, so that recovery occurs slowly; and/or
    (d) are located in regions that have experienced especially rapid losses of wetlands of a similar type.

Considerably more investigation may be required before candidate indicators of wetland ecological condition can be fairly rated relative to one another, and exact numerical criteria specified. Thus, users of the report are urged to obtain, whenever possible, assistance from local wetland scientists when attempting to apply the information reported herein.

In this report, the representativeness, replication, and field and data analysis techniques used by cited studies were not evaluated; the overwhelming majority of citations are peer-reviewed papers from professional journals. Also, no attempt is made to give equal coverage to all topics within the general theme, because availability of data varies greatly among topics. .

Table 5. Stressors Addressed in this Report.

Enrichment/Eutrophication. Increases in concentration or availability of nitrogen and phosphorus. Typically associated with fertilizer application, cattle, ineffective wastewater treatment systems, fossil fuel combustion, urban runoff, and other sources.

Organic Loading and Reduced DO. Increases in carbon, to the point where an increased biological oxygen demand reduces dissolve oxygen in sediments and the water column and increases toxic gases (e.g., hydrogen sulfide, ammonia). Typically associated with ineffective wastewater treatment systems.

Contaminant Toxicity. Increases in concentration, availability, and/or toxicity of metals and synthetic organic substances. Typically associated with agriculture (pesticide applications), aquatic weed control, mining, urban runoff, landfills, hazardous waste sites, fossil fuel combustion, wastewater treatment systems, and other sources.

Acidification. Increases in acidity (decreases in pH). Typically associated with mining and fossil fuel combustion.

Salinization. Increases in dissolved salts, particularly chloride, and related parameters such as conductivity and alkalinity. Typically associated with road salt used for winter ice control, irrigation return waters, seawater intrusion (e.g., due to land loss or aquifer exploitation), and domestic/industrial wastes.

Sedimentation/Burial. Increases in deposited sediments, resulting in partial or complete burial of organisms and alteration of substrate. Typically associated with agriculture, disturbance of stream flow regimes, urban runoff, ineffective wastewater treatment plants, deposition of dredged or other fill material, and erosion from mining and construction sites.

Turbidity/Shade. Reductions in solar penetration of waters as a result of blockage by suspended sediments and/or overstory vegetation or other physical obstructions. Typically associated with agriculture, disturbance of stream flow regimes, urban runoff, ineffective wastewater treatment plants, and erosion from mining and construction sites, as well as from natural succession, placement of bridges and other structures, and resuspension by fish (e.g., common carp) and wind.

Vegetation Removal. Defoliation and possibly reduction of vegetation through physical removal, with concomitant increases in solar radiation. Typically associated with aquatic weed control, agricultural and silvicultural activities, channelization, bank stabilization, urban development, defoliation from airborne contaminants and other stressors included in this report, grazing/herbivory (e.g., from muskrat, grass carp, geese, crayfish, insects), disease, and fire.

Thermal Alteration. Long-term changes (especially increases) in temperature of water or sediment. Typically associated with power plants, other industrial facilities, and global climate change.

Dehydration. Reductions in wetland water levels and/or increased frequency, duration, or extent of desiccation of wetland sediments. Typically associated with ditching, channelization of nearby streams, invasion of wetlands by highly transpirative plant species, outlet widening, subsurface drainage, global climate change, and ground or surface water withdrawals for agricultural, industrial, or residential use.

Inundation. Increases in wetland water levels and/or increase in the frequency, duration, or extent of saturation of wetland sediments. Typically associated with impoundment (e.g., for cranberry or rice cultivation, flood control, water supply, waterfowl management) or changes in watershed land use that result in more runoff being provided to wetlands.

Fragmentation of Habitat. Increases in the distance between, and reduction in sizes of, patches of suitable habitat.

Other Human Presence. Increases in noise, predation from pets, disturbance from visitation, invasion by aggressive species capable of outcompeting species that normally characterize intact communities; electromagnetic, ultraviolet (UV-B), and other radiation, and other factors not addressed above.

In the "Use as Indicators" subsections, discussions focus on the community metrics that are defined in Table 4. An important metric that is frequently discussed is " richness." References in this report to the response of richness to stressors should be assumed, unless otherwise noted, to refer to changes in taxonomic richness within a wetland. However, readers should be aware that some stressors may increase richness of a major taxonomic group within a wetland (alpha diversity) while decreasing richness on a regional level (beta and gamma diversity). This may occur as the result of a net increase in species within the wetland, but an increase in which regionally rare species originally inhabiting the wetland are replaced by a larger number of regionally common and widespread species. Thus, no value judgement should necessarily be attached to statements that richness increases in response to a stressor. Moreover, design of future studies evaluating changes in community richness should in many cases include information on the regional rarity of species that may be displaced.

The subsection discussions of Sampling Protocols and Equipment focus on techniques for sampling each taxonomic group, e.g., how, where, when, and how often sampling has been done. However, this report is not intended to be a prescriptive manual. Rather, the intent is to present the user with choices. Choices are provided by summarizing the types of equipment, protocols, and community metrics that have been used previously to monitor wetland communities. Choices, rather than prescriptions, are given because rigid standardization of wetland monitoring techniques may not be desirable or feasible given the current lack of comparative studies. Exceptions may include situations where litigation is probable or efficacy of a regulatory program must be determined. Also, the need for diverse and adaptive sampling stategies is suggested by the extreme temporal and spatial variability within and among wetlands, and the variety of purposes for which wetlands are monitored.

The Sampling Protocols subsection also notes where data are indicate that one protocol, type of sampler, or metric is better than another. However, we have not evaluated these ourselves, except to note situations where the use of a particular sampler, protocol, or community metric seems clearly inappropriate.

Finally, the subsection discussions of Spatial and Temporal Variability--Data Gaps summarize numerical data, both temporal and spatial, on wetland community ecology. The range in values of, say, macroinvertebrate density, is noted for wetland types for which such data are available.

Data on variability is potentially useful for helping develop wetland biocriteria. For example, taxa whose community structure naturally varies the least with time and space tend to be most practical for use as indicators of anthropogenic influences. Also, the spatial variability in community composition among wetlands may be less in disturbed landscapes than in natural landscapes, if inferences from other ecosystem types are applicable (Sheehan 1984). Such information is useful in design of regional monitoring programs.

If data that describe variability were drawn from a sufficient number of wetlands to represent the wetland resource of a region, and with a sufficient frequency to capture the range of changing conditions, then such data might be used as one basis for establishing numeric criteria for protection of wetland aquatic life. They might also be used to target gaps and reduce costs in the statistical design of more rigorous biomonitoring efforts. Such an approach has been proposed for use in EPA's new Environmental Monitoring and Assessment Program (EMAP), and has been applied successfully to stream ecosystems in Ohio and Arkansas (e.g., Giese et al. 1987).

However, existing data, such as those presented, are of uncertain statistical representativeness. They were compiled from all relevant, published studies. As such, they may represent only a first-guess or "default" estimate of expected or baseline levels of community-level metrics, relevant only when local data are lacking. As noted earlier, conclusions drawn from these data cannot be extrapolated to other wetlands with known certainty.

Areas of missing biological information ("data gaps") are also noted. As appropriate, gaps are identified by geographic region, by wetland type, and by type of stressor. Emphasis is on geographic gaps, rather than on thematic gaps (thematic gaps have been identified in Adamus 1989, USEPA 1988, and in many other documents). Information on gaps was gained partly by plotting all relevant studies on state maps (Appendix B).

1.2 HOW THE REPORT WAS PREPARED

In August 1988, EPA's Wetlands Research Program sponsored a workshop in Easton, Maryland, a part of which focused on identifying organisms and metrics that might be useful for indicating wetland ecological condition. Findings were summarized in an EPA report , "Wetlands and Water Quality: EPA's Research and Monitoring Implementation Plan for the Years 1989 - 1994" (Adamus 1989). That report noted a need for synthesizing existing regional literature in ways that would allow candidate bioindicators to be identified and available data to be numerically compiled. Potential categories of indicators applicable to surface waters (in general) were targeted in EPA contracted reports ( AMS 1987, Mittleman et al. 1987,) and by another EPA workshop held in early 1989 (Temple, Barker, & Sloane 1989).

A preliminary synthesis of wetland indicator literature was completed in August 1989 (Brown et al., unpublished) as part of EPA's planning efforts for the new Environmental Monitoring and Assessment Program (EMAP). That effort included a review of abiotic as well as biotic indicators, but did not attempt a comprehensive review of technical literature. At the same time, EPA's Office of Policy, Planning, and Evaluation (OPPE), acting on a request from EPA's Office of Wetlands Protection, asked EPA's Corvallis Environmental Research Laboratory to modify and expand the scope of the similar, unpublished EMAP report. Representatives of EPA's Office of Water Regulations and Standards (OWRS) were also involved in early discussions of the scope of the effort. It was agreed that the modified report would focus more strongly than did the EMAP effort on compiling quantitative measurements of wetland ecological communities. In particular, it would attempt to describe the variability in community responses by region, stressor type, and taxon. Additional support from EMAP would complement OPPE's support. This report represents that effort.

Literature review began with an automated bibliographic search of the Wetland Values Database of the U.S. Fish and Wildlife (Ruta Stuber 1986). Other bibliographic databases were also searched using terms wholly or partly synonymous with wetlands, e.g.:

alluvial; aquatic moss; aquic; aquod; backwater; bayou; benthic/aquatic/submersed/submerged plant/vegetation; black(-)water; bog; bosque; brown(-)water; depression; ditch; dystroph-; fen; floodplain; fluventic; fluvisol; histic; histosol; hydrophy-; intermit- stream; inundated soil; lagoon; lentic; littoral; lowland; macrophy-; marsh; mire; muck; muskeg; oxbow; playa; pluvial; pocosin; pond; poorly drained; pothole; riparian; saprophilic; seep; shallow lake; shoal; sphag-; stockpond; stream corridor; swamp; vernal pool; wash; water log-; wet land; wet meadow; wet prairie

Literature was included if it met the following criteria:

  • quantitative biological measurements were described (i.e., not just species lists or faunistic surveys);
  • inland nontidal wet areas were covered;
  • oriented towards the community level of ecological structure (i.e., transects or point data in which a full range of vascular plant, fish, bird, amphibian, or mammal species was measured, not just single species);
  • if not community-oriented, then focused on the sensitivity of ecosystem process (e.g., productivity, decomposition) to environmental stressors, or on the relative usefulness of particular species as "bioindicators."

References resulting from the preliminary literature review were compiled by state and circulated, with the criteria, for comment to persons from the following groups:

  • wetland coordinators from the EPA Regions and wetland biologists from other EPA Labs
  • selected offices of the Corps of Engineers in each region
  • a majority of members of the Society of Wetland Scientists
  • wetland coordinators for all state highway departments
  • state biologists of the Soil Conservation Service
  • refuge managers of the National Wildlife Refuges
  • attendees from the Easton workshop
  • other persons selected from Wetland Research Program mailing lists

In addition to soliciting comments on published literature, we asked these persons to suggest data meeting our criteria that could be found in the following types of less-available literature:

  • student theses
  • biomonitored mitigation sites
  • impact statements or permit applications
  • Superfund site assessments
  • water quality bioassessment reports
  • utility siting plans
  • fish/wildlife agency studies
  • forest management monitoring plans
  • grazing management monitoring plans
  • aquatic weed control impact studies

A large number of responses were received, and along with secondary citations discovered in literature we collected, resulted in significant expansion of our bibliography. Some unpublished and ongoing data sets recommended by respondees were included as well. Despite the considerable effort, some experts were undoubtedly not contacted and it is likely that some number of references meeting our criteria were not discovered.

Subsequently, all literature contained in the bibliography but not presently in the EPA - Corvallis wetlands library was obtained. Study locations were plotted on state maps (Appendix B) using a geographic information system at the Lab (ArcInfo GIS), quantitative data were extracted and compiled for chapter tables, the "Methods" sections of papers were reviewed, and the narrative descriptions presented in the following chapters were prepared. Quality of individual data sets or their locations on the maps could not be checked or assured.

In addition, various national databases exist that frequently contain wetland community data. Data from sites associated with these databases were obtained and/or the site locations were plotted on the digital maps. These include:

  • LTER network (all areas plotted; Long Term Environmental Research sites sponsored by the National Science Foundation);
  • Christmas Bird Count database (all areas plotted); from Cornell Laboratory of Ornithology;
  • Breeding Bird Survey database (all areas plotted); from U.S. Fish and Wildlife Service;
  • Breeding Bird Census database (only wetland areas plotted); from Cornell Laboratory of Ornithology;
  • Waterfowl Surveys (Migrating, Wintering, Spring Waterfowl Surveys, Summer Brood Count/ Breeding Ground Surveys); from Waterfowl Flyway Technical Representatives in each state;
  • International Shorebird Survey (all inland wetlands); from Manomet Bird Observatory, Manomet, Massachusetts.

In addition, several data sets exist that may include relevant wetlands biological data, but with the limited effort of this project, such data could not be easily compiled or separated from non-wetland data. Examples of these include:

  • wetland boundary determinations by consultants and agencies (a vast source of botanical data);
  • measured data collected in support of HEP analyses by numerous consultants and agencies;
  • river basin reports of government water quality monitoring programs (a source of fish and invertebrate data, if "wetland" stations could be separated from others);
  • monthly bird counts of the National Wildlife Refuges;
  • data from the Nest Card and Colonial Waterbird databases of the Cornell Laboratory of Ornithology;
  • private notes of birders, botanists, and other naturalists.

Wetland data not included because of their failure to meet one or more of our criteria included the following:

  • National Contaminant Biomonitoring Program data of the U.S. Fish and Wildlife Service (focuses on bioaccumulation and generally does not include measurement of community-level variables);
  • Inventories of wetland threatened/ endangered species (not measurement of community-level variables);
  • Inventories of wetland acreage and distribution (not measurement of community-level variables).
  • Databases of The Nature Conservancy and state heritage programs (field data often not quantitative)

ACKNOWLEDGEMENTS

We acknowledge the support jointly provided to this effort by EPA's Office of Policy, Planning, and Evaluation (OPPE) and EPA's Environmental Monitoring and Assessment Program (EMAP). We also acknowledge with appreciation the contribution made by many individuals during the preparation of this report. John Maxted, Doreen Robb, and Diane Fish at the EPA Office of Wetlands Protection and F. Kim Devonald at the EPA Office of Policy, Planning, and Evaluation were instrumental in initiating the effort. Dr. Mark Brown at the University of Florida served as project officer of the Cooperative Agreement which provided assistance on the effort.

At the EPA Environmental Research Laboratory in Corvallis, Oregon, Dr. Eric M. Preston, the EPA Project Officer and Manager of EPA's Wetland Research Program, facilitated external communications necessary to the project's success. Barbara Hagler was instrumental in locating hundreds of journal articles for subsequent review. The tasks of data plotting and literature database construction and retrieval were capably handled by Robin Renteria, Eric Schneidermann, and Jeff Irish, with assistance from Scott Leibowitz and Donna Frostholm. Jo Ellen Honea and Kristina Heike assisted with formatting and layout.

Within EPA, the final draft was reviewed, in part or in toto, by Doreen Robb, Diane Fish, and Martha Stout (Office of Wetlands Protection), William Shippen (Office of Water Regulation and Standards), Ruth Miller (Office of Policy, Planning, and Evaluation), Wayne S. Davis (Region 5), and Louisa Squires (NSI, Corvallis Environmental Research Laboratory).

From other agencies, reviews (in part or in toto) were provided by Carl Armour, Greg Auble, R. Bruce Bury, Richard Schroeder, and Michael Scott of the U.S. Fish and Wildlife Service; Barbara Kleiss, K. Jack Kilgore, Charles Klimas, Thomas Roberts, William Taylor, and James Wakeley of the U.S. Army Corps of Engineers Waterways Experiment Station; and Dr. James LaBaugh of the U.S. Geological Survey.

From the scientific community, reviews of the final draft were provided by Drs. Robert Brooks, Joan Ehrenfeld, Jerry Longcore, William Niering, and Fredrick Reid. Early drafts of the report were reviewed externally by Drs. Robert Brooks, David Cooper, James Karr, and R. Wayne Nelson.

The contributions of the many wetland specialists who responded to our written inquiries are particularly appreciated. Access to the Wetland Values Database was kindly expedited by Craig Johnson of the U.S. Fish and Wildlife Service, Division of Endangered Species and Habitat Conservation. Dr. Ronald Hellenthal of Notre Dame University graciously accessed bioindicator data in the ERAPT database. Bird data collected by thousands of volunteers and compiled by the Cornell Laboratory of Ornithology and the U.S. Fish and Wildlife Service was provided by these institutions.


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