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> Wetlands > Impacts on Quality of Inland Wetlands of the United States > Appendix A. Summary of Advantages and Disadvantages of Use of Major Taxa in Monitoring Wetland Ecological Condition

Appendix A.
Summary of Advantages and Disadvantages of Use of Major Taxa in Monitoring Wetland Ecological Condition

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)

Microbial Communities

ADVANTAGES

• tight linkage to fundamental processes (eg, decomposition, denitrification, respiration)

• samples easily collected, transported, and analyzed

• some taxa linked to animal welfare (eg, streptococci)

• EPA protocols available

• immediate response to contamination

• measurable in wetlands which lack surface water

• sensitive to presence of some contaminants (eg, Ames test, Microtox test)

• "indicator taxa" relatively well-known (especially protozoans)

• some culture bioassay data are available

DISADVANTAGES

• response is often not identifiably stressor-specific

• laborious and slow (plate culture) identification; process measurements difficult to interpret with regard to ecological significance

• general absence of existing regional field databases

• rapid turnover requires frequent sampling; do not integrate conditions over time very well

• naturally great micro-spatial variation, especially in tidal wetlands

• drifting cells in riverine wetlands complicate interpretation

• low social recognition of their importance

• bioaccumulation is irrelevant and impractical to detect

Algae

ADVANTAGES

• tight linkage to fundamental processes (eg, photosynthesis, respiration)

• pivotal relationships in food webs

• EPA protocols available (may need modification to wetlands)

• measurable in some wetlands which lack surface water

• tolerances and indicator value are relatively well-known, particularly to nutrients, and most are very sensitive to herbicides

• simple collection procedures with minimal wetland impact

• response to stressors is usually immediate

• generally immobile and thus reflective of site conditions, useful for in situ exposure assessments and whole-effluent bioassays

DISADVANTAGES

• response is often not identifiably stressor-specific

• laborious identification

• some regional field databases exist, but not for wetlands

• rapid turnover requires frequent sampling

• cannot be effectively sampled during dormant season

• low social recognition of their importance

• bioaccumulation is unmeasurable

• drifting cells of unattached species complicate interpretation

• most relatively insensitive to heavy metals and pesticides (Hellawell 1986)

Mosses, Liverworts, Ferns

ADVANTAGES

• a few taxa are reputed indicator species for physicochemical contaminants

• perhaps the most sensitive indicator of hydric regimes

• the only integrator of the long-term geologic record (ie, peat core analyses for metals accumulation, land cover change, ground water flow reversals)

• immobile and thus reflective of site conditions, useful for in situ exposure assessments

DISADVANTAGES

• response is often not identifiably stressor-specific

• laborious sampling and identification

• low social recognition of their importance

• few regional field databases exist

Submersed Aquatic Vascular Plants

ADVANTAGES

• extremely sensitive to turbidity, eutrophication, hydroperiod

• sensitivities of several indicator species are well known

• relatively important in food webs (eg, waterfowl)

• immobile and thus reflective of site conditions, useful for in situ exposure assessments

• patterns interpretable using remote sensing

DISADVANTAGES

• difficult to sample systematically throughout a wetland

• cannot be effectively sampled during dormant season

• absent from wetlands that lack standing water (eg, bogs)

• tolerant of intermittent pollution

• laborious identification

• low social recognition of their importance

• few regional field databases exist

Non-rooted Aquatic Vascular Plants

ADVANTAGES

• extremely sensitive to nutrient additions

• sensitivities of some indicator species (eg, Lemna) are well known

• important in food webs (eg, waterfowl)

• mostly immobile and thus reflective of site conditions, useful for in situ exposure assessments

• patterns sometimes interpretable using remote sensing

DISADVANTAGES

• difficult to sample systematically throughout a wetland

• limited bioaccumulation due to short lifespan

• absent from wetlands that lack standing water (eg, bogs)

• laborious identification

• low social recognition of their importance

• few regional field databases exist

• cannot be effectively sampled during dormant season

Emergent (Herbaceous) Vascular Plants

ADVANTAGES

• occur in virtually all wetlands

• sensitivities of some indicator species (eg, Typha, Phragmites, Phalaris) to nutrients/sediment are well known

• immobile and thus reflective of site conditions, useful for in situ exposure assessments

• bioaccumulate to a moderate degree

• patterns interpretable using remote sensing

• sampling techniques and community metrics well-developed

• moderately sensitive to nutrients and hydroperiod alteration

• some regional field databases exist

DISADVANTAGES

• not highly sensitive to contaminants and sedimentation

• lagged response to stressors (episodic contamination may not be reflected)

• low social recognition of importance

• sampling and identification is laborious

• community cannot be completely characterized during the dormant season

• dispersal, herbivory, soil type and other factors often overshadow contaminant effects

Forested/Shrub (Woody) Vascular Plants

ADVANTAGES

• occur widely

• sensitivities of many species to hydroperiod change are relatively well known

• immobile and thus reflective of site conditions

• bioaccumulate to a moderate degree

• patterns interpretable using remote sensing

• sampling techniques and community metrics well-developed

• some regional field databases exist

• trends can be inferred (with care) using tree ring analyses

• signs of stress (eg, die-offs) are socially recognized

• sampling and identification are fairly easy

• community can be characterized even in the dormant season

DISADVANTAGES

• not highly reflective of contaminants and sedimentation

• long lagged response to stressors (episodic contamination may not be reflected); in situ experimentation is impractical

• response difficult to interpret where past management (eg, silviculture) has been practiced

Aquatic Insects (eg, dragonflies, midges)

ADVANTAGES

• occur in all wetland types, even those lacking surface water

• community metrics/indices well-developed (eg, Index of Biotic Integrity) but may need adaptation for wetlands

• intermediate lifespans reflect episodic events without requiring extremely frequent sampling

• bioaccumulate to a moderate degree

• can be caged for whole-effluent bioassays or in situ assessments

• relatively important in food webs

• community can usually be sampled year-round

• some regional field databases exist, though few for wetlands

• show characteristic response to all major wetland stressors (hydroperiod, sediment, nutrients, contaminants)

• some taxa linked to human welfare (eg, mosquitoes)

• EPA sampling protocols available, but need modification for wetlands

• contaminants may induce identifiable deformities

DISADVANTAGES

• occurrence in isolated wetlands may be strongly tied to sources of colonizers and their dispersal mechanisms

• sampling difficult and true densities very difficult to determine in wetlands with herbaceous vegetation

• laborious identification

• low social recognition of their importance

• naturally great micro-spatial variation

• community composition potentially affected by selective predation (eg, by fish, waterfowl)

Benthic/Epiphytic Macro-crustaceans (eg, amphipods, crayfish, oligochaetes, isopods)

ADVANTAGES

• less subject to dispersal than aquatic insects (and thus more reflective of conditions in a particular wetland)

• may be more sensitive than aquatic insects to contaminants

• fairly simple sampling and identification

• social recognition of some species (eg, crayfish, sandworms)

• other advantages --- similar to Aquatic Insects, above

DISADVANTAGES

• mostly absent from wetlands which lack standing water

• naturally great micro-spatial variation

• community composition potentially affected by selective predation (eg, by fish, waterfowl)

Mollusks

ADVANTAGES

• highly immobile and thus most reflective of site conditions, useful for in situ exposure assessments

• highly bioaccumulative (eg, clams, mussels)

• depuration procedures can indicate potential contaminant uptake rates

• bioassay data fairly extensive

• contaminants may induce identifiable deformities

• can be sampled year-round

• historic recreation of growth is possible (with care)

• presumptive indicator of hydroperiod (complete, sustained wetland drawdown)

• EPA protocols available

• high social importance of coastal species (shellfish)

DISADVANTAGES

• very localized occurrence, related largely to dissolved solids rather than contaminants

• laborious sampling and (in freshwater) identification

Fish

ADVANTAGES

• community metrics well-developed (Index of Biotic Integrity), though not for wetlands; many reputed indicators (eg, carp)

• most comprehensive set of bioassay data

• can be caged for whole effluent bioassay and in situ studies, or avoidance measured using radiotelemetry

• moderately bioaccumulative

• fairly simple identification (except larval stages)

• population characteristics, growth fairly easy to discern

• contaminants may induce identifiable deformities

• can be sampled year-round

• presumptive indicator of hydroperiod (absent from isolated wetlands with complete, sustained drawdown)

• EPA protocols available

• integrate broad, longer-term, landscape-level impacts because of their mobility, high trophic position, and longer life span

• high social importance of most species; existing water quality standards for aquatic life focus on fish

DISADVANTAGES

• mobility makes it difficult to locate specific contaminant sources

• absent (or present for only brief periods) in most wetlands

• laborious sampling

• early life stages and non-game species may be difficult to identify

Amphibians and Reptiles

ADVANTAGES

• small home range relative to larger vertebrates

• highly (eg, snapping turtle, alligator) to moderately bioaccumulative; can be caged for in situ assessments

• some social recognition

• fairly simple identification

• fairly well-established sampling protocols

• sensitive to hydroperiod alteration

• present in most inland wetland types

DISADVANTAGES

• sampling limited to certain seasons in some regions

• mostly absent from tidal wetlands

• sampling can be laborious

• presence can be strongly influenced by natural dispersal conditions

Birds

ADVANTAGES

• high social recognition, particularly waterfowl

• have the only relatively extensive nationwide databases on trends, habitat needs, distribution

• moderately extensive bioassay data

• some species (eg, wading birds, harrier) are highly bioaccumulative

• avoidance is measurable using radiotelemetry, and in situ assessments are possible (caged or clipped individuals)

• simple sampling and identification

• present in all wetland types

• established sampling protocols are available

• the only suitable indicator of degradation occurring at the landscape scale

DISADVANTAGES

• in general, community structure is highly controlled by physical habitat, and perhaps hunting mortality, rather than contaminants

• mobility makes it difficult to locate specific causes of mortality sources (could be thousands of miles away)

• essentially absent from some wetlands in winter

Mammals

ADVANTAGES

• many (eg, otter) are highly bioaccumulative

• high social recognition and value (eg, muskrat)

• avoidance is measurable using radiotelemetry, and in situ assessments are possible (caged individuals)

• fairly simple sampling and identification

• some sign (eg, beaver dams) can be remotely sensed

• present in all wetland types

• established sampling protocols are available

• an extensive database of acute toxicity data for mice/rats may be partially transferable

DISADVANTAGES

• great temporal and spatial variation (many species are cyclic) makes data interpretation difficult

• in general, community structure is highly controlled by physical habitat, and perhaps trapping mortality, rather than contaminants

• mobility (and frequent use of non-wetland habitat) makes it difficult to locate specific causes of mortality sources

Biological Processes (Functions)

Definition: Whole-wetland measurement of photosynthesis, primary productivity, respiration, denitrification, nitrogen fixation, decomposition, leaching, and/or similar processes

ADVANTAGES

• most important indicators of wetland sustainability and life support function

DISADVANTAGES

• not as sensitive to contamination as is community structure or tissue analysis (Schindler 1987)

• measurement is laborious, time-consuming (eg, isotopes)

• social recognition of importance is weak

• extreme spatial and temporal variation

• measured values may reflect natural successional stage rather than human-induced stress

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