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